Calcite
Calcite is a mineral found in many rocks that fizzes when it touches vinegar.
Think of it this way
Baking soda in a bowl fizzes when you pour vinegar on it. Calcite does the same thing — it is a rock mineral that reacts with acid. Pour acid on calcite, and bubbles form fast. This fizz test is how scientists spot calcite in rocks.
Explaining calcite by grade level
Some rocks have calcite inside them. You can test for it with vinegar. Pour a little vinegar on the rock and watch. If you see tiny bubbles, the rock has calcite in it.