Chemical Reaction: Class 10 Science Notes

Chemical Reaction : Class 10 Science Notes

Chemical Reaction Class 10 Science Complete Notes. This note include all the excercise given in Chemical Reaction chapter of science book such as question answer, numericals, give reason, diagrammatic questions and define the following. This note is published for helping students to solve their problems.

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  Chapter - 8  
Chemical Reaction

2. Answer the following questions:

a. Define exothermic reaction? Give an example.

Ans: The reaction in which heat energy is released to the surrounding are called exothermic reaction. 
Eg: C + O₂ → CO₂ + heat

b. What are the conditions required for a chemical reaction? Explain any three with an example.

Ans: The condition required for a chemical reaction are as follows :

  • Surface Area
  • Catalysts
  • Pressure
  • Heat
  • Light


Some chemical reaction take place by the application of pressure for example; nitrogen reacts under with hydrogen under high pressure to give ammonia gas.
N₂ + 3H₂ → 2NH₃


Most of the reaction take place only when the reactants are heated with high temperature. For example, there is a fast reaction between Copper and Sulphuric acid on heating and So₂ , gas is produced. 
Cu + Conc. 2H₂So₄ → CuSO₄ + So₂ + 2H₂0


Some reactions require light. Light stimulates the reaction for chemical reaction. for example, hydrogen reacts violently with chlorine in the of Presence diffused sunlight to produce hydrogen chloride.
H₂ + cl₂ → 2HCL

c. Name the chemical reaction in which two substance exchange ions. 

Ans: The chemical reaction in which two substance exchange ions is given below:
Silver Nitrate + Sodium Chloride → Silver Chloride  + Sodium Nitrate
i.e AgNo₃ + NaCl → AgCl + NaNo₃

d. Explain the following types of chemical reactions with example an example. 

i. Additional Reaction
Ans: The reaction in which a single compound is formed by the direct combination of two or more reactants is known as additional reaction.
Example:  2Na + Cl₂ → 2NaCl

ii. Single Displacement Reaction
Ans: The reaction in which an atom in a molecule is replaced by another atom forming the end product is Called single displacement reaction. 
Example: Zn + H₂So₄ → ZnSo₄ + H₂

iii. Decomposition reactions 
Ans: Decomposition reaction is a type of reaction in which a single compound or substance is decomposed into two or more simple molecules in the form of product during a chemical reaction. 
Example: CaCo₃ → CaO + O₂

iv. Double displacement reaction
Ans: Double displacement reaction is that reaction in which two compound react together to form two other compound by mutual exchange of their ions. 
Exampl: AgNO₃ + NaCl → AgCl + NaNo₃

e. What is acid-base reaction with an example.

Ans: Acid-base reaction is a type of double displacement reaction of acid and base in which the characteristic properties of both of them are destroyed or neutralized to give salt and water.
Example: NaOH + HCl → NaCl + H₂O

f. How do combination and decomposition reaction differ from each other?

Ans: Combination and decomposition reaction are differ from each other because in combination reaction two or more reactants get combined and form a single compound during chemical reaction but in decomposition reaction a single compound or substance is decomposed into two or more simple molecules during the chemical reaction.

g. Write the characteristics of a catalyst.

Ans: The characteristics of a catalyst are as follows :
  • A catalyst remains unchanged in its mass and Chemical Composition in the chemical reaction
  • A small quantity of a catalyst is required.
  • A catalyst does not initiate the chemical reaction

h. Define the following terms:

 i. Endothermic reaction
The reaction in which heat is absorbed from the Surroundings are called endothermic reactions.

ii. Chemical reaction
Ans: Chemical reaction is a chemical change which takes place by addition, decomposition or displacement of the atoms or molecules of the matter into new substances 

i. Describe an experiment to demonstrate that the rate of chemical reaction increases with the increase of the surface area of the reactants.

Ans: Materials required:
Apparatus: Watch glasses, glass rod, beakers, grinders
Chemicals: Marble Pieces, Powder of marble or calcium carbonate, dilute hydrochloric acid

Methods :

  • Take two beakers and Pour some of dilute hydrochloric acid in each.
  • Weigh 10gm Marble Pieces and 10 gm marble Powder take them in separate watch glasses.
  • Add Marble pieces in beaker marked as A and Marble Powder in the beaker marked B.
  • Observe each beaker. In which beaker do air bubbles released out rapidly or efferverse.

The air bubbles released out more rapidly from mixture B which contains marble Powder and dilute hydrochloric acid than from the beaker A that contains marble Pieces.

j. Describe experiment to demonstrate that the rate of chemical change /reaction increases with the increase of temperature.

Ans: Materials required:
Apparatus: Beaker, tripod, wire gauze, spirit lamp or bunsen's burner, glass rod, match stick.

Chemicals: Potassium thiosulfate ( k₂S₂O₃) dilute Sulphuric acid (H₂So₄), Potassium permangan ate (kmNo₄), water, oxalic acid [ C₂H₂O₄  or ( CooH )₂  ]

Methods :

  •  Take 5 gm of oxalic acid crystals in two beakers each and mark A and B.
  •  Pour 15 ml dilute sulphuric acid and then 10 ml of potassium perimanganate solution one by one in each beaker.
  • Stir the mixture of each beaker with a glass rod and the mixture of solution in both the beakers appears Pink.
  • Heat the solution of beaker A with a Spirit lamp or Bunsen's burner box about 50⁰C to 70°C and leave the solution of beaker B for one hour without disturbance. 
  • Observe the change of color of the solution in each beaker. Does the Pink Colour of the solution of both beakers disappear at the same period of time?

The Pink Colour of the solution A is decolorized while heating but the solution of beaker B takes long time to get decolourize at ordinary temperature.

The rate of chemical reaction between oxalic acid, dilute sulphuric acid and Potassium Parmanganate solution is faster due to increase in temperature.

k. Write the balanced chemical equation of the reaction between Nitrogen and hydrogen to ammonia which is carried out by different necessary Conditions. Which type of chemical reaction is it? Define it.

Ans: Nitrogen + Hydrogen → Ammonia 
N₂ + H₂ → NH₃
N₂ + 3H₂ →  2NH₃ ( Balanced )
It is composition combination reaction because two substance react to form one product.

3. Differentiate Between:

a. Physical Change and Chemical Change

Ans: The differences between Physical Change and Chemical Change are as follows:

HTML Table Generator
Physical Change Chemical Change
Physical change is a temporary change Chemical change is a  permanent change 
 No new substance are formed One or more new substances are formed
 It affects only physical properties It affect both physical and chemical properties 
 Generally, they are reversible  They are generally non-reversible 

b. Exothermic reaction and Endothermic reaction.

Ans: The differences between Exothermic and Endothermic reactions are as follows:

HTML Table Generator
Endothermic Reaction Exothermic Reaction 
 The reaction in which heat are absorbed from the Surrounding is called endothermic reaction The reaction in which heat is released to the surroun ding is called exothermic reaction
 It has more energy It has less energy
 Product are less stable than reactants Products are more stable than reactants
 Example: Melting Ice, Cooking, photogothesis etc. Example: Rusting iron, nuclear fission etc. 

c. Positive Catalyst and Negative Catalyst

Ans: The differences between Positive catalyst and Negative Catalyst are as follows:

HTML Table Generator
Positive Catalyst  Negative Catalyst 
 Positive Catalyst increase the rate of chemical reaction  Negative catalyst decrease the rate of chemical reaction 
 It decrease the activation energy of reactant molecules  It increase the activation energy of the reactant molecules 
 It is also called the Promoter It is also called Inhibitor 

4. Give reasons

a. Glycerine is known as a negative catalyst.

Ans: Glycerine is known as a negative catalyst because it decrease the rate of chemical reaction.

b. Paper burns to ash is a chemical change.

Ans: Paper burns to ash is chemical change because, it is a permanent change and after the reaction new substance with different properties is formed. 

c. Acid base reaction is also called neutralization reaction. 

Ans: Acid base reaction is also called neutralization reaction because the properties of acid is cancelled by base and the properties of base is cancelled by acids and neutral substance is formed after the reaction.

d. Physical change is a temporary change.

Ans: Physical change is a temporary change because it last for certain period of time and it can be reversed.

5. Change the following word equations into balanced equation.

a. Hydrogen + chlorine → Hydrogen chloride
H₂ + Cl₂ →HCl
H₂ + Cl₂ →2HCl { Balanced }

b. Lead oxide + Carbon → Carbon monoxide + Lead
Pbo + C →CO + Pb
Pbo + C →CO + Pb { Balanced }

c. Hydrogen + Nitrogen →Ammonia
H₂ +N₂ →NH₃
3H₂ +N₂ →2NH₃ { Balanced }

d. Potassium chlorate → Potassium chloride + Oxygen 
KClO₃ → KCl + O₂
2KClO₃ → 2KCl + 3O₂ { Balanced }

e. Aluminium+ Chlorine → Aluminium chloride
Al + Cl₂ → AlCl₃
2Al + 3Cl₂ → 2AlCl₃ { Balanced }

f. Zinc+ Hydrochloric acid → Zinc chloride + Hydrogen
Zn + HCL → ZnCl₂ + H₂
Zn + 2HCL → ZnCl₂ + H₂ { Balanced }

g. Magnesium + Sulphuric acid → Magnesium sulphate + Hydrogen 
Mg + H₂SO₄ →MgSO₄  + H₂
Mg + H₂SO₄ →MgSO₄  + H₂ { Balanced }

h. Ammonium chloride + Sodium nitrite →  Sodium chloride + Water+Nitrogen 
NH₄ Cl + NaNO₂ → Nacl + H₂O + N₂ 
NH₄ Cl  + NaNO₂ → Nacl + 2H₂O + N₂ { Balanced }

i. Aluminium + Sulphuric acid → Aluminium sulphate + Hydrogen
Al₂ + HSO₄ →Al₂ (SO₄ )₃ + H₂
2Al₂ + 3HSO₄ →Al₂ (SO₄ )₃ + 3H₂ { Balanced }

 j. Lime water + Carbon dioxide → Calcium carbonate + Water
Ca(OH)₂ + Co₂ →CaCo₃ + H₂O
Ca(OH)₂ + Co₂ →CaCo₃ + H₂O { Balanced }

k. Sodium carbonate + Silica → Sodium silicate + Carbon dioxide
Na₂Co₃ + SiO₂ → Na₂SiO₃ + Co₂
Na₂Co₃ + SiO₂ → Na₂SiO₃ + Co₂ { Balanced }

l. Ammonia + Sulphuric acid → Ammonium sulphate
NH₃ + H₂SO₄  → ( NH₄ )₂ SO₄ 
2NH₃ + H₂SO₄  → ( NH₄ )₂ SO₄ { Balanced }

m. Iron + Oxygen → Iron oxide 
Fe + O₂ → Fe₂O₃
4Fe + 3O₂ → 2Fe₂O₃ { Balanced }

n. Aluminium + oxygen → Aluminium oxide
Al + O₂ →  Al₂O₃
4Al + 3O₂ → 2Al₂O₃ { Balanced }

o. Phosphorus + oxygen → Phosphorus pentoxide 
P + O₂  → P₂O₅
4P + 5O₂  → 2P₂O₅ { Balanced }

p. Water + Carbon dioxide → Glucose + Oxygen 
H₂O + Co₂ →  C₆H₁₂O + O₂
6H₂O + 6Co₂ →  C₆H₁₂O + 6O₂ { Balanced }

6. Fill in the gaps and balance the following equations. 

a. CuO₃   →   CuO + Co₂
b. CH₄ + 2O₂   →   Co₂ + H₂O
c. 6HCL + 2Al   →   2AlCl₃ + 3H₂
d. Mg(HCO₃)₂   →   MgCo₃ + H₂O + Co₃
e. 2Al + 3H₂SO₄  →   Al₂ (So₄)₃ + 3H₂  
f. HNO₃ + NH₄OH   →  NH₄NO₃ + H₂O
g. Ca(OH)₂ + Co₂    →  CaCo₃ + H₂O
h. 2KClO₃      →   2KCl + 3O₂
i. 2H₂O₂  →  2H₂O + O₂

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