Question

A student heats a liquid on a burner. What happens to the portion of liquid that first begins to warm?

It loses energy.
It becomes less dense.
It sinks downward.
Its molecules get closer together.

Answer 1

It becomes less dense.

Explanation: heating increases the kinetic energy of the molecules, they move faster and tend to occupy more space, so the heated portion has lower density and rises (it does not lose energy or sink, and the molecules move farther apart rather than closer together).