What does Gay Lussac's Law relate in a gas when volume is constant?

Gay Lussac's Law specifically describes the relationship between the pressure and temperature of a gas when the volume is held constant. According to this law, as the temperature of a gas increases, the pressure also increases, provided that the volume does not change. This is because increasing the temperature causes gas molecules to move more quickly, leading to more frequent and forceful collisions with the walls of the container, which results in higher pressure.

In the context of the other options, the volume and temperature relationship is covered by Charles's Law, which states that the volume of a gas increases as the temperature increases when pressure is constant. The volume and pressure relationship is described by Boyle's Law, which states that at constant temperature, the pressure of a gas decreases as the volume increases. Lastly, there is no direct law connecting pressure and density in the way that Gay Lussac's Law connects pressure and temperature, making the correct answer focus purely on the defined relationship under constant volume conditions.