Gas - GCSE Chemistry Definition

Gas is one of the states of matter, alongside solids and liquids. In a gas, the particles are spread out and move freely, filling any container they are in. This is different from solids, where particles are tightly packed, and liquids, where particles are close but can still flow. Gases do not have a fixed shape or volume, meaning they take the shape and volume of their container. Common examples of gases include air, which is a mixture of gases like oxygen, nitrogen, and carbon dioxide. Understanding gases is important in chemistry because they behave differently from other states of matter, especially under changes in pressure and temperature.