Heat and Motion in a Glass

The Action

Students will see that food colouring will disperse more quickly in a glass of warm water than in a glass of cold water.

Grade Level

Grade 3 - Properties of Matter


2 clear glasses

A kettle (or burner for heating the water)


Food colouring

Oven mitts


Heat enough water to fill one of the glasses 3/4 full.

Place both empty glasses in so the students can see them. Fill one glass 3/4 full of cold water and the other 3/4 full of the hot water.

Add food colouring to the glass containing the cold water and observe the results. Then add food colouring to the glass containing hot water and observe the difference.


No safety concerns. Use care when handling the hot water. Be careful when using food colouring as it may stain clothing.

Science Principle

Water molecules are always moving but at different speeds. In the cold water, the water molecules are moving more slowly than the hot water molecules. As a result, the increased movement of the molecules will cause the food colouring to disperse more quickly in the hot water.

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