CLASS 7 PHYSICAL AND CHEMICAL CHANGES

 

Chemical and Physical Changes

Worksheet 1 

Class: 7 

Section A: Fill in the Blanks

1. A change in which no new substance is formed is called a __________ change.
2. Rusting of iron is an example of a __________ change.
3. Melting of ice is a __________ change.
4. A chemical change is usually __________ (reversible/irreversible).
5. Burning of paper is a __________ change.

Section B: True or False

1. Boiling of water is a chemical change. ( )
2. Digestion of food is a chemical change. ( )
3. Breaking of glass is a physical change. ( )
4. Formation of curd from milk is a physical change. ( )
5. Burning of wood produces new substances. ( )

Section C: Match the Following

Column A	Column B
Burning of coal	Physical Change
Dissolving sugar in water	Chemical Change
Cooking of food	Irreversible change
Evaporation of water	No new substance formed
Rusting of iron	Chemical reaction with air

Section D: Short Answer Questions

1. Define physical change with two examples.
2. Define chemical change with two examples.
3. Why is burning of paper a chemical change?
4. How does rusting of iron occur? How can it be prevented?
5. Differentiate between a physical and a chemical change with examples.

Section E: Experiment Based Questions

1. You have a piece of aluminum foil. You tear it into small pieces. Is it a physical or chemical change? Why?
2. If you burn a magnesium ribbon, what will you observe? Write the reaction involved.
3. When vinegar is mixed with baking soda, bubbles are formed. What kind of change is this and why?

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Worksheet 2

Section A: Multiple Choice Questions (MCQs)

1. Which of the following is a chemical change?
   a) Melting of ice
   b) Rusting of iron
   c) Breaking of glass
   d) Dissolving sugar in water

2. Which of the following processes is reversible?
   a) Burning of paper
   b) Boiling of water
   c) Cooking of rice
   d) Rusting of iron

3. What is formed when iron reacts with water and oxygen?
   a) Copper oxide
   b) Rust
   c) Water vapor
   d) Carbon dioxide

4. What happens when magnesium ribbon burns in air?
   a) It produces black smoke
   b) It forms a white powder (magnesium oxide)
   c) It turns into liquid magnesium
   d) It remains unchanged

5. A physical change occurs when:
   a) Paper is burned
   b) A nail rust
   c) Water freezes
   d) Milk turns sour

Section B: Identify the Type of Change

State whether the following changes are Physical or Chemical:

1. Boiling of water
2. Burning of candle
3. Cutting of paper
4. Cooking of food
5. Formation of curd from milk

Section C: Fill in the Blanks

1. A physical change is usually __________ (reversible/irreversible).
2. Chemical changes result in the formation of a __________ substance.
3. The process of iron reacting with oxygen and water to form rust is called __________.
4. A change that does not produce a new substance is called a __________ change.
5. Digestion of food is an example of a __________ change.

Section D: Short Answer Questions

1. What is a chemical change? Give two examples.
2. How is a physical change different from a chemical change?
3. Why is melting of wax a physical change, but burning of wax a chemical change?
4. Write two ways to prevent rusting of iron.
5. What happens when baking soda is added to vinegar? Explain the observation.

Section E: Application-Based Questions

1. You accidentally drop a glass bottle, and it breaks into small pieces. Is this a chemical or physical change? Explain why.
2. Your mother boils water to make tea. What kind of change is boiling water? What happens to the water molecules?
3. A candle burns with a flame and melts at the same time. Explain how two types of changes are happening simultaneously.
4. If you leave a slice of apple in the open for a few hours, it turns brown. What type of change is this? Why does it happen?
5. Is dissolving salt in water a physical or chemical change? Explain your answer.