A heating curve shows the relationship of the temperature and heat input of a system as that system is heated over time, the University of Texas at Austin explains. The curve indicates how the system?s temperature changes in response to heat and when phase transitions occur.
The effects of heat on a system depend on what, if any, chemical processes are occurring in that system, and whether the system is changing phase. The heating curve displays these effects at different points of applying the heat over time. A system?s temperature will rise if heat is applied consistently and no chemical processes or phase transitions are occurring. On the heating curve, the slope of the line (the ratio of temperature and time) is the heat capacity of the system at that point.
If chemical processes or a phase transition is occurring, the system?s temperature can remain the same despite heat being applied. This happens because the energy entering in the form of heat is turned not into kinetic energy but into the potential energy of breaking down intermolecular forces. These forces are what keeps the system in the state of matter it is currently in. Generally, a greater amount of heat is required to convert a liquid to a gas than is required to convert a solid to a liquid. This is because the former requires completely overpowering the intermolecular forces, while the latter only requires weakening them.