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Changes Around Us: Physical and Chemical — Science STD 7 — Question

Gujarat BoardEnglish MediumSTD 7ScienceChanges Around Us: Physical and Chemical2 Marks
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
✓

Answer

(a) Photosynthesis is a chemical change because new substances like glucose and oxygen are formed.
(b) Dissolving sugar in water is a physical change because no new substance is formed and sugar can be recovered.
(c) Burning of coal is a chemical change because new substances like carbon dioxide and ash are produced.
(d) Melting of wax is a physical change because only the state of wax changes and no new substance is formed.
(e) Beating aluminium to make aluminium foil is a physical change because only the shape of aluminium changes.
(f) Digestion of food is a chemical change because food is converted into new substances.

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