Final answer:
Temperature is the measure of the average kinetic energy of the particles in a sample of matter. It's a central concept in thermodynamics, reflecting how the motion of particles increases with temperature and is expressed on a scale measured by a thermometer.
Step-by-step explanation:
The average kinetic energy of the particles in a sample of matter is expressed as temperature. This concept is a fundamental part of the kinetic-molecular theory. While different particles within the sample will have varying kinetic energies, the temperature is the measure of the average kinetic energy of all the particles. When the temperature of a substance is increased, it indicates that the average kinetic energy of its particles has increased as well. Therefore, particles in two samples of matter at the same temperature, regardless of their sizes, states, or the types of molecules, will have the same average kinetic energy.
At a lower temperature, particles move or vibrate more slowly, and thus have a lower average kinetic energy. As the temperature rises, so does this kinetic energy. This is observable in phenomena like the changing of states of matter, where an increase in temperature can cause a solid to become a liquid by imparting additional kinetic energy to the particles.