Question

A Study of Changes
Exercises
A. Answer the following in not more than 20 words.
1. What do you mean by a reversible change?
2. What do you mean by an irreversible change?
3. What are physical changes? Give two examples.
4. What are chemical changes? Give two examples.
5. Describe a reversible change that you can bring about by heating.
6. Describe an irreversible change that you can bring about by heating.
7. Mention two changes that can be brought about by applying pressure.​

Answer 1

Answer:

(1)reversible change:

changes which can be reversed is called a reversible change in the chain the products formed can be converted back into their original forms.

example something iron with magnet, the stretching of the rubber band again comes to original place.

(2)irreversible:

itching which cannot be Lewis is called an irreversible change in the change the product cannot be converted back into their original form.

example curdling of milk, when paper is burnt it changes to Ash and smoke and action snow cannot get back paper.

(3)physical changes:

the change takes place only in state colour ,texture, electrical, and magnetic properties composition remains the same

no new substances are formed

specific properties of substance do not change

there is no net absorption or release of energy

it is temporary change and can be irreversible

example: melting of ice glowing of electrical bulb

(4)chemical changes:

the change takes place in state, colour, texture and etc.. along with the change in composition

specific properties of a substance change completely

new substance is formed

there is always need absorption or release of energy

permanent change and cannot be reversed

examples: burning of petrol, burning of diesel, burning of candle wax

(5)the heating of an electric heater on switching on and cooling on switching off are reversible changes

(6) when is sparkle is on set on fire it burns with a bright flame

when paper is burnt it changes to Ash and smoke. from Ash and smoke we cannot get back

(7) when we apply pressure on Dough it changes its shape

when we apply pressure on on sponge duster then it changes its shapes and if we release pressure again changes to its original shape.

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