A sample of gas is held at constant pressure. Increasing the Kelvin temperature of this gas sample causes the average kinetic energy of its molecules to

(1) decrease and the volume of the gas sample to decrease

(2) decrease and the volume of the gas sample to increase

(3) increase and the volume of the gas sample to decrease

(4) increase and the volume of the gas sample to increase

The answer is (4). When the pressure is constant, he temperature increasing can cause both the average kinetic energy of its molecules and the volume of gas sample increase.

Increasing the temperature of a gas sample means that heat energy is been supplied to the System. When energy is been supplied heat energy is transformed into kinetic energy of the gas molecules.

Therefore kelvin temperature increases means more energy given to the system therefore average kinetic energy of molecules increase.

When the kinetic energy of molecules increase they move about more and take up more space. Hence volume too increases.

Therefore the correct answer is

4) average kinetic energy of molecules increase and volume of the gas sample increases