Rocks and Minerals > Rock Cycle Activities

Physical Weathering: Temperature Changes

by Deborah Hanuscin

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Concept: Erosion of rocks caused by rapid temperature changes

Rocks subjected to rapid temperature changes may expand or contract, which may cause them to fracture. The fractures may then lead to further breakdown of the rock through other physical and chemical weathering processes.

Objective:

Students will be able to describe what happens to rocks that are subjected to rapid changes in temperature.

Materials:

• goggles
• oven mitt
• ice water
• pan
• heat source
• shale (or pieces of glass)
• tongs
• balloons

Procedure:

1. Blow up a balloon about half way. Place it in warm water or near a hot object. What happens to the balloon?
2. Place the balloon in ice water. What happens?
3. Put on goggles and oven mitt and use tongs to heat shale (or glass).
4. Drop heated shale or glass into a container of ice water. What happens? What does rapid temperature change do to some rocks? Why? Where might rocks be exposed to this kind of temperature change?

When heated, a substance expands because its molecules are moving faster and farther apart. The molecules themselves do not expand. In a similar way, cooling contracts a substance because its molecules move more slowly and closer together. Rocks that are exposed to sudden heating and cooling may be subject to uneven contraction and expansion. Such stress may cause them to break. This is one type of physical weathering.

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