Question

IMPORTANT NOTES
1. Define Physical and chemical change
give example

2 what are reversible and irreversible
changes ? give examples?
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Answer 1

Answer:

1. a) Physical changes only change the appearance of a substance, not its chemical composition.

eg :- Melting of ice

b) Chemical changes cause a substance to change into an entirely substance with a new chemical formula. Chemical changes are also known as chemical reactions.

eg :- Burning of magnesium ribbon

2. A change which can be reversed is called a reversible change.

eg :- Stretching of rubber band

A change which cannot be reversed is called an irreversible change.

eg :- Cutting of paper

Explanation:

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Answer 2

Answer:

1)Some examples of physical change are freezing of water, melting of wax, boiling of water, etc. A few examples of chemical change are digestion of food, burning of coal, rusting, etc. ... In a physical change, no new substance is formed. A chemical change is always accompanied by one or more new substance(s).

2)Reversible changes - where a change is made physically and can be undone or reversed. For example: freezing water to make ice. Irreversible changes - where the change is made chemically and can't be reversed into its original states. For example: baking a cake.