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Transcript
SUPPORT MATERIAL SCIENCE CLASS - X 2013 - 2014
SUPPORT MATERIAL
CLASS - X
SCIENCE
2013 - 2014
Venue :
G.S.K.V. Nangloi, Delhi-110041
Published by :
Directorate of Education Govt. of NCT of Delhi
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[X – Science]
Group Leader
Mr. RAJPAL SHERAWAT
Principal, R.P.V.V., Sec.-XI, Rohini, Delhi
Sl. No.
Name
Designation
1.
Mrs. Geeta Shokeen
T.G.T. (N.Sc.)
G.S.K.V. Nangloi,
Delhi-110041
2.
Mrs. Anuradha
T.G.T. (NSc.)
R.P.V.S. A-6,
Paschim Vihar,
Delhi-110063
3.
Mr. Kamal Sharma
T.G.T. (N.Sc.)
Govt. Co. Edu. S.S.S.
Punjabi Bagh, Nangloi,
Delhi-110041
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CONTENTS
Unit
Chapter
Page
1. Chemical Reactions and Equations
2. Acid, Bases and Salts
3. Metals and Non Metals
4. Carbon and its compound
5. Periodic Classification of Elements
6. Life Processes
7. Control and Coordination
8. How do Organisms Reproduce
9. Heredity and Evolution
10. Light - Reflection and Refraction
11. Human eye and colourful World
12. Electricity
13. Magnetic effects of Electric Current
14. Sources of Energy
15. Our Environment
16. Management of Natural Resources
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CHAPTER – 1
SECTION A : READING
Chemical Reaction : Whenever a chemical change occurs we can say
that a chemical reaction has taken place
e.g. –
–
Food gets digested in our body
Rusting of iron.
Chemical Equation : A chemical reaction can be expressed symbolically
by using chemical equation
e.g. magnesium is burnt in air to form magnesium oxide. This chemical
reaction can be represented as
Mg + O2
MgO
– We can observe or recognise a chemical reaction by observing change
in state, colour, by evolution of gas or by change in temperature.
Physical state of the reactants and the products are mentioned to make
chemical reaction more informative. e.g. we use (g) for gas, (l) for liquid, (s)
for solid and (aq) for aqueous.
Balancing Equation : We balance a chemical equation so that no. of
atoms of each element involved in the reaction remains the same at the reactant
and product side.
e.g.
Fe + H2O
Fe2O3 + H2 can be written as
3 Fe(s) + 4H2O(g)
Fe2O3(s) +4H2(g)
Types of Reaction
I.
Combination Reaction :– The reaction in which two or more substances
combine to form a new single substance
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e.g.
(i)
CaO(s)
+
Calcium
oxide
Quick lime
H2O(l)
Ca(OH)2
Water
(slaked lime)
Calcium hydroxide
(aq)
– Ca(OH)2 slaked lime is used for white washing walls. It reacts with
CO2 to form Calcium Carbonate and gives a shiny finish to the walls.
Ca(OH)2
(aq)+
CO2
(g)
Calcium
hydroxide
CaCO3
(s)+
H2O (l)
Calcium
Carbonate
(ii) Burning of Coal
C(s) + O2(g) CO2(g) + heat + light
(iii) Formation of water
2H2(g) + O2(g) 2H2O(l)
Exothermic Reactions : Reaction in which heat is released along with
the formation of products.
eg. CH4(g) + 2O2(g) CO2(g) + 2H2O(g)
– Respiration is also exothermic reaction.
– De composition of vegetable matter into compost.
II.
Decomposition Reactions : The reaction in which a single substance
decomposes to give two or more substances. De composition reactions
can be of three types
(i) Thermal Decomposition : When a decomposition reaction is
carried out by heating
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–
Silver bromide behaves similarly
Sunlight
2Ag Br 2Ag(s) + Br2(g)
–
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The above two reactions are used in black and white photography.
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Endothermic Reactions – The reactions which require energy in the
form of heat, light or electricity are called Endothermic Reactions.
2Ba(OH)2 + NH4Cl 2BaCl2 + NH4OH
III. Displacement Reaction : The chemical reaction in which an element
displaces another element from its solution
Fe(s) + CuSO4(aq) FeSO4 + Cu(s)
Copper
Sulphate
(aq)
Iron Sulphate
– The nail becomes brownish in colour and the blue colour of copper
sulphate solution fades.
– Other examples Zn(s) + CuSO4 ZnSO4 + Cu(s)
(aq)
(aq)
Copper
Sulphate
Zinc
Sulphate
Pb(s) + CuCl2 PbCl2
(aq)
(aq)
Copper
Chloride
Lead
Chloride
+ Cu(s)
– Zinc and lead are more reactive elements than copper. They displace
copper from its compounds.
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IV Double Displacement Reaction : The reaction in which two different
atoms or group of atoms are mutually exchanged
eg. Na2 SO4
BaSO4(s) + 2NaCl
+ BaCl2
(aq)
(aq)
(aq)
Sodium Barium
Barium
Sodium
Sulphate Chloride
Sulphate Chloride
A white substance is formed due to above reaction. The insoluble
substance is called precipitate.
Precipitation Reaction – Any reaction that produces a precipitate is
called a precipitation reaction.
eg. Pb(NO3)2
(aq)
+
2KI PbI2 +2KNO3
(aq)
(aq)
Lead Nitrate
Potassium Lead Potassium
Iodide
Iodide Nitrate
V Oxidation : Oxidation is the gain of oxygen or loss of hydrogen
Heat 2CuO
2Cu + O2
eg.
When copper is heated a black colour appears. If this CuO is reacted
with hydrogen gas then again Cu becomes brown as reverse reaction
takes place
Heat Cu + H2O
CuO + H2
VI Reduction : Reduction is the loss of oxygen or gain of hydrogen.
–
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Redox Reaction : The reaction in which one reactant gets
oxidised while other gets reduced
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ZnO + C Zn + CO
eg.
MnO2 + 4HCl MnCl2 + 2H2O + Cl2
–
Corrosion : When a metal is attacked by substances around it
such as moisture, acids etc.
eg. Reddish brown coating on iron.
(ii)
Black coating on Silver.
–
Rancidity : When fats and oils are oxidised they become rancid
and their smell and taste change.
–
Antioxidants are added to foods containing fats and oil.
EXERCISE
(Question Bank)
Answer the following questions very briefly
(1 Mark)
1. What happens when the milk is left at room temperature during summer?
2. Write a balanced chemical for the reaction that takes place equation
when magnesium is burnt in air to give magnesium oxide.
3. A substance under goes chemical reactions to produce simpler products,
what type of reaction is this?
4. Why do copper vessels lose their shine when exposed to air?
5. Which gas is produced by the action of dilute hydrochloric acid on zinc
granules? How will you test for the presence of this gas?
6. Fe2O3 + 2Al Al2O3 + 2Fe
The above reaction is an example of which type of reaction.
7. Name the type of reaction in which energy is absorbed.
8. Why does the colour of copper sulphate solution change when an iron
nail is dipped into it?
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9. Give an example of decomposition reaction which proceeds by absorbing
electric energy.
10. Why do we balance a chemical equation?
11. Why is respiration called as an exothumic reaction?
12. Why is digestion called as decomposition reaction?
13. Why are the bags of potato chips usually flushed with nitrogen gas?
Answer the following questions briefly
(2 mark)
1. Write down the observations which indicate the occurence of a chemical
reaction.
2. Write the balanced chemical equation for the given word equations–
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Potassium metal reacts with water to give potassium hydroxide
and hydrogen gas.
3. Identify the substances that are oxidised and the substances that are
reduced in the following reactions.
(i)
Na
+
(s)
(ii)
CuO
(s)
O2 Na2O
(g)
+
H2
(s)
Cu + H2 O(l)
(g)
(s)
4. What happens when silver chloride is exposed to sunlight? Give one
practical application of this reaction. Write the balanced chemical
equation also.
5. Write any two changes observed by you when ferrous sulphate is heated.
Write the balanced chemical equation of the reaction.
6. BaCl2 + Na2SO4 2NaCl + BaSO4
(i) Identify the type of chemical reaction represented by the above
chemical equation.
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(ii) Give another example of this type of chemical reaction with
equation.
7. Compound ‘X’ decomposes to form compound ‘Y’ and CO 2 gas.
Compound ‘Y’ is used in the manufacturing of cement.
(i) Name the compounds X and Y.
(ii) Write the chemical equation for this decomposition reaction.
8. What is rancidity? Write two ways by which it can be prevented?
Answer the following questions in detail
(3 marks)
1. Write down the balanced chemical equations for the following reactions.
(a) Zinc carbonate(s) Zinc oxide + Carbon dioxide(g)
(b) Aluminium(s) + Chlorine(g) Aluminium chloride(s)
(c) Magnesium(s)+ Water(l)
hydrogen(g)
Heat
Magnesium hydroxide(l)+
2. Classify the given chemical reactions into combination, displacement
and double displacement reactions.
(i) MnO2(s) + 4HCl(l) MnCl2(s) + Cl2(g) + 2H2O(l)
(ii) CaO(s) + CO2(g) CaCO3(s)
(iii) 2AgCl(s) 2Ag(s) + Cl2(g)
3. What happens when CO2(g) is passed through slaked lime? Write the
balanced chemical equation. Write the type of reaction that has occurred.
4. Define corrosion. Give two examples. Why is the corrosion of iron a
serious problem.
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Explain the following questions detail
(5 marks)
1. Balance the following chemical equations and identify the type of
reaction they represent
KClO3 KCl + O2
NH3 + O2 NO + H2O
Na2O + H2O NaOH
Na + H2O NaOH + H2
FeCl3 + NaOH Fe (OH)3 + NaCl.
2. Define the various types of chemical reactions. Write one example of
each type with chemical equations.
[X – Science]
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CHAPTER – 2
ACIDS, BASES AND SALTS
Acids
– Sour in taste
Bases
– Bitter in taste
– Change the blue litmus to red
– Change red litmus to blue
– eg. Hydrochloric acid HCl
eg. Sodium hydroxide NaOH
– Sulphuric acid H2SO4
Potassium hydroxide KOH
– Nitric acid HNO3
Calcium hydroxide Ca(OH)2
– Acetic acid CH3 COOH
– Ammonium hydroxide NH4OH
Some naturally occuring acids
Vinegar
–
Acetic Acid
Orange
–
Citric Acid
Lemon
–
Citric Acid
Tamarind
–
Tartaric Acid
Tomato
–
Oxalic Acid
Sour milk (Curd)
–
Lactic Acid
Ant and Nettle sting
–
Methanoic Acid
Acid – Base Indicators – Indicate the presence of an acid or base in a
solution.
Litmus solution – It is a natural indicator. It is a purple dye extracted
from Lichens. Other examples are Red Cabbage and coloured petals of
Petunia and turmeric.
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Olfactory indicators – Show odour changes in acidic or basic media.
eg. onion and clove.
Acid – Base Indicators
S. No.
Name of the
Indicator
Colour Change Colour Change
with Acid
with Base
A.
Blue litmus solution
To red
No change
B.
Red litmus solution
No change
To blue
C.
Turmeric
No change
To red
D.
Methyl orange
To red
To yellow
E.
Phenolphthalein (colourless) No change
To pink
Dilute Acid : Contains only a small amounts of acid and a large amount
of water.
Concentrated Acid : A concentrated acid contains a large amount of
acid and a small amount of water.
Chemical Properties of Acids and Bases
(i) Reaction with metal
Acid + Metal Salt + Hydrogen
(Refer activity 2.3 on page No. 19 of NCERT Book)
ZnCl2 + H2
2HCl + Zn
2HNO3 + Zn Zn (NO3)2 + H2
H2SO4 + Zn ZnSO4 + H2
2CH3COOH + Zn (CH3COO)2 Zn + H2
Pop test : When a burning candle is brought near a test tube containing
hydrogen gas it burns with a ‘Pop’ sound. This test is conducted for
examining the presence of hydrogen gas.
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Base + Metal Salt + Hydrogen
NaOH + Zn Na2ZnO2 + H2
Sodium Zincate
Note – Such reactions are not possible with all the metals.
Action of Acids with metal Carbonates and metal bicarbonates
Metal Carbonate + Acid Salt + Carbondioxide + Water
Na2CO3(s) + 2HCl(aq) 2NaCl(aq) + H2O(l) + CO2(g)
Metal bicarbonate + Acid Salt + Carbondioxide + Water
NaHCO3 + HCl NaCl + CO2 + H2O
Lime water Test : On passing the evolved CO2 gas is Passed through
lime water,
Ca(OH)2 (aq) + CO2(g) CaCO3(s) + H2O(l)
Lime water
White precipitate
On passing excess CO2 the following reaction takes place
CaCO3(s) + H2O(l) + CO2(g) Ca(HCO3)2 aq
Soluble in water
Reaction of acids and bases with each other.
Neutralisation Reactions
Base + Acid Salt + Water
NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)
Neutralisation reaction : The reaction between an acid and a base to
give salt and waste is called as neutralization reaction takes place when
the effect of a base is nullified by an acid and vice versa to give salt
and water.
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Reactions of metal oxides with acids
Metal Oxide + Acid Salt + Water
CuO
+
Copperoxide
HCl
CuCl2 +
Hydrochloric
Copper + Water
acid
chloride
H2O
Note : Appearance of blue green colour of the solution because of
formation of CuCl2.
Metallic oxides are said to be basic oxides because they give salt and
water on reacting with acids.
Reaction of Non Metallic Oxide with Base
Non metallic oxide + Base Salt + Water
Ca(OH)2 + CO2 CaCO3 + H2O
Note : Non Metallic oxides are said to be acidic in nature because on
reacting with a base they produce salt and water.
All acidic solutions conduct electricity because of formation of (H+
ions in eq, solution.
Refer activity 2.3 on page 22 of NCERT Book
–
Glowing of bulb indicates that there is a flow of electric current
through the solution.
Acids or bases in a Water Solution
Acids produce H+ions in the presence of water
HCl + H2O H3O+ + Cl–
H3O+ – Hydronium ion.
–
H+ion cannot exist alone. It exists as H+(aq) or (H3O+) hydronium
ion.
H+ + H2O H3O+
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–
Bases provide (OH–) ions in the presence of water
HO
2
NaOH(s)
Na+(aq) + OH–(aq)
HO
2
KOH(s)
K+(aq) + OH–(aq)
HO
2
Mg(OH)2(s)
Mg2+(aq) + 2OH–(aq)
Alkalis
All bases donot dissolve in water. An alkali is a base that dissolves in
water. Common alkalis are
NaOH
Sodium hydroxide
KOH
Potassium hydroxide
Ca(OH)2
Calcium hydroxide
NH4OH : Ammonium hydroxide
Note : All alkalis are bases but all bases are not alkalis.
Precaution must be taken while mixing acid or base with water. The
acid must always be added to water with constant stirring as it is a
highly exothermic reaction.
When an acid or a base is mixed with water they become dilute. This
results in the decrease in the concentration of H3O+ or OH– per unit
volume in acids and bases respectively.
Strength of an Acid or Base
Strength of acids and bases depends on the no. of H+ions and OH–ions
produced respectively.
With the help of a universal indicator we can find the strength of an
acid or base as it shows different colours at different concentrations of
hydrogen ions in a solution.
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A scale for measuring hydrogen ion conc. in a solution is called pH
scale has been developed.
pH = Potenz in German means power.
This scale measures from 0 (very acidic) to 14 (very alkaline) 7 Neutral
(water in neutral).
pH paper : Is a paper which is used for measuring pH.
Variation of PH
S.
PH
No. Value
Colour of the
pH Paper
Nature of
Solution
H+ion
Conc.
Highly acidic very high
1.
0
Dark red
2.
4
Orange or yellow
Acidic
high
low
3.
7:
Green
Neutral
Equal
Equal
4.
10 Bluish green or blue
Alkaline
low
high
5.
14
Dark blue or violet
highly basic very low
– strong Acids give rise to more H+ions.
eg. HCl, H2SO4 and HNO3.
– Weak Acids give rise to less H+ ions
eg. CH3 COOH, H2 CO3 (Carbonic acid)
– Strong Bases – Strong bases give rise to more OH– ions.
eg. NaOH, KOH, Ca(OH)2
– Weak Bases : give rise to less OH– ions.
eg. NH4OH
O H –i o n
Conc.
More about Salts
Salts and their derivation
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very low
very high
S. No. Name of Salt
Formula
Derived from Derived from
1.
Potassium Sulphate
K2SO4
KOH
H2SO4
2.
Sodium Sulphate
Na2SO4
NaOH
H2SO4
3.
Sodium Chloride
NaCl
NaOH
HCl
4.
Ammonium Chloride NH4Cl
NH4OH
HCl
Note : NaCl and Na2 SO4 belong to the family of sodium salts as they
have the same radicals. Similarly NaCl and KCl belong to the family
of chloride salts.
Importance of pH in our daily life
Importance of pH in our digestive system – Our stomach produces
hydrochloric acid. This dilute hydrochloric acid help in digestion of
good. In case of indigestion our stomach produces acid in a very large
quantity because of which we feel pain and irritation in our stomach.
To get relief from this pain antacids are used. These antacids neutralise
the excess acid and we get relief.
pH of Acid Rain : When pH of rain water is less than 5.6 it is called
acid rain. When this acidic rain flows into rivers these were also get
acidic, which causes a threat to the survival of aquatic life.
pH of Soil : Plants require a specific range of pH for their healthy
growth. If pH of soil of any particular place is less or more then normal
than the farmers add suitable chemicals to it.
Our body functions between the range of 7.0 to 7.8 living organisms
can survive only in the narrow range of pH change.
Tooth decay and pH : Bacteria present in the mouth produces acids by
degradation of sugar and food particles remaining in the mouth. Using
toothpaste which is generally basic, can neutralise the excess acid and
prevent tooth decay.
Bee sting or Nettle sting contains methanoic acid which causes pain
and irritation. When we use a weak base like baking soda on it, we get
relief.
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Neutral Salts : Strong Acid + Strong base
pH value is 7
eg. NaCl, CaSO4
Acidic Salts : Strong Acid + weak base
pH value is less than 7
eq. NH4Cl, NH4 NO3
Basic Salts : Strong base + weak acid
pH value is more than 7
eg. CaCO3, CH3 COONa
Chemicals from Common Salt
–
Sodium chloride is called as common salt is used in our food.
It is derived from seawater.
–
Rock Salt is the brown coloured large crystals. This s mined
like coal.
–
Common salt is an important raw material for many materials
of daily use such as.
Sodium hydroxide
Washing Soda
Bleaching Power.
Sodium Hydroxide : NaOH, Common Name – caustic soda.
Preparation : Prepared by the method called chlor-alkali process. It is
called so because we get chlorine and a base in this process.
2NaCl(aq) + 2H2O(l) 2NaOH(aq) + Cl2(g) + H2(g)
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Calcium oxy chloride – CaOCl
Common Name : Bleaching Power
Preparation Ca(OH)2
+
calcium hydroxide
Cl2 CaOCl2
chlorine
+
bleaching
power
H2O
water
use in textile, factories and laundry, used as disinfectant
Sodium Hydrogen Carbonate – NaHCO3
–
Common name – Baking Soda
Preparation NaCl + H2O + CO2 + NH3 NH4Cl + NaHCO3
Sodium
Water
chloride
Carbon
Ammonia
dioxide
Sodium
hydrogen
carbonate
On heating NaHCO3 produces :
NaHCO3
Heat
Na2CO3 + H2O + CO2
CO2 produced causes dough to rise and make cakes, pastries
spongy.
Uses :
In household, ingredients of antacid
In making baking power
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On heating baking powder produces
NaHCO3 + H+ CO2 + H2O + Sodium Salt of acid
Sodium Carbonate – Na2CO3
Common name : Washing Soda
Preparation : Recrystallisation of sodium carbonate
Na2CO3 + 10H2O
Heat
Na2CO3. 10H2O
Uses
–
Used in glass, soap and paper industry
–
Cleaning agent for domestic purposes.
–
Removal of hardness of water.
–
Manufacturer of borax.
Common Name : Plaster of Paris Calcium Sulphate hemihydrate
CaSO4.
1
HO
2 2
Water of crystallisation : Fixed no. of water molecules present in one
formula unit of a salt.
–
On heating copper sulphate crystals water droplets appear,
formula of hydrated copper sulphate – CuSO4. 5H2O.
–
gypsum also contains water of crystallisation. CaSO4.2H2O
–
Preparation : On heating gypsum at 373K it becomes
1
CaSO4. H2O is plaster of paris.
2
373 K
CaSO 4 .2H 2O CaSO 4
–
[X – Science]
1
H 2O
2
When Plaster of Paris is mixed with water it changes to gypsum.
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CaSO4.½ H2O + 1½ H2O CaSO4.2H2O
Uses of plaster of Paris : Making toys, decorative material and smooth
surfaces, plaster for fracture bones.
EXERCISE
(Question Bank)
Very Short answer type questions
(1 mark)
1. Two solution A and B have pH 4 and 9 respectively. Which solution
has more H+ ion concentration?
2. Why should curd and sour substances not be kept in brass and copper
vessel?
3. What is the chemical name of bleaching powder?
4. Write down the molecular formula of one strong and one weak acid.
5. Explain why Plaster of Paris should be stored in a moisture proof
container?
6. Name the gas evolved when dil. sulphuric acid acts on sodium carbonate.
How will you test for the presence of the gas.
7. What is the use of common salt in soap industry?
8. What do you observe when a buring candle is brought near the testtube containing zinc and hydrochloric gas?
9. Name the indicator used to measure pH values over the whole range.
10. Write the formula of washing soda and baking soda.
Short Answer Type Questions
(2 marks)
1. Write two physical properties of an acid
CO
2
name the products
2. Complete the reaction CaCO3 + H2O
formed.
3. A testtube contains solution of NaOH and Phenolphthalein. What is the
colour of the solution? On adding HCl, what colour change is observed
and why?
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4. Why are metallic oxides are called as basic oxides and non-metallic
oxides as called acidic oxides?
5. In a beaker a solution of HCl is poured and an electric circuit with a
is placed systematically. What happens to the bulb and why?
What will happen if HCl is replaced by NaOH?
6, Identify the type of reaction
H X + M OH MX + HOH
Explain this reaction with an example.
7. Why an all bases not alkalies but all alkalis are bases?
8. What is pH value. What is the pH value of a salt formed by a
(i) weak acid and strong base
(ii) strong acid and strong base.
9. Name the process used for the production of sodium hydroxide. Write
the chemical equation for this process.
10. Why is sodium hydrogen carbonate used as an ingredient in antiacid.
Give one more use of this compound.
Answer the following questions in detail
(3 marks)
1. What is acid rain? What colour does it give with the pH paper? How
does it affect the aquatic life?
2.
(i) What happens when a metal react with dilute hydrochloric acid?
Write the balanced chemical equation also.
(ii) Complete the following equation.
© NaOH + Zn _________ + _________.
3. What happens when an acid or a base is added to the water? Why does
the beaker appear warm? Why should we always add acid or base to
the water and not water to the acid or base.
[X – Science]
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4. Give reasons
(i) Use of a mild base like baking soda provides relief on the area
stung by honey bee.
(ii) Baking powder is added to make the cakes spongy and soft.
(iii)
The colour of blue copper sulphate crystals changes to white on
heating.
Answer the following question in detail
1.
(5 marks)
(a) Write down five products formed with the help of common salt
on industrial level.
(b) Write down the chemical name of these compounds and one
use of each of them.
2. Fill in the blanks
a) Acid + ______ Salt + Water..
b) _____ + Metal Salt + _____
c) Metal carbonate / metal hydrogen carbonate + acid
_______ + _______ + _______.
H2 O
d) NaOH
_______ + _______
e) Na2CO3 + 10H2O _______.
3.
(i) A compound ‘X’ is added to make pakoras crispy and also for
faster cooking.
Write the chemical name and formula of the compound ‘X’.
Also write the balanced chemical equation of the reaction of
production of compound ‘X’. List two other uses of compound ‘X’.
(ii) Write the chemical equation of the reaction used in the
preparation of bleaching powder and washing soda.
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
[X – Science]
CHAPTER – 3
METALS AND NON-METALS
About 118 elements are known today. There are more than 90 metals,
22 non metals and a few metalloids.
Sodium (Na), potassium (K), magnesium (Mg), aluminium (Al), calcium
(Ca), Iron (Fe), Barium (Ba) are some metals.
Oxygen (O), hydrogen (H), nitrogen (N), sulphur (S), phospho rus(P),
fluorine (F), chlorine (Cl), bromine (Br), iodine (l) are some nonmetals
Physical properties of Metals
Solid at room temperature except mercury
Ductile (drawn into wires)
Malleable (beaten into thin sheets)
Sonorous (produce sound)
Lustrous (natural shine)
Have high melting point. Cesium and gallium have very low melting
point.
Generally good conductor of heat and electricity, except lead and
mercury which are comparatively poor conductors. Silver and copper
are the best conductors.
Have high density. Sodium and potassium can be cut with knife, they
have low density.
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
Physical properties of Non-Metals:
Occur as solid liquid or gas.
Solid : Carbon, Sulphur,
Liquid : Bromine
Gas : Oxygen, Chlorine
Generally bad conductors of heat and electricity. Graphite, a natural
form of carbon is a good conductor.
Non-sonorous.
Non-lustrous, only iodine has lustre.
Metals form basic oxides e.g., Magnesium oxide (MgO), while nonmetals form acidic oxides e.g., SO2, CO2.
*Chemical properties of metals:
1. Reaction with air : Different metals show different reactivities towards
oxygen present in air.
Metals can burn in air, react or don't react with air.
Metal
+ oxygen Metal Oxide
Some metals like Na and K are kept immersed in kerosene oil as they
react vigorously with air and catch fire.
Some metals like Mg, Al, Zn, Pb react slowly with air and form a
protective layer.
Mg can also burn in air with a white dazzling light to form its oxide
Fe and Cu don't burn in air but combine with oxygen to form oxide.
When heated, iron filings burn when sprinkled over flame.
Metals like silver, platinum and gold don't burn or react with air.
2Na
+ O2
Na2O
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[X – Science]
2Mg
+ O2
2MgO
2Cu
+ O2
2CuO
4Al
+ 302
2Al2O3
Amphoteric Oxides : metal oxides which react with both acids as well
as bases to form salt and water e.g. Al2O3, ZnO.
Al2O3
+
HCl
AlCl3
+
H2O
Al2O3
+
NaOH
NaAlO2
+
H2O
2. REACTION WITH WATER :
Na
+
H2O
NaOH
+
H2
K
+
H2O
KOH
+
H2
Ca
+
H2O
Ca(OH)2
+
H2
Mg +
H2O
Mg(OH)2 +
H2
In case of Ca and Mg, the metal starts floating due to bubbles of
hydrogen gas sticking to its surface.
Al
+
H2O
Al2O3
+
H2
Fe
+
H2O
Fe3O4
+
H2
Try Balancing these Chemical equations yourself
3. Reaction with dilute acids:
Metal + dilute acid Salt + Hydrogen gas
Metals react with dilute hydrochloric acid and dilute sulphuric acid to
form salt and hydrogen gas.
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
+
2HCl
FeCl2
+
H2
Mg +
2HCl
MgCl2
+
H2
Zn
+
2HCl
ZnCl2
+
H2
2Al +
6HCl
2AlCl3
+
3H2
Fe
Copper, mercury and silver don’t react with dilute acids.
Hydrogen gas produced is oxidised to water. This happens because
HNO3 is a strong oxidising agent when metals react with nitric acid
(HNO3). When metals react with nitric acid. But Mg and Mn, react
with very dilute nitric acid to evolve hydrogen gas.
Mg +
2HNO3
Mg(NO3)2 +
H2
4. Reaction of metals with other metal salts :
Salt
Metal A +
solution
Salt
solution
of B
+
Metal B
of A
All metals are not equally reactive. Reactive metals can displace less
reactive metals from their compounds in solution. This forms the basis
of reactivity series of metals.
Reactivity series is a list of metals arranged in order of their decreasing
activities.
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[X – Science]
Fe
+
CuSO4
FeSO4
+
Cu
Zn
+
CuSO4
ZnSO4
+
Cu
Reaction between Metals and Non-Metals :
– Reactivity of elements can be understood as a tendency to attain a
completely filled valence shell.
– Atom of metals can lose electrons from valence shells to form cations
(+ve ions).
– Atom of non-metals gain electrons in valence shell to form anions (–
ve ions).
– Oppositely charged ions attract each other and are held by strong
electrostatic forces of attraction forming ionic compounds.
Formation of MgCl2
Mg
2,8,2
Cl2
+
2e–
Mg2+
+
2,8 (Magnesium ion)
2Cl–
2,8,7
2,8,8 (Chloride ion)
Properties of Ionic Compounds :
– Are solid and mostly brittle.
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
2e–
– Have high melting and boiling points. More energy is required to break
the strong inter-ionic attraction.
– Generally soluble in water and insoluble in kerosene, petrol.
– Conduct electricity in solution and in molten state. In both cases, free
ions are formed and conduct electricity.
Occurrence of Metals
Minerals : Elements or compounds occurring naturally are minerals.
ORES : mineral from which metal can be profitably extracted is an
ore. For example, sulphide ore, oxide ore, carbonate ore.
– Metals at the bottom of activity series like gold, platinum, silver, copper
generally occur in free state. But copper and silver also occur as sulphide
and oxide ores.
– Metals of medium reactivity (Zn, Fe, Pb etc.) occur mainly as oxides,
sulphides or carbonates.
– Metals of high reactivity (K, Na, Ca, Mg and Al) are very reactive and
are thus found in combined state.
GANGUE : ores are naturally found mixed with impurities like soil,
sand, etc. called gangue. The gangue is removed from the ore.
METALLURGY : step-wise process of obtaining metal from its ore.
I. *Enrichment of ore
II. *Obtaining metal from enriched ore.
III. *Refining of impure metal to obtain pure metal.
I.
II.
Enrichment of Ores : It is the process of the removal of impurities
such as soil, sand etc. from the ore prior to extraction of the metal.
Different separation in physical or chemical properties.
Extracting Metals from the Enriched Ore
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Extracting Metals Low in the Activity Series :
By heating the ores in air at high temperature.
*Mercury from cinnabar
Heat 2HgO + 2SO2
2HgS + 3O2
Heat 2Hg + O2
2HgO
* Copper from copper sulphide
Heat 2Cu2O _ 2SO2
Cu2S + 3O2
Heat 6Cu + SO2
2Cu2O + Cu2S
Extracting Metals in the Middle of Activity Series :
*Metals are easier to obtain from oxide ores, thus, sulphide and carbonate
ores are converted into oxides.
*Metal ore heated strongly in excess of air (Roasting)
Heat 2ZnO + 2SO2
2ZnS + 3O2
Metal ore heated strongly in limited or no supply of air (Calcination)
Heat ZnO + CO2
ZnCO3
Reduction of Metal Oxide :
1. USING COKE : Coke as a reducing agent.
Heat Zn + CO
ZnO + C
2. USING DISPLACEMENT REACTION : highly reactive metal like
Na, Ca and Al are used to displace metals of lower reactivity from their
compounds. These displacement reactions are highly exothermic.
Heat 3Mn + 2Al2O3 + heat
MnO2 + 4Al
Heat 2Fe + Al2O3 + heat
Fe2O3 + 2Al
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
–
In the above reaction molten iron is formed and is used to join
railway tracks. This is called thermit reaction.
Extracting Metals at the Top of Activity Series :
These metals
– have more affinity for oxygen than carbon so they cannot be obtained
from their compounds by reacting with carbon.
– are obtained by electrolytic reduction. Sodium is obtained by electrolysis
of its molten chloride NaCl Na+ + Cl–
As electricity is passed through the solution metal gets deposited at
cathode and non-metal at anode.
– At cathode :
Na+ + e– Na
– At anode :
2Cl– Cl2 + 2e–
III. Refining of Metals :
– Impurities present in the obtained metal can be removed by electrolytic
refining.
Copper is obtained using this method. Following are present inside
the electrolytic tank.
– Anode – slab of impure copper
– Cathode – slab of pure copper
– Solution – aqueous solution of copper sulphate with some dilute
sulphuric acid
– From anode copper ions are released in the solution and equivalent
amount of copper from solution is deposited at cathode.
– Insoluble impurities containing silver and gold gets deposited at the
bottom of anode as anode mud.
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[X – Science]
Corrosion :
– Metals are attacked by substances in surroundings like moisture and
acids.
– Silver - it reacts with sulphur in air to our form silver sulphide and
articles become black.
– Copper - reacts with moist carbon dioxide in air and gains a green coat
of copper carbonate.
– Iron-acquires a coating of a brown flaky substance called rust. Both air
and moisture are necessary for rusting of iron.
Prevention of corrosion:
–Rusting of iron is prevented by painting, oiling, greasing, galvanizing, chrome
plating, anodising and making alloys.
–In galvanization, iron or steel is coated with a layer of zinc because zinc is
preferably oxidized than iron.
Alloys : These are homogeneous mixture of metals with metals or nonmetals.
– Adding small amount of carbon makes iron hard and strong.
– Stainless steel is obtained by mixing iron with nickel and chromium.
It is hard and doesn’t rust.
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
– Mercury is added to other metals to make amalgam.
Brass : alloy of copper and zinc.
Bronze : alloy of copper and tin.
– In brass and bronze, melting point and electrical conductivity is lower
than that of pure metal.
Solder : alloy of lead and tin has low melting point and is used for
welding electrical wires.
Name of Alloy
Constituent metal/non-metal
1. Steel
Iron and carbon
2. Stainless steel
Iron, nickel and chromium
3. Brass
Copper and zinc
4. Bronze
Copper and tin
5. Solder
lead and tin
6. Amalgam
mercury and any other metal
– Stainless Steel is hard and doesn’t rest.
– Solder is used for welding electrical wires.
QUESTION BANK
(1 Mark)
1 Name a metal which is the best conductor of electricity and one which
is poor conductor of electricity.
2 Why food cans are coated with tin and not with zinc?
3. Name any two alloys whose electrical conductivity is less than that of
pure metals.
4. Name the non-metal with lustre.
5. What are amphoteric oxide. Give one example.
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[X – Science]
6. An aqueous solution of Al 2O3 is electrolysed. Name the element
collected at anode.
7. An oxide of an element was dissolved in water. The final solution
turned red litmus blue. What is the nature of oxide. Is the element
metal, non-metal or a metalloid?
8. What happens when cinnabar is heated? Write the balanced chemical
equation.
9. Ionic compounds have high melting point. Why?
10. Name two metals which are found in nature in free state.
(2 MARKS)
1. Why do magnesium and calcium float when they react with water?
2. Write the chemical equations of heating of Cu and Fe.
3. Write two chemical equations to show that Al2O3 is an amphoteric
oxide.
4. What is galvanization? Why it is done?
5. Why is hydrogen gas generally not evolved when metals react with
nitric acid. Name two metals which react with HNO3 to evolve H2 gas.
6. Explain the thermit process. Write the chemical equation involved.
7. Distinguish between roasting and calcination.
8. Every ore is a mineral but not every mineral is an ore. Explain.
9. Why can highly reactive metals not be obtained from their oxides using
coke as a reducing agent?
10. What is an amalgam? Write the constituent metals of brass?
(3 MARKS)
1. Diagrammatically show the formation of MgO.
[X – Science]
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
2. Ionic compounds are good conductors of electricity under specific
conditions. Name the two conditions and give reasons.
3. Why are metal sulphides and carbonates converted to oxides prior to
reduction. Write the equation for the chemical reactions that take place
during (i) roasting; (ii) calcination of zinc ores.
4. What is an alloy? How is it prepared? Name the alloy which is used
for welding electrical wires together.
(5 MARKS)
1.
(i) What is reactivity series of metals? Arrange the metals zinc,
magnesium, aluminium, copper and iron in a decreasing order
of reactivity.
(ii) What will you observe when you put
(a)
Some zinc pieces are put into blue copper sulphate
solution.
(b)
Some copper pieces are put into green ferrous sulphate
solution.
(iii) write the balanced chemical equations only.
2. Give reasons:
(i) Platinum, gold and silver are used to make jewellery.
(ii) Sodium and potassium are stored under oil.
(iii) Aluminium is a highly reactive metal, still it is used to make
utensils for cooking.
(iv) Carbonate and sulphide ores are usually converted into oxides
during the process of extraction.
(v) Highly reactive metals are obtained from their ores by the process
of electrolysis and not reduction with carbon.
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
[X – Science]
METALS AND NON-METALS : IN BRIEF
– Metals are generally solid, sonorous, lustrous, good conductor of heat
and electricity, malleable, ductile, high melting point, high densities,
form basic oxides, form +vely charged ion.
– Non-metals are generally solid or gas, non-lustrous, non-sonorous, bad
conductor of heat and electricity, have low melting point, form acidic
oxides and form -vely charged ions.
– Metals like Na, K and Ca are highly reactive, while others like
Magnesium, Aluminium, Zinc and Lead are less reactive and some
others are least reactive like silver, gold and platinum.
– Metals generally displace hydrogen from acids.
– Reactivity series is based on displacement capability of metals and is
a series of metals in the order of their decreasing reactivity.
– Metals and non-metals react to form ionic compounds which are soluble
in water, have high melting point and are good conductor of electricity
in their aqueous solution or molten state.
– Ores are minerals from which a metal can be profitably extracted.
– Metals are extracted from their ores according to their reactivity.
– Sulphide and chloride ores are roasted while carbonate ores are roasted.
– Pure metals can be obtained using electrolytic refining process.
– Metals are generally attacked by air and corrode. To alter the properties
of metals alloys are made.
– Steel, stainless steel, amalgams, brass, bronze and solder are some
alloys.
[X – Science]
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
CHAPTER – 4
CARBON AND ITS COMPOUNDS
Carbon is a versatile element.
In earth’s crust, carbon is 0.02% and found in form of minerals.
Atmosphere has 0.03% of carbon dioxide.
All living structures are carbon based.
Covalent Bond in Carbon
– The atomic number of carbon is 6 and its electronic configuration is 2,
4. To attain a noble gas configuration it can
1. gain 4 electrons. But it would be difficult for nucleus to hold 4 extra
electrons.
2. lose 4 electrons. But it would require a large amount of energy to
remove 4 electrons.
–
It is difficult thus for an atom of carbon to either gain or lose
electrons.
–
Carbon attains the noble gas configuration by sharing its valence
electrons with other atoms. Atoms of other elements like
hydrogen, oxygen, nitrogen, chlorine also show sharing of
valence electrons.
–
Formation of H2, O2 and N2 is shown as below :
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
[X – Science]
– It is evident that the number of shared pair of electrons can be one, two
or three. Try making the structures of H2O and CH4.
– Bond formed by the sharing of an electron pair between two atoms is
called covalent bond.
– Covalently bonded molecules have low melting and boiling points
because of comparatively weaker intermolecular forces, unlike ionic
compounds.
– These molecules are generally poor conductor of electricity since no
charged particles are formed.
Versatile Nature of Carbon Atoms:
Two important properties of carbon atom enable carbon to form enormously
large number of compounds.
[X – Science]
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
CATENATION : property of carbon atom to form bond with other atoms
of carbon is called catenation. Like carbon, silicon forms compounds with
hydrogen upto seven or eight atoms of silicon.
TETRAVALENCY : Having a valency of 4, carbon atom is capable of
bonding with atoms of oxygen, hydrogen, nitrogen, sulphur, chlorine and other
elements.
The smaller size of carbon atom enables nucleus to hold the shared pair
of electrons strongly, thus carbon compounds are very stable in general.
Saturated and Unsaturated Carbon Compounds
– ALKANE : CnH2n+2
– ALKENE : CnH2n
– ALKYNE : CnH2n–2
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
[X – Science]
– Electron dot structure of a saturated carbon compound, ethane is as
follows:
– Electron dot structure of an unsaturated carbon compound, ethene is as
follows:
TRY DRAWING THE ELECTRON DOT STRUCTURE OF ETHYNE
Formulae and Structures of Saturated Compounds of
Carbon and Hydrogen
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
On the basis of structures the hydrocarbons can be:
Structural isomers : these are the compounds having identical molecular
formula but different structures. For example, isomers of butane.
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Heteroatom and Functional Group
*In hydrocarbon chain, one or more hydrogen atoms can be replaced by
other atoms in accordance with their valencies. The element that replaces
hydrogen is called a heteroatom.
*These heteroatoms and the group containing them impart chemical
properties to the compound and hence are called functional groups.
Homologous Series
– It is a series of compounds in which the same functional group substitutes
for hydrogen in a carbon chain.
– For instance, the ALCOHOLS: CH3 OH, C2H5 OH, C3H7 OH, C4H9 OH.
– The successive member differs by –CH2-; unit and 14 units of mass.
– The chemical properties are imparted by the functional group thus all
members have similar chemical properties. But the members have
different physical properties.
– The physical properties vary among the members of homologous series
due to difference in their molecular mass.
– Melting point and boiling point increases with increasing molecular mass.
[X – Science]
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
Nomenclature of Carbon Compounds
1. Identify the number of carbon atoms in the compound.
2. Functional group is indicated either by prefix or suffix.
Functional Group
Suffix
Alkene
ene
Alkyne
yne
Alcohol
ol
Aldehyde
al
Ketone
Prefix
one
Carboxylic acid
oic acid
chlorine
chloro
3. If a suffix is added, then final ‘e’ is removed from the name eg. methanol
(methane-e = methan + ol).
Chemical properties of Carbon compounds
1. COMBUSTION
*Carbon compounds generally burn (oxidize) in air to produce carbon
dioxide and water, and release heat and light energy.
CH4 + O2 CO2 + H2O + heat and light
*Saturated hydrocarbon burns generally with a blue flame in good supply
or air and with a yellow sooty flame in limited supply of air.
*Sooty flame is seen when unsaturated hydrocarbons are burnt.
*Burning of coal and petroleum emits oxides of sulphur and nitrogen
which are responsible for acid rain.
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
[X – Science]
2. OXIDATION :
*Alcohols can be converted to carboxylic acids by oxidizing them using
alkaline potassium permanganate or acidified potassium dichromate (they add
oxygen to the reactant, thus are called oxidizing agents).
Alkaline KMnO4 + heat
CH 3 – CH 2 OH
CH 3COOH
Acidified K 2 Cr2 O7 +heat
3. ADDITION REACTION
Hydrogen is added to unsaturated hydrocarbon in presence of palladium
or nickel as catalyst.
Vegetable oils are converted into vegetable ghee using this process.
Saturated fatty acids are harmful for health and oils with unsaturated fatty
acids should be used for cooking.
4. SUBSTITUTION REACTION
In saturated hydrocarbons, the hydrogen attached to carbon can be replaced
by another atom or group of atoms in presence of sunlight.
CH 4
+ Cl2 CH3Cl + HCl (sunlight required)
IMPORTANT CARBON COMPOUNDS : Ethanol and Ethanoic Acid
Ethanol
[X – Science]
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
*Consumption of dilute ethanol causes serious health issues and intake of
pure alcohol is lethal.
CHEMICAL PROPERTIES OF ETHANOL
C2H5OH Reacts with Sodium
to form Sodium Ethoxide and
Hydrogen
When C 2 H 5 OH is heated with
concentrated Sulphuric Acid at 443
k, it is dehydrated to Ethene
Ethanoic Acid (CH3COOH) / Acetic Acid :
*5-8% solution of acetic acid in water is called vinegar.
*Pure acetic acid is called glacial acetic acid.
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
[X – Science]
5
NaOH
Sodium ethanoate
and water.
5
2
1
3
4
Esterification
Carboxylic acids react with alcohols in presence of few drops of concentrated
sulphuric acid as catalyst and form sweet smelling compounds called ester.
conc.
C2 H5OH CH3COOH
CH 3COOC2 H5
H HSO
ethanol of ester
2
ethanoic acid
4
ethyl ethanoate
Hydrolysis
On heating with an acid or a base the ester forms back the original
alcohol and carboxylic acid.
[X – Science]
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
CH3COO CH2CH3 + NaOH CH3COONa + CH3-CH2OH
CH3COO CH2CH3
Dil.H 2 SO 4
HEAT
CH3COOH + CH3-CH2OH
*Alkaline hydrolysis of ester is also called saponification.
Soaps and Detergents
– Soap is sodium and potassium salt of carboxylic acids with long chain.
– Soaps are effective with soft water only and ineffective with hard water.
– Detergents are ammonium or sulphonate salts of carboxylic acids with
long chain. They are effective with both soft as well as hard water.
An ionic part (hydrophilic) and a long hydrocarbon chain (hydrophobic)
part constitutes the soap molecule.
Structure of a Soap molecule.
Cleansing Action of Soaps :
– Most dirt is oily in nature and the hydrophobic end attaches itself with
dirt, while the ionic end is surrounded with molecules of water. This
result in formation of a radial structure called micelles.
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[X – Science]
– An emulsion is thus formed by soap molecule. The cloth needs to be
mechanically agitated to remove the dirt particles from the cloth.
– Scum : The magnesium and calcium salts present in hard water reacts
with soap molecule to form insoluble products called scum, thus
obstructing the cleansing action. Use of detergents overcome this
problem as the detergent molecule prevents the formation of insoluble
product and thus clothes get cleaned.
QUESTION BANK
(1 MARK)
1. How does an atom of carbon attain noble gas configuration?
2. Draw the electron dot structure of a molecule of water.
3. Define catenation.
4. The kerosene/gas stove used at home has inlets for air. Give reason.
5. Write only the balanced chemical equation for dehydration of ethanol
by hot conc. sulphuric acid.
6. Write the number of covalent bonds present in propane.
7. Define the term: oxidising agent with an example
8. Write the formula and name of first member of ketone.
9. Would you be able to check if water is soft by using a soap?
10. Write the molecular formula of an alkyne containing 10 atoms of
hydrogen.
(2 MARKS)
1. Define saponification. Write a chemical equation for it.
2. Covalent compounds generally don't conduct electricity. Why?
[X – Science]
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twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
3. Specify the condition in which ethanol undergo oxidation to form
ethanoic acid. Write the chemical equation.
4. Define isomerism. Draw the structures of the two isomers of butane.
5. Identify the functional group present in the following compounds:
HCOOH, HCHO, CH3Br and C10H21OH.
6. Why is ethanoic acid called as glacial acetic acid. Write the equation
of the reaction that takes place when ethanoic acid reacts with ethanol
in the presence of conc. H2SO4.
7. Draw that structures of the following compounds – (a) methanoic acid
(b) pentanal.
8. Why are carboxylic acids called as weak acids? Name the alcohol
which produces methanoic acid on oxidation.
9.
(i) Which property of ethanol makes it suitable for preparing
medicines such as tincture iodine, cough syrup and other tonics.
(ii) What is the function of concentrated sulphuric acid in the
formation of ethane from ethanol?
10. Define esterification. Explain with an example.
(3 MARKS)
1. What is a homologous series? Write any two characteristic features of
any homologous series using one example.
2. Write any three differences between soaps and detergents.
3. Write the main difference between addition and substitution reactions.
Which reaction’s commonly used in the hydrogenation of vegetable
also.
(5 MARKS)
1. Differentiate between ethanol and ethanoic acid on the basis of any
three physical properties and two chemical properties.
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[X – Science]
2. An organic compound 'A' is used as a preservative in pickles and has
molecular formula C2H4O2. This compound reacts with ethanol to form
a sweet smelling compound 'B'.
(i) Identify the compound 'A' and write the chemical formula and
chemical name.
(ii) Write the chemical equation for its reaction with ethanol to
form compound 'B'.
(iii) Write any two uses of compound 'B'.
(iv) Which gas is produced when compound 'A' reacts with washing
soda? Write the balanced chemical equation
(v) How can vinegar be obtained from compound 'A'?
CARBON AND ITS COMPOUNDS IN BRIEF
– Carbon is a versatile non-metal.
– Carbon atom like atoms of other non-metals like oxygen, nitrogen,
hydrogen and chlorine shares electrons.
– Carbon forms large number of compounds due to catenation and
tetravalency.
– Carbon can form single, double and triple covalent bonds.
– The compounds of hydrogen and carbon are called hydrocarbons, which
can be saturated or unsaturated.
– Structurally hydrocarbons can have straight chain, branches or cyclic
structure.
– Difference in structural arrangement of same molecule gives rise to
isomerism.
– In a hydrocarbon, a heteroatom can replace the hydrogen atom and
imparts it chemical properties.
[X – Science]
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– Homologous series is a series of compounds with same general formula
and same chemical properties but different physical properties.
– Carbon based compounds are excellent fuels.
– Ethanol is an important industrial compound. It reacts with reactive
metals and is also dehydrated to ethene.
– Ethanoic acid is another important compound. It combines with ethanol
to form sweet smelling esters.
– Soaps and detergents are used as cleansing agents. Detergents efficiently
cleanses with soft and hard water.
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[X – Science]
CHAPTER – 5
PERIODIC CLASSIFICATION
OF ELEMENTS
Elements : Substances containing atoms of only one type. eg. Na, Au,
Mg etc.
–
There are around 118 elements known to us.
Elements are classified to make the study easy.
Dobereiner’s Traids : When the elements were written in order of
increasing atomic masses the atomic mass of the middle was the average
of the atomic mass of the other two elements.
eg.
Elements
Atomic Mass
Ca
40.1
Sr
87.6
Ba
136.3
Limitations : Only three triads were recognised from the elements known
at that time.
Atomic mass of an element is the relative mass of its atom as compared
with the mass of a Carbon-12 atom taken as 12 units
Newland’s law of octaves :
–
Based on increasing atomic mass of elements.
–
When elements are arranged it was found that every eighth
element had properties similar to that of the first. eg properties
of sodium and Lithium are the same.
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Limitations
– Applicable only upto Calcium
– Properties of new elements couldn’t fit in it.
– In some cases properties of the elements were not same as defined by
octave.
– Worked well only with lighter elements.
Mendeleev's periodic law :– The properties of elements are the periodic
function of their atomic mass.
Mendeleev's periodic table based on the chemical properties of elements.
It contains vertical columns called groups and horizontal rows called
periods.
Achievements of Mendeleev’s Periodic table
–
Elements with similar properties could be grouped together
–
Some gaps were left for the undiscovered elements.
–
Noble gases could be placed without disturbing the existing order.
Limitations
– No fixed position for hydrogen
– No place for isotopes
– No regular trend in atomic mass.
Modern Periodic Table
Modern Periodic Law : Properties of elements are a periodic function
of their atomic number.
– Atomic Number – denoted by Z and equals to the no. of protons in the
nucleus of an atom.
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– Modern periodic table contains 18 vertical columns known as groups
and 7 horizontal rows known as periods.
– Elements in a group have the same number of valence electrons
– No. of the shells increases as we go down the group.
– Elements in a period have same number of shells.
– Each period marks a new electronic shell getting filled.
– No. of elements placed in a particular period depends upon the fact that
how electrons are filled into various shells.
– Maximum no. of electrons that can be accommodated in a shell depend
on the formula 2n2 where n is the no. of the given shell.
e.g. K shell – 2 × (1)2 = 2 elements in the first period L shell – 2 ×
(2)2 = 8 elements in the second period.
– Position of the element in the periodic table tells about its reactivity.
Trends in the Modern Periodic Table
– VALENCY : No. of valence electrons present in the outermost shells.
Valency remains the same down a group but changes across a period.
– ATOMIC SIZE : Atomic size refers to radius of an atom.
– Atomic size or radius decreases in moving from left to right along a
period due to increase in nuclear charge
– Atomic size increases down the group because new shells are being
added as we go down the group.
METALLIC CHARACTER : Metallic character means the tendency
of an atom to lose electrons.
– Metallic character decreases across a period because the effective nuclear
charge increases that means the tendency to lose electrons decreases.
– Metals are electropositive as they tend to lose electrons while forming bonds.
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– Metallic character increases as we go down a group as the effective
nuclear charge is decreasing. Non metals are electronegative. They tend
to form bonds by gaining electrons.
– Metals are found on the left side of the period table while non-metals
are towards the right hand side of the periodic table.
– In the middle we have semi-metals or metalloid because they exhibit
some properties of both metals and non metals.
– Oxides of metals are basic in nature while oxides of non-metals are
acidic in nature.
(Refer the table given on side page)
Gradation in Periodic Properties
S. Property Variation
No.
across period
Reason
Variation
along group
Reason
1. Atomic size Decreases
Due to increase Increases
in nuclear charge
due to addition
of new shells.
distance between
outer most electron
and nucleus increases
due to addition of
new shells.
2. Metallic
Character
due to increase Increases
in effective
nuclear charge,
tendency to lose
valence electrons
decreases.
decrease in
effective nuclear
charge experienced
by valence electrons
Tendency to lose
electrons (metallic
character) increases.
due to increase Decreases
in effective
nuclear charge
tendency to gain
electrons increases
due to decrease in
effective nuclear
change experienced
by valence election
(due to addition of
new shell), tendency
to gain electrons
decreases
Decreases
3. Non-Metallic Increases
Character
(electro-negativity)
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[X – Science]
QUESTION BANK
Very Short Answer type Questions.
(1 mark)
1. Write down three elements which represent Dobereiner’s triad.
2. Write down two drawbacks of Newland’s law of octaves.
3. Which important property did Mendeleev used to classify the elements
in his periodic table.
4. Explain why the number of elements in the third period is 8?
5. Name two elements you would expect to show chemical reactions
similar to lithium.
6. Define Isotopes.
7. What was the need for classification of elements?
8. Name two elements that have only two electrons in their outermost shell.
9. How many vertical columns and horizontal rows are there in modern
periodic table, What is the special name assigned to them?
10. Name the element having electronic configuration 2, 8, 3. What is its
Valency?
Short Answer type Questions
(2 Marks)
1. Why He, Ne and Ar are called inert gases?
2. Which one has greater atomic size – Cl or Br? Why?
3. What were the drawbacks of Mendeleev’s periodic table? Write any
two.
4. How does the tendency to lose electrons change in a group and why?
5. Justify the statement – Atomic size of an element decreases along a
period whereas increases down the group.
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6. What is the metallic character of an element? How does it vary as we
go down a group? Give reason for this variation.
7. How does electronegativity of an element change as you go down a
group and across a period? Give reason for the variation.
Long Answer Type
(3 Marks)
1. How do we calculate the valency of an element from its electronic
configuration?
–
How does the valency vary in a period?
–
How does the valency vary in going down a group?
2. Study the variation in the atomic radii of elements given below and
arrange them in an increasing order
Na
186
Li
152
Rb
Cs
K
246
262
231
(ii) Name the element which has the smallest and the largest atoms.
(iii)
How does the atomic size vary as we go down a group. Give
reason for your answer.
3. Four elements ABCD along with their electronic configurations are
given below
Elements
–
Electronic Configuration –
A
B
C
D
2, 1
2, 8
2, 8, 1
2, 8, 8
4. Why did Mendeleev choose formulae of compounds as the basis for
deciding the position of an element in his table? Why did he leave
some gaps in his periodic table? Name two elements which were
discovered later but filled in the gaps left by Mendeleev.
5. Now answer the following questions
(a) Which two elements belong to the same period.
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[X – Science]
(b) Which two elements belong to the same group
(c) Which element out of A and C is more reactive and why?
Long Answer Type Question
(5 Marks)
1. Write down five major differences between Mendeleev periodic table
and modern periodic table.
2. Examine elements of the third period and classify them as metals and
non metals.
(ii) On which side of the table do you find metals and why.
(iii) On which side of the table do you find the non-metals and why?
[X – Science]
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CHAPTER – 6
LIFE PROCESSES
All living things perform certain life processes like growth, excretion,
respiration, circulation etc.
The basic functions performed by living organisms for their survival and
body maintenance are called life process.
Basic life processes are :
1. Nutrition
2. Respiration
3. Transportation
4. Excretion
5. Control and Coordination
6. Growth and repair
Green Plants are
Autotrophs
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Kinds of nutrition in which inorganic
materials like CO2, water etc are utilized
to prepare organic food by the process of
photosynthesis
Kinds of nutrition in which organisms do not
possess the ability to synthesize their own
food. They depend on autotrophs for their
food supply directly or indirectly.
Eg. Green Plants
Eg. Animals, Fungi
Autotrophic Nutrition
The organisms which carry out autotrophic nutrition are called autotrophs
(green plants)
Autotrophic nutrition is that mode of nutrition in which autotrophs take
in CO2 and H2O and convert these into carbohydrates in the presence of
chlorophyll and sunlight. This process is also called PHOTOSYNTHESIS
Equation of photosynthesis
Sunlight
6CO 2 6H 2O
C6 H12O6 6O 2
Chlorophyl
Glucose
Raw Materials for Photosynthesis
1. CO2 enters through Stomata, and Oxygen (O2) is released as by
product through stomata on leaf surface.
2. Water water and dissolved minerals like Nitrogen, phosphorous etc
are taken up by the roots from the soil.
Site of Photosynthesis
Chloroplast in the leaf. Chloroplast contain chlorophyll. (green pigment)
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Main Events of Photosynthesis
1. Absorption of Sun light energy by chlorophyll
2. Conversion of light energy into chemical energy and splitting (breaking)
of water into hydrogen and oxygen by light energy.
3. Reduction of CO2 to carbohydrates.
STOMATA : Tiny pores present on the surface of the leaves.
Functions of Stomata
(i) Exchange of gases O2/CO2
(ii) Loses large amount of water [water vapour] during transpiration.
STOMATA
GUARD CELL
it
),
How do organisms obtain their food?
Unicellular/single celled organism : food is taken up through entire surface.
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Example : (i) Amoeba. (ii) Paramoecium
Take in (food vacuole formed)
FOOD PARTICLE
NUTRITION IN HUMAN BEINGS
The human digestive system comprises of alimentary canal and associated
digestive glands.
Mouth
Intake of whole food
Teeth
Chewing/grinding of food.
Tongue
Rolling of food
+
Tasting of food
+
Swallowing / pushing down of the food
[X – Science]
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Salivary Glands
Secrete Saliva + Mucus.
Salivary
amylase
[Saliva]
Starch
Oesophagus
Stomach
Sugar
Taking food from mouth to stomach by
Peristaltic movements
[contraction and expansion of muscles of the oesophagus]
Gastric glands secrete Gastric juice
Small Intestinal
Small Intestine
Villi [finger like projections] (1) helps in
absorption of food into the blood.
(2) Increases the surface area for absorption.
small intestine
Receives
secretion from
Emulsified Fats
Fatty acid
Glycerol
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Large intestine
Emulsification : The process of breakdown of large
fat globules into smaller fat globules by bile juice.
Absorb excess of water.
The unabsorbed food is removed from the body via
the anus. (Egestion)
RESPIRATION
Respiration Involves
(i) Gaseous exchange : Intake of oxygen from the atmosphere and release
of CO2 Breathing
(ii) Breakdown of simple food in order to release energy inside the cell
Cellular Respiration
[X – Science]
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Breakdown of Glucose by various pathways
Glucose
C6H12O6
( in
* Takes place in the presence of
oxygen
* Occurs in mitochondria
* End products are CO2 and H2O
* More amount of energy is
released (38 ATP)
mu
sc
les
)
* Takes place in the absence of
oxygen
* Occurs in cytoplasm
* End products are alcohol or
lactic acid.
* Less amount of energy is
released. (2 ATP)
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Human Respiratory System
Passage of air through the respiratory system.
Nostril
Nasal Passage
Nasal Cavity
Pharynx
Larynx
Trachea
Bronchi
Lungs
Bronchioles
Alveolar sac Blood capillaries
1. During inhalation the thoracic
cavity (chest cavity) expands
1. Thoracic cavity contracts
2. Ribs lift up
3. Diaphragm become flat in shape
3. Diaphragm becomes dome
shaped
4. Volume of lungs increases and
air enters the lungs
4. Volume of lungs decreases and
air exits from the lungs.
[X – Science]
2. Ribs move downwards
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Exchange of Gases between alveolus, blood and tissues.
Terrestial Organism – use atmospheric oxygen for respiration
Aquatic Organisms – use oxygen dissolved in water.
Respiration in Plants
Respiration in plants is simpler than the respiration in animals. Gaseous
exchange occur through
1. Stomata in leaves
2. Lenticels in stems
3. General surface of the roots.
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LIFE PROCESS
Transportation and Excretion
– Human beings like other multicellular organism need regular supply of
food, oxygen etc., This function is performed by circulatory system or
Transport system.
The circulatory system in human beings consists of :
A Pumping Organ
Heart
Deoxygenated
Blood
(from body)
Blood vessels
- Arteries & Veins
Vena
Cava
Body Parts
Right
Atrium
(Relaxed)
A circulatory medium
Blood & Lymph
Right
Atrium
(contracts)
Right
ventricle
contracts
Blood Circulation
in Human Heart
via AORTA
Right
Ventricle
(relaxed)
Lungs
Left
Ventricle
(contracts)
Left
Ventricle
(relaxed)
Left
Atrium
(contracts)
AORTA
Left
Atrium
(relaxed)
Section view of the Human Heart
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Oxygenated
blood
Blood
(A fluid Connective Tissue)
Solid Component
Blood Corpuscles
R.B.C.s
Blood
Platelets
Liquid Component
PLASMA
W.B.C.
- Lymph - a yellowish fluids escapes from the blood capillaries into the
intercellular spaces contain less proteins than blood. Lymph flows from
the tissues to the heart assisting in transportation and destroying germs.
Blood Vessels
Arteries
Veins
1.
Carry Oxygenated blood from
heart to body part except
pulmonary Artery
1.
Carry deoxygenated blood
from body parts to heart
except pulmonary vein.
2.
Also called distributing Vessel
2.
Also called collecting Vessel.
3.
Thick and elastic
3.
Thin and Less elastic.
4.
Valves absent
4.
5.
Deep seated
Valves present to prevent
back flow of blood.
5.
Superficial
TRANSPORTATION IN PLANTS
– There are two main conducting Pathways in a Plant
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Pathways
Xylem
Phloem
1.
Carries water & minerals
from the roots to other part
of the plant
1.
Carries product of
photosynthesis from leaves
to the other part of the plant.
2.
No energy is used.
2.
Energy is used from ATP
Transpiration is the process of loss of water as vapour from aerial
parts of the plant.
Role of Transpiration
1. Absorption and upward movement of water and minerals by creating
PULL.
2. helps in temperature regulation in Plant.
Translocation
Transport of food from leaves (food factory) to different part of the
plant is called Translocation.
Excretion
The process of the removal of the harmful metabolic wastes from the
body is called excretion.
Excretory system of human beings includes :
(i) A pair of kidney
(ii) A Urinary Bladder
(iii) A pair of Ureter
(iv) A Urethera
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Procession of Excretion
– Rend artery bring in blood containing waste substances to kidney.
– Kidney silters out waste in form of urine.
– Urine produced in the kidneys passes through the ureters into the urinary
bladder where it is stored until it is released through the urethera.
– The purpose of making urine is to filter out waste product from the
blood i.e., urea which is produced in the liver.
– Each kidney has large numbers of filtration units called nephrons.
– Nephron is the structural and functional unit of Kidney.
– The Urine formation involves three steps
1.
Glomerular Filtration : Nitrogenous wastes, glucose, water,
amino acid filter from the blood into Bowman Capsule of the
nephron.
2.
Tubular reabsorption : Now, Useful substances from the filtrate
like Na+, k+, glucose, amino acids etc. are reabsorbed back by
capillaries surrounding the nephron.
3.
Secretion Urea, Extra, water and salts are secreted into the
tubule which open up into the collecting duct & then into the
ureter.
– Haemodialysis : The process of purifying blood by an artificial kidney.
It is meant for Kidney failure patient.
Excretion in Plants
–
Through stomata
(Transpiration)
Oxygen, CO2 & H2O
– Other wastes may be stored in leaves, bark etc. which fall off from the
plant.
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– Plants excrete some waste into the soil around them.
– Gums, Resin
In old Xylem
– Some metabolic wastes in the form of crystals of Calcium oxalates in
the leaves of colocasia and stem of Zamikand.
Question Bank
Very Short Answers
(1 Mark)
1. State one difference between autotrophic and heterotrophic mode of
nutrition.
2. What will happen to a plant if the xylem is removed?
3. What is the role of saliva in the digestion of food?
4. Name the tissue that transports water and minerals in plants.
5. What is the role of acid in our stomach?
6. What is emulsification?
7. Name the cell organelle in which photosynthesis occur.
8. Name the largest artery in the human body.
9. Define transpiration
10. What is the structural and functional unit of kidney called?
Short Answers (2 Marks or 3 Marks)
1. How is small intestine designed to absorb digested food?
2. What are stomata? Draw a labelled diagram of stomata.
3. Write the equation for the process of breakdown of glucose in a cell
(i) in the presence of oxygen
(ii) in the absence of oxygen.
4. Write the difference between inhalation and exhalation.
5. List the three events which occur during photo synthesis.
[X – Science]
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6. How does transpiration helps in upward transport of substances.
7. Write the functions of the components of blood.
8. Why is small intestine longer in herbivores than in carnivores?
9. Why muscles cramps occur after heavy physical exercise?
10. Why a person with haemoglobin count 7g/dL (below normal range)
suffers from breathing problems?
Short Answer
(3 Marks)
1. Describe the process of double circulation in human beings.
2. What are the methods used by plants to get rid of their waste products?
3.
(i) State the role of vales present in heart.
(ii) Why it is necessary to separate oxygenated and deoxygenated
blood in mammals and birds?
4. Give reason for the following :
(i) Arteries are thick walled blood cessels.
(ii) Veins are thin walled blood vessels
(iii)
Veins have valves in them.
Long Answers
(5 Marks)
1. Explain the process of digestion of food in mouth stomach and small
intestine in human body. Draw a well labelled diagram of human
digestive system.
2. Draw a diagram showing Human Respiratory system. Label the
following parts
(i) Larynx
(ii) Trachea
(iii) Bronchus
(iv) Lungs
3. Draw a well diagram of nephron.
Explain the mechanism of urine formation in man.
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[X – Science]
CHAPTER – 7
CONTROL AND COORDINATION
Living organisms respond and react to various stimuli like heat, light,
cold, touch, pressure etc. Plants and animals both respond to stimuli
but in different manner.
Example : Withdrawal of hand on touching a hot object.
Control and Coordination in Animals
It is brought about in all animals with the help of two main systems
(a) Nervous System
(b) Endocrine System
Nervous System
Functions
(i) To receive the information from environment
(ii) To receive the information from various body parts.
(Stimuli Response)
(iii) To act accordingly through muscles and glands.
Stimulus : Any change in environment to which the organisms respond
and react is called stimulus. E.g., touching a hot plate.
Response : The reaction of our body to a stimulus. E.g. withdrawal
of our hand on touching hot plate.
How do we detect that we are touching a hot object?
[X – Science]
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Receptors : Are specialised tips of some nerve cells that detect the
information from the environment.
Receptors
are
Sense Organs
Photo receptors Thermoreceptors Olfactory
Eyes
(Skin)
Receptor
(Nose)
Hearing/
Balance of
the body
Visual
Stimulus
Pain
Touch
Heat
Gustatory
Receptor
(Tongue)
Smell
Detection
Taste
Detection
Neuron : It is the structural and functional unit of nervous system.
Neuron (3 main parts)
I
II
III
Dendrite
Cell body
and Axon
Synapse
Information is
acquired
Information
travels as an
electrical impulse
Nucleus
Nerve
ending
Dendrite
Axon
Cellbody
Structure of neuron
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[X – Science]
Synapse : The point of contact between the terminal branches of axon of
one neuron with the dendrite of another neuron is called synapse.
REFLEX ACTION
Reflex action is quick, sudden and immediate response of the body to a
stimulus. Eg. withdrawal of hand, knee jerk etc.
Reflex arc : The pathway through which nerve impulses pass during
reflex action is called reflex arc.
Response
Responses are of three main types
Voluntary :
Controlled by fore brain
eg. Talking, Writing
Involuntary :
Controlled by mid and hind brain
eg. Heart beat, vomiting, regulation of heartbeat
Reflex action : Controlled by spinal cord
eg. Withdrawl of hand on touching a hot object.
[X – Science]
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Human Brain
Human brain has three major parts or regions
a) Forebrain b) Mid Brain c) Hind Brain
Forebrain
Most complex/specialized part of the brain is CEREBRUM
Functions
1. Thinking part of the brain
2. Control the voluntary actions.
3. Store information (Memory)
4. Centre associated with HUNGER
5. Receives sensory impulses from various body parts and integrates it
Mid Brain :
HYPOTHALAMUS : Chemical co-ordination
PITUITARY GLAND : Secretes hormones
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Hind Brain :
CEREBELLUM i) Controls posture and balance
ii) Control precision of voluntary actions
MEDULLA
Controls involuntary actions
eg. blood pressure, salivation, vomiting
PONS
Involuntary action, regulation of respiration
PROTECTION OF BRAIN AND SPINAL CORD
Brain : Brain is protected by a fluid filled balloon which acts as shock
absorber and is enclosed in cranium (Brain Box)
Spinal Cord : Spinal Cord is enclosed in Vertebral column.
Coordination between Nervous and Muscular Tissue
Information
[collected by
Nervous tissue]
(Sensory Nerve)
Central
Nervous
System
[CNS]
Information
Processed
by
[CNS]
Decesion
made
[by CNS]
Action
[X – Science]
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Decesion
made
[by CNS]
Action
Muscle shorten
Contraction
[Muscle cell]
Muscles
[Change in shape
and arrangement
of proteins]
(Motor Nerves)
Message
Passed to
muscles
Coordination in Plants
Movement in Plants
Movement dependent
on growth
Movement independent
of growth
[immediate response
to stimulus]
eg. dropping of leaves
of Touch-me-not
plant on touching it
(Thigmotropism)
Tropic movements
[directional movements
in response to stimulus]
Phototropism
Movement
towards light
Geotropism
Chemotropism
Movement
Movement
towards gravity towards Chemicals/
(growth of pollen
tube towards ovule)
Hydrotropism
Movement
towards /
water
Plant Hormones
Are chemical compounds which help to coordinate growth, development
and responses to the environment.
Plant hormones : Main plant hormones are :
(a) Auxin : [Synthesized at shoot tip]
Function :
Helps in growth
Phototropism : more growth of cells towards light.
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(b) Gibberellin : Helps in the growth of the stem
(c) Cytokinins :
Promotes cell division
(d) Abscisic acid : Inhibits growth, cause witting of leaves. (Stress
hormone)
HORMONES IN ANIMALS
Hormones : These are the chemical messengers secreted by endocrine
glands, in very small amounts, into the blood stream. They act on target
tissues/organs usually away from their source.
Endocrine System helps in control and coordination through chemical
compounds called HORMONES
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S.
No.
Hormone
Endocrine
Gland
Location
Functions
1.
Thyroxine
Thyroid
Neck/
Throat
region
Regulation of metabolism
of carbohydrates, fats
and proteins.
2.
Growth
hormone
Pituitary
(master
gland)
Mid brain
Regulates growth and
development.
3.
Adrenaline
Adrenal
Above
both
kidneys
4.
Insulin
Pancreas
Below
stomach
Regulation (increasing)
of blood pressure, heart
heat, carbohydrate
metabolism (during
emergency)
Reduces and regulates
blood sugar level
5.
SEX
Testosterone
in Males
ormone
estrogen
Testes
Genital/
lower
abdomen
area
Ovaries
Changes associated
with puberty
(Sexual maturity)
Iodised Salt is Necessary Because :
Iodine mineral is essential part of thyronine hormone so it is important
that we must consume iodised salt as in turn it is essential for thyroid gland
as it controls carbohydrate, proteins and fat metabolism for best balance of
growth. Deficiency of iodine cause disease called goitre
Diabetes
Cause : It is due to deficiency of Insulin hormone secreted by Pancreas
that is responsible to lower/control the blood sugar levels.
Treatment : Patients have to internally administer injections of insulin
hormone which helps in regulating blood-sugar level.
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Feedback Mechanism
The excess or deficiency of hormones has a harmful effect on our body.
Feedback mechanism makes sure that hormones should be secreted in
precise quantities and at right time.
SWITCH OFF
Feedback sent
Sugar level in the blood rises
Detected by cells of Pancreas
Synthesis insulin
Blood sugar level falls
(like a float in watertank)
Stop secreting more
insulin
Question Bank
Very Short Answers
(1 Mark)
1. Where is auxin synthesized in plants?
2. Which gland is known as Master gland?
3. Name the hormone that regulates blood sugar level.
4. What is synapse?
5. What are tropic movements? Give one examples
6. Which part of brain is responsible for maintaining posture and balance
of our body?
7. Which hormone has inhibiting effect on growth of plants.
8. What is phototropism?
9. What are the components of central Nervous System?
10. What happens at synapse between two neurons?
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Short Answers
(2 Marks)
1. Draw diagram of neuron and label cell body, dendrites and axon.
2. What is reflex arc? Explain with the help of a flow-chart.
3. Mention one function of each of the following
(i) Cerebellum
(ii) Pons.
4. What is the cause of diabetes? How it can be controlled?
5. Why it is advisable to use iodised salt?
6. What are the different receptors present in our body? What are their
functions?
7. What are plant hormones? Name a plant hormone that promotes growth
in plants.
8. What are sensory and motor neurons? Write their functions.
9 Why is Abscisic acid called as stress hormone?
10. Why a plant appears to bend towards light when light is coming from
one side of the plant?
Short Answer
(3 Marks)
1. What is the significance of tropic movement in plants? Explain any
two types of tropic movements.
2.
(i) What are endocrine glands?
(ii) Name a gland which have both endocrine and exocrine functions.
Also write its endocrine and exocrine secretions.
3. Which hormone is known as emergency hormone in our body? How it
helps in coping during emergency?
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[X – Science]
Long Answers
(5 Marks)
1. What are hormones (in animals) List four characteristics of hormones.
Name the hormone required for the following.
(i) Development of moustache and beard in human male
(ii) Lowering of blood glucose.
2. Mention the functions of
(a) Fore brain
(b) Mid brain
(c) Hind brain
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CHAPTER – 8
HOW DO ORGANISM REPRODUCE
Reproduction is the process by which living organisms produce new
individuals similar to themselves.
Reproduction ensured continuity of life on earth.
Reproduction – A bridge to hereditary transmission.
It involves continuation of characters from the parents to daughter cells
by Copying of DNA (Deoxyribose Nucleic Acid) molecules present in
the chromosomes of the cell.
Copying of DNAs is also not a foolproof exercise, even minute changes
bring about Variation in the blue print of the offsprings.
The useful variations are retained while the harmful one does not go
beyond.
Actually variations help the species to withstand drastic environmental
changes, thus save the species from becoming extinct and promotes its
survival for a longer time.
This inbuilt tendency of variation is the ‘‘fuel’’ for Evolution.
REPRODUCTION
Asexual Reproduction
1. A single parent is involved
Sexual Reproduction
1. Both Parents involved
2. Gametes not formed
2. Gametes are formed
3. Progeny is Identical to parent
eg. Fission in Amoeba
3. Progeny is only genetically
similar to the parent.
Asexual Reproduction is extremely useful as a mean of rapid
multiplication. It is common in lower plants and animals.
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MODES OF ASEXUAL REPRODUCTION
1. FISSION : the parent cell divides/splits into two daughter cell-Binary
Fission; splits into many cells-multiple Fission.
FISSION
Binary Fission
The parent cell divides into two
equal halves (daughter cells)
Multiple Fission
The parent cell divides into many
daughter cell simultaneously.
E.g. Amoeba
Eg. Plasmodium
cytoplasm divides
Daughter
Ameobae
nucleus
nucleus lengthens
2. BUDDING : A bud develops as an outgrowth on parent body due to
repeated cell division at a specific site. These buds develop into thing
individuals, which detach from parent body when they mature.
Eg. Hydra, yeast.
3. Spore Formation : Spores are small, bulb like structure develops at
the top of the erect hyphae of the fungus plant, released into the air and
germinate, into new individuals after landing into food or soil.
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4. FRAGMENTATION : It is the accidental process when the broken
pieces of an organism (fragments) grows into a complete organism.
Eg. fragmentation in
spirogyra
5. REGENERATION : When the simple animals like Hydra Planaria
develop a new individual from their broken older part it is known as
regeneration. It is carried out by specialised cells which divide and
differentiate to form the complete individual.
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Vegetative Propagation
A mode of reproduction in many plants which part like the stem, root,
leaves develop into new plant under favourable conditions.
Methods of Vegetative Propagation
1. By Roots : Eg. adventitious roots of Dahlias
2. By Stems : Eg. Potato (tuber), ginger (rhizome)
3. By Leaves : Eg. leaves of bryophyllum bear adventitious buds (in the
notches of leaf margin) which develop into new plants.
4. Grafting : Eg. Mango.
5. Cutting : Eg. Rose
6. Layering : Eg. Jasmine
7. Tissue adture : Eg. Orchids, Ornamental Plants.
Benefits of Vegetative Propagation
1. Plants can bear flowers, fruits earlier than those produced from seeds.
2. Growing plants like Banana, orange, rose, jasmine that have lost the
capacity to produce seeds.
3. Genetical similarity is maintained in the plants.
4. Helps in growing seedless fruits.
5. Cheaper and easier method of growing plants.
Sexual Reproduction
When reproduction takes place as a result of fusion of two gameets, one
from each parent, it is called sexual reproduction.
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The process of fusion of male and female gametes is called fertilization.
The formation of gamets involves exchange of chromosomal (genetic)
fragments between homologous chromosomes causing genetic
recombination which leads to variation.
Sexual Reproduction in Plants
It occurs mostly in flowering plants. In fact flowers are the reproductive
organ of plants.
FLOWERS
Bisexual Flowers
Both male and female
reproductive part i.e., stamen
& carpel are present.
Unisexual Flowers
Either male or female
reproductive part is present.
Eg. Papaya, Watermelon
Stigma
Anther
(Carpet)
Stamen
Eg. Hibiscus, mustard
A typical flower consists of four main whorls namely calyx (sepals),
Corolla (Petals), Androecium (Stamens) and Gynoecium (Carpels).
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Reproductive Part of Flower
STAMEN
(male part)
Filament
CARPEL
(female part)
(2n)
Anther
MEIOSIS
Pollen grain
(male gamet)
(n)
Style
(2n)
Ovary Stigma
Egg cell (ovule)
[n]
Pollen grains of a flower transfer to the stigma of the carpel of the
same flower (Self-Pollination) or to the stigma of carpel of the another
flower (Cross-Pollination).
This transfer of pollens is achieved by agent like wind, water or animals.
After Pollination, a pollen tube grows out of pollen grains, through
which male germ cell reaches the ovary and fusses with the female
germ cell.
Fertilization : The fusion between the pollen grain and female egg
cell. It occurs inside the ovary. Zygote is produced in this process.
Zygote divides several times to form an embryo within the ovule. The
ovule develops a tough coat and is converted into a seed.
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Ovary grows rapidly and ripens to forms a fruit, while the seed contains
the future plant or embryo which develops into a seedling under suitable
condition. This process is known as Germination.
Reproduction in Human Beings
Humans use a Sexual Mode of reproduction.
It needs sexual maturation which includes creation of the germ cells
i.e., egg (ova) in the female and sperm in the male partner & this
period of sexual maturation is called Puberty.
Human beings have a well developed male and female reproductive
system.
The formation of male germ cell (sperms) takes place in the testes
(male reproductive organ)
Actually a pair of testes are located inside scrotum situated outside the
abdominal cavity. It is meant to keep relatively a low temperature
needed for the production of sperms by testes.
Moreover testes release a male sex hormone called testosterone whose
function is to:
1.
Regulate the production of sperm
2.
Brings about changes in appearance seen in boys at the time of
puberty.
The sperms along with the secretion of prostate gland and seminal
vesicle, together constitute semen, which is released and made to enter
into the female genital tract during Copulation.
Diagram of the male reproductive system.
Female Reproductive System
The female germ cells or eggs are made in the ovaries, a pair of which
is located in both side of abdomen.
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When a girl is born, the ovaries already contain thousands of immature
eggs.
At the puberty, some of these eggs start maturing. One egg is produced
every month by one of the ovaries.
The Egg is carried from the ovary to the womb through a fallopian
tube. These two fallopian tube unite into an elastic bag like structure
known as uterus.
The Uterus opens into the vagina through the cervix.
Fertilization occurs in the fallopian tube of female genital tract.
The fertilized egg also called zygote (2n) gets implanted in the lining
of the uterus, and start dividing. Actually uterus is richly supplied with
blood to nourish the growing embryo. If zygote is not formed, the inner
wall of uterus breaks which causes bleeding through vagina. This process
is called MENSTRUATION. It occurs at a regular interval of 28 days.
The Embryo gets nutrition from the mother's blood with the help of a
special tissue called PLACENTA. It provides a large surface area for
glucose and oxygen to pass from the mother to the embryo. Similarly
the wastes from developing embryo are removed to mother's blood
through placenta.
The child is born as a result of rhythmic contractions of the muscles
in the uterus. After nine months (36 weeks) of development inside
mother's womb. This is called Gestation Period.
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The sexual cycle in a woman continues upto the age of 45 to 50 years.
After that the ovary do not release egg. This stage is called Menopause.
It a also marks the end of menstruation in the woman.
Female sex hormones are oestrogen and progesterone which are
produced in ovary.
Reproductive Health
Reproductive Health means a total well-being in all aspects of
reproductive, i.e., physical emotional, social and behavioural.
Contraception : It is the avoidance of pregnancy. It can be achieved by
preventing the fertilization of ova.
Methods of contraception
PHYSICAL
BARRIER
SURGICAL
METHOD
To prevent union
of sperm & egg.
Also called
sterilization in
Vasectomy, the vas
deferens of male is
blocked to prevent
sperm transfer.
Use of condoms,
Diaphragm &
cervical caps.
In Tubectomy, the
fallopian tube of
female is blocked
to prevent egg to
reach uterus.
CHEMICAL
METHOD
Oral
contraceptive
(OCs) changes the
hormonal
balance to
check the egg
release in
females. OCs
cause side
effect.
IUCD
Intrauterine
contraceptive
device
Copper-T or
loop is placed
in uterus to
prevent
pregnancy.
Healthy society needs a balanced sex ratio that can be achieved by
educating the people to avoid malpractices like female foeticide & prenatal sex determination.
Sexually Transmitted Disease (STDs)
VIRAL STDs
Eg. H.I.V. - AIDS
Warts
Bacterial STDs
Eg. Syphilis &
Gonorrhoea
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STDs are communicated during unsafe sexual contact.
These diseases (STDs) can be prevented by using physical barrier i.e.,
condom.
Question Bank
(1 Mark)
1. Where is the DNA present in the cell?
2. What is a bisexual flower? Give one example.
3. Write suitable condition necessary for seed germination..
4. Write the function of the secretion of seminal vesicle and prostate
gland.
5. Name the part of female genital track where the egg is fertilized.
6. How does the chemical method helps in preventing pregnancy?
7. Name the floral parts of a plant that develop into
(i) Fruit
(ii) Seeds
8. What method will you use for growing Jasmine and Rose (plants)?
9. Name the hormones responsible for secondary sexual characters in
(i) Girls
(ii) Boys.
10. Give example of an organism whose cell divides in a specific orientation.
(2 Marks)
1. What is importance of DNA copying in reproduction.
2. Why is variation beneficial to the species but not necessarily for the
individual?
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3. Why is vegetative propagation practised for growing some types of
plants?
4. Distinguish between male & female gamete.
5. Write two important functions of testosterone.
6. What is placenta? Also write its two functions.
7. Why regeneration not considered as reproduction.
8. With the help of flow diagram trace the path of sperm from the site of
its formation to outside the body of males.
9. What is tissue culture in plants?
10. State the role of reproduction in providing stability to populations of
various species.
(3 Marks)
1. Draw a well labelled diagram of human female reproductive system.
Explain the menstrual cycle of female.
2. Draw a labelled diagram to explain the fertilization in the higher plant.
3.
(i) Give two reasons for avoiding frequent pregnancies by women.
(ii) Explain the following methods of contraception giving one
example of each.
(a)
Barrier method.
(b) Surgical method.
4. In human females, what happens when
(i) egg is fertilised
(ii) egg is not fertilised?
5. Give two examples each of sexually transmitted diseases (STDs) caused
by (i) Virus; (ii) bacteria.
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[X – Science]
(5 Marks)
1. Trace and explain the steps involved in the formation of seed starting
from pollination.
2. List any four modes of asexual reproduction. Give one example of
each.
Explain any two modes of asexual reproduction.
[X – Science]
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CHAPTER – 9
HEREDITY AND EVOLUTION
Genetics : Branch of science that deals with Heredity and variation.
Heredity : It means the transmission of features/ characters/ traits from
one generation to the next generation.
Variation : The differences among the individuals of a species/
population are called variations.
Mendel and His Work on Inheritance
Gregor Johann Mendel (1822&1884) : Started his experiments on
plant breeding and hybridisation. He proposed the laws of inheritance
in living organisms.
Mendel was known as Father of Genetics
Plant selected by Mendel : Pisum sativum (garden pea). Mendel used
a number of contrasting characters for garden pea.
(TABLE OF CONTRASTING CHARACTERS. SEVEN PARTS)
CHARACTER
DOMINANT
RECESSIVE
TRAIT
TRAIT
Flower colour
Violet
White
Flower position
Axial
Terminal
Seed colour
Yellow
Green
Seed shape
Round
Wrinkled
Pod shape
Inflated
Constricted
Pod colour
Green
Yellow
Height of plant
Tall
Dwarf/Short
Seven pairs of contrasting characters in Garden Pea.
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Mendels Experiments : Mendel conducted a series of experiments in
which he crossed the pollinated plants to study one character (at a time)
Monohybrid Cross
Cross between two pea plants with one pair of contrasting characters
is called a monohybrid cross.
Example : Cross between a tall and a draft plant (short).
MONOHYBRID CROSS
PARENT
Tall plant
ALLELIC PAIR
OF GENES
GAMETES
TT
T
t
Tt
F1 GENERATION
(first filial generation)
GAMETES
t
T
Gametes
[X – Science]
t
All tall plants
Tt
F2 GENERATION
Phenotypic ratio
Genotypic ratio
tt
T
SELF POLLINATION
of F1 gametes
Dwarf plant
Tt
T
T
t
TT
Tt
tall tall
Tt
tt
tall dwarf
3:1
1:2:1
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t
inflated/full
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TT
tt
Both dominant traits
Both recessive alleles
Pure or homozygous
conditon
Tt
One dominant, one
recessive trait
Hetrozygous
condition - Hybrid
Phenotypic ratio : 3:1
Genotypic ratio : 1:2:1
Phenotype Physical appearance [Tall or Short]
Genotype Genetic make up [TT, Tt or tt]
Observations of Monohybrid Cross
1. All F1 progeny were tall
(no medium height plant (half way characteristic)
2. F2 progeny ¼ were short, ¾ were tall
3. Phenotypic ratio F2 – 3:1 (3 tall : 1 short)
Genotypic ratio F2 – 1:2:1
TT : Tt : tt
1 : 2 : 1
Conclusions
1. TT and Tt both are tall plants while tt is a short plant.
2. A single copy of T is enough to make the plant tall, while both copies
have to be ‘t’ for the plant to be short.
3. Characters/Traits like 'T' are called dominant trait (because it express
itself) and ‘t’ are recessive trait (because it remains suppressed)
Dihybrid Cross : A cross macle between two plants having two pairs of
contrasting characters is called dihybrid cross.
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PARENT
GENERATION
ROUND
GREEN SEEDS
WRINKLED
YELLOW SEEDS
yy
y
YY
rY
GAMETES
RrYy
[round, yellow]
F1
F1
RY
Ry
rY
ry
Rr Yy
F1 gametes
F1
RY
Ry
rY
ry
Rr Yy
G
A
M
E
T
E
S
RY
RY
RRYY
Ry
RRYy
rY
RryY
ry
RrYy
Ry
RRYy
RRyy
RrYy
Rryy
rY
RrYY
RrYy
rrYY
rrYy
ry
RrYy
Rryy
rrYy
rryy
Selfing F1
gametes
Phenotypic Ratio
Round, yellow
: 9
Round, green
: 3
Wrinkled, yellow : 3
Wrinkled, green
: 1
Observations
1. When RRyy was crossed with rrYY in F1 generation all were Rr Yy
round and yellow seeds.
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2. Self pollination of F1 plants gave parental phenotype and two mixtures
(recombinants round yellow & wrinkled green) seeds plants in the ratio
of 9:3:3:1
9
Round
Yellow
:
3
Round
green
:
3
Wrinkled
yellow
:
1
wrinkled
green
Conclusions
1. Round and yellow seeds are DOMINANT characters
2. Occurrence of new phenotypic combinations show that genes for round
and yellow seeds are inherited independently of each other.
SEX DETERMINATION
Phenomenon of decision or determination of sex of an offspring
FACTORS
Responsible for Sex Determination
Environmental
In some animals the temperature
at which the fertilised eggs are
kept decides the gender.
eg. in Turtle
Genetic
In some animals like humans gender or
individual is determined by a pair of
chromosome called sex chromosome
XX – Female
XY – Male
Sex Chromosomes : In human beings there are 23 pairs of chromosome.
Out of these 22 chromosomes pairs are called autosomes and the last pair of
chromosome that help in deciding gender of that individual is called sex
chromosome.
XX – female
XY – male
[X – Science]
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Sex determination in Human beings
PARENTS :
FATHER
XY
GAMETES
(Reproductive cells)
Zygote
formed
after fusion
of gametes
X
MOTHER
XX
Y
X
XX
FEMALE
XX
FEMALE
X
XY
MALE
50% probability
of a female child
offspring
XY
MALE
50% probability
of a male child
This shows that half the children will be boys and half will be girls. All
children will inherit an X chromosome from their mother regardless whether
they are boys or girls. Thus sex of children will be determined by what they
inherit from their father, and not from their mother.
EVOLUTION
Evaluation is the sequence of gradual changes which takes place in the
primitive organisms, over millions of years, in which new species are produced.
Situation-I
Group of red beetles
Colour variation arises during reproduction
All beetles red except
one that is green
One beetle Green
Reproduction
Crows feed on red beetle
Progeny beetles green
No. of beetles reduces
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Crow could not feed on
green beetles as they
got camouflaged
in green bushes
Number of green
beetles increases
Situation 1 : Green beetles got the survival advantage or they were
naturally selected as they were not visible in green bushes. This natural selection
is exerted by crows resulting in adaptations in the beetles to fit better in their
environment
Situation-II
Group of red beetles
Reproduction
All beetles are red except one
that is blue
Reproduces
One blue beetle
Reproduces
Number of red beetle
increases
No. of blue
beetle increases
Crows can see both blue and red beetles and can eat them
Number reduces but still red beetles are more and blue ones are few
Suddenly elephant comes and stamps on the bushes
But now beetles left are mostly blue.
Situation 2 : Blue beetles did not get survivals advantage. Elephant
suddenly caused major havoc in beetle population otherwise their number
would have been considerably large.
From this we can conclude that accidents can change the frequency of
some genes even if they do not get survival advantage: This is called genetic
drift and it leads to variation.
[X – Science]
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MECHANISM OF HEREDITY
Characters or traits of an organism are controlled by the genes
A Section of DNA (cellular)
Gene
Provides information
For synthesis of Proteins
Proteins controls a character
Example :
Gene T
responsible for
synthesis of efficient
enzyme (Protein)
Gene t
responsible for
synthesis of less
efficient enzyme
More
production
of growth
hormone
Less
production
of growth
hormone
Results
in
Tall
Plants
Results
in
short
Plants
Genetic drift. It leads to diversity without any adaptation
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SITUATION-III
Group of red beetles
Habitat of beetles (bushes)
Suffer from plant disease
Average weight of beetles
decreases due to poor nourishment
Number of beetles kept on reducing
Later plant disease gets eliminated
Number and average weight of the beetles
increases again
Situation 3 : No genetic change has occurred in the population of beetle.
The population gets affected for a short duration only due to environmental
changes.
ACQUIRED AND INHERITED TRAITS
Acquired Traits
Inherited Traits
1. These are the traits which are
developed in an individual due
to special conditions
1. These are the traits which are
passed from one generation to
the next.
2. They cannot be transferred to
the progeny
2. They get transferred to the
progeny.
3. They cannot direct evolution
3. They are helpful in evolution.
eg. Low weight of starving
beetles.
[X – Science]
eg. Colour of eyes and hair
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SPECIATION
Micro evolution : It is the evolution which is on a small scale. eg.
change in body colour of beetles.
The process by which new species develop from the existing species is
known as speciation.
Speciation : it is the process of formation of new species.
Species : A group of similar individuals within a population that can
interbreed and produce fertile offspring.
Geneflow : It is exchange of genetic material by interbreeding between
populations of same species or individuals
WAYS BY WHICH SPECIATION TAKES PLACE
Speciation takes place when variation is combined with geographical
isolation.
Gene flow : occurs between population that are partly but not completely
separated
Sub Population
X1 (local)
Interbreeding
[Reproduction]
Gene
flow
Sub Population
X1 (migrant)
Variation
in
Local
population
GENETIC DRIFT
It is the random change in the frequency of alleles (gene pair) in a
population over successive generations.
*Natural Selection : The process by which nature selects and consolidate
those organisms which are more suitably adapted and possesses favorable
variations
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POPULATION Z
GEOGRAPHICAL
BARRIER
ISOLATION
(River, Mountain)
Sub Population
Z1
Sub Population
Z2
Over many-many generations
Results in Accumulation of different variations in
Sub population Z1 and Z2
Genetic drift
Natural selection
Sub population Z1 and Z2 incapable
of interbreeding
Reproductive
Barrier
Formation of
Formation of
new Species 1
new Species 2
Genetic drift takes place due to
(a) Severe changes in the DNA
(b) Change in number of chromosomes
Evolution and classification
Both evolution and classification are interlinked.
1. Classification of species is reflection of their evolutionary relationship.
2. The more characteristic two species have in common the more closely
they are related.
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3. The more closely they are related, the more recently they have a common
ancestor.
4. Similarities among organisms allow us to group them together and to
study their characteristic.
TRACING EVOLUTIONARY RELATIONSHIPS
(Evidences of Evolution)
I.
Homologous Organs : (Morphological and anatomical evidences. These
are the organs that have same basic structural plan and origin but
different functions.
Homologous organs provides evidence for evolution by telling us that
they are derived from the same ancestor.
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Example :
Forelimb of Horse
Winds of bat
Paw of a cat
II.
(Running)
(flying)
(walk/scratch/attack)
Same basic structural
plan, but different
functions perform.
Analogous Organs : These are the organs that have different origin
and structural plan but same function example :
Example : Analogous organs provide mechanism for evolution.
Wings of bat elongated fingers
with skin folds
Wings of bird Feathery covering
along the arm
Different basic
structure, but
perform similar
function i.e.,
flight.
III. Fossils : (Palaeontological evidences)
The remains and relics of dead organisms of the past.
FOSSILS ARE PRESERVED TRACES OF LIVING ORGANISMS
Fossil Archeaopteryx possess features of reptiles as well as birds. This
suggests that birds have evolved from reptiles.
Examples of Fossils
AMMONITE
-
Fossil-invertebrate
TRILOBITE
-
Fossil-invertebrate
KNIGHTIA
-
Fossil-fish
RAJASAURUS
-
Fossil dinosaur skull
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AGE OF THE FOSSILS
I.
Deeper the fossil, older it is.
II. Detecting the ratios of difference
of the same element in the fossil
material i.e. Radio-carbon dating
[C-(14) dating)
Recent
1. ...........................
2. ...........................
3. ...........................
4. ...........................
5. ..........................
6. .......................... Older
Evolution by stages
Evolution takes place in stages ie bit by bit over generations.
I.
Fitness advantage
Evolution of Eyes
Evolution of complex organs is not sudden it occurs due to minor changes
in DNA, however takes place bit by bit over generations.
enough to
Flat worm has rudimentary eyes give fitness
advantage
Insects have compound eyes
Humans have binocular eyes
II.
Functional Advantage
Evolutions of feathers
Feathers provide insulation in cold weather but later they might
become useful for flight.
Example : Dinosaurs had feathers, but could not fly using feathers.
Birds seem to have later adapted the feathers to flight.
Evolution by Artificial Selection : Humans have been a powerful
agent in modifying wild species to suit their own requirement through
out ages by using artificial selection. eg (i) From wild cabbage many
varieties like broccoli, cauliflower, red cabbage, kale, cabbage and
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kohlrabi were obtained by artificial selection. (ii) Wheat (many varieties
obtained due to artificial selection).
WILD
CABBAGE
KALE
CABBAGE
with larger
leaves
with short distance
between the leaves
BROCCOLI
KOHL RABI
CAULIFLOWER
Arrested flower
development
With Swollen
parts
Has sterile
flowers
Molecular Phylogeny
It is based on the idea that changes in DNA during reproduction are the
basic events in evolution
Organisms which are more distantly related will accumulate greater
differences in their DNA
HUMAN EVOLUTION
Tools to Study Human Evolutionary Relationship
Excavating
Time dating
Fossils
Determining
DNA
Sequences
Although there is great diversity of human forms all over the world get
all humans are a single species
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GENETIC FOOTPRINTS OF HUMANS
Hundreds/thousand of years ago
Earliest members arose in Africa
East Asia
South Africa
Africa
Philippines
Island
of
Indonesia
West
Asia
Central
Asia
Australia
They did not go in a single line
They went forward and backward
Moved in and out of Africa
Sometimes came back to mix with each other.
Eurasia
EXERCISE
(Question Bank)
Very Short Answers
(1 Mark)
1. Define variation
2. What is monohybrid cross?
3. What are genes?
4. If an individual has XX chromosome [22 + XX] will that individual be
male or female.
5. Which plant Mendel had choose for his experiments.
6. Name the branch of science that deals with Heredity and variation.
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7. Name two human traits which show variation.
8. What will you get in F1 generation when a pea plant having violet
coloured flowers is crossed with white coloured flowers? Give reason.
9. Who is the father of Genetics?
10. Write the scientific name of men and garden pea.
11. Where can be the Genetic foot print of human traced?
Short Answers
(2 Marks)
1. Differentiate between acquired and Inherited traits? Give example of
each.
2. Explain what are fossils? How the age of fossils be determined
3. What is speciation? What factors lead to formation of a new species.
4. Explain the mechanism of sex determination in humans.
5. Differentiate between homologous and analogous organs by giving
examples.
6. Define inheritance. What are the units of inheritance
7. What is genetic drift? How it contributes to the formation of new
species
8. Explain monohydrid cross by taking tall and dwarf plants. Mention the
phenotypic and genotypic ratio of F1 and F2 off springs.
9. How does creation of variations in a species promote survival?
10. Why mendel selected pea plants for conducting his experiments on
inheritance?
11. Why father is responsible for the sex of the new born baby?
12. Why acquired traits not passed on to their progeny?
[X – Science]
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Short Answer
(3 Marks)
1. Describe any three ways in which individuals with a particular trait
may increase in a population.
2. Name two fossils. What do fossil tells us about the process of evolution?
3. What are the important sources which provide evidence for evolution?
Explain them with example.
Long Answer
(5 Marks each)
1. Explain the process of artificial selection by taking the example of wild
cabbage plant.
2. Explain about the human evolution.
3. What are dominant and recessive traits? How do Mendel’s experiment
show that traits may be dominant or recessive? Illustrated with an
example?
4. How do mendel’s experiments show that traits are inherited
independently? Explain with a Dihybrid cross.
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CHAPTER – 10
LIGHT REFLECTION & REFRACTION
Light is a form of energy, which enable us to see the object.
In this chapter we will study the phenomena of reflection and refraction
using the property of light i.e. straight line propagation (Light wave travel
from one point to another, along a straight line).
Reflection of Light
When the light is allowed to fall on highly polished surface, such as
mirror, most of the light gets reflected.
Laws of Reflection
1. The angle of incidence is always equal to angle of reflection.
i = r
normal
Reflected
ray
Incident
ray
i
r
Points of incidences
2. The incident ray, reflected ray and thenormal to the reflecting surface
at the point of incidence lie in the same plane.
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Image formed by Plane Mirror (Plane reflecting surface)
Plane Mirror
1
A
A
Object
B
Image
i
r
B1
1. Virtual (imaginary) & Erect (Virtual The image that do not form on
screen.)
2. Laterally inverted (The left side of object appear on right side of image)
3. The size of image is equal to that of object.
4. The image formed is as for behind the mirror as the object is in front
of it.
Reflection of light by spherical Mirrors
Mirrors, whose reflecting surface are curved inward or outward spherically
are called spherical mirror.
For example - Spoon } The curved surface of shinning spoon can be
considered as curved mirror.
Reflecting
side
Reflecting
side
Concave Mirror
OR CONVERGING MIRROR
Convex mirror
OR DIVERGING MIRROR
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If it is curved inward Act as concave mirror
If it is curved outward Act as a convex mirror..
Few Basic terms related to Spherical Mirror
Principal
Axis
C
Radius of curvature
R
F
f
focal length
Concave
Mirror
P
Radius of curvature
R
Principal
Axis
P
f
F
focal length
Convex
Mirror
C
1. Principal axis : Line joining the pole and centre of curvature of the
spherical mirror.
2. Pole : The geometrical central point of the reflecting spherical surface.
(aperture), denoted by (P).
3. Aperture : The width of reflecting spherical surface.
4. Centre of curvature : The centre of the hollow glass sphere of which
the spherical mirror is a part is called as centre of creature.
5. Radius of curvature : The distance between the pole and the centre
of curvature. ie. PC = R or The radius of the hollow sphere of which
the mirror is a part.
6. Focus point : The point on the principal axis, where all parallel rays
meet after reflection is called as Principal Focus or Focus. It is denoted
by letter ‘F’.
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7. Focal length : The distance between the pole and focus point i.e. PF = f
8. Relationship between focal length and Radius of curvature.
F= R
2
Image formation by Spherical Mirror
Before we learn the formation of image or ray diagram, let us go through
few tips
(a) Remember, A say of light which is parallel to principle axis always
pass through focus (meet at focus) or vice-versa
P
Principal
Axis
C
P
Principal C
Axis
F
F
CONCAVE
MIRROR
CONCAVE
MIRROR
Principal
Axis
P
C
F
CONVEX MIRROR
Appear as if coming
from focus pt in case of convex mirror
Principal
Axis
P
F
C
(b) A ray of light which passes through centre of curvature (it is also
known as normal at the point of incidence on spherical mirror) will
retrace their path after reflection
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Pole (P)
Principal
Axis
F
C
CONCAVE
MIRROR
P
Principal
Axis
F
CONVEX
MIRROR
C
(c) A ray of light falling on pole get reflected at the same angle on the
other side of principal axis.
P
C
i = r
F
i = r
i
r
C
F
Note : A ray of light passes through centre of curvature reflecting spherical
surface is always act as normal at the point of incidence. If we know the
normal we can draw angle of incidence and angle of reflection
i
r
g
(passin c)
gh
u
o
r
th
[X – Science]
C
al
norm ence
incid
f
o
t
at p
F
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P
r
i
P
F
C
Note 1 : The image will only form when two or more rays meets at a point.
Image formation by a concave mirror for different position of the object.
The ray diagrams given in NCERT Books are also good to be followed.
1.
Object
At infinity
Position of
Image
At focus
P
C
2.
Object
Beyond C
F
Size of
Image
Highly diminished
(point size)
A
object
B1
B
P
F
C
Object
At C
A
1
B B
P
F
A
Object
B1
B
C
Position of
Image
At C
Nature
Real and
Inverted
F
i
r
i = r
Position of
Image
P
Beyond C
Nature
Real and
Inverted
Image
A
Nature
Real and
Inverted
Size of
Image
Same Size
of object
A
Object
4.
Between C&F
Position of
Image
Between F&C
Size of
Image
Small
A1
3.
Nature
Real and
Inverted
Size of Image
Enlarged
1
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5.
Object
At F
i = r
Position of
Image
At (infinity)
A
B
C
F
i
r
P
Nature
Real and
Inverted
Size of Image
Highly enlarged
A1
6.
Object
Between F&P
(Special Case)
A
C
F
i
B r
P
B1
Position of Image
Behind the mirror
Size of Image
Enlarged
Nature
Virtual
and
Erect
Image formation by Convex Mirror
1.
Object
At infinity
P
F
Position of Image
At focus
[X – Science]
Size of Image
Highly diminished
C
Nature
Virtual & erect
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2.
Object
Anywhere between
infinity and pole A
of the mirror
A1
P
B
Position of Image
Between P & F
B1
Size of Image
Very small
F
Nature
Virtual & erect
Uses of Concave Mirror
1. Used in torches, search light and headlight of vehicle.
2. Used to see large image of face as shaving mirror
3. Used by dentist to see large images of the teeth
4. Large concave mirror used to focus sunlight (heat) in solar furnaces.
Uses of Convex Mirror
1. Used as rear-view mirror in vehicles because it gives erect image. It
also helps the driver to view large area.
Sign Convention for Reflection by Spherical Mirror
1.
The object is always placed to the left side of mirror.
2. All distance should be measured from pole (P); parallel to principal
axis.
3. Take 'P' as origin. Distances measured
Right of the origin (+x-Axis) are taken positive
Left of the origin (–x-Axis) are taken negative
Perpendicular to and above principal axis (+y-Axis) are taken positive
Perpendicular to and below principal axis (–y-Axis) are taken negative
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+y
o
–x
(Cartesian system)
+x
–y
Mirror Formula
1
1
1
=
+
f
v
u
R
where f = 2
fdistance between F and Pole
vdistance of image from Pole
u distance of object from Pole
Rdistance between centre of curvature and pole.
Magnification
It is expressed as the ratio of the height of the image to height of the
object
m=
height of image h1
=
height of object h
1
It is also related to 'u' and 'v'
–v
m= u
2
from 1 and 2 equation
1
m=
h1
– v where h image height from principle axis
h1 Object height from principle axis.
h = u
It magnitude m > 1 _____ Image is magnified
m = 1 _____ Image is of same size
m < 1 _____ Image is dimirushed
Few tips to remember sign convention for Spherical mirror
Mirror :
f–u–v
Concave : –ve –ve
[X – Science]
–ve (Real +ve virtue)
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Convex :
+ve, –ve
+ve,
h – is always –ve
h1 – is +ve for virtue –ve for Real.
Refraction of Light
Refraction of Light : Happens in Transparent medium when a light
travels from one medium to another, refraction takes place.
A ray of light bends as it moves from one medium to another
Refraction is due to change in the speed of light as it enters from one
transparent medium to another.
Speed of light decreases as the beam of light travel from rarer medium
to the denser medium.
normal
normal
Incident
Ray
Raver medium
Denser medium
Denser medium
Rarer medium
Refracted Ray
When ray travel from Rarer to Denser it bends When ray travel from denser
towards normal after refraction
to rarer medium it bends
away from normal
Some Commonly observed phenomenon due to Refraction
1. The stone at the bottom of water tub appears to be raised.
2. A fish kept in aquarium appears to be bigger than its actual size.
3. A pencil partially immersed in water appears to be displaced at the
interface of air and water.
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Refraction through a Rectangular Glass Slab
Here light ray changes is
direction at O and O1 , the
point at the interface of
transparent medium.
When a incident ray of light AO passes from a rarer medium (air) to a
denser medium (glass) at point. O on interface KL, it will bends towards the
normal. At pt O1, on interface NM the light ray entered from denser medium
(glass) to rarer medium (air) here the light ray will bend away from normal
OO1is a refracted ray OB is an emergent ray. If the incident ray is extended
to C, we will observe that emergent ray O1B is parallel to incident ray. The
ray will slightly displaced laterally after refraction.
Note : When a ray of light is incident normally to the interface of two media
it will go straight, without any deviation.
Laws of refraction of light
1. The incident ray, the refracted ray and the normal to the interface of
two transparent media at the point of incidence, all lie in the same
plane.
2. The ratio of sine of angle of incidence to the sine of angle of refraction
is a constant i.e.
Sin i
constant
Sin r =
(r)
[X – Science]
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for given colour and pair of media, this law is also known as Snells Law
Constant n is the refractive index for a given pair of medium. It is the
refractive index of the second medium with respect to first medium.
n2
Sin i
=
n1 = n21
Sin r
Where 2 is for second
medium and 1 is for first
medium
Refractive Index
The refractive index of glass with respect to air is given by ratio of speed
of light in air to the speed of light in glass.
nga =
Speed of light in air
c
= v
Speed of light in glass
C Speed of light in vacuum = 3•108 m/s speed of light in air is
marginally less, compared to that in vacuum.
Refractive index of air with respect to glass is given by
a air
g glass
nag =
Speed of light in glass
v
= c
Speed of light in air
The absolute refractive index of a medium is simply called refractive
index
Speed of light in air
c
nm =
= v
Speed of light in the medium
Refractive index of water (nw) = 1.33
Refractive index of glass (ng) = 1.52
Spherical Lens
A transparent material bound by two surface, of which one or both surfaces
are spherical, forms a lens.
Convex Lens
A lens may have two spherical surfaces, bulging outwards, is called double
convex lens (or simply convex lens.
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It is also known as converging lens because it converges the light.
Concave Lens
A lens bounded by two spherical surfaces, curved inwards is known as
double concave lens (or simply concave lens)
It is also known as diverging lens because it diverges the light.
Few Basic Terms Related to Spherical Lens.
R
Principal
Axis
C1
or (2F1)
f
O
F1
F2
Optical
centre (O)
R
Principal
Axis
C1
C2
or (2F2)
Optical centre (O)
O
F1
F2
C2
f
C1
[X – Science]
O
C2
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Convex
Lens
Concave
Lens
1. Centre of curvature : A lens, either a convex lens or a concave lens
is a combination of two spherical surfaces. Each of these surfaces form
a part of sphere. The centre of these two spheres are called centre of
curvature represented by C1 and C2.
2. Principal axis : Imaginary straight line passing through the two centres
of curvature
3. Optical Centre : The central point of lens is its optical centre (O). A
ray of light, when passes through 'O' it remains undeviated i.e. it goes
straight.
4. Aperture : The effective diameter of the circular outline of a spherical
lens.
5. Focus of lens : Beam of light parallel is principal axis, after refraction
from
1.
Convex lens, converge to the point on principal axis, denoted
by F, known as Principal focus
Principal Axis
F1
2.
O
F2
Concave lens, appear to diverge from a point on the principal
axis, known as principal focus.
F1
O
F2
Principal
Axis
The distance OF2 and OF1 is called as focal length
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Tips for drawing Ray diagram
(a) After refraction, a ray parallel to principal axis will pass through F.
(b) A ray passes through F, after refraction will emerge parallel to principal
axis.
(c) A ray passes through optical centre 'O', passes without any deviation.
Image formation by a convex lens for various position of object
1.
Object
At infinity
2F1
2.
F1
F2
2F2
Object
Beyond 2F1
Position of Image
At focus
F2
Size of Image
Highly
diminished
(point size)
Nature
Real &
inverted
Position of Image
Between F2 & 2F2
Nature
Real &
inverted
Size of Image
Small
[X – Science]
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3. Object
At 2F1
A
B
B1
2F1
F1
2F2
F2
A1
4.
Object
Between F1 & 2F1
Position of Image
At 2F2
Size of Image
Same size of
object
Position of Image
Beyond 2F2
Size of Image
Enlarged
5.
Object
At focus F1
Position of Image
at infinity
Size of Image
Highly Enlarged
6.
(Special Case)
Object
Between F1 and
optical centre 'O'
Size of Image
Enlarged
Nature
Real &
inverted
Nature
Real &
inverted
Nature
Real &
inverted
Nature
Virtual &
Erect
Position of Image
On the same
side of the
object
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Image formation by concave lens
1.
Object
At infinity
Position of Image
At F1
Size of Image
Highly Diminished
2F1
2.
F1
F2
O
Nature
Virtual &
Erect
2F2
Object
Between infinity
and optical centre
(at any point)
Position of Image
Between F1 & O
Size of Image
Very small
A
Nature
Virtual
& Erect
A
B
2F1
F1 B
F2
O
2F2
Sign Convention for Refraction by spherical lens
Similar to that of spherical mirror, only the difference is that all the
measurement are made from optical centre 'O'
+ y-axis
o
+ x-axis
– x-axis
– y-axis
Lens Formula
1
1 – 1
=
f
v
u
[X – Science]
'O' optical centre
f - distance between F and 'O'
u - distance of object from 'O'
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f=
v - distance of image from 'O'
r - distance between centre
of curvature & 'O'
R
2
Magnification
It is defined as the ratio of the height of image to the height of object.
m=
height of image
height of object
1
h
= 1
h
=
h1 – image height
from principal axis
h – object height
from principal axis
It is also related to 'u' & 'v'
m=
v
u
2
From equation 1 & 2
1
h
m=
h
=
v
u
If magnitude of m > | Image is magnified
m = 1 Image is of same size
m < | Image is deminished
Few Tips to Remember Sign Convention for Spherical Lens
Lens :
f–u–v
Concave : –ve –ve
–ve (Real)
+ve (virtual)
Convex :
+ve, –ve
+ve,
h – is always +ve
n´ –
–ve for Real and
+ve for virtual & Errect.
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Power of Lens
The degree of convergence or divergence of light ray achieved by a lens
is known as power of a lens.
It is defined as the reciprocal of its focal length Represented by P.
f=
1
f
It f is given in meter, then
1
P=
f
It f is given in cm, then
100
P=
f
SI unit of power of a lens is "dioptre" denoted by 'D'
I dioptre or ID It is the power of lens whose focal length is 1m
1
1D =
OR 1D = 1m–1
1m
Power convex lens or converging lens is always positive
f is +ve
Power of concave lens or diverging lens is always negative
f is –ve
If any optical instrument have many lens, then net power will be
P = P1 + P2 + P3....
[X – Science]
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Question Bank
Very Short Answers Type Questions
(1 Mark)
1. If the angle of incidence is 0°, what is the angle of reflection?
2. What is the nature of image formed by concave mirror if the
magnification produced by the mirror is +3?
3. Give two uses of concave mirror?
4. Find the focal length of a convex mirror, whose radius of curvature is
30 cm?
5. What do you understand by magnification of a spherical mirror?
6. An object is held at the principal focus of a concave lens of focal
length f. Where the image will form?
7. Show the angle of incidence and angle of refection.
F
8. Complete the ray diagram.
9. Define the SI unit of power of lens.
10. When light undergoes refraction at the surface of separation of two
media, what happens to speed of light.
11. How can we find the focal length of a Convex lens quickly but
approximately.
Short Answer Type Questions
(2-3 Marks)
1. What do you understand by refraction of light. Draw the labelled ray
diagram, when ray passes through glass slab.
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2. The refractive index of glass is 1.54 and the speed of light in air is 3
× 108 m/s. Calculate the speed of light in glass?
3. A convex mirror used on an automobile has a focal length of 6m. If
vehicle behind is at a distance of 12m. Find the nature and location of
image.
(4m, virtual erect small)
4. A concave lens of focal length 15cm, forms an image 10 cm from the
lens. How far is the object placed from the lens? Draw the ray diagram?
5. Two thin lens of power +3.5D and - 2.5D are placed in contact. Find
the power and focal length, if the lens are in combination.(p = + 10,
f = 1m)
6. What are the law of refraction. Define refractive index of a medium.
7. How we can differentiate between convex and concave lens without
touching it.
8. The Power of a combination of two lens ×2y is 5d if the focal length
of lens × is 15 cm. State the Nature & focal length of lens y. (–60 cm.
Concave lens.)
Very Long Answer Type Questions
(5 Marks)
1. Draw the ray diagram, showing the image formed by concave mirror,
when object is placed at
(a)
at infinity
(b) between F22F
(c) At 2F
(d) At F
(e) between F&P
2. Draw the ray diagram, showing the image formed by convex lens,
when object is placed at.
(a) At infinity
(b) between F1 & 2F1
(c) At 2F1
(d) Beyond 2F1
(e) between F1 & optical centre 'O'
[X – Science]
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CHAPTER – 11
THE HUMAN EYE AND
THE COLOURFUL WORLD
In this chapter we will study Human eye that uses the light and enable
us to see the objects.
We will also use the idea of refraction of light in some optical phenomena
in nature i.e. Rainbow formation, twinkling of star, blue and red colour
of sky etc.
Human Eye : A Sensitive sense organ
It acts like a camera, enable us to capture the colourful picture of the
surroundings.
It forms an inverted, real image on light sensitive surface Retina
The Various Parts of Eye and their Functions
1. Cornea : It is a thin membrane through which light enters. It forms the
transparent bulge on the front of eyeball. Most of the refraction occurs
at the outer surface of the cornea.
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2. Eyeball : it is approximately spherical in shape, with a diameter of
about 2.3cm.
3. Iris : It is a dark muscular diaphragm that controls the size of pupil.
It is behind the cornea.
4. Pupil : It regulates and control the amount of light entering the eye. It
is the black opening between aqueous humour & lens.
5. Crystalline eye lens : Provides the focussed real & inverted image of
the object on the retina. It is composed of a fibrous, jelly like material.
This is convex lens that converges light at retina.
6. Ciliary muscles : It helps to change the curvature of eyelens and hence
changes its focal length so that we can see the object clearly placed at
different position.
7. Retina : Thin membrane with large no. of light sensitive cells.
8. When image is formed at retina, light sensitive cells gets activated and
generate electrical signal. These signals are sent to brain via optic
nerve. Brain analyse these signals after which we perceive object as
they are.
How Pupil Works?
Example : You would have observed that when you come out of the
cinema hall after watching movie, in the bright sun light, your eyes get
closed . And when you enter the hall from the bright light, you won't
be able to see but after some time you would be able to see.
Here the pupil of an eye provides a variable aperture, whose size is
controlled by iris
(a) When the light is bright : Iris contracts the pupil, so that less
light enters the eye.
(b) When the light is din : Iris expand the pupil, so that more light
enters the eye.
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Pupil opens completely, when iris is relaxed.
Persistence of Vision : It is the time for which the sensation of
an object continue in the eye. It is about 1/16th of a second.
Power of Accommodation
The ability of eye lens to adjust is focal length with the help of ciliary
muscles is called accommodation.
Ciliary Muslces
Relaxed
Contract
1. Eye lens becomes thick
2. Decreases the focal length
3. Enable us to see nearby
object clearly
Near point of the Eye
It is 25cm for normal eye. The
minimum distance at which object can
be seen most distinctly without strain.
For point of the Eye
It is infinity for normal eye. It is the
farthest point upto which the eye can
see objects clearly.
Defects of Vision and their Correction
1. CATARACT : The image can not be seen distinctly because eye lens
become milky and cloudy. This condition is known as cataract, it can
cause complete or partial loss of vision.
This can be corrected by surgical removal of extra growth (cataract
surgery)
2. Myopia : (Near Sightedness)
A person can see nearby object clearly, but cannot see distant object
distinctly.
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Image formed in front of the retina.
Normal
Eye
O
Image
formed
at Retina
Object
O1
Myopic
Eye
O
The Reason of defect
1. Excessive curvature of eye lens means Eye lens becomes thick and its
focal length decreases.
2. Elongation of the eye ball.
Correction
Corrected by using a Concave Lens of appropriate power.
O1
O
Correction of Myopita
3. Hypermetropia (Far - Sightedness)
A person cannot see nearby object clearly, but can see distant object
distinctly.
[X – Science]
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Image formed at a point behind the retina
NORMAL
EYE N
NORMAL
EYE N
Image formed
at Retina
Hypermetropic
eye
N1
The Reason of defect
1. Increase in focal length of the eye lens (Thin eye lens)
2. Eye ball has become too small.
Correction
Corrected by using a Convex Lens of appropriate power..
N
N1
Correction of Hypermetropic eye
4. Presbyopia
As we become old, the power of accommodation of the eye usually
decreases, the near point gradually recedes away. This defect is called
Prebypoia, a special kind of Hypermetropia.
Person may suffer from both myopia and hypermetropia.
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Reason of defect : Gradual weakening of ciliary muscles and decreasing
the flexibility of the eye lens.
Correction : Using of Bifocal lens with appropriate power.
Bifocal lenses consist of both concave and convex lens, upper position
consist of concave lens and lower portion consist of convex lens.
Refraction of Light through a Prism
Prism : It has two triangular bases and three rectangular lateral surfaces.
These surfaces are inclines to each other. The angle between its two
lateral faces is called Angle of Prism.
A
i- incident angle
Angle of Prism
(Angle of deviation)
D
i
t
ligh
Sun
r
B
e
(emergent angle)
C
Em
erg
ent
ray
Angle of Deviation (D) The angle between the incident ray and emergent ray.
Dispersion of white light by a Glass Prism
D for red colour
D for violet colour
ht
te lig
Whi
beam
R
While light
Spectrum
D for violet colour > D for red colour
V
Inclined refracting surfaces of glass prism show exciting phenomenon.
[X – Science]
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Splitting of White Light into Band of Colours
The band of the coloured components of light beam as called Spectrum
i.e. VIBGYOR
The splitting of light into its component colours is called Dispersion.
The different component colour of light bends at different angle with
respect to incident angle the red light bends the least while the violet bends
most.
ISSAC NEWTON He was the first, who obtained spectrum of sunlight
by using glass prism.
He tried to split the spectrum of white light more by using another similar
prism, but he could not get any more colours.
He repeated the experiment using second prism in on inverted position
with respect to the first prism.
Allowed all the colours of spectrum to pass through second prism. He
found white light emerges on the other side of second prism.
en
Scre
ght
te li
whi
S
R
R
V
V
te
whi
t
ligh
e
ourc
He concluded that sun is made up of seven visible colour ‘VIBGYOR’
RAINBOW It is the spectrum of sunlight in nature It is formed due
to the dispersion of sunlight by the tiny water droplet, present in atmosphere.
Water Droplet Act like Prism
It refracts and disperses the incident sunlight, then reflects it internally
(internal reflection) and finally refracts it again, when it emerges out of the
water droplet.
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A rainbow is always formed in a direction opposite to that of sun.
Due to dispersion and internal reflection of light, different colours reached
to observer’s eye.
Red colour appears on top & violet at the bottom of rainbow
Sunlight
Rain drop
A
At ‘A’ Refraction & dispersion takes place
B
At ‘B’ Internal refraction takes place
C
At ‘C’ Refraction & dispersion takes place
R
V
Atmospheric Refraction
1. Apparent Star Position : It is due to atmospheric refraction of star
light.
The temperature and density of different layers of atmosphere keeps
varying. Hence we have different medium.
Distant star act as point source of light. When the starlight enter the
earth’s atmosphere it undergoes refraction continuously, due to changing
refractive index i.e. from Rarer to denser. It bends towards the normal.
Due to this the apparent position of the star is different from actual
position.
The star appears higher than its actual position.
Actual
position
of Star
Apparent position of star
In atmosphere layer
Refractive index
decreases
Atmosphere
[X – Science]
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2. Twinkling of Star : It is also due to atmospheric refraction
Distant star act like a point source of light. As the beam of starlight
keeps deviating from its path, the apparent position of star keeps on
changing because physical condition of earth’s atmosphere is not
stationary
Hence the amount of light enters our eyes fluctuate some time bright
and some time faint.
This is the “Twinkling effect of star”
Q.
Ans.
Why Planets do not twinkle?
Planets are closer to earth and are seen as extended source of light i.e.
the collection of large no: of point sized sources of light. Therefore the
total amount of light entering our eyes from all individual point source
will nullify the twinkling effect.
3. Advance Sunrise and delayed sunset : This is also due to atmospheric
refraction.
Because of this sun is visible about 2 minutes earlier than actual sunrise
and about 2 minutes after the actual sun set.
Ob
se
Ea rve
rt h r o
n
Atmosphere
Apparent
position
of sun
Horizon
EARTH
Actual
Sun
Apparent flattering of the sun’s disc at sun set and sun rise is due to
atmospheric refraction.
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Scattering of Light
Tyndall Effect : When a beam of light strikes the minute particle of
earth’s atmosphere suspended particles of dust and molecule of air the path of
beam becomes visible. The phenomenon of scattering of light by the colloidal
particle gives rise to Tyndall Effect.
It can be observed when sunlight passes through a canopy of a dense
forest.
The colour of the scattered light depends on the size of the scattering
particles
Very fine particle
(scatter mainly
blue colour short
wave length)
Large size particle
(Scatter light of
longer wave length
i.e. red)
Very large enough
(The sky appear
white)
1. Why cloud Appear white : The size of water droplet (scattering particle)
is very large, hence scattered all wavelength of light almost equally.
2. Why colour of sky is blue : The molecules of air and other fine
particles in the atmosphere have size smaller than the wavelength of
visible light. Since the blue has shorter wavelength than red, hence it
will scattered the most.
According to Rayleigh scattering
1
Scattering of light 4 – Wavelength)
Scattering of light decreases with increase in wavelength
Q.
Ans.
If there is no earth’s atmosphere? What will happen to scattering
phenomenon?
There will be no scattering and sky will appear dark.
3. Colour of the Sun of Sunrise and Sunset
While sunset and sunrise, the colour of the sun and its surrounding
appear red.
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During sunset and sunrise, the sun is near horizon, and therefore the
sunlight has to travel larger distance in atmosphere. Due to this most
of the blue light (shorter wavelength) are scattered away by the particles.
The light of longer wavelength (red colour) will reach our eye. This is
why sun appear red in colour.
4. Why the danger signal or sign are made of red colour.
Red colour scattered the least when strikes the small particle of fog and
smoke because in has the maximum wavelength (visible spectrum).
Hence at large distance also, we can see the red colour clearly.
5. At noon sun appear white :
At noon the, sun is overhead and sunlight would travel shorter distance
relatively through the atmosphere. Hence, at noon, the Sun appear
while as only little of the blue and violet colours are scattered.
(In the afternoon)
(In the early morning
or evening)
Light travel less
distance in atmosphere.
(Less blue
scattered)
(Blue scattered away
sun appear reddish
Sun near
horizon
Atmosphere
EARTH
Question Bank
Very Short Answers
(1 Mark)
1. What is the phenomenon responsible for the blue colour of sky?
2. What is the near and far point of a normal eye?
3. Name the component of eye that is responsible for the adjustment of
eyelens?
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4. To an astronaut why does the sky appear dark instead of blue?
5. How can your remove the defect of vision ‘Presbyopia’.
6. Name three primary colour? (Ans. RED, BLUE, GREEN)
7. Write the nature of image formed by our eye?
8. What do you understand by Dispersion of light?
9. What is Tyndall Effect?
10. A student has difficulty reading the black board while sitting in the last
row. What is the defect of vision and how it can be corrected?
11. What is the value of Power of Accommodation of Person having normal
eyesight?
12. Name the Part of the retina which is incentive of light?
Short Answers
(2 Marks)
1. Name the phenomenon responsible for formation of rainbow? Explain
it with the help of diagram?
2. What is power of accommodation. How ciliary muscles helps in
accommodation?
3. Why the sun appear red while sunset and sunrise. Explain?
4. Why the star twinkle but not earth (Plants)?
5. Explain the function of
(i) Iris (ii) Pupil (iii) Retina
6. Explain the refraction of light through glass prism with the help of
diagram. Show angle of emergence and angle of deviation?
7. Neme
(a) the Eye defect which can’t be corrected by any
(b) the Old age hypermetropia.
[X – Science]
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Long Answer Type Questions
(5 Marks)
1. What is myopia. State the two causes of myopia? With the help of
labelled ray diagram show
(a) Eye defect
(b) Correction of myopia
2. What is hypermetropia. State the two causes? With the help of labelled
ray diagram show
(a) Eye defect
(b) Correction of hypermetropia.
3. Draw the labelled diagram of human eye and explain the image
formation?
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CHAPTER – 12
ELECTRICITY
Think life without “electricity” in this modern society. Is it possible to
survive without electrical energy in world of technology. Since we are science
student, so it is necessary to understand the basic concept behind the word
“electricity”
Charge (q)
It is a very small particle present in an atom it can be either negative
(electron) or positive (proton)
“Coulomb” is the SI unit of charge, represented by C.
Net charge (Q) – Total charge
IC Net charge is equivalent to the charge contained in nearly electrons
6 × 1018
Q = ne (n is no: of electron)
–19
If Q = 1C, e = 1.6 × 10 C (negative charge on electron)
Q
1
n= e =
–19
1.6 ×10
100
18
18
=
× 10 = 6.2 × 10
16
18
n = 6 × 10 electron
Current (I)
Rate of flow of net charge is called current. Denoted by (I)
I =
[X – Science]
Q
t
t is time
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SI unit of current is “Ampere” rep. by A.
Ampere Defined as one coulomb of charge flowing per second.
1A =
1C
1s
In an electric circuit the electric current flow in a opposite direction to the
flow of electron (–ve charge) conventionally. It flows from the +ve terminal
of battery or cell to –ve terminal.
Small quantity of current are expressed in
mA (milli Ampere) = 10–3 A
µA (micro Ampere) = 10–6 A
Ammeter : It is an instrument used to measure the electric current in a
circuit.
It is always connected in series in a circuit
It is represented by the symbol –––––––– – A + ––––––– in an electric
circuit. It has low resistance.
Electric Circuit : It is a closed path along which the electric current
flows.
Bulb
The arrow shows the direction
of electric current in circuit.
–
Ammeter A
+
+
Key
–
In this circuit ammeter is
connected in series.
Battery
(Having 3 cells)
The electrons can only flow when there is difference of electric
pressure. For example “water flowing through a tube” It is only possible when
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there is high pressure at one side and low at another side, then it will move
from high pressure to low pressure.
In case of electric current, the flow of charge is made possible due to
chemical action with in a cell that generates the potential difference across the
terminals of the cell.
Electric potential Difference : It is defined as the work done in carrying
a unit charge from one point to another between the two points of an electric
circuits.
W
V=
Q
V – Potential Difference
W – Work
Q – Net Charge
SI unit of potential difference – Volts rep. by “V”
One Volt When 1 Joule of work is done in carrying one coulomb (1C)
of charge from one point to another of a current carrying conductor then the
potential difference is send to be IV.
1J
1C
IV =
Voltmeter It is an instrument, used to measure the potential difference
+V –
and represented by the symbol
in an electric circuit. It is
always connected in parallel across the points between which the potential
difference is to be measured. It has high resistance.
Symbols for some commonly used instrument in circuit diagrams
+
(1) Cell
(2) Battery
+
(3) Key (switch) open
[X – Science]
–
–
OR
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(4) Key (Closed)
OR
(5) Joint wire
(6) Wires with no join
(7) Bulb
(8) Ammeter
+
(9) Voltmeter
+
–
A
–
V
George Simon Ohm (physicist) 1787 – 1854
Found the relationship between the current (I) flowing through a conductor
and potential difference (V) across the terminals of a conductor using the
circuit diagram.
+ V–
GRAPH
–
A
+
V
(V)
+
O
–
VI
I (A)
In this circuit diagram we come across two new symbols
RESISTANCE (R)
OR
RHEOSTAT (Variable Resistance)
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Ohm’s Law He stated that the electric current flowing through a
conductor is directly proportional at to the potential difference across its ends,
provided the temperature remain constant
VI
V = IR
Where “R” is the proportionality constant for the given metal at given
temperature and is said to be resistance, the graph between V and I is always
straight line.
Resistance : It is the property of a conductor that opposes the flow of
current. It is represented by ‘R’ and symbol is
SI unit of resistance “Ohm” OR
1 Ohm : The resistance of a conductor is said to be one Ohm, when the
potential difference across the conductor is 1V and the current flowing through
it is 1A.
V = IR
R = V
I
1 Ohm or 1 = 1V
1A
Rheostate
As we know that
V = IR
1 = V
R
Shows that current through
conductor resistor is inversely
proportional to its resistance
So to increase or decrease the current accordingly in the circuit a component
is used is called “Rheostat”, that regulates the current without changing potential
difference. Represented by “Rh”
Its symbol is
[X – Science]
OR
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If a conductor has less Resistance, then more current will flow through it.
Factors on Which Resistance of a Conductor Depends
1. On its length (l)
2. On its cross sectional area (A)
3. On the nature of material.
(Resistance)
Rl
R 1
A
R l
A
R= l
A
(Directly prop. to length)
(inversely prop to cross-sectional area)
Where “ ” (rho) is a proportionality constant known as resistivity of the
material of conductor.
Resistivity ( ) : The resistance offered by a wire of unit length and unit
cross-sectional area is called resistivity.
Since R =
Its SI unit is m
l
A
m2
m
SI unit of m.
R.A =
l
For a material irrespective of length and area, the resistivity is a constant.
Resistantly of a Material varies with Temperature
Resistivity of an alloy (homogeneous mixture of metals) is generally
higher than of its constituent metals. Example Constantan (alloy of Cu & Ni)
Alloys have high resistivity and do not oxidise (burn) readly at high
temperature, for this reason they are commonly used in electrical heating devices,
like electric iron, heater, toasters etc. For example “Tungsten” as filament of
electric bulb.
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Resistance in Series (Maximum Effective Resistance)
Let us take three resistance R1, R2 and R3 that are connected in series
in a circuit.
R1
R2
R3
V1
V2
V3
I
+
–
V
Ohm’s low stated
V = IR
The current (I) flowing through the resistance in series will remain same,
where as the potential difference (V) across each resistor will be different.
V = IR
V1 = IR1 , V2 = IR2 , V3 = IR3
Total potential difference (V) = V1 + V2 + V3
V = IR1 + IR2 + IR3 Putting the value of
V, V1, V2 & V3
I R = I (R1 + R2 + R3 )
Reff = R1 + R2 + R3
Thus, we conclude that effective Resistance of the several resistors joined
in series is equal to the algebraic sum of their individual resistance.
Resistance in Parallel (Minimum Effective Resistance)
Let us take three R1, R2 and R3, that are connected in parallel in the
electric circuit.
R1
I1
I2
I1
R2
I3
R3
+
–
V
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Now,
I1 = V , I2 = V , I3 = V
R1
R2
R3
Total current (I) = I1 + I2 + I3 substitute the value of I1, I2, I3 and I
V = V + V + V
R
R1
R2
R3
V = V
R
1 + 1 + 1
R1
R2
R3
1 = 1 + 1 + 1
Reff
R1
R2
R3
Thus, we conclude that the reciprocal of total effective resistance of the
several resistors connected in parallel is equal to the sum of the reciprocals of
the individual resistance.
Disadvantage of Series Connection in an Electric Circuit
1. In series connection if any of the component fail to work, the circuit
will break and then none of the component (ex. TV, bulb, fan..) will
work.
2. It is not possible to connect a bulb and a heater in series, because they
need different value of current to operate properly.
Hence, to overcome this problem we generally use parallel circuit.
Heating Effect of Electric Current
Explanation Battery or a cell is a source of electrical energy.
Battery or Cell
(Chemical reaction in
it will produce potential
difference at its
two terminals)
Electron
will come in motion
to flow current
through resistor
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Rest of energy of source is
converted into heat, that
raises the temperature
of gadget.
Part of this energy is
consumed in useful
work
(like rotating of fan)
This is known as heating
effect of electric current
To maintain this
current, the source
has to keep expending
its energy
This effect is utilized in
devices such as electric
heater, iron etc.
Mathematical Expression
Let us suppose that current (I) is flowing through a resistor of resistance
(R) for the time (t). The potential difference across the resistance is (V).
W
V= Q
Work done in morning the charge Q will be
W = VQ
W
Then power, P = t [Rate of change of work done]
VQ
= t
Q
P = VI
I= t
– (1)
Heat energy supplied by the source for time t will be
Energy or Work
H=Pt
P=
– (2)
time
Put equation (i) in equation (2)
H = VIt
= (IR) It
V = IR Ohm’s Law]
H = I2Rt
This is known as Joule’s Law
The law stated that the heat produced in a resistor is
(i) directly proportional to square of the current(I)
(ii) directly proportional to resistance (R) for given current
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(iii) directly proportional to time (t) for which current flow through resistor.
Application of Heating Effect of Electric Current
1. Used in electric iron, toaster, oven, heater etc.
2. It is also used in bulb to produce light.
(Filament of bulb is made of strong metal with high melting point such
as tungsten (m.pt = 3380°C). This filament can retain as much of the
heat generated as possible, to become very hot and emit light)
3. It is also used in the “fuse connected in an electric circuit {Fuse a
safety device, protect the circuits and appliance by stopping the flow
of high current. The wire of fuse is made of an alloy of metals e.g.,
Aluminium Copper, Iron lead etc. The alloy should be of low melting
point and high resistivity, fuse is always connected in series circuit.
When large current flows through the circuit, the temperature of fuse
wire will increase. This melts the fuse wire and breaks the circuit.
“ Fuses” used for domestic purposes are rated as 1A, 2A, 3A, 5A, 10A
etc. for various operation depending upon the power of appliance using.
Example : let us consider an appliance “electric Iron” which consume
1KW electric power, at 220V
P = VI
I = P = 1KW = 1000W
V
220V
220V
I = 4.54A
In this case a 5A fuse is required.
Electric Power : In case of electricity, it is defined as the rate of change
of electrical energy dissipated or consumed in an electric circuit.
P = VI
2
or P = I R
2
V
or P =
R
( V = IR Ohm’s Law)
( I= V )
R
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or P = Electrical Energy (E)
time (t)
SI unit of electric power is “Watt” (W).
1 Watt Defined as the power consumed by a device, when 1A of
current passes through it at the potential difference of 1V.
P = VI
1 Watt = 1 Volt ×1 Ampere
Electrical Energy
P=
E
t
E – Electrical Energy
t – time
E = P t
SI unit of electrical energy = Ws or J
Commercial unit of electrical energy = KWh or One unit
E=P×t
KWh = 1KW × h
= 1000W ×3600 s
5
= 36 ×10 Ws
6
= 3.6 ×10 J
(SI unit Ws = J)
6
KWh = 3.6 × 10 J
One horse power = 746W
EXERCISE
(Question Bank)
Very Short Answers
(1 Mark)
1. Define the SI unit of (one mark each)
(a) Current
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(b) Potential Difference
(c) Resistance
(d) Electric Power
(e) Electric Energy (Commercial)
2. What is the conventional direction of flow of current?
3. Define the term resistivity?
4. On what factors does the resistance of a conductor depend?
5. How is the voltmeter and ammeter connected in the electric circuit.
6. Heating effect of current carrying conductor is due to –
(Ans : loss of kmectic energy of electron)
7. Why the filament of bulb has high melting point?
8. How does use of a fuse wire protect electrical appliance?
9. What is the relationship between power, current and potential difference
(Ans : P = VI)
10. How many joules are there in 1KWh?
Short Answer Type Questions
(2-3 Marks)
1. Draw a schematic diagram of a circuit consisting of a battery of six cell
of 1.5V each, three resistor each of 3W in series and a plug key.
2. State Ohm’s law. Draw the graph between V&I?
3. What is joule’s Heating effect of current, derive its expression?
4. A wire of length L and R is stretched so that its length’s doubled and
the area of cross section is halved. How will its
(i) Resistance change
(ii) Resistivity change.
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5. An electrical appliance of power 2KW works at potential difference of
220V. Does it require fuse of 5A, give reason?
6. Calculate the total effective resistance between points A and B
(i)
1
1
1
1
A
1
1
B
1
(ii)
3
3
A
B
3
3
(iii)
2
2
A
2
2
B
7. A Heating coil has a resistance of 200W. At what Rate will heat be
produced in it when a current of 2–5A of flow through it?
8. Which is the better way to connect lights and other appliances in
domestic wiring and why?
9. How does the resistance of a wire change when
(a) its length is Triplled. (b) its diameter is doubled?
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Long Answer Type Questions
(5 Marks)
1. On what factor the resistance of conductor depends give its mathematical
expression. Give the SI unit of resistivity?
Calculate the resistivity of a metal of length 2m at 20°C having the
resistance of 20W and diameter 0.3mm?
2. In a circuit below, calculate
4
2
6
+
–
6
(a) Calculate total effective resistance
(b) The total current through the circuit.
(c) Potential difference across 4 and 2.
3. Three resistance of 2, 3 and 5 are connected in the electric circuit.
Calculate the
(a) Maximum effective resistance
(b) Minimum effective resistance
4. Explain Joulie how of hearing? How and on what factor does the heat
produced in a conduct depends?
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CHAPTER – 13
MAGNETIC EFFECTS OF
ELECTRIC CURRENT
In this chapter, we will study the effects of electric current :
1. Hans Christian Oersted (1777-1851)
Oersted showed that electricity and magnetism are related to each other.
His research later used in radio, television etc.
The unit of magnetic field strength is name Oersted in his honour.
2. Oersted Experiment
R
K
X
XY is conductor (Cu wire)
through which current is passed
Y
–
+
On passing the current through the copper wire XY in the circuit, the
compass needle which is placed near the conductor gets deflected. If
we reverse the direction of current, the compass needle deflect in reverse
direction. If we stop the flow of current, the needle comes at rest.
Hence, it conclude that electricity and magnetism are linked to each
other. It shows that whenever the current will flow through the conductor,
then magnetic field around it will developer.
3. Magnetic Field : It is the region surrounding a magnet, in which force
of magnet can be detected. It is a vector quantity, having both direction
& magnitude.
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4. Compass Needle : It is a small bar magnet, whose north end is pointing
towards north pole and south end is pointing towards south pole of
earth.
5. Magnetic Field Lines : When a bar magnet is placed on a card board
and iron fillings are sprinkled, they will arrange themselves in a pattern
as shown below.
N
S
The lines along which the iron filling align themselves represent
magnetic field lines.
Hence, magnetic field line is a path along which a hypothetical free
north pole tend to move towards south pole.
6. Characteristics of Magnetic field lines :
(a) The direction of magnetic field lines outside the magnet is always
from north pole to south pole of bar magnet and are indicated
by an arrow.
Inside the magnetic, the direction of field lines is from its south
pole to north pole
Thus magnetic field lines are closed curve
(b) The strength of magnetic field is expressed by the closeness of
magnetic field lines. Closer the lines, more will be the strength
and farther the lines, less will be the magnetic field strength.
(c) No two field lines will intersect each other.
If they intersects, then at point of intersection the compass needle
will show two direction of magnetic field which is not possible.
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Tangent at the
point of intersection
shows two direction.
7. Magnetic field due to Current Carrying Conductor
N
x
S
Cu wire
+
N
y
S
x
y
Cu wire
+
–
–
(a)
(b)
The above electric circuit in which a copper wire is placed parallel to
a compass needle, shows the deflection in needle gets reversed, when
the direction of current reversed. Hence electricity and magnetism are
related to each other.
8. Right Hand Thumb Rule
It is a convenient way of finding the direction of magnetic field
associated with current carrying conductor.
Hold the straight wire carrying current in your right hand such that
thumb points towards the direction of current, then your folded fingers
around the conductor will show the direction of magnetic field.
Direction of magnetic
field lines.
This rule is also called Maxwell’s corkscrew rule.
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9. Magnetic Field due to Current through a Straight Conductor
+
A
–
Direction of
Current
Direction can be
explained using
Right Hand Thumb
Rule
+
on
ecti netic
r
i
D ag
of m
d
fiel
–
Pheostat
Z
S
10. Magnetic Field due to Current through a circular Loop
–
+
Every point on the wire carrying current give rise to the magnetic field,
appearing as a straight line at the centre of loop. By applying Right
hand Thumb rule, we can find the direction of magnetic field at every
section of the wire.
11. Solenoid : A Coil of many circular turns of insulated copper wire
wrapped closely in the shape of a cylinder is called solenoid.
12. Magnetic field due to a current in a solenoid :
S
N
+
–
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–
Using R.H. Thumb Rule, we can draw the pattern of magnetic
field lives around a current carrying solenod.
–
One end of the solenoid behaves as a magnetic north pole,
white the other end behave as the South Pole.
–
The filed lines inside the solenoid are in form of parallel straight
lines, that implies that magnetic field inside the solenoid is
same at all points i.e. Field is uniform.
The strength of the magnetic field produced depends upon
(a) the number of terms (b) Strength of current in the solenoid
used in making solenoid.
13. Electromagnet : Strong magnetic field inside the solenoid can be used
to magnetise a magnetic material for example soft iron, when it is
placed inside the coil. The magnet so formed is called electromagnet.
14. Force on a current carrying conductor in a magnetic field.
Andre Marie Ampere (1775–1836) suggested that the magnet also exert
an equal and opposite force on the current carrying conductor.
Iron Stand
Experiment
+
–
Current Carrying
Aluminium rod should lie
between the two poles
of magnet
Horse shoe magnet
We will observe that the rod will displace i.e. the rod will experience
a force, when it is placed in magnetic field, in a perpendicular direction
to its length.
–
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The direction of the exert force will be reversed if the direction
of current through the conductor is reversed.
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–
If we change the direction of field by inter changing the two
poles of the magnet, again the direction of exert force will
change.
–
Therefore the direction of exerted force depends on
(a)
direction of current
(b)
direction of magnetic field lines.
15. Left Hand Flaming Rule
M other
F ather
(Force) Motion
C hild
Field
T humb
Current
Fore finger
Middle finger
Thrust (force)
Three of them perpendicular to each other.
OR
A
Cursor
B
East
For
ce o
rM
otio
n
South D
C
Vertically
downwards
–
According to this rule, stretch
thumb ,
forefinger
and
middle finger
of your left hand such that they are mutually perpendicular
to each other.
If fore finger represent direction of magnetic field & middle
finger represent direction of current, then thumb will point in
the direction motion or force acting on the conductor.
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–
Functioning of electric motor is based on this rule. It convert
electrical energy into mechanical energy.
16. Michael Faraday : Gave the law of Electro magnetic Induction
17. Galvanometer : It is an instrument that can detect the presence of a
current in a circuit. If pointer is at zero (the centre of scale) the there
will be no flow of current.
If the pointer deflect on either side right or left, this will show the
direction of current. Represented by
o
G
18. Electro Magnetic Induction : Can be explained by two experiments
(a) First Experiment “Self Induction”
N
S
G
G
G
In this experiment, when the north pole of bar magnet is brought closer
to the coil or away from the coil, we see momentary deflection in the
needle of galvanometer on either side of null point. First right and then
left.
Similarly, if we keep the magnet stationary and coil is made to move
towards or away from the north pole of magnet. Again we will observe
deflection in the needle of galvanometer.
If both bar magnet and coil kept stationary, there will be no deflection
in galvanometer.
This experiment can also be done with the south pole of magnet, we
will observe the deflection in galvanometer, but it would be in opposite
direction to the previous case.
It concludes that motion of magnet with respect to coil or viceversa, changes the magnetic field. Due to this change in magnetic field
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lines, potential difference is induced in the same coil, which set up an
induced current in the circuit.
(b) Second Experiment : Mutual Induction
Primary Coil
+
Secondary Coil
–
Coil 1
G
Coil 2
In this experiment plug in the key that connects coil with battery and
observe the deflection in galvanometer. Now plug out the key that
disconnect the coil-1 from battery and observe the deflection in
galvanometer, which will be in reverse direction.
Hence, we conclude that potential difference is induced in secondary
coil (coil-2), whenever there is a change in current, in primary coil
(coil-1) (by on and off of key).
This is because, whenever there is change in current in primary coil
Magnetic field associated with it also changes
Now, magnetic field lines around the secondary coil (coil-2) will change
and induces the electric current in it (observed by the deflection of
needle of Galvanometer in secondary circuit)
This process, by which changing of strength of current in primary coil,
induces a current in secondary coil is called Electromagnetic Induction”
The induced current is found to be highest when the direction of motion
of coil is at right angles to the magnetic field.
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19. Fleming’s Right Hand Rule
(1)
(2)
M other
(3)
F ather
Motion
(movement of conductor)
Field
(Magnetic)
Thumb
C hild
Current
(Induced)
Fore finger
Middle finger
OR
D North
Introduced
current
Map field
A
West
Motron
C
Vertically
downwards
Rule can be defined at–
Stretch thumb , forefinger and middle finger of right hand, so
that they are perpendicular to each other. The forefinger indicates
direction of magnetic field, thumb shows the direction of motion of
conductor, then the middle finger will shows the direction of induced
current.
Electrical generator is based on the principle of electro magnetic
induction. It convert mechanical energy into electrical energy.
Current
Alternate Current (AC)
Direct Current (DC)
(1) Changes the direction periodically
after equal interval of time
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Does not change its direction
with time it is unidirectional
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Current
I
(A)
I
(A)
time
(s)
time
(s)
It has frequency
50Hz in India
60 Hz in America
It has frequency
OHz
21. Advantages of Alternate Current (AC) over Direct Current (DC)
Electric power can be transmitted to longer distances without much
loss of energy. Therefore cost of transmission is low.
In India the frequency of AC is 50Hz. It means after every 1/100
second it changes its direction.
22. Domestic Electric Circuits :
In our homes, the electric power supplied is of potential difference V
= 220V and frequency 50Hz.
It consist of three wires :–
(1) Wire with red insulation cover – LIVE WIRE (POSITIVE)
Live wire is at high potential of 220V
(2) Wire with black insulation cover – NEUTRAL WIRE
(NEGATIVE)
Neutral wire is at zero potential
Therefore, the potential difference between the two is 220V.
(3) Wire with Green insulation cover – EARTH WIRE
it is connected to a copper plate deep in the earth near house.
The metallic body of the appliances is connected with the earth
wire as a safety measure.
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Function
Earth wire provide a low resistance to the current hence any leakage of
current to the metallic body of the appliances, keep its potential equal to that
of earth. That means zero potential and the user is saved from severe electric
shock.
Earth wire
Live wire
Distribution Box
containing main
switch & fuse
for
each
current
Ueutral wire
Electrical
Fuse board
Electricity
meter
Point to be noted in domestic circuit
(a) Each appliance has a separate switch of ON/OFF
(b) In order to provide equal potential difference to each appliance, they
should be connected parallel to each other. So that they can be operated
at any time.
(c) We have two electric circuit in our home
One consist of current
of 15A for high power
appliances
Other circuit consist
of current 5A for low
power appliances.
24. Short Circuiting : Due to fault in the appliances or damage in the
insulation of two wires, the circuit will offer zero or negligible resistance
to the flow of current. Due to low resistance, large amount of current
will flow.
According to Joule’s law of heating effect (HI2) heat is produced in
live wire and produces spark, damaging the device and wiring.
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25. Overloading : Overloading can be caused by (1) Connecting too many
appliances to a single socket or (2) accidental rise in supply voltage if
the total current drawn by the appliances at a particular time exceeds
the bearing capacity of that wire, it will get heated up. This is known
as overloading.
Fuse a safety device can prevent the circuit from overloading and short
circuiting.
Question Bank
Very Short Answers
(1 Mark)
1. What is the frequency of AC used in India?
2. Name the point where the iron filling are collected more?
3. Who discovered electro magnetic induction?
4. Why does a compass needle get deflected when brought near the bar
magnet?
5. If both the coil and the magnet are stationary, will there be deflection
in galvanometer?
6. Why magnetic field lines do not intersect each other?
7. What is the advantage of Alternate Current over Direct current?
8. What do you understand by short circuiting?
9. When the force experienced by a current carrying conductor placed in
a magnetic field is maximum?
10. Write the factors affecting the magnetic field due to a straight conductor?
Short Answers
(2 Marks)
1. A charged particles enters at right angles into a uniform magnetic field.
What is the nature of charge particle, if it experiences a force in a
direction pointing vertically out of the page.
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Magnetic field
Charge particle
(use left hand flemings rule)
2. Name the Rule–
(a)
Force experience by a current - carrying conductor placed in a
magnetic field.
(b) Direction of magnetic field lines associated with a current
carrying conductor.
(c) Direction of induced current in a coil due to its rotation in
magnetic field.
3. What is solenoid? Where the magnetic field is uniform in solenoid?
4. Draw the pattern of magnetic field lines due to current carrying straight
conductor?
5. Name two safety measures commonly used in electric circuit and
appliances?
6. What is overloading?
7. What is an earth wire? How it works in our domestic circuit?
8. If the current in a wire is flowing in the vertically downwards direction
and a magnetic field is applied from west to east. What is the direction
of force on the wire?
Long Answer
(5 Marks)
1. Explain the phenomenon of Electro magnetic Induction with the help
of an activity. Write its one application.
2. Draw the schematic diagram of domestic circuit. Write the colour and
function of Neutral wire, Live wire and Earth wire.
3. What is an electro magnet? Which material is used for making core of
an electromagnet? Can we use steel as a material for core of the
electromagnet?
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CHAPTER – 14
SOURCES OF ENERGY
Energy comes in different forms and one form can be converted to
another. For example if we drop a plate from a height, the potential
energy of the plate is converted mostly to sound energy when it hits the
ground.
If we light a candle, the process is highly exothermic so that the chemical
energy of the wax is converted into heat energy and light energy on
burning.
A Good Source of Energy would be one
which has high calorific value
be easily accessible
be easy to store and transport
be economical
SOURCES OF ENERGY
Conventional Source of Energy
Non-Conventional Source of Energy
Fossil Fuels
Eg. Coal & Petroleum
Thermal Power Plant
Hydro Power Plants
Bio-Mass bio gas plant
Wind Energy
Solar Energy
Eg. Solar Cooker, Solar Cell
Panel
Energy From the Sea
Eg. Tidal & wave energy, O.T.
Energy
Geothermal Energy
Nuclear Energy.
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Amount the sources of energy, some of them get exhausted (NonRenewable) While some of them do not get exhausted, therefore called
as Renewable source of energy. Examples
1.
Non Renewable source of energy Coal, Petroleum, Natural
Gas
2.
Renewable Source of energy Air, Water, Solar radiation,
Geothermal Energy, ocean waves etc.
Conventional Source of Energy
1. Fossil Fuels : Fuels developed from the fossils. Eg. Coal & Petroleum.
Formed over million of years ago have only limited reserves
These are non-renewable source of energy
India has about 6% share in the world reserved coal, that may
last 250 years more at the present rate of consumption.
Disadvantages of Burning Fossil Fuels
released oxides of Carbon, Nitrogen, Sulphur (acidic in nature)
cause Air pollution & Acid rain & green-house effect.
Dynamo
Pressure
Cooker
Heat
(Fossil Fuel)
Bulb
Tennis Ball
fitted with metal plate
A Model of Thermo Electric Production.
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The Tennis ball having three slits filled with semicircular (plaster
or Metallic) tins is our Turbine for generating electricity. Actually
the steam/produced impart energy to rotor of turbine which can
move shaft of the generator to produce electricity. A very large
amount of fossil fuels are burnt in Thermal Power Plant to heat
up water to produce steam.
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Hydropower Plants Convert the Potential energy of falling water
into Electricity since there are few water-falls which could be
used a source of potential energy, hence this is the reason, a
large number of DAMS are built all over the world.
Around 25% of our country’s energy requirement is met by
Hydro Power Plants
Dams are constructed to :
Prevent flooding of river, provide water for irrigation & to generate
hydroelectricity.
Disadvantages of construction of Big Dams
1. Submerging/Loss of large variety of Flora fauna and human settlements
& roting of submerged vegetation release green house gas (CH4).
2. They pose dangers of earthquakes, landslides etc.
3. Biomass is Agricultural & animal wastes that can be used as a fuel. Eg.
of Biomass – Firewood, cattle dung, sewage, dry leaves, stems &
bagasse.
Normally biomass has low calorific value & produce lot of
smoke when they are burnt. Their efficiency as a good fuel has
been increased tremendously with the application of technology.
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For Eg. cowdung becomes efficient & cheap good fuel in a Biogas plant.
Charcoal is better fuel than wood because it do not contain
water & other volatile material which are present in wood.
Wood
Limited
Supply of O2
Charcoal
Charcoal burns without smoke, flames & has high calorific value.
Bio-gas is an excellent fuel & contains 75% of Methane (CH4).
It burns without smoke, leaves no residues like ash, with high
heat capacity.
Biogas is produced by anerobic decomposition of the slurry
(cowdung + water mixture) by microbes. This process is applied
in a Bio gas plant.
Gas Outlet
SLURRY
Manure
Digestel
The Biogas is stored in the gas tank from which they are drawn
through pipes for use in a Bio-gas plant
Bio gas is used for lighting, cooking in the rural areas. While
the slurry left behind is used as excellent manure, rich in nitrogen
and phosphorous
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The large scale use of Bio-wastes & sewage material provide a
safe and efficient method of waste-disposal besides supplying
energy and manure.
WIND ENERGY
Unequal heating of the landmass and water bodies by solar radiation
generates air movement & causes winds to blow. This kinetic energy
of the wind can be used to do work.
This energy is utilised to lift water from the well & to generate electricity
in the wind mill.
Actually the rotatory motion of the windmill is used to turn the rotor of
the turbine which then generate electricity through Dynamo.
The output of a single windmill is quite small so a number of windmills
are erected over a large area - called wind energy farm.
India Ranked Fifth in the world in harnessing wind energy for the
production of electricity. It is estimated that nearly 45,000 MW of electric
power can be generated if India’s wind potential is fully exploited.
The minimum wind speed for wind mill to serve as a source of
energy is 20KMPH.
Advantages of Wind Energy
1. Eco friendly
2. Efficient source of renewable energy.
3. No recurring expenses for production of electricity
Limitations of Wind Energy
1. Wind energy farms need large area of land
2. Difficulty in getting regular wind speed of 15-20 KmPH.
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3. Initial cost of establishing wind energy farm is very high.
4. High level of maintenance of blades of wind mill.
Non Conventional Sources of Energy
Solar Energy
The energy emitted by the sun in form of heat and light is called solar
energy.
Solar Constant = 1.4kJ/s m2
Outer edge of the earth receives solar energy equal to 1.4 kJ/sm2 which
is known as solar constant.
Solar Energy Devices
A large number of devices that utilize solar energy directly like :
(i) Solar Cooker
(ii) Solar furnaces
(iii) Solar cells
(iv) Solar water heaters
Solar Heating Devices
Use black painted surface because black surface absorbs more heat as
compared to white or other surface.
Use of glass plate because it allows shorter wave lengths infrared
radiations to pass through it but doesn’t allow the infrared radiations to
pass through it, causing more green House effect that results in increase
in temperature.
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Solar Cooker
Box type solar Cooker
It consists of a rectangular box which is made up of material such as
plastic or wood.
Box is covered with black sheet and its inner walls are painted black
to increase heat absorption.
Solar cookers are covered with glass plate and have mirrors to focus
the rays of the sun and achieve a higher temperature.
PLANE MIRROR
INNER METALLIC
BOX
GLASS COVER
BLACK CONTAINER
WOODEN BOX
SOLAR COOKER (Box Type)
Advantages
1. Use energy which is available in plenty (Solar Energy)
2. Is pollution free.
3. More than one food can be cooked simultaneously
Disadvantages
1. Cannot be used for frying or baking purpose.
2. Food cannot be cooked at night or on a cloudy day.
3. Direction of reflector of solar heating has to be changed from time to
time to keep it facing the sun
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Solar Cells
Solar cells are device that convert Solar energy into electricity.
Develops a voltage of 0.5 – IV and can produce about 0.7W of electricity.
Advantages of Solar Cell
1. Require a little maintenance
2. Have no moving part.
3. No focussing device is required
4. Can be set up in remote areas.
5. Environment - friendly i.e. do not cause pollution.
Disadvantage of Solar Cells
1. It require high cost
2. Efficiency is low
3. Initial cost of installation is quite high.
Uses of Solar Cell
1. Used in calculators, watches etc.
2. Used in artificial satellites and space probes.
3. It is used in radio or wireless transmission system.
Solar Panel
A large number of Solar Cells connected to each other in an arrangement
is called solar panel.
Material used for Making Solar Cells
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Silicon
Silver is used for inter connection of cells.
ENERGY FROM THE SEA OR OCEAN
The energy from the sea is available in the following forms.
(i) Energy of sea waves
(ii) Tidal energy
(iii) Ocean Thermal Energy.
(i) Energy of Sea Waves
The waves are generated by the strong winds that blows across the sea.
The kinetic energy of this moving water rotates the turbine of a generator
Limitation
When strong winds stop blowing, the generator stops producing electricity
(ii) Tidal Energy
The tidal energy possessed by water during tides.
The tides are caused due to gravitational force of attraction exerted by
the moon on the water of the ocean.
This form of energy is harnessed by constructing a dam across a narrow
opening to the sea.
A turbine fixed at the opening of the dam converts tidal energy to
electricity.
(iii) Ocean Thermal Energy
The power plants used to harness the ocean thermal energy is known as
“Ocean Thermal Energy Conversion plant) (OTEC)
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Temperature difference between surface water and water at the depth
of 2km should be 20°C or more.
The warm surface water is used to boil ammonia (liquid)
The vapours of the liquid are used to run the turbine of generator.
The cold water (from deeper layers) is pumped up to condense the
vapour into liquid.
Geothermal Energy
1. Energy stored as heat inside the earth
2. The steam of underground water is taken out by sinking pipes through
holes drilled in the earth’s crust. The steam under high pressure is used
to rotate the turbines of the generator to produce electricity.
NUCLEAR ENERGY
Nuclear energy is the energy which is stored in the nucleus of an atom.
Nuclear energy is of two types
(i) Nuclear fission nucleus of a heavy atom (Uranium) when
bombarded with low energy neutron split (break down) into
lighter nuclei and huge amount of energy is released
(ii) Nuclear Fusion When two lighter nucleic join up to form
heavy nucleus and tremendous amount of energy is released.
Nuclear fission process is utilized in nuclear reactors to produce
electricity.
Major Nuclear power plants : Tarapur, Rana Pratap Sagar, Kalpakkam.
Advantages of Nuclear Energy
1. Large amount of energy is released.
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2. In nuclear power plant, the nuclear fuel is inserted once to get energy
over a long period of time.
Disadvantages of Nuclear Energy
1. High cost of installation.
2. Environmental contamination may occur due to improper nuclear waste
disposal.
ENVIRONMENTAL CONSEQUENCES
1. Energy sources should be used judiciously otherwise it would disturb
the environment.
2. Use of clean fuels like CNG (compressed natural gas) because burning
of fossil fuel causes green house effect.
3. Assembly of devices like solar cell (otherwise renewable source of
energy) would have caused environmental damage.
How long will energy source last
The sources of energy can be divided into two categories :
(i) Renewable sources of energy eg wind, sun, biogas
(ii) Non renewable sources of energy eg. Coal, Petroleum, Natural Gas.
Continuous use of non renewable source of energy is a matter of concern
because ultimately the deposit of these sources will be completely finished on
the other hand renewable sources of energy will last forever eg sun as a source
of energy will be available for a very long period of time.
Question Bank
Very Short Answers
(1 Mark)
1. What is a good source of energy.
2. Expand CNG and LPG
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3. What is the minimum wind velocity required to obtain useful energy
with a wind mill?
4. Name the main constituent of biogas.
5. Give two examples of fossil fuels
6. Name the device which directly converts solar energy into electric
energy.
7. What does “OTEC” stand for?
8. What is nuclear energy?
9. Which one out of these is renewable source of energy solar energy,
coal, petroleum, bio gas.
10. Which source of energy would you use to heat your food and why?
11. What are ‘‘Hot Spots’’?
Short Answers
(2 or 3Marks)
1. State two disadvantages of using fossil fuels as a source of energy.
2. Write two disadvantages of constructing high rising dams.
3. Give (i) two limitations and (ii) two advantages of wind mill.
4. Name any three forms of energy of the oceans which can be converted
into usable energy forms. Describes how it is done in each case.
5. Explain the working of biogas plant with the help of labelled diagram
6. Explain the principle on which the solar cooker works.
7. Write the advantages and disadvantages of using a solar cooker.
8. How does hydro electric power plant operate? Draw diagram
9. How is Charcoal produced? Why is it a better fuel then wood?
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Long Answer Type Questions
1.
(5 Marks)
(a) Why is the solar cooker box covered with plane glass plate?
(b) Why is nuclear fission reaction considered better.
(c) Use of wood as a domestic fuel is not considered as good. State
two reasons for it
2. Distinguish between renewable and non renewable sources of energy?
Which one of them you consider as better? Why?
3. Describe the construction and working of a biogas plant (fixed door).
Write any two uses of Biogas. Also, any two advantages of Bio-gas.
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CHAPTER – 15
OUR ENVIRONMENT
Environment means everything which surrounds us. It may include
living (biotic) and non-living (abiotic) components. So, it may includes
besides all creatures, water & air also.
Environment affect the life and development of an organism in its
natural habitat & vice a versa.
Substances that can be decomposed by the action of micro-organised
like bacteria are called bio-degredable. Eg. organic wastes, while some
substances like plastics, some chemicals (DDTs & fertilizers) are inert
and can’t be decomposed, are called Non-biodegradable.
Example of biodegradable wastes : cattle dung, cotton, jute, paper, fruit
and vegetable peels, leaves etc.
Examples of non-biodegradable wastes : plastics, polythene bags,
synthetic fibres, metals, radioactive wastes.
Actually non-biodegradable persist in the environment for a long time
or may harm the various members of the eco system.
ECO SYSTEM & ITS COMPONENT
All the interacting organisms in an area together with non living
components form an ecosystem. So an ecosystem consists of both biotic
(living creatures) and abiotic components like temperature, rainfall,
wind, soil etc.
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Ecosystem
Man-made Ecosystem
Eg. Crop-field, Aquarium etc.
Natural Ecosystem
Aquatic Ecosystem
Marine
Ecosystem
Eg. Sea, Oceans
Fresh water
Ecosystem
River, Lake,
Pond, pool
Terrestrial Ecosystem
land Ecosystem
Eg. Forest,
Desert, Grassland etc.
All living organisms are classified on the basis of the manner in which
they survive in the Ecosystem. These groups include
I Producers : All green plants, blue green algae can produce
their food (Sugar & starch) from inorganic substance using light
energy (Photosynthesis).
II Consumers : Include organisms which depend on the producers
either directly or indirectly for their sustenance. In other word
consumers consume the food produced by producers.
CONSUMERS
Herbivores
– Grass eaters
Carnivores
Flesh Eaters
Eg. Cow, dear
Lion, Tiger
Parasite
Live & feed
on the host body
Plasmodium
Omnivores
Feed on both plant
and flesh.
Eg. Crow
III Decomposers : Fungi & Bacterias which break down
(decompose) the dead plant, animals complex compounds into
the simpler one. Thus decomposers help in the replenishment of
the natural resources.
Food chain refers to an arrangement of different biotic groups
in a sequence of energy transfer. These biotic groups are producer
herbivores and carnivores.
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For Eg.
T1
Grass
T2
DearA
T3
Lion
A 3-setp Food chain
In a food chain, these biotic components where transfer of energy takes
place is called a trophic level.
The green plants capture 1% of sunlight falls on their leaves.
The flow of energy is unidirectional in a food chain.
There is gradual decrease in the amount of energy transfer from one
trophic level to next trophic level in a food chain.
Tertiary
consumers
1kJ
10kJ
100kJ
1000 kJ
Energy
Secondary
Consumer
Primary
Consumer
Producer
Energy Flow
TROPHIC LEVEL
So only 10% of Energy is transferred to next trophic level while 90%
of energy is used by present trophic level in its life processes.
While the conc. of harmful chemical increases with every next trophic
level in a food chain. It is called Bio-magnification For e.g.
Grass
(10 ppm)
DDT
Dear
(200 ppm)
DDT
Lion
(5000ppm)
DDT
Maximum concentration of such chemicals accumulated in human
bodies.
Naturally the food chains are inter-connected with each other forming
a web like pattern, which is known as FOOD WEB.
The loss of energy at each step (trophic level) is very high, so very little
amount of energy remains after four trophic levels.
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There are generally a big population at lower trophic levels of an
ecosystem. For Eg. the population of the producer is higher than the
consumer carnivore (lion) population.
ENVIRONMENTAL PROBLEMS
Changes in environment affect us and our activities change the
environment around us. This led to the slow degradation of environment
that arose many environmental problems. Eg. depletion of the Ozone
Layer and waste disposal.
I. Depletion of Ozone Layer
Ozone (O3) layer is largely found in the stratosphere which is a part of
our atmosphere from 12 km – 50km above sea level.
Ozone is a deadly poison at the ground level.
Ozone is formed as a result of a following photochemical reaction.
O2
hv
(1800°A to 2000°A)
O2 + O
O+O
(Splitting of
molecular oxygen)
O3 (Ozone)
Ozone layer is a protective blanket around earth which absorbs most of
the harmful U.V. (Ultraviolet) radiation of the Sun, thus protecting the
living beings of the earth from health hazards like skin cancer, cataract
in eyes, weaken immune system, destruction of plants etc.
The decline of Ozone layer thickness in Antartica was first observed in
1985 and was termed as OZONE HOLE.
Reason of Ozone Depletion
Excessive use of CFCs (Chloro Flouro Carbon) a synthetic, inert chemical
Eg. Freon which are used as refrigerants and in fire extinguishers, caused
Ozone depletion in the upper atmosphere. A single chlorine atom can destroys
1,00,000 Ozone molecules. U.N.E.P. (United Nation Environment Programme)
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did an excellent job in forging an agreement to freeze CFC production at 1986
levels (KYOTO Protocol) by all countries.
Garbage Disposal
Industrialization and rise in demand of consumer goods have created a
major problem in the form of wastes/garbage accumulation and its disposal
especially in urban area.
The different methods of solid wastes disposal commonly used around
the world are.
1. Open dumping : A conventional method in which solid wastes dumped
in selected areas of a town. It actually cause pollution
2. Land fillings : Wastes are dumped in low living area and are compacted
by rolling with bulldozers
3. Composting : Organic wastes are filled into a compost pit (2m × 1m
× 1m). It is then covered with a thin layer of soil. After about three
months the same garbage filled inside the pit changes into organic manure.
4. Recycling : The solid wastes is broken down into its constituent simpler
materials. These materials are then used to make new items. Even nonbio degradable solid wastes like plastic, metal can be recycled.
5 Reuse : A very simple conventional technique of using an item again
& again. For Eg. paper can be reused for making envelops etc.
EXERCISE
(Question Bank)
Very Short Answers
(1 Mark)
1. Define Biomagnification
2. Expand the term CFC & U.N.E.P.
3. Define Ozone hole
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4. Which of the following is/are Biodegradable plastic cups, cowdung,
Aluminium foil, cotton.
5. Define food web
6. Define Ecosystem
7. Which bag would you prefer for shopping and why?
(i) Jute bag
(ii) Polythene bag
8. Why is ozone layer very important for the existence of life on earth?
Short Answer
(2 Marks)
1. Differentiate between Biodegradable and non biodegradable wastes.
Give two examples.
2. Use of Kulhads was not environment friendly idea. Why?
3. Draw an Energy Pyramid showing different trophic level.
4. What is the advantage of disposable paper cup use over plastic cups?
5. How can we help in reducing the problem of waste disposal? Give any
two methods.
6. What is role of decomposer in Ecosystem.
7. Give any two ways in which non biodegradable substance would affect
the environment.
8. What are trophic levels? Give an example of a food chain and state the
different trophic levels in it.
9. What will happen if we kill all the organisms in one trophic level?
10. Study the food chain given below.
(i) Grass Grasshopper Frog
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(ii) Wheat Rat Snake Hawk
Which of the two consumers frog/hawk will get more available energy
and why?
Short Answer
(3 Marks)
1. State various modes of waste disposal.
2. Explain how harmful chemicals enter our body.
3. Why concentration of harmful chemicals increases whereas energy level
decreases, from lower to higher tropic level in a food chain?
Long Answer
1.
(5 Marks)
(i) What is ozone? How it is formed.
(ii) State the significance of ozone layer.
(iii) Give reason for depletion of ozone layer.
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CHAPTER – 16
MANAGEMENT OF NATURAL RESOURCES
Natural Resources
Resources provided to us by nature
Soil, air, water, forests
wildlife, coal and petroleum are used by man for his survival.
Management of natural resources is needed for conservation of natural
resources.
There are national and international laws and Acts to protect the
environment.
Ganga Action Plan : Multi Crore Project came in 1985 to improve the
quality of Ganga
Accordingly a survey was conducted and a data was collected of total
coliform (a group of bacteria found in human intestine) between 19931994 which was as below.
1993-94 Total Coliform (MPN/100ml)
Minimum found
in Rishikesh
600-650MPN/100ml
Minimum desired level
450MPN/100ml
Maximum found in Kannauj
1400MPN/100ml
MPN Most probable number.
National Award for wildlife conservation – in the memory of Amrita
Devi Bishnoi who lost her life in the protection of Khejri trees in
Rajasthan alongwith 363 other people.
Chipko Andolan : Movement originated in Garhwal in early 1970s
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that was the result of a grassroot level effort to end the alienation of
people from their forest.
Protection of Sal forest in West Bengal in 1972.
Three R’s to save the environment.
Reduce
means use less
Save the resource
by not wasting them
Recycle
Segregate the waste that
can be recycled and use to make
required things.
Reuse
use the things again
and gain.
Reuse is better than recycling as it saves energy.
Management of Natural Resources is necessary so that these may last
for the generations to come and are not exploited for short term gains.
Also see the damage they cause to the environment when they are used
or mixed.
Forest and wild life conservation – Forests are biodiversity hot spots
Biodiversity of an area is the number of species of different life forms
like bacteria, fungi, flowering plants, insects, birds etc.
Hotspot means an area full of biological diversity.
– loss of diversity may lead to a loss of ecological stability/ecological
imbalance
STAKE HOLDERS
A person having interest or concern for some thing is called as stake holder.
Stakeholders : their dependence on forests
Local People
(dependent on
forests for their
survival)
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Forest Department
(Govt. who owns
the land and controls
resources
Industrialists
(Who use various
forest products)
Wild life
enthusiasts
(who want to
conserve nature)
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Sustainable Management
Management of forest resources wisely to make it available for future
generations.
Water as a Resource
Water is a basic necessity for all terrestrial forms of life.
Regions of water scarcity are closely correlated to the regions of acute
poverty.
Failure to sustain water availability has resulted in loss of vegetation
cover, diversion for high water demanding crops and pollution from
industries and urban wastes and less rain.
Irrigation methods like dams, tanks and canals have been used in various
part of India.
Dams
Advantages of Dams – Ensures adequate water for irrigation.
Generate electricity.
Continuous supply of water in regions.
Disadvantages
No equitable distribution of water.
Large no. of people displaced without compensation.
Involves huge amount of Public money without giving proper benefits.
Causes deforestation and loss of biological diversity.
Water Harvesting : Aim is to develop primary resources of land and
water and to produce secondary resources of plants and animals for use
in a manner which will not cause ecological imbalance.
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Various ancient methods of water harvesting
Method
State
Khadin, tanks, nadis
Rajasthan
Bandharas, tals
Maharashtra
Bundhis
Madhya Pradesh and U.P.
Pynes, ahars
Bihar
Kulhs
Himachal Pradesh
Ponds
Jammu Region
Eris (tanks)
Tamilnadu
Bawlis – old method of water harvesting in Delhi and near by region.
These techniques are local, specific to ensure the mismanagement and
over-exploitation of these resources
Advantages of Khadin System :
–
Water does not evaporate
–
Recharge wells and moisture for vegetation.
–
does not provide breeding ground for mosquitoes.
–
Ground water is protected from human and animal waste.
Coal and Petroleum
Generally called fossil fuel.
Formed from the disintegration of bio-mass millions of years ago.
They will get exhausted in the future no matter how carefully we use
them.
Petroleum will last us for about 40 years and the coal resources will
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last for another two hundred years.
These contain hydrogen, nitrogen and sulphur.
Why to use fossil fuels judiciously?
–
By using public transport instead of private one, by using C.F.L.
tubes, by using stairs instead of lift, by saving electricity as
much as possible.
Question Bank
Very Short Answers
(1 Mark)
1. Why is it necessary to conserve our environment?
2. Define sustainable development
3. Name any two exhaustible resources
4. What is the most conductive PH range for the life of fresh water
plants?
5. List two advantages of water harvesting.
6. Why reuse is better than recycle?
7. What are Dhadin? Where there found?
8. List two steps you would take to conserve electricity in your house.
9. Who are called stake holders?
10. Name some traditional water harvesting systems in India.
Short Answers
(2 Marks)
1. How mining is a cause of pollution?
2. Make a list of four forests products that we use.
3. How burning of fossil fuels is effecting our environment?
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4. Suggest two measures for controlling CO2 levels in atmosphere.
5. Why should we conserve forest and wild life?
Short Answers
(3 Marks)
1. What are three main problems from dams?
2. How can you reduce energy consumption at your level. Suggest at least
three points.
3. Explain the maximum of ‘Reduce’, ‘Recycle’ and ‘Reuse’ in your own
words.
Long Answers
(5 Marks)
1. What is the main objective of water harvesting techniques? Name &
ancient water harvesting structures used in India. Mention 3 causes for
failure to sustain water availability under ground?
2. Discuss the damage caused to forest by the following activities:
(a) Building rest houses for 10% tourists in national parks.
(b) Grazing domestic animals on National Parks.
(c) Tourists throwing plastic bottles, covers and other litter in
National Parks.
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