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

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Solution

Chemical Change
The change in which the molecular composition is altered and a new product is formed is called a chemical change.
Chemical changes create a new product.
The changes in Chemical change are irreversible and permanent.
Example: Burning of wood
Physical change
In physical change, the arrangement of molecules is altered leading to change in state.
No new products are formed, and the molecular composition remains totally the same.
Example, the molecular composition of ice and water is not altered, during melting of ice.
Difference between changes that can or cannot be reversed
Reversible changes
Irreversible changes
Reversible changes are those in which system can be returned to its original state by following a reversible path ..

Irreversible changes are those in which system cannot return to its original state.

2. Example: Melting of ice

2. Example: Burning of a piece of paper.

3. Ice gains heat and starts melting to form water, these water can be turned into ice by lowering the temperature (keeping it in the freezer), therefore, it is a reversible change. 3. When a piece of paper is burnt, it turns into ash, releasing carbon dioxide and water vapour. These ashes cannot be turned back into paper, therefore, it is a irreversible change.

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Similar questions

Q. Give examples to explain the difference between changes that can or cannot be reversed.

Q. Conversion of ice into water and water into ice is an example of change that can be reversed. Give four more examples where you can say that the changes can be reversed.

Q. Give an example in the given case:
(a) Change which occurs on heating but can be reversed.
(b) Change that occurs on heating but cannot be reversed.
(c) Change occurs on cooling but can be reversed.
(d) Change occurs on mixing two substances but can be reversed.
(e) Change which occurs on mixing two substances, but cannot be reversed.

Question 15

Give one example in each case.
Change which occurs on heating but can be reversed.
Change which occurs on heating but cannot be reversed.
Change which occurs on cooling but can be reversed.
Change which occurs on mixing two substances but can be reversed.
Change which occurs on mixing two substances but cannot be reversed.

Q. Give two examples for each of the following cases:
(a) Physical changes that are reversible
(b) Physical changes that are not reversible
(c) Chemical changes

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Fast and Slow Changes

Standard VIII Chemistry

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Reversible changes	Irreversible changes
Reversible changes are those in which system can be returned to its original state by following a reversible path ..	Irreversible changes are those in which system cannot return to its original state.
2. Example: Melting of ice	2. Example: Burning of a piece of paper.
3. Ice gains heat and starts melting to form water, these water can be turned into ice by lowering the temperature (keeping it in the freezer), therefore, it is a reversible change.	3. When a piece of paper is burnt, it turns into ash, releasing carbon dioxide and water vapour. These ashes cannot be turned back into paper, therefore, it is a irreversible change.