Why are gases compressible?

Gases are compressible because they are less dense than other states of matter and have fewer atoms or molecules per unit of volume. Because there is more space between the molecules, it is easy to compress the gas into a smaller space.

The initial pressure and temperature of a gas determine how compressible it is. Compressing a gas makes it more dense. Although there is a limit to how much any given gas can be compressed, in general, doubling the pressure on a gas decreases its volume by 50 percent.

Gases also expand easily. All gases expand uniformly to fill any container in which they are placed.