As the temperature of a substance decreases, the
average kinetic energy of its particles
(1) decreases
(2) increases
(3) remains the same

Option (1) is the correct answer.

Explanation:

Kinetic energy is the energy that arises due to the motion of molecules. Average kinetic energy involves the sum of vibrational, translational and rotational kinetic energies.

When we decrease the temperature then the movement of molecules starts to decrease. As a result, there will be decrease in the average kinetic energy of its particles.

Thus, we can conclude that as the temperature of a substance decreases, the  average kinetic energy of its particles decreases.