The particle of a substance expands or becomes loose when the temperature increases. Hence, the material is said to undergo expansion. When the temperature decreases, the particles of the substance contract or become tight. Hence, the material is said to undergo contraction.The amount of expansion or contraction varies in solids, liquids, and gases. There are physical changes that take place when a substance or material moves from one state of matter to another. Water is a classic example as it can exist as either solid, liquid, or gas. It shows exceptional contraction and expansion when cooled or heated.