Question

Unit 2 & 3: Energy Test
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Question
Possible Points: 2
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 is less dense than the cold water
because the hot water is less dense than the 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 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 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 more dense than the cold water
because the hot water is more dense than the cold water

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

Answer 1

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

- **because the hot water is less dense than the cold water**
- **because the hot water molecules move faster than those of cold water**

Hot water is less dense than cold water due to the increased kinetic energy of the water molecules, which causes them to move faster and occupy more space. As a result, the hot water rises to the top when released into the cold water.