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Limestone

Photograph by DonNichols, iStockphoto

Rock On

Try this experiment to find out the differences in the composition of rocks.

HERE'S HOW

Pour a half cup of vinegar into a glass. Add a small chunk of limestone rock. (Find limestone outside using a rock identification book or buy a piece at a hobby shop). Watch closely. After a few minutes the rock will start to fizz. Now try the same test with other rocks and minerals. You may not see any bubbles.

WHY?

Vinegar, an acid, dissolves bits of a material called calcium carbonate in the limestone. This releases carbon dioxide, a gas that rises to the surface as a stream of bubbles. Rocks that don't contain calcium carbonate won't fizz.