As water is heated, the correct understanding of what happens to water molecules includes the following aspects:
- The molecules gain energy and move faster, which causes them to spread apart. This leads to an increase in volume and a decrease in density.
- Therefore, heated water becomes less dense than cooler water, which is why it rises to the top.
Given the options:
a. The molecules get closer together. (Incorrect) b. The molecules become less dense. (Correct) c. The molecules sink. (Incorrect)
So, the best answer is b. The molecules become less dense.