A solid is a form of matter that has its own definite shape and volume. Wood, iron, paper and sugar are examples of solids. the pariticles of matter in a solid are very tightly packed; when heated a solid expands, but only slightly because its shape is definite.

A liquid is a form of matter that flows, has constant volume, and takes the shape of its container. Common examples of liquids include water, blood and mercury. The particales in liquid are not rigidly held in place and are lesss closely packed than are the partivles in a solid: liquid particles are able to move past each other.

A gas is a form of matter that flows to conform to the shape of its container and fills the entire volume of its container. Examples of gases include neon, methane, which is used in cooking: and air, which is a mixture of gases. Compared to solids and liquids, the particles of gases are very far apart.