What happens to the density of a gas as absolute pressure increases, at a constant temperature?

As absolute pressure increases while maintaining a constant temperature, the density of a gas increases as well. This relationship is a direct consequence of the ideal gas law, which states that the density of a gas is directly proportional to its pressure when temperature is held constant.

In a closed environment (like a scuba cylinder), if the pressure increases, more gas molecules are compressed into the same volume, thus increasing the mass of gas per unit volume. Consequently, the density — defined as mass per unit volume — becomes greater. This principle is key when considering gas behaviors in diving contexts, especially when utilizing nitrox mixtures, as proper understanding of density can affect buoyancy and gas exchange mechanisms underwater.

While the other options may seem plausible, they do not align with the established gas laws under the specified conditions of constant temperature and increasing pressure.