A cooling curve shows the reverse process as a substance is cooled. It consists of similar distinct regions, but in reverse order (Figure 2.2).
Gas Phase (Higher Temperature to E)
Segment higher temperature to E: The temperature of the gas decreases as it loses heat. The kinetic energy of the gas particles decreases, causing them to move less rapidly.
Condensation (E to D)
Segment E to D: The temperature remains constant as the gas condenses into a liquid. The lost heat energy is released as the intermolecular forces bring the particles closer together, resulting in the latent heat of vaporization being released.
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Liquid Phase (D to C)
Segment D to C: The temperature of the liquid decreases as it loses more heat. The kinetic energy of the particles decreases, causing them to move more slowly.