We encounter many changes in our surroundings. Burning firecrackers, melting wax, cooking food, rusting iron, and settling curd are some changes observed in daily life. It may involve a change in the physical or chemical property of the substance. The change in the chemical property of a substance is classified as a chemical change. In contrast, a change in the physical property of a substance is classified as a physical change.
Download Class 7 Chemistry Worksheet on Chapter 6 Physical and Chemical Changes Set 3 PDF
CBSE Class 7 Chemistry Chapter 6 Physical and Chemical Changes Worksheet – Set 3
Q1. Which of the following is a physical change?
(a) Burning of fossil fuels
(b) Magnetisation of an iron rod
(c) Fermentation of food
(d) Rusting of iron
Q2. Which of the following is a chemical change?
(a) Magnetisation of an iron rod
(b) Dissolution of salt in water
(c) Both (a) and (b)
(d) None of the above
Q3. Digestion of food is an example of _______.
(a) Physical change
(b) Chemical change
(c) Biological change
(d) None of the above
Q4. What is the molecular formula of rust?
(a) Fe2O3
(b) FeO
(c) FeSO4
(d) None of the above
Q5. _______ is a process of depositing a layer of zinc on iron articles.
(a) Aluminisation
(b) Galvanisation
(c) Ironing
(d) None of the above
Q6. A change that can not be reversed is called a ______ change.
Q7. State true or false.
Rusting takes place faster near the sea coast.
Q8. State true or false.
Iron objects are galvanised with a layer of aluminium metal.
Q9. State true or false.
Condensation of steam is not a chemical change.
Q10. Match the following.
| Column A | Column B |
|---|---|
| Physical Change | Blue |
| Chemical Change | Green |
| Burning of magnesium | Physical properties are changed |
| Iron Sulphate | Magnesium Oxide |
| Copper Sulphate | New substances are produced |
Q11. Define crystallisation.
Q12. Define galvanisation.
Q13. Why do stainless steel utensils not rust?
Q14. Name the product formed when a piece of magnesium is burnt in the air.
Q15. What is rust?
Q16. When baking soda is mixed with lemon juice, bubbles are formed with the evolution of gas. What kind of change is it? Explain.
Q17. How does painting an iron grill prevent it from rusting?
Q18. What is a chemical change? State any four characteristics of chemical change.
Q19. What is rusting? How can it be prevented?
Q20. Differentiate between a chemical and physical change.
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