Science4MyKid
Science Project: Rock Tester Viewed: 2614
Return To Project List Printable View

Rock Tester

How do geologists identify their specimens? This is one way.

You need:

  • a small sampling of various rocks including limestone or marble.
  • 2 oz. lemon juice , or vinegar (60 ml) 

What to do:

Pour the lemon juice or vinegar over the rock.

What happens:

The liquid bubbles on some but not on others.

Why:

When the lemon juice bubbles, the rock sample is either limestone or marble. Limestone, a sedimen­tary rock formed under water from mud and silt, contains a carbonate form of calcium, an alkaline earth metal. When you add the lemon (an acid) to the alkaline of the limestone, it forms carbon dioxide. That makes the liquid bubble up, just as pan­cakes and cakes puff up when you add baking soda to the batter. Actually, baking soda can be made from limestone. Marble is a rock formed under great heat and pressure from limestone. It reacts to acid just as limestone does. You get similar results if you add lemon juice to the chalk, because it too is made of limestone.

Be careful not to get the lemon juice or vinegar in your eyes, it will burn