NCERT Solutions: Change Around Us

# NCERT Solutions for Class 8 Science - Change Around Us

Ques 1: To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?

Ans 1: Yes, by unfolding the dress this change can be reversed.

Ques 2: You accidentally dropped your favorite toy and broke it. This is a change you did not want. Can this change be reversed?

Ans 2: No, it cannot be reversed, so it is an irreversible change.

Ques 3: Some changes are listed in the following table. For each change, write in the blank column, whether the change can be reversed or not.

 S. No. Change Can be reversed (Yes/ No) 1. The sawing a piece of wood 2. The melting of ice candy 3. Dissolving sugar in water 4. The cooking of food 5. The ripening of a mango 6. Souring of milk

Ans 3:

 S. No. Change Can be reversed (Yes/ No) 1. The sawing a piece of wood No 2. The melting of ice candy Yes 3. Dissolving sugar in water Yes 4, The cooking of food No 5. The ripening of a mango No 6. Souring of milk No

Ques 4: A drawing sheet changes when you draw a picture on it. Can you reverse this change?

Ans 4: It all depends on situations:

• By erasing the drawing we can undo the change. For example, if we draw with the help of a pencil, we can erase the drawing by using an eraser. Then, it is a reversible change.
• If we draw using a pen, we cannot erase the drawing. Then this change cannot be reversed, so it is irreversible change.

Ques 5: Give examples to explain the difference between changes that can or cannot be reversed.

Ans 5: Examples of Reversible Changes:

• Melting of Ice into water: By freezing the water we can obtain ice again.
• Folding a paper: By unfolding it, we can undo the change.
• Hot milk to cold milk: By boiling milk, we can make it warm.
• Dissolving sugar in water: By evaporating water, sugar crystals can be obtained.
Example of Irreversible Changes:
• Burning of a candle.
• Bursting of crackers.
• Cutting of trees.
Burning of a Candle

Ques 6: A thick coating of a paste of Plaster of Paris (POP) is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immobilised. Can the change in POP be reversed?

Ans 6: When water is added to POP, it undergoes a chemical change. Its composition changes and is converted into another substance. Since it is a chemical change, so it cannot be reversed.

Ques 7: A bag of cement lying in the open gets wet due to rain during the night. The next day the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed?

Ans 7: Due to water, the cement hardens and its composition changes. Since it is a chemical change which cannot be reversed.

The document NCERT Solutions for Class 8 Science - Change Around Us is a part of the Class 6 Course Science Class 6.
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## FAQs on NCERT Solutions for Class 8 Science - Change Around Us

 1. What are the different types of changes around us?
Ans. There are three types of changes around us - Physical, Chemical and Biological changes. Physical changes are reversible changes that do not result in the formation of a new substance, Chemical changes are irreversible changes that result in the formation of a new substance and Biological changes are changes that take place in living organisms.
 2. What is the difference between physical and chemical changes?
Ans. Physical changes are reversible changes that do not result in the formation of a new substance, whereas chemical changes are irreversible changes that result in the formation of a new substance. Physical changes do not alter the chemical composition of the substance, while chemical changes alter the chemical composition of the substance.
 3. How can we observe physical changes in everyday life?
Ans. We can observe physical changes in everyday life by observing changes in the state of matter, such as melting or freezing of ice, boiling of water, and evaporation of water. We can also observe physical changes in the appearance of substances, such as tearing paper, cutting vegetables or fruits, and crushing a rock into smaller pieces.
 4. How can we differentiate between physical and chemical changes?
Ans. We can differentiate between physical and chemical changes by observing whether a new substance is formed or not. In a physical change, the substance remains the same, and no new substance is formed. In a chemical change, a new substance is formed, and the properties of the substance change.
 5. What are the examples of biological changes?
Ans. Examples of biological changes include growth, reproduction, digestion, and respiration. These changes occur in living organisms and are essential for their survival. Biological changes are different from physical and chemical changes as they involve living organisms and their processes.

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