Carbonate acid test

Drop different rocks or minerals into vinegar - carbonate rocks will bubble. Sea shells are made of carbonate and also bubble.
Science content
Earth/Space: Rock cycle, Earth Materials, Natural resources (5)
Lessons activity is in
  • ice cube trays (darker colour shows bubbles best)
  • shell pieces e.g. oyster or clam shells from a beach
  • pieces of calcite, limestone, marble (carbonate rocks)
  • pieces of quartz, quartzite (or other non-carbonate rocks; test first as some carbonate is present in many rocks)
  • vinegar in squeeze bottles
  • flashlights to view bubbles more easily
  • optional worksheet (attached)

Carbon in the ocean is assimilated into animal shells and rocks.
A test for a carbonate-containing shell or rock is the "acid test". When a shell or carbonate rock is dropped in vinegar (or other acid), the shell or rock bubbles.

Using an ice cube tray to keep tests separate, students can test for carbonate.
First add vinegar to a beach shell, and see bubbles streaming off the shell, as it reacts with the acid. These bubbles are from the carbonate in the shell as it chemically reacts with the acid, to make carbon dioxide gas.
A flashlight helps to see the tiny bubbles.

Students can then be given different kinds of minerals or rocks, some carbonates and some other rock families, to try the acid test on each, and group them into their families (carbonate and other). Use the optional worksheet (attached below).
We used carbonate rocks (calcite, limestone and marble) and silica rocks (quartz and quartzite).

Note that many rocks contain little seams of calcite (which bubbles), so to find a rock that does not bubble at all these must be absent. Test rocks first. We used quartz (easy to find in rock shops) and quartzite (harder to find).

Grades taught
Gr 5
Gr 6