168 Unit 2: The Structure of Matter. Solids have a definite volume and shape. A piece of ice,a block of wood,and a ceramic cup are solids.They. have shapes that do not change and volumes that can be measured. Any matter that is a solid has a definite shape and a definite volume. The molecules in a solid are in fixed positions and are close together.Although the molecules can still vibrate,they cannot move from one part of the solid to another part.As a result,a solid does not easily change its shape or its volume.If you force the molecules apart, you can change the shape and the volume of a solid by breaking it