g a s e s


steam animation


When you have finished this page, try the Gases Quiz.


A gas is a state of matter in which the substance has no definite shape or volume (size). Gases take the shape and fill any container in which they are placed. The molecules in gases move more quickly than those in liquids or solids and are spread out much more than in either liquids or solids.

Gases change to liquids or solids if they are cooled or if enough pressure is applied to them. The cooling of a gas so it becomes a liquid is called condensation. If a gas changes directly to a solid, it is called sublimation.

There are several important scientific laws relating to gases. One is Boyle's Law, named after Robert Boyle. This states that the greater the pressure upon a gas, the smaller the volume that gas will take up and the less the pressure, the greater the volume or space a gas will take up in a closed space.


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