It's Getting Hot in Here

Question

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.
The picture shows a particle model.

The particles in the model are tightly packed and show slight vibration.

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

A.
A

B.
B

C.
C

D.
D

E.
E

F.
F

Answer 1

The particle model described indicates that the particles are tightly packed and show slight vibration, which is characteristic of a solid state. Based on the graph description:

• Point A represents the initial state of water (ice) before any heat is added.
• Point B reflects the increase in temperature of the ice as heat energy is absorbed, leading to a higher temperature but still remaining solid.
• Point C likely represents the phase change from solid to liquid (melting) where the temperature remains constant while the ice melts.
• Point D would represent the complete transition to liquid, no longer showing solid characteristics.
• Point E marks the point where the water has fully transitioned to liquid and begins to heat up.
• Point F shows the water reaching a new higher temperature beyond point E.

Since the particle model illustrates tightly packed particles with slight vibration, it best represents the state at Point A (solid ice), and potentially Point B (just before melting begins) where the particles are still in a solid state but gaining energy. However, for clarity, it primarily represents Point A.

Therefore, the three points that the model best represents would be:

• A (ice before heating starts)
• B (ice warming before melting starts)
• C (transition point where melting begins)

Answer: A, B, C