16. Heat is added between B and C as shown on the graph above. However, the temperature does not increase. Why? a. The energy is used to decrease the temperature. b. The energy is used to break the bonds of the liquid. c. The energy is used to break the bonds (overcome intermolecular forces) of a solid. d. The energy is used to boil the substance. 17. If heat is removed from point E and the temperature does not change, the substance will __ a. condense b. boil c. melt d. evaporate 18. For the parts of the graph that slope up from left to right, which statement below is TRUE? a. Energy is being added to the substance. b. The substance is getting hotter c. The particles are spreading out. d. All of the above are true.

## Step1<br />For question 16, the graph shows that heat is added between points B and C, but the temperature does not increase. This indicates that the added energy is not being used to increase the temperature, but rather to change the state of the substance. The most likely explanation is that the energy is being used to break the bonds of the liquid, which is option b.<br /><br />## Step2<br />For question 17, the graph shows that heat is removed from point E, but the temperature does not change. This indicates that the substance is undergoing a phase change. The most likely explanation is that the substance is condensing, which is option a.<br /><br />## Step3<br />For question 18, the graph shows that the slope is positive from left to right, indicating that energy is being added to the substance. This means that the substance is getting hotter, the particles are spreading out, and all of the above statements are true, which is option d.