Section A: Worksheet
Learning science class 6 solutions
A. Tick the correct options :
1. Burning of coal is a/an_________change.
a) reversible b) irreversible c) natural d) human-made
Ans : b) irreversible
2. Baking of cake is an example of __________change.
a) reversible b) irreversible c) natural d) fast
Ans : b) irreversible
3. Which of the following is a reversible change?
a) dough to chapatis b) burning of candle wax c)melting of ice d) growth of a plant
Ans : c) melting of ice
4. Which of the following is not an irreversible change?
a) ripening of fruits b) baking of cake c) blooming of flowers d) contraction of metals
Ans: d) contraction of metals
5. Which of the following is an irreversible change?
a) burning of paper b) boiling of water c) melting of ice d) contraction of metals
Ans : a) burning of paper
learning Science class 6 solutions
B. Circle the odd ones. Give reason for your choice :
1. burning of paper, ageing of humans, cooking of food, boiling of water
Ans: Boiling of water
Reason– because it is a reversible change.
2. change of seasons, formation of glacier, hammering of metals, beating of heart
Ans: Hammering of metals
Reason– Because it is not a natural change.
3. digestion of food, burning of coal, rusting of iron, tearing of paper
Ans: Tearing of paper
Reason- Because it is a physical change.
learning science class 6 solutions
C. Fill in the blanks :
1. The changes that can be reversed are called reversible changes.
2. Ripening of fruits is an example of irreversible change.
3. Freezing of water is an example of physical change.
4. Heat causes water to change into steam.
Section – B
A. Multiple Choice questions (MCQs) Scientific/ Practical skills:
1. On applying force on the spring, by hanging a weight, we see the length of the spring ___________________ .
a) increases b) decreases c) does not change d) contracts
Ans: a) increases
2. We add a spoonful of _________ in the warm milk to obtain curd.
a) cold milk b) sugar c) honey d) curd
Ans: d) curd
3. Which is more soluble in water?
a) sugar b) salt c) both of these d) none of these
Ans: b) both of these
learning science class 6 solutions
B. Very Short Answer Question:
1. What kind of change is burning of paper?
Ans: Chemical change
2. What happens when an aluminium rod is heated?
Ans: When an aluminium rod is heated it expands.
3. What happens on cooling of steam?
Ans: On the cooling of steam, it changes into water.
4. What type of change is melting of wax?
Ans: The melting of wax is an irreversible change.
5. Is the formation of day and night, a natural or human-made change?
Ans: The formation of day and night is a natural change.
6. What change do you observe on applying pressure on brittle substances?
Ans: When we apply pressure on brittle substances, they break into pieces which is an irreversible change.
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C. Short Answer Questions:
1. What are reversible changes?
Ans: The change that can be reversed easily by reversing the conditions to obtain a substance in its original form is called a reversible change. For example, stretching of a spring.
2. What are irreversible changes.
Ans: The change that cannot be reversed even by changing the conditions to obtain a substance back in its original form is called an irreversible change.
3. Neha’s mother is sick. Neha makes vegetable soup for her mother and serves it to her.
(a) Can we get the vegetables back from the soup? What type of change does it represent?
(b) What value does Neha’s action show?
Ans: a) We can not get the vegetables back from the soup. It represents the irreversible type of change.
b) Neha’s actions show concern and compassion for her mother.
4. What are the different ways to bring about changes?
Ans: We can bring about changes by heating, cooling, applying pressure, or by mixing two or more things together.
5. What change do you observe on keeping milk in refrigerator?
Ans: When we keep milk in the refrigerator, it stays cool and does not get spoiled.
6. Classify the following as reversible or irreversible changes:
burning of coal, freezing of water, digestion of food, ironing of a shirt, baking of a chapati, knitting of a sweater, folding of paper and rusting of iron
Ans: Reversible change – freezing of water, ironing of a shirt, knitting of a sweater, and folding of paper.
Irreversible change – burning of coal, digestion of food, baking of chapati and rusting of iron.
learning science class 6 solution
D. Long Answer Questions:
1. Explain how heating or cooling of water brings changes in the state of matter.
Ans: On heating, ice changes to water, and water changes to steam. Similarly, on cooling steam changes to water and water changes to ice.
2. Explain how a metal rim is fixed around the wooden wheel of a cart.
Ans: We heat the metal rim to expand it in size. Then it is nicely put around the wooden wheel. On cooling, the hot metal rim contracts, and fits tightly around the wheel.
3. How are physical changes different from chemical changes?
Ans: In a physical change no new substances are formed while in a chemical change new substances with different properties are formed. Most of the physical changes are temporary and reversible. On the other hand, chemical changes are permanent and irreversible.
4. Is the buring of a candle, a chemical or physical changes? Explain with reasons.
Ans: The burning of a candle is a chemical change because new substances like carbon and gases are formed during this change and it is an irreversible change.