The pressure of a gas will increase when the volume decreases.
This relationship is explained by Boyle’s Law, which states that the pressure of a given mass of gas is inversely proportional to its volume when the temperature is held constant. In simpler terms, if you reduce the space that the gas occupies (decrease the volume), the gas molecules are forced closer together, leading to more frequent collisions with the walls of the container. Since pressure is defined as the force exerted by these collisions over an area, a decrease in volume results in an increase in pressure. Therefore, when the volume decreases, the pressure definitely increases.