Question

Water is boiling in a clear pot, as shown in the picture.


How do the water molecules closest to the burner compare to the water molecules closest to the surface of the liquid?

They are more spread out and moving faster than those at the surface.
They are closer together and moving faster than those at the surface.
They are more spread out and moving slower than those at the surface.
They are closer together and moving slower than those at the surface.

Answer 1

They are more spread out and moving faster than those at the surface.

Explanation: the water near the burner is hotter, so its molecules have higher kinetic energy (move faster) and are slightly farther apart due to thermal expansion; cooler surface molecules move more slowly and are more closely packed.