We can change a substance by performing one or more of the following processes:
- Heating or cooling.
- Making use of force.
- Mixing it with something else.
Chemical changes occur when the chemical properties of a substance change and a new substance is formed. As an example, consider food preparation. Physical changes are those that affect only the physical properties of a substance and do not result in the formation of a new substance.
Reversible changes are the changes that can be reversed. As an example, consider rubber stretching. Irreversible changes are changes that cannot be reversed. For instance, paper burning.
Download PDF of Class 6 Chemistry Chapter 6 Changes Around Us – Set 3
CBSE Class 6 Chemistry Worksheet Chapter 6 Changes Around Us – Set 3
Q1. A physical change can be characterised by-
a.) Change in shape
b.) Change in colour
c.) Change in temperature
d.) All of the above
Q2. Which of the following is a permanent change?
a.) Blooming of flowers
b.) Melting of ice
c.) Boiling of water
d.) All of the above
Q3. On heating, a metal-
a.) Expands
b.) Contracts
c.) No change is observed
d.) Both expands and contracts
Q4. Fill in the blanks.
a.) Melting of wax is a ___ change, but the burning of wax is a ___ change.
b.) If we blow a balloon. The shape and size of the balloon change. This is a ____ change.
c.) Water vapour can be reversed to ____.
Q5. State True or False.
a.) When an object heats, it contracts.
b.) Physical changes are reversible.
c.) The heating of milk can be considered as a reversible change.
Q6. List a few ways to create change.
Q7. How does a blacksmith transform a piece of iron into different tools, and what changes occur in iron when heated?
Q8. Are all the changes taking place in a substance permanent, temporary or reversible?
Q9. How is the formation of curd an irreversible change?
Q10. Differentiate between reversible and irreversible changes.
Q11. What are the characteristics of a chemical change?
Q12. Explain why the stretching of the rubber band is a reversible change.
Q13. How does a blacksmith change a piece of iron into different tools?
Q14. Give some applications of expansion and contraction.
Q15. Classify the following as reversible or irreversible changes:
i.) Growth of a plant
ii.) Ploughing a field
iii.) Melting of wax
iv.) Falling of rain
v.) Pulling of rubber string
vi.) Breaking of a glass rod
vii.) Cooking of food.
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