Natural factors, such as wind, rain, etc., help in the formation of soil from rocks. Is this change physical or chemical and why?
The formation of soil from rocks involves both physical and chemical changes.
Physical changes occur when temperature changes due to climatic conditions, growing roots of trees, and freezing of water within cracks cause rocks to break into smaller pieces.
Chemical changes occur when water or chemicals present in water react with the rocks and change their composition.
For example, a black-coloured basalt rock containing iron can chemically change to produce a red-coloured layer of iron oxide when exposed to water or air containing water vapour.
These combined physical and chemical changes are called weathering, which eventually leads to soil formation.
Explanation
The chapter section 5.7.1 on Weathering of rocks explains that rocks undergo both physical and chemical changes. Physical changes break rocks into smaller pieces through temperature changes, growing roots, and freezing water. Chemical changes occur when water or chemicals react with rocks, such as iron in basalt reacting to form iron oxide. These processes together are called weathering.
Solution Steps
The formation of soil from rocks involves both physical and chemical changes.
Physical changes break rocks into smaller pieces through temperature changes, growing roots, and freezing water.
Chemical changes occur when water or chemicals react with rocks and change their composition.
Example: Iron in basalt rock reacts to form red iron oxide when exposed to water or air containing water vapour.
These combined processes are called weathering, which leads to soil formation.