Answer:
decrease
Step-by-step explanation:
As gas is compressed, the spaces between the particles reduces. When a gas is compressed the pressure applied to the gas in the container is increased. 
- According to Boyle's law, the volume of a fixed mass of a gas varies inversely as the pressure changes if the temperature is constant. 
- So, as the pressure on the gas increases the volume decreases. 
- This reduces the spaces between the particles. 
- Volume is the space occupied by a body within a given space.