What a Drip

Age/Grade Appropriate

Grades 3 through 6

Post-Visit Activity for Geologist in Your Classroom

Key Concepts

Erosion

Observation

Background

A Taoist proverb says that "water, so soft and yielding, will in time wear away the hardest stone." Erosion is a strong force in nature.

Purpose

Can water be stronger than something solid? Understanding that water can carve solid objects.

Procedure

Obtain two new bars of soap that are the same size and brand.

Get permission to let a faucet run for a few hours or, better yet, overnight.

Adjust the water flow so that the faucet drips slowly but steadily.

Unwrap the two bars of soap. Put one bar directly under the dripping faucet.

Put the other bar in a dry place. This is called the "control" bar.

At the end of observation period, turn off the water. Bring both bars of soap to the same location and compare them.

Results

The bar exposed to water will be carved by the water with either a groove or a "pit." The other bar should be unchanged or slightly dried.

Why?

Extensions

How could this process be speeded up? Try it with water at a faster drip rate.

What happens to the bar of soap that has been dripped on if you let it dry? Some soaps will crack into layers. This is weathering.

Materials

Two bars of soap, same size and brand

Faucet or some way of steadily but slowly dripping water