How do the water molecules closest to the burner compare to those near the surface in a pot of boiling water?

How do the water molecules closest to the burner compare to those near the surface in a pot of boiling water?

• A. They are more spread out and moving faster than those at the surface.
• B. They are closer together and moving faster than those at the surface.
• C. They are more spread out and moving slower than those at the surface.
• D. They are closer together and moving slower than those at the surface.

Answer: (A)

When you heat water, the layer closest to the burner receives energy first, so those molecules gain more kinetic energy and move faster. In a liquid, higher temperature also makes things expand a bit, so the molecules are, on average, a bit farther apart. The surface region, while also hot, loses energy to vaporization and is not as energized as the bottom layer, so its molecules are moving slower and are not as spread out. That combination means the water molecules near the burner are moving faster and are more spread out than those near the surface.

When you heat water, the layer closest to the burner receives energy first, so those molecules gain more kinetic energy and move faster. In a liquid, higher temperature also makes things expand a bit, so the molecules are, on average, a bit farther apart. The surface region, while also hot, loses energy to vaporization and is not as energized as the bottom layer, so its molecules are moving slower and are not as spread out. That combination means the water molecules near the burner are moving faster and are more spread out than those near the surface.