What happens to pressure as the volume of a gas decreases, given a constant amount of gas?

When the volume of a gas decreases while keeping the amount of gas constant, the pressure increases. This relationship is described by Boyle's Law, which states that for a given mass of gas at a constant temperature, the pressure of the gas is inversely proportional to its volume. Therefore, as the volume decreases, the gas molecules are forced closer together, resulting in more frequent collisions with the walls of the container. This increase in collisions leads to an increase in pressure.

For example, if you compress a gas in a piston, the space for the gas molecules is reduced, causing them to collide more often with the piston walls, which raises the pressure inside the container. This principle is fundamental in understanding gas behavior in various physiological contexts, such as in the function of the lungs during breathing.