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Q7 (Medium): Natural factors, such as wind, rain, etc., help in the formation of soil from rocks. Is this change physical or chemical and why?
Answer:
Soil formation involves
both physical and chemical changes
.
Physical changes — wind, rain, and temperature changes break large rocks into smaller and smaller pieces. No new substance is formed; the rock material simply becomes smaller particles.
Chemical changes — water and other chemicals react with the rock minerals over long periods. For example, certain rocks like basalt react to form iron oxide (similar to rusting), which gives red soil its characteristic colour. These reactions create entirely new substances.
Therefore, soil formation is not merely a physical change — it is a combination of both physical and chemical changes acting together over thousands of years.
- Wind and rain — break rocks physically into smaller particles
- Temperature changes — crack and split rocks (physical change)
- Water and chemicals — react with rock minerals to form new substances (chemical change)
- Example: basalt reacts to form iron oxide — giving red soil its colour
