If the volume of a gas increases, what effect does it have on pressure?

When the volume of a gas increases, its pressure decreases, provided that the temperature and the amount of gas remain constant. This relationship is described by Boyle's Law, which states that for a given mass of an ideal gas at constant temperature, the pressure of the gas is inversely proportional to its volume.

In simple terms, when the volume expands, gas particles have more space to move around, which leads to fewer collisions between the gas particles and the walls of the container. Since pressure is defined as the force exerted by gas particles colliding with the walls of the container per unit area, fewer collisions translate to decreased pressure. Thus, an increase in volume results in a decrease in pressure, confirming that the correct answer is that pressure decreases when volume increases.