The image shows a particle model.

Question

The particles in the model are loosely packed and show significant vibration.

Which two points on the graph does this model best represent?

A.
A

B.
B

C.
C

D.
D

E.
E

F.
F
It's Getting Hot in Here
Water is poured into a beaker and then frozen. In order to monitor the temperature of the water, a small hole is cut into the ice and a thermometer is placed in the hole. The beaker is then placed on a hotplate. Exactly 15 minutes later, the water in the beaker becomes entirely liquid. The diagrams show the beaker when it is first placed on the hotplate and then 15 minutes later.



The graph shows the change in temperature as heat energy is added to the beaker.

The graph is titled 'Temperature of Water as Energy Is Added'. The vertical axis shows temperature increasing and the horizontal axis shows heat energy being added. The plot line starts at the origin, labelled as point A. It shows a sharp rise from point A to point B as energy is added, and it continues to rise until point C. Then as energy is continuously added, it shows no rise until point E. From point E to point F the temperature rises sharply again, and continues to rise thereafter, at the same rate.

Answer 1

Based on the description of the particle model and the changes in temperature as heat energy is added, the most likely best representation of the particle model you described (with loosely packed particles that vibrate significantly) corresponds to the states of matter represented in the graph.

1. Loosely packed particles that vibrate significantly describes a liquid state of matter, as liquids have a definite volume but take the shape of their container. The particles in liquids are closer together than in gases, but still have the ability to move, allowing for vibration.

2. In the context of the graph titled "Temperature of Water as Energy Is Added," the initial part of the graph from point A to point B represents the heating of ice (solid state). The plateau between point C and point E represents the phase change from solid (ice) to liquid (water), where temperature remains constant as the ice melts. Finally, the rise from point E to point F reflects the heating of liquid water.

Since the particle model best represents a liquid and we are looking for two points that correspond to the temperature during the existence of water in its liquid state:

• Point D (temperature where water is just beginning to be in the liquid state after ice has melted).
• Point E (temperature near the end of phase change after ice has fully melted into water).

Thus, the two points on the graph that this model best represents are D and E.