Answer:
It shows how the temperature of the substance falls as heat is removed.
Explanation:
The two typical phase diagram curves are heating curve and cooling curve.
The heating curve shows the dependence of temperature on time when constant heat is applied to the material. Since heat is applied, the temperature rises and we see a typical curve showing an increase in temperature of a solid phase followed by a horizontal line depicting the phase change from solid to liquid, then the same scenario for liquid and gas.
Similarly, cooling curve shows the opposite process: instead of heating the substance, we're now removing heat at a constant rate and the temperature is decreasing now.
That said, it shows how the temperature of the substance falls as heat is removed.
