Smart study notes of 10th chapter first

                     Class 10 Science

Chapter 1: Chemical Reactions and Equations – Notes & MCQ Test

📘 1. Chemical Reaction

A chemical reaction is a process in which one or more substances change into new substances with different properties.

Example:  Mg + O₂ → MgO

📘 2. Chemical Equation

A chemical equation is the symbolic representation of a chemical reaction.

Example: Zn + HCl → ZnCl₂ + H₂

📘 3. Balanced Chemical Equation

A balanced chemical equation has equal number of atoms of each element on both sides.

Example:  2Mg + O₂ → 2MgO

📘 4. Types of Chemical Reactions

1. Combination Reaction

Two or more substances combine to form one product.

Example:CaO + H₂O → Ca(OH)₂

2. Decomposition Reaction

A compound breaks down into simpler substances.

Example: CaCO₃ → CaO + CO₂

3. Displacement Reaction

A more reactive element displaces a less reactive element.

Example: Zn + CuSO₄ → ZnSO₄ + Cu

4. Double Displacement Reaction

Two compounds exchange ions.

Example: AgNO₃ + NaCl → AgCl + NaNO₃

📘 5. Oxidation and Reduction

Oxidation: Gain of oxygen or loss of hydrogen.

Reduction: Loss of oxygen or gain of hydrogen.

Example: CuO + H₂ → Cu + H₂O

📘 6. Corrosion

Corrosion is the slow damage of metals due to air and moisture.

Example: Rusting of iron

📘 7. Rancidity

Rancidity is the oxidation of fats and oils causing bad smell and taste in food.

Example: Spoiled butter or chips

             🧠 Revision MCQ              Test (20 Questions)

1. A chemical reaction is a process in which

A) Only colour changes

B) New substances are formed

C) Only heat is produced

D) Only gas is produced

2. Which represents a chemical reaction?

A) Chemical equation

B) Mathematical equation

C) Physical change

D) Temperature change

3. Balanced equation means

A) Same number of atoms on both sides

B) Same molecules

C) Same compounds

D) Same colour

4. Which is a combination reaction?

A) CaO + H₂O → Ca(OH)₂

B) Zn + CuSO₄ → ZnSO₄ + Cu

C) CaCO₃ → CaO + CO₂

D) None

5. Which is a decomposition reaction?

A) CaCO₃ → CaO + CO₂

B) CaO + H₂O → Ca(OH)₂

C) Zn + CuSO₄ → ZnSO₄ + Cu

D) None

6. Which is a displacement reaction?

A) Zn + CuSO₄ → ZnSO₄ + Cu

B) CaCO₃ → CaO + CO₂

C) CaO + H₂O → Ca(OH)₂

D) None

7. Which is a double displacement reaction?

A) AgNO₃ + NaCl → AgCl + NaNO₃

B) CaCO₃ → CaO + CO₂

C) Zn + CuSO₄ → ZnSO₄ + Cu

D) None

8. Rusting of iron is an example of

A) Corrosion

B) Rancidity

C) Reduction

D) Neutralisation

9. Rancidity occurs due to

A) Reduction

B) Oxidation of fats and oils

C) Heating

D) Freezing

10. Gain of oxygen is called

A) Oxidation

B) Reduction

C) Neutralisation

D) Decomposition

11. Loss of oxygen is called

A) Oxidation

B) Reduction

C) Combination

D) Displacement

12. Which gas is formed in reaction with acids and metals?

A) Oxygen

B) Hydrogen

C) Nitrogen

D) Carbon dioxide

13. Example of corrosion is

A) Rusting of iron

B) Boiling water

C) Freezing

D) Melting

14. Which reaction forms one product?

A) Combination reaction

B) Decomposition reaction

C) Displacement reaction

D) Reduction

15. Breaking a compound into simpler substances is

A) Combination reaction

B) Decomposition reaction

C) Oxidation

D) Corrosion

16. The substance formed in a reaction is called

A) Product

B) Reactant

C) Atom

D) Molecule

17. The starting substances in a reaction are called

A) Products

B) Reactants

C) Solutions

D) Catalysts

18. Zn + CuSO₄ → ZnSO₄ + Cu is

A) Combination reaction

B) Decomposition reaction

C) Displacement reaction

D) Neutralisation

19. AgCl formed in reaction of AgNO₃ and NaCl is

A) Precipitate

B) Gas

C) Liquid

D) Acid

20. A chemical equation uses

A) Words

B) Symbols and formulas

C) Numbers only

D) Diagrams

✅ Answers

1. B

2. A

3. A

4. A

5. A

6. A

7. A

8. A

9. B

10. A

11. B

12. B

13. A

14. A

15. B

16. A

17. B

18. C

19. A

20. B