Final answer:
A temperature change is represented by sloping lines in heating curves, not by the plateaus. The plateaus or horizontal lines indicate phase changes where the temperature remains constant even as heat is added, making the correct option B. False.
Step-by-step explanation:
The statement that a temperature change is represented by lines in heating curves (phase change diagrams) is false. In heating curves, temperature changes are indicated by the sloping lines, whereas phase changes are represented by horizontal lines, or plateaus. These plateaus occur because, during a phase change, the temperature of a substance does not change even though heat is being added.
The energy added during these periods is used to break or form the bonds between molecules, which corresponds to the substance changing its state, such as from solid to liquid (melting) or from liquid to gas (boiling).
For example, when we look at the heating curve for water, as the ice melts at 0°C, the temperature remains constant until all ice has melted. Similarly, during boiling at 100°C, water's temperature stays constant until it has all vaporized. The length of the horizontal lines in these curves directly correlates with the enthalpies of fusion and vaporization. Specifically, the horizontal line at 100°C is much longer than the one at 0°C because the enthalpy of vaporization is several times greater than the enthalpy of fusion. Thus, the mention of the correct option is B. False.