PHYSICAL AND CHEMICAL CHANGE CLASS 7 NCERT

 

Worksheet 1 

Physical and Chemical Changes

A. Multiple Choice Questions (MCQs)

  1. Which of the following is a physical change?
    a) Rusting of iron
    b) Melting of ice
    c) Burning of paper
    d) Cooking of food

  2. A chemical change involves:
    a) Formation of a new substance
    b) Change in shape only
    c) Reversible process
    d) No change in energy

  3. Which of these is a chemical property of a substance?
    a) Density
    b) Ability to rust
    c) Color
    d) Shape

  4. Boiling of water is an example of:
    a) Physical change
    b) Chemical change
    c) Both physical and chemical changes
    d) None of these

  5. Which of the following is NOT a physical change?
    a) Freezing of water
    b) Dissolving salt in water
    c) Formation of curd
    d) Breaking of glass

B. Fill in the Blanks

  1. _______ change is usually reversible, while _______ change is irreversible.
  2. The burning of a candle is a _______ change, while melting of wax is a _______ change.
  3. The rusting of iron forms a brown substance called _______.
  4. In a chemical change, _______ substances are formed.
  5. Tearing a sheet of paper is a _______ change.

C. True or False

  1. Physical changes do not form new substances.
  2. A change in state of matter is an example of a chemical change.
  3. Cooking of food is a physical change.
  4. Rusting of iron requires air and moisture.
  5. Dissolving sugar in water is a chemical change.

D. Match the Following

Column AColumn B
1. Melting of icea. Chemical change
2. Photosynthesisb. Physical change
3. Burning of paperc. Irreversible change
4. Boiling of waterd. Formation of a new substance
5. Dissolving salt in watere. Reversible change

E. Short Answer Questions

  1. Define a physical change and give two examples.
  2. What is a chemical change? Write two characteristics of chemical changes.
  3. Why is rusting of iron considered a chemical change?
  4. Give two differences between physical and chemical changes.
  5. Explain how the formation of curd is a chemical change.

F. Activity-Based Questions

  1. Observation-Based Question:
    Take a piece of paper and try these:

    • Tear the paper into small pieces.
    • Burn the paper.
      Identify which activity shows a physical change and which shows a chemical change.

  2. Experiment-Based Question:
    Dissolve a spoonful of salt in a glass of water.

    • Write your observations.
    • Is this a physical or chemical change? Justify your answer.

Worksheet 2

Physical and Chemical Changes

A. Define the Following Terms

  1. Physical change
  2. Chemical change
  3. Rusting
  4. Crystallization

B. Classify the Following Changes

Classify the following as physical or chemical changes:

  1. Melting of butter
  2. Digestion of food
  3. Freezing of water
  4. Baking of a cake
  5. Formation of clouds
  6. Burning of wood
  7. Dissolving sugar in water
  8. Explosion of a firecracker

C. Answer the Following Questions

  1. Why is burning of wood considered a chemical change?
  2. Describe any two characteristics of physical changes with examples.
  3. Why is photosynthesis considered a chemical change?
  4. Explain why rusting of iron is harmful.

D. Fill in the Blanks

  1. In a _______ change, no new substances are formed.
  2. The process of _______ is used to obtain pure crystals of a substance from its solution.
  3. The change of water to steam is a _______ change.
  4. Chemical changes are generally _______ (reversible/irreversible).
  5. The green substance formed on a copper surface when exposed to air is called _______.

E. Differentiate Between

  1. Physical change and chemical change (any three points).
  2. Reversible and irreversible changes (any two points).

F. True or False

  1. Formation of curd from milk is a physical change.
  2. Evaporation of water is a chemical change.
  3. Chemical changes always produce heat.
  4. Melting of ice is a reversible physical change.
  5. Cooking of food produces new substances.

G. Match the Following

Column AColumn B
1. Rusting of irona. Formation of new substances
2. Dissolving sugar in waterb. Physical change
3. Digestion of foodc. Requires air and moisture
4. Freezing of waterd. Chemical change
5. Melting of waxe. Change of state

H. Activity-Based Questions

  1. Observation Activity:

    • Heat a candle and observe both the melting of wax and the burning of the wick.
    • Which part of this process is a physical change, and which is a chemical change? Explain why.

  2. Think and Answer:

    • You dissolve some salt in water, and then heat the solution until all the water evaporates. What is left behind? Is this a physical or chemical change?

I. Application-Based Question

  1. Rust Prevention:
    • What methods can you suggest to prevent rusting of iron objects? Explain how each method works.
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