Class 7 Science Chapter 5 Practice Question Answers - Physical and Chemical Changes

Q1. Neutralisation is a:
(a) physical change
(b) chemical change
(c) both (a) and (b)
(d) none of these
Ans: (b)
Neutralisation is a chemical change.

Q2. Rusting can be prevented by:
(a) preventing iron from coming in contact with air and moisture by applying greese or paint
(b) deposit a layer of a metal like chromium or zinc on iron
(c) both (a) and (b)
(d) none of these
Ans: (c)
Rusting can be prevented by applying grease or paint and by depositing a layer of zinc.

Q3. The process of forming substances in their pure state from their solution is known as:
(a) galvanisation
(b) neutralisation
(c) crystallisation
(d) all of these
Ans: (c)
The process of forming substances in their pure state from the solution is called crytalisation.

Q4. The process of depositing a layer of zinc on iron is called:
(a) galvanisation
(b) neutralisation
(c) crystallisation
(d) none of these
Ans: (a)
The process of depositing a layer of zine on iron is called galvanisation.

Q5. Ships suffer a lot of damage from rusting inspite of being painted because:
(a) sea water contains many salts
(b) sea water is bitter
(c) sea water is sour
(d) sea water is sweet
Ans: (a)
Ship suffers a lot of damage due to the sea water which contains many salts.

Q6. Food items when kept carefully get spoiled is a:
(a) chemical change
(b) physical change
(c) both (a) and (b)
(d) none of these
Ans: (a)
When food items get spoiled by keeping carelessly, is a chemical change.

Q7. When you leave a piece of iron in the open for some time, it acquires a film of brownish

substance. The substance is called:
(a) acid
(b) base
(c) rust
(d) none of these
Ans: (c)
When a film of brownish substance acquire on iron piece is called rust.

Q8. Burning the magnesium ribbon is a:
(a) physical change
(b) chemical change
(c) rusting
(d) all of these
Ans: (b)
Burning of magnesium ribbon is a chemical change.

Q9. The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder it exists as

a liquid. When it comes out from the cylinder it becomes a gas (Change-A) then it burns

(Change-B). The following statements pertain to these changes. Choose the correct one.
(a) Process-A is a chemical change
(b) Process-B is-a chemical change
(c) Both proceses A and B are chemical changes.
(d) None of these processes are . chemical changes
Ans: (b)
Process-B is a chemical change as when gas burns, it is always a chemical change.

Q10. Which of the following is a reversible change ?
(a) Rusting
(b) Chemical
(c) Physical
(d) All of these
Ans: (c)
Physical change is reversible.

Q11. Anaerobic bacteria digests animal waste and produces biogas (Change-A). The biogas is then

burnt as fuel (Change-B). The following statements pertain to these changes. Choose the

correct one.
(a) Process-A is a chemical change
(b) Process-B is a chemical change
(c) Both processes A and B are .chemical changes
(d) None of these processes are chemical changes
Ans: (c)
Both Changes-A and B are chemical changes as producing biogas and burning as fuel is chemical change.

Q12. Which of the following is an irreversible change ?
(a) Physical
(b) Rusting
(c) Chemical
(d) None of these
Ans: (c)
Chemical change is irreversible change.

Q13. The chemical name of baking soda is:
(a) hydrogen carbonate
(b) calcium carbonate
(c) sodium hydrogen carbonate
(d) none of these
Ans: (c)
The chemical name of baking soda is sodium hydrogen carbonates.

Q14. Condensation of steam is not a:
(a) chemical change
(b) physical change
(c) rusting
(d) both (a) and (c)
Ans: (d)
Condensation of steam in not chemical change and rusting.

Q15. Beating the alluminium in the boil is a:
(a) chemical change
(b) rusting
(c) physical change
(d) none of these
Ans: (c)
Beating the alluminium into the foil is physical change.

Q16. When baking soda is mixed with lemon juice, bubbles are formed with evolution of a gas. A new substance carbon dioxide gas is formed, is a:
(a) physical change
(b) crystallisation
(c) galvanisation
(d) chemical change
Ans: (a)
When baking soda is mixed with lemon juice, bubbles are formed is a chemical change.

Q17. Blooming of flower is a:
(a) chemical change
(b) physical change
(c) rusting
(d) galvanisation
Ans: (a)
Blooming of flower is a chemical change.

Q18. A change that affects iron articles and slowly destroys them is:
(a) Rusting
(b) Galvanisation
(c) Chemical change
(d) Crystallisation
Ans: (a)
A change that affect iron articles and destroys them is rusting.

Q19. Photosynthesis is a:
(a) chemical change
(b) physical change
(c) rusting
(d) crystallisation
Ans: (a)
Photosynthesis is a chemical change.

Q20. Stainless steel, which doesn’t rust, is made by mixing iron with carbon and metals like:
(a) chromium
(b) nickel
(c) manganese
(d) all of these
Ans: (d)
All metals like chromium, nickel and manganese are mixed with iron and carbon.

Q21. Rusting of iron objects is faster in:
(a) deserts
(b) coastal areas
(c) both (a) and (b)
(d) none of these
Ans: (b)
Rusting of iron object is faster in coastal areas because the presence of moisture, is higher.

Q22. Lighting of torch bulb using dry cell is:
(a) Chemical change
(b) Physical change
(c) Physical and chemical changes
(d) None of these
Ans: (c)
Lighting of torch using dry cells is a physical and chemical change.

Q23. Which of the following is not a chemical change ?
(a) Digestion of food
(b) Formation of milk
(c) Burning of coal
(d) Melting of ice
Ans: (d)
Melting of ice is a chemical change.

Q24. Which of the following is true for physical change ?
(a) No new substances are formed
(b) New substances are formed
(c) Sometimes new substances are formed
(d) None of these
Ans: (a)
No new substance is formed is the true statement.

Q25. In a chemical change:
(a) Gas may be formed
(b) Heat may be given off or absorbed
(c) Sound may be produced
(d) All of these
Ans: (d)
In chemical changes all heat, gas and sound may be produced.

Q26. For rusting:
(a) Only moisture is required
(b) Only air is required
(c) Both air and moistured are required
(d) None of these
Ans: (c)
For rusting both air and moisture are required.

Q27. When carbon dioxide is passed through lime water, it turns milky due to the formation:
(a) calcium oxide
(b) calcium carbonate
(c) magnesium carbonate
(d) magnesium oxide
Ans: (b)
When carbofi dioxide is passed through lime water it turns milky due to calcium carbonate

Q28. When a candle burns, then first the wax melts. Melting of wax is :
(a) physical change
(b) chemical change
(c) both (a) and (b)
(d) none of these
Ans: (a)
Melting of wax is a physical change because it doesn’t change in its properties

Q29. When wax vapours burns then smoke and carbon dioxide are formed which are new

substances, is a:
(a) physical change
(b) chemical change
(c) both (a) and (b)
(d) none of these
Ans: (b)When wax vapours burn, gas is produced, it is a chemical change.

Q30. Curd can not be converted into milk again so it is a:
(a) chemical change
(b) physical change
(c) both (a) and (b)
(d) none of these
Ans: (a)
As curd cannot become milk again, so it is a chemical change