What is measured as the average kinetic energy of particles in a substance?

The measure of the average kinetic energy of particles in a substance is temperature. Temperature quantifies how hot or cold a substance is, and it relates directly to the motion of the particles within that substance. As the temperature increases, the particles move faster, indicating higher kinetic energy. Conversely, a decrease in temperature corresponds to slower particle movement and lower kinetic energy.

In contrast, heat refers to the transfer of energy from one body to another due to a temperature difference, not the average kinetic energy itself. Pressure measures the force exerted per unit area by the particles of a substance, which can be influenced by temperature but does not directly indicate kinetic energy. Volume is the amount of space a substance occupies and does not correlate to the motion of its particles. Thus, the concept of temperature distinctly captures the average kinetic energy of particles, making it the correct choice in this context.