Carbon dioxide can be detected by bubbling the gas through limewater, which is a solution of calcium hydroxide. If carbon dioxide is present, the limewater turns milky or cloudy white due to the formation of calcium carbonate.

1. Prepare a test tube or small beaker containing limewater (calcium hydroxide solution). Limewater can be made by adding pieces of calcium metal to distilled water.
2. Bubble the suspected gas through the limewater using a delivery tube.
3. Observe any color change in the limewater.
4. If carbon dioxide is present, the limewater will turn cloudy or milky.

Testing for CO2 (Carbon dioxide) with Limewater - Wayne Breslyn (Dr. B.):

Limewater Test for Carbon Dioxide. - Primrose Kitten Academy:

📄 Tests for gases - BBC Bitesize: https://www.bbc.co.uk/bitesize/guides/z6dtgwx/revision/1

• Use a straw to gently blow into limewater to demonstrate exhaled carbon dioxide.
• Compare with bubbling oxygen, nitrogen, or hydrogen through limewater to confirm no change occurs.

• Wear safety glasses to protect eyes from splashes.
• Do not inhale directly from the gas delivery tube.
• Avoid prolonged blowing into limewater, as it may increase risk of contamination or ingestion.
• Handle calcium hydroxide carefully, as it is mildly caustic.

• What chemical forms when carbon dioxide reacts with limewater? (Calcium carbonate.)
• Why does the limewater eventually clear if excess carbon dioxide is added? (Because calcium carbonate reacts with more carbon dioxide and water to form soluble calcium hydrogencarbonate.)
• Why is this test unique to carbon dioxide? (Other common gases do not react with limewater to produce a cloudy precipitate.)