Question

describing the relationship between energy and temperature
explain what happens to the average kinetic energy,
thermal energy, and temperature of a substance when the
particles in the substance slow down.

Explanation:

• Average kinetic energy: Kinetic energy is related to the motion of particles. When particles slow down, their average kinetic energy decreases as kinetic energy formula \(KE=\frac{1}{2}mv^{2}\) (where \(v\) is velocity) shows a direct relation with speed.
• Thermal energy: Thermal energy is the sum of the kinetic and potential energies of the particles in a substance. Since the average kinetic energy (a major component of thermal energy for many substances, especially in the gas phase where potential energy due to intermolecular forces is less significant compared to kinetic energy in some cases) decreases, thermal energy also decreases.
• Temperature: Temperature is a measure of the average kinetic energy of the particles in a substance. As the average kinetic energy of particles decreases, temperature (which is directly proportional to average kinetic energy for an ideal gas, \(E_{k}=\frac{3}{2}kT\) where \(E_{k}\) is average kinetic energy, \(k\) is Boltzmann's constant and \(T\) is temperature) of the substance decreases.

Answer:

When the particles in a substance slow down, the average kinetic energy of the particles decreases. Since thermal energy is related to the total kinetic (and potential, but kinetic is a major part here) energy of the particles, thermal energy also decreases. Temperature, which is a measure of the average kinetic energy of the particles (for example, in the ideal - gas model \(E_{k}=\frac{3}{2}kT\)), decreases as well.