What are Gases?
Gas is one of four natural states of matter, along with liquid, solid and plasma. A gas has no fixed shape or volume. The atoms or molecules that make up the gas fill the container that holds them. The gas expands until it is uniformly distributed throughout the container, even in the presence of gravity.
No definite shape or volume: Unlike solids and liquids, a gas will take the shape and volume of its container.
Highly compressible: Due to the large spaces between particles, gases can be easily compressed.
Particle movement: The particles in a gas are constantly moving at high speeds in random directions.
Examples: Air, helium, oxygen, carbon dioxide.