Sam slowly heats a beaker of liquid on a hot plate. The liquid has a boiling point of 78 degrees Celsius. Sam makes the graph shown below from the data he records as the liquid is heating. Which of the following statements best describes what happens to the molecules of the liquid between the 5 and 10 minutes of heating?
A.
The mass of the molecules increases.
B.
The molecules undergo a chemical change.
C.
The molecules absorb energy to change phase.
D.
The average kinetic energy of the molecules decreases.