Why does freezing water in cracks break rocks in cold mountains?

Correct answer: Water expands on freezing

Correct answer: A, water expands on freezing. In a cold mountain environment, liquid water can enter small cracks in a rock. When the temperature falls below freezing, the water changes into ice and occupies more space than the same amount of liquid water. The expanding ice presses against the crack walls. Repeated freezing and thawing increases the pressure and gradually widens the crack until pieces of rock break away. This is called frost action or freeze-thaw weathering, a type of physical weathering because the rock's chemical composition need not change. B is wrong because freezing changes water into a solid, not a gas. C is wrong because freezing does not normally turn pure water into an acid. D is wrong because ice does not become soil simply by freezing. Memory cue: freeze, expand, press, crack—four steps of frost action.