1. Take some crushed egg shells in a test tube and pour dilute sulphuric acid until the egg shells completely sink. Egg shell is made of calcium carbonate.
2. We will observe that a gas being released.
3. Bring a lighting match stick near the mouth of test tube.
4. The gas that put off the lighting match stick indicating that the gas is carbon dioxide.
5. This confirms that carbon dioxide releases when acid reacts with calcium carbonate.