Question

Classify the changes involved in the following processes as physical or chemical changes:
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d)Melting of wax
(e) Beating aluminium to make aluminium foil
(f)Digestion of food
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Answer 1

Answer:

Physical changes only lead to changes in physical properties of the substance and are reversible chemical changes lead to change in composition or the structure and are irreversible in nature.

(a) Photosynthesis: irreversible, chemical changes.

6CO

2

+6H

2

O⟶C

6

H

12

O

6

+6O

2

(b) Dissolving of water : reversible, physical change.

(c) Bumping of coal − irreversible, chemical change.

(d) Melting of wax − reversible by cooling, physical change.

(e) Physical change as mallacbility (beating metal into then sheets) does not change composition.

(f) Digestion − chemical change.