The volume of a fixed amount of gas held at a constant temperature varies inversely with the pressure

P1V1=P2V2

If the temperature and the amount of gas are constant, doubling the pressure decreases the volume by one half. Reducing the pressure by one half doubles the volume.

A diver blows a 0.75-L air bubble 10 m under water. As it rises to the surface, the pressure goes from 2.25 atm to 1.03 atm. What will be the volume of the air bubble at the surface?

The volume of a given amount of gas is directly proportional to it's kelvin temperature at constant pressure

V1/T1=V2/T2

As temperature increases so does the volume of a gas sample when the amount of gas and the pressure remain constant.

A helium balloon in a closed car occupies a volume of 2.23 L at 40.0 C. If the car is parked on a hot day and the temperature inside rises to 75.0 C, what is the new volume of the balloon, assuming the pressure remains constant?

The pressure of a fixed amount of gas varies directly with the kelvin temperature when the volume remains constant

P1/T1=P2/T2

An increase in temperature increases collision frequency and energy, so raising the temperature should raise the pressure if the volume is not changed.

The pressure of the oxygen gas inside a canister is 5.00 atm at 25.0 C. The canister is located at a camp high on Mount Everest. If the temperature there falls to -10.0 C, what is the new pressure inside the canister?