How does the pressure behave when the volume of air decreases?

When the volume of air decreases, the pressure increases due to a fundamental principle known as Boyle's Law. This law states that, for a given amount of gas at constant temperature, the pressure of the gas is inversely related to its volume. In simpler terms, when you compress a gas (reducing its volume), the molecules of that gas are forced closer together. As the volume decreases, the number of collisions between the gas molecules and the walls of the container increases, thus raising the pressure.

This phenomenon is observable in various everyday situations, such as when pumping air into a tire. As you pump more air into the tire, you are decreasing the volume inside it, which consequently increases the pressure. Understanding this relationship is crucial in fields such as meteorology, engineering, and even breathing physics.

Other choices do not align with this principle: pressure does not remain constant, as a reduction in volume must lead to an increase in pressure if the temperature is held steady; pressure cannot decrease since that would contradict the behavior outlined by Boyle's Law; and pressure does not fluctuate in a stable environment where volume is being decreased continuously.