This document discusses the differences between chemical and physical changes. It states that there are two types of changes - chemical changes, which involve new substances or molecules forming in a permanent change, and physical changes, which do not create new substances and can be reversed by changing the arrangement of molecules in a temporary change. Examples of chemical changes provided are iron rusting, burning of wood, milk souring, and digestion of food. Examples of physical changes are cutting of wood, boiling water, melting of ice into water, and dissolving salt in water.