Which sections of the heating curve illustrate this process?

B followed by D

Explanation:

The heat energy absorbed at B goes into potential  energy that breaks the inter-molecular bonds and thus the constant temperature. Once the molecules have gained enough energy they escape the closely bonded  structure and thus are free to move in random directions due to high kinetic energy. At this point (part D)  an increase in heat energy leads to an increase in the kinetic energy leading to an increase in the temperature.

higher potential

explanation:

because it is in a high speed so it must move into a of high potential