Video Transcript
Chemists measure the energy of water molecules before and after they vaporize. Which graph shows their results?
This question asked about the process of vaporization. Vaporization is the change in phase from liquid to gas when gaining thermal energy. Specifically, the question is asking which graph shows the correct energy levels of water molecules in the liquid and gas phases during the process of vaporization. One clue to the correct answer is in the definition. Vaporization involves the molecules gaining energy. We can think of heating a tea kettle to produce steam as a simple example of a liquid gaining energy to vaporize into a gas. In general, we can say that gases are more energetic than liquids.
The graphs in answer choices (B) and (D) show a decrease in energy from the liquid to the gas phase, while the graph in answer choice (C) shows no change in energy. These answers are incorrect. The graph in answer choice (A) shows a strong increase in energy from the liquid to the gas phase. Since the gas phase should be much more energetic than the liquid phase, this is the correct graph.
So, which graph shows the results of this experiment? That’s the graph shown in answer choice (A).
