The Composition of Rocks and Minerals

NC Standard:  2.01, 2.02, 2.04, 2.06

Activity:  Acid Test

Question: How do rocks react to vinegar?

Vocabulary: Acid test

Materials: Assortment of rocks, plastic cups, vinegar, chalk

Background: This test is called the acid test and is normally performed with diluted hydrochloric acid. Vinegar is a weak acid and works satisfactorily. The acid test is used to identify rocks that contain calcium carbonate. Any such rock will fizz when vinegar is applied. Limestone, marble, calcite and chalk are made of calcium carbonate and will fizz in the presence of vinegar. Before applying the vinegar, scratch the surface of the rock to expose fresh material.

Procedures: 

Put a small sample of each rock in a separate cup. Put a small piece of chalk in a cup as one of the rock samples. Pour a small amount of vinegar on each sample. Record what happens. Group the rocks according to the way they respond to the vinegar.

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Line of Learning:  This line is drawn to provide students with a space to share their experimental learning in words or pictures.
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