Question

A student fills a large container with cold water. He fills another, smaller container with hot water and red food coloring, and seals it with a lid. Next, he places the small container of hot water into the larger container of cold water. When he removes the lid on the small container, he observes the colored water rising up to the top of the cold water. Why does this occur? Select all that apply.
Responses

because the hot water molecules move slower than those of cold water
because the hot water molecules move slower than those of cold water

because the hot water molecules move faster than those of cold water
because the hot water molecules move faster than those of cold water

because the hot water is less dense than the cold water
because the hot water is less dense than the cold water

because the hot water molecules move as fast as those of cold water
because the hot water molecules move as fast as those of cold water

because the hot water has the same density as the cold water
because the hot water has the same density as the cold water

because the hot water is more dense than the cold water
because the hot water is more dense than the cold water

Answer 1

The correct responses for why the colored hot water rises to the top of the cold water are:

- **because the hot water molecules move faster than those of cold water**: Hot water is made up of molecules that have more kinetic energy and move more rapidly than those in cold water, which contributes to its tendency to rise.

- **because the hot water is less dense than the cold water**: Hot water is less dense than cold water due to the increased energy and kinetic motion of the hot water molecules, which causes them to occupy a greater volume and results in lower density.

The other options, regarding slower movement of hot water molecules, equal density, and greater density, are incorrect.