Class X Science Support Material

1 [X – Science]
twinklegraphics*laxmiprinter*supporting material*Science-Xth Class*1st proof
SUPPORT MATERIAL
CLASS - X
Venue :
G.S.K.V. Nangloi, Delhi-110041
Published by :
Directorate of Education Govt. of NCT of Delhi
SCIENCE
2013 - 2014

[X – Science] 2
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

3 [X – Science]
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

[X – Science] 4
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

5 [X – Science]
e.g.
(i) CaO(s) + H2O(l)
 Ca(OH)2 (aq)
Calcium Water Calcium hydroxide
oxide (slaked lime)
Quick lime
– 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)
 CaCO3(s)+ H2O (l)
Calcium Calcium
hydroxide 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

[X – Science] 6
– Silver bromide behaves similarly
2Ag Br 
Sunlight
2Ag(s) + Br2(g)
– The above two reactions are used in black and white photography.

7 [X – Science]
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 (aq)
Sulphate 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 Zinc
Sulphate Sulphate
Pb(s) + CuCl2
 PbCl2 + Cu(s)
(aq) (aq)
Copper Lead
Chloride Chloride
– Zinc and lead are more reactive elements than copper. They displace
copper from its compounds.

[X – Science] 8
IV Double Displacement Reaction : The reaction in which two different
atoms or group of atoms are mutually exchanged
eg. Na2 SO4 + BaCl2
 BaSO4(s) + 2NaCl
(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 + 2KI  PbI2 +2KNO3
(aq) (aq) (aq)
Lead Nitrate Potassium Lead Potassium
Iodide Iodide Nitrate
V Oxidation : Oxidation is the gain of oxygen or loss of hydrogen
eg. 2Cu + O2 Heat 2CuO
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
CuO + H2 Heat Cu + H2O
VI Reduction : Reduction is the loss of oxygen or gain of hydrogen.
– Redox Reaction : The reaction in which one reactant gets
oxidised while other gets reduced

9 [X – Science]
eg. ZnO + C  Zn + CO
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?

[X – Science] 10
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 + O2
 Na2O
(s) (g) (s)
(ii) CuO + H2
 Cu + H2 O(l)
(s) (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.

11 [X – Science]
(ii) Give another example of this type of chemical reaction with
equation.
7. Compound ‘X’ decomposes to form compound ‘Y’ and CO2 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) Heat Magnesium hydroxide(l)+
hydrogen(g)
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.

[X – Science] 12
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.

13 [X – Science]
CHAPTER – 2
ACIDS, BASES AND SALTS

Acids Bases
– Sour in taste – 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.

[X – Science] 14
 Olfactory indicators – Show odour changes in acidic or basic media.
eg. onion and clove.
 Acid – Base Indicators
S. No. Name of the Colour Change Colour Change
Indicator 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)
2HCl + Zn  ZnCl2 + H2
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.

15 [X – Science]
 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.

[X – Science] 16
 Reactions of metal oxides with acids
Metal Oxide + Acid  Salt + Water
CuO + HCl  CuCl2 + H2O
Copperoxide Hydrochloric Copper + Water
acid chloride
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+

17 [X – Science]
– Bases provide (OH–) ions in the presence of water
NaOH(s)
2H O
Na+
(aq) + OH–
(aq)
KOH(s)
2H O
K+
(aq) + OH–
(aq)
Mg(OH)2(s)
2H O
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.

[X – Science] 18
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 Colour of the Nature of H+ion OH –i on
No. Value pH Paper Solution Conc. Conc.
1. 0 Dark red Highly acidic very high very low
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 very high
– 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
 More about Salts
Salts and their derivation

19 [X – Science]
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.

[X – Science] 20
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)

21 [X – Science]
 Calcium oxy chloride – CaOCl
Common Name : Bleaching Power
Preparation  Ca(OH)2 + Cl2
 CaOCl2 + H2O
calcium hydroxide chlorine bleaching water
power
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 Carbon Ammonia Sodium hydrogen
chloride dioxide 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

[X – Science] 22
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
2
H2O
 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
CaSO4.
1
2
H2O is plaster of paris.
373 K
4 2 4 2
1
CaSO .2H O CaSO H O
2

– When Plaster of Paris is mixed with water it changes to gypsum.

23 [X – Science]
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 test-
tube 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
2. Complete the reaction CaCO3 + H2O 2CO
 name the products
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?

[X – Science] 24
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.

25 [X – Science]
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 (5 marks)
1. (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
 _______ + _______ + _______.
d) NaOH 2H O _______ + _______
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.

[X – Science] 26
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 non-
metals
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.

27 [X – Science]
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 non-
metals 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

[X – Science] 28
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.

29 [X – Science]
Fe + 2HCl  FeCl2 + H2
Mg + 2HCl  MgCl2 + H2
Zn + 2HCl  ZnCl2 + H2
2Al + 6HCl  2AlCl3 + 3H2
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 Salt
Metal A + solution  solution + Metal B
of 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.

[X – Science] 30
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  Mg2+ + 2e–
2,8,2 2,8 (Magnesium ion)
Cl2 + 2e–  2Cl–
2,8,7 2,8,8 (Chloride ion)
Properties of Ionic Compounds :
– Are solid and mostly brittle.

31 [X – Science]
– 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. 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.
II. Extracting Metals from the Enriched Ore

[X – Science] 32
Extracting Metals Low in the Activity Series :
By heating the ores in air at high temperature.
*Mercury from cinnabar
2HgS + 3O2 Heat 2HgO + 2SO2
2HgO Heat 2Hg + O2
* Copper from copper sulphide
Cu2S + 3O2 Heat 2Cu2O _ 2SO2
2Cu2O + Cu2S Heat 6Cu + SO2
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)
2ZnS + 3O2 Heat 2ZnO + 2SO2
Metal ore heated strongly in limited or no supply of air (Calcination)
ZnCO3 Heat ZnO + CO2
Reduction of Metal Oxide :
1. USING COKE : Coke as a reducing agent.
ZnO + C Heat Zn + CO
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.
MnO2 + 4Al Heat 3Mn + 2Al2O3 + heat
Fe2O3 + 2Al Heat 2Fe + Al2O3 + heat

33 [X – Science]
– 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.

[X – Science] 34
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 non-
metals.
– 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.

35 [X – Science]
– 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.

[X – Science] 36
6. An aqueous solution of Al2O3 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.

37 [X – Science]
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.

[X – Science] 38
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.

39 [X – Science]
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 :

[X – Science] 40
– 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.

41 [X – Science]
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

[X – Science] 42
– 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

43 [X – Science]
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.

[X – Science] 44
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.

45 [X – Science]
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 Prefix
Alkene ene
Alkyne yne
Alcohol ol
Aldehyde al
Ketone 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.

[X – Science] 46
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).
4
2 2 7
Alkaline KMnO + heat
3 2 3Acidified K Cr O +heat
CH – CH OH CH COOH
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.
C H 4 + Cl2
 CH3Cl + HCl (sunlight required)
IMPORTANT CARBON COMPOUNDS : Ethanol and Ethanoic Acid
Ethanol

47 [X – Science]
*Consumption of dilute ethanol causes serious health issues and intake of
pure alcohol is lethal.
CHEMICAL PROPERTIES OF ETHANOL
Ethanoic Acid (CH3COOH) / Acetic Acid :
*5-8% solution of acetic acid in water is called vinegar.
*Pure acetic acid is called glacial acetic acid.
C2H5OH Reacts with Sodium
to form Sodium Ethoxide and
Hydrogen
When C2H5OH is heated with
concentrated Sulphuric Acid at 443
k, it is dehydrated to Ethene

[X – Science] 48
5 Sodium ethanoate
and water.
NaOH
12
3 4
5
Esterification
Carboxylic acids react with alcohols in presence of few drops of concentrated
sulphuric acid as catalyst and form sweet smelling compounds called ester.
2 4
conc.
2 5 3 3 2 5H HSO
ethanol of ester ethanoic acid ethyl ethanoate
C H OH CH COOH CH COOC H 
Hydrolysis
On heating with an acid or a base the ester forms back the original
alcohol and carboxylic acid.

49 [X – Science]
CH3COO CH2CH3 + NaOH  CH3COONa + CH3-CH2OH
CH3COO CH2CH3 2 4Dil.H SO
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.

[X – Science] 50
– 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?

51 [X – Science]
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.

[X – Science] 52
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.

53 [X – Science]
– 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.

[X – Science] 54
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.

55 [X – Science]
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.

[X – Science] 56
– 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.

57 [X – Science]
– 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 Reason Variation Reason
No. across period along group
1. Atomic size Decreases Due to increase Increases due to addition
in nuclear charge of new shells.
distance between
outer most electron
and nucleus increases
due to addition of
new shells.
2. Metallic Decreases due to increase Increases decrease in
Character in effective effective nuclear
nuclear charge, charge experienced
tendency to lose by valence electrons
valence electrons Tendency to lose
decreases. electrons (metallic
character) increases.
3. Non-Metallic Increases due to increase Decreases due to decrease in
Character in effective effective nuclear
(electro-negativity) nuclear charge change experienced
tendency to gain by valence election
electrons increases (due to addition of
new shell), tendency
to gain electrons
decreases

[X – Science] 58
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.

59 [X – Science]
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 Li Rb Cs K
186 152 246 262 231
(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 – A B C D
Electronic Configuration – 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.

[X – Science] 60
(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?

61 [X – Science]
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

[X – Science] 62
Kinds of nutrition in which inorganic
materials like CO2, water etc are utilized
to prepare organic food by the process of
photosynthesis
Eg. Green Plants
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. 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
2 2 6 12 6 2Chlorophyl
Glucose
6CO 6H O C H O 6O  
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)

63 [X – Science]
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.

[X – Science] 64
Example : (i) Amoeba. (ii) Paramoecium
FOOD PARTICLE
Take in (food vacuole formed)
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

65 [X – Science]
Salivary Glands  Secrete Saliva + Mucus.
 Starch

Salivary
amylase
[Saliva]
Sugar
Oesophagus  Taking food from mouth to stomach by
 Peristaltic movements
[contraction and expansion of muscles of the oesophagus]
Stomach  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

[X – Science] 66
Emulsification : The process of breakdown of large
fat globules into smaller fat globules by bile juice.
Large intestine  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

67 [X – Science]
Breakdown of Glucose by various pathways
Glucose
C H O6 12 6
(in muscles)
* Takes place in the presence of
oxygen
* Occurs in mitochondria
* End products are CO2 and H2O
* More amount of energy is
released (38 ATP)
* 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)

[X – Science] 68
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
2. Ribs lift up
3. Diaphragm become flat in shape
4. Volume of lungs increases and
air enters the lungs
1. Thoracic cavity contracts
2. Ribs move downwards
3. Diaphragm becomes dome
shaped
4. Volume of lungs decreases and
air exits from the lungs.

69 [X – Science]
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.

[X – Science] 70
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
Blood vessels
- Arteries & Veins
A circulatory medium
Blood & Lymph
Deoxygenated
Blood
(from body)
Vena
Cava
Right
Atrium
(Relaxed)
Right
Atrium
(contracts)
Right
Ventricle
(relaxed)
Body Parts
via AORTA
Right
ventricle
contracts
Lungs
Blood Circulation
in Human Heart
Left
Ventricle
(contracts)
Left
Ventricle
(relaxed)
Left
Atrium
(contracts)
Left
Atrium
(relaxed)
Oxygenated
blood
AORTA
Section view of the Human Heart

71 [X – Science]
Blood
(A fluid Connective Tissue)
Solid Component
Blood Corpuscles
Liquid Component
PLASMA
R.B.C.s Blood
Platelets
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
pulmonaryArtery
2. Also calleddistributingVessel
3. Thick andelastic
4. Valves absent
5. Deep seated
1. Carry deoxygenated blood
from body parts to heart
exceptpulmonaryvein.
2. Also calledcollectingVessel.
3. ThinandLess elastic.
4. Valves present to prevent
back flowofblood.
5. Superficial
TRANSPORTATION IN PLANTS
– There are two main conducting Pathways in a Plant

[X – Science] 72
Xylem Phloem
1. Carries water & minerals
from the roots to other part
ofthe plant
2. Noenergy is used.
1. C a r r i e s p r o d u c t o f
photosynthesis from leaves
tothe otherpartof theplant.
2. Energyis usedfromATP
Pathways
 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

73 [X – Science]
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
Oxygen, CO & H O2 2
Through stomata
(Transpiration)
–
– Other wastes may be stored in leaves, bark etc. which fall off from the
plant.

[X – Science] 74
– 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.

75 [X – Science]
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.

[X – Science] 76
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?

77 [X – Science]
Receptors : Are specialised tips of some nerve cells that detect the
information from the environment.
Receptors
are
Sense Organs
Photo receptors
Eyes
Thermoreceptors
(Skin)
Olfactory
Receptor
(Nose)
Gustatory
Receptor
(Tongue)
Hearing/
Balance of
the body
Visual
Stimulus
Pain
Touch
Heat
Smell
Detection
Taste
Detection
Neuron : It is the structural and functional unit of nervous system.
I II III
Neuron (3 main parts)
Dendrite Cell body
and Axon
Synapse
Information is
acquired
Information
travels as an
electrical impulse
Nucleus
Dendrite
Axon
Nerve
ending
Cellbody
Structure of neuron

[X – Science] 78
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.

79 [X – Science]
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

[X – Science] 80
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

81 [X – Science]
Decesion
made
[by CNS]
(Motor Nerves)
Message
Passed to
muscles
Muscles
[Change in shape
and arrangement
of proteins]
Contraction
[Muscle cell]
Muscle shorten
Action
Coordination 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)
Movement in Plants
Tropic movements
[directional movements
in response to stimulus]
Phototropism
Movement
towards light
Geotropism
Movement
towards gravity
Chemotropism
Movement
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.

[X – Science] 82
(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

83 [X – Science]
S.
No.
Hormone Endocrine
Gland
Location Functions
1. Thyroxine Thyroid Neck/ Regulation ofmetabolism
Throat of carbohydrates, fats
region andproteins.
2. Growth Pituitary Midbrain Regulates growth and
hormone (master development.
3. Adrenaline Adrenal Above Regulation (increasing)
both of bloodpressure, heart
kidneys heat, carbohydrate
metabolism(during
emergency)
5. Testosterone Testes Genital/ Changes associated
SEX in Males lower withpuberty
ormone abdomen (Sexual maturity)
estrogen Ovaries area
gland)
4. Insulin Pancreas Below Reduces and regulates
stomach blood sugarlevel
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.

[X – Science] 84
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.
Sugar level in the blood rises
Detected by cells of Pancreas
Synthesis insulin
Blood sugar level falls
Stop secreting more
insulin
(like a float in watertank)
SWITCHOFF
Feedbacksent
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?

85 [X – Science]
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?

[X – Science] 86
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

87 [X – Science]
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 Sexual Reproduction
1. Asingleparent is involved
2. Gametes notformed
3. Progeny is Identical to parent
eg. FissioninAmoeba
1. BothParents involved
2. Gametes are formed
3. Progeny is only genetically
similarto the parent.
 Asexual Reproduction is extremely useful as a mean of rapid
multiplication. It is common in lower plants and animals.

[X – Science] 88
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 Multiple Fission
The parent cell divides into two
equal halves (daughtercells)
E.g.Amoeba
The parent cell divides into many
daughtercellsimultaneously.
Eg. Plasmodium
nucleus lengthens
cytoplasm divides
nucleus
Daughter
Ameobae
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.

89 [X – Science]
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.

[X – Science] 90
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.

91 [X – Science]
 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 Unisexual Flowers
Both male and female
reproductive part i.e., stamen
& carpel are present.
Eg. Hibiscus, mustard
Either male or female
reproductive part is present.
Eg. Papaya,Watermelon
Stigma
(Carpet)
Stamen
Anther
A typical flower consists of four main whorls namely calyx (sepals),
Corolla (Petals), Androecium (Stamens) and Gynoecium (Carpels).

[X – Science] 92
Reproductive Part of Flower
STAMEN
(male part)
CARPEL
Filament Anther
(2n)
MEIOSIS
Pollen grain
(male gamet)
(n)
(female part)
Style StigmaOvary
(2n)
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.

93 [X – Science]
 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.

[X – Science] 94
 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.

95 [X – Science]
 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.
PHYSICAL
BARRIER
SURGICAL
METHOD
CHEMICAL
METHOD
To prevent union
of sperm & egg.
Use of condoms,
Diaphragm &
cervical caps.
Also called
sterilization in
the vas
deferens of male is
blocked to prevent
sperm transfer.
In the
fallopian tube of
female is blocked
to prevent egg to
reach uterus.
Vasectomy,
Tubectomy,
Oral
contraceptive
(OCs) -
changes the
hormonal
balance to
check the egg
release in
females. OCs
cause side
effect.
Methods of contraception
Intrauterine
contraceptive
device
or
is placed
in uterus to
prevent
pregnancy.
Copper-T
loop
IUCD
 Healthy society needs a balanced sex ratio that can be achieved by
educating the people to avoid malpractices like female foeticide & pre-
natal sex determination.
VIRAL STDs
Eg. H.I.V. - AIDS
Warts
Bacterial STDs
Eg. Syphilis &
Gonorrhoea
Sexually Transmitted Disease (STDs)

[X – Science] 96
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?

97 [X – Science]
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.

[X – Science] 98
(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.

99 [X – Science]
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
TRAIT
RECESSIVE
TRAIT
Flower colour
Flower position
Seed colour
Seed shape
Pod shape
Pod colour
Height of plant
Violet
Axial
Yellow
Round
Inflated
Green
Tall
White
Terminal
Green
Wrinkled
Constricted
Yellow
Dwarf/Short
Seven pairs of contrasting characters in Garden Pea.

[X – Science] 100
 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
ALLELIC PAIR
OF GENES
GAMETES
F GENERATION
(first filial generation)
1
SELF POLLINATION
of F gametes1
Tall plant  Dwarf plant
TT
T t
tt
Tt All tall plants
GAMETES
Tt Tt
F GENERATION2
Phenotypic ratio
Genotypic ratio
3:1
1:2:1
T t
tT tT
T t
TT
tall
Tt
tall
tt
dwarf
Tt
tall
Gametes

101 [X – Science]
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