Physical Weathering Of Rocks: Sugar Cube Breakdown

The rocks that compose the Earth's crust are subjected to a variety of forces. Depending on the environmental factors at work, the rocks can be altered in size or in composition. Factors such as wind, water, plants, and animals cause weathering, physical changes in rocks that affect their size. However, physical changes do not affect the composition of rock. In this activity you will see the effect of physical weathering on rocks.

Materials

Piece of sandpaper; Tape; Small jar with a lid; Three sugar cubes; Paper plate

Activity

1. Open the jar and line the inside of it with the piece of sandpaper so that the rough surface is facing the interior and the smooth surface is against the glass. Tape the sandpaper onto the inside walls of the jar.
2. Look at the sugar cubes and note their sizes.
3. Drop the three sugar cubes in the jar and close the lid.
4. Shake the jar vigorously for two minutes.
5. At the end of two minutes, open the lid and carefully pour the contents of the jar onto the paper plate.

Follow-Up Questions

1. How did the size and consistency of the sugar cubes change after being agitated in the jar?
2. What type of environmental force do you think you were simulating when you shook the jar? What did the sugar cubes represent in this activity?
3. Chemical weathering changes the composition of rocks. How do you know that the type of weathering in this activity was physical and not chemical?

Answers

1. The sugar cubes were smaller and more irregular.
2. Shaking represents erosion. The sugar cubes represent rocks.
3. The sugar cubes did not change in composition—only in appearance.

Extension

Plan another activity to show the physical weathering of sugar cubes in which you can collect quantitative data by finding the mass of the chunks of sugar cubes before and after the activity. Show your plan to your teacher.