This document discusses physical and chemical changes in various processes like photosynthesis, dissolving sugar in water, burning of coal, and digestion of food. It also provides examples of chemical changes like setting of curd and burning of wood versus the physical change of cutting wood. The document describes how crystals of copper sulfate are prepared using crystallization. It explains how painting prevents rusting of iron by creating a barrier between the iron, oxygen, and water. Rusting is faster in coastal areas due to higher humidity levels compared to deserts.