In Chemistry, we use simple test methods to identify common gases. These tests rely on observable chemical changes and are easy to carry out in the lab.

Test for hydrogen

✅ Lit splint test

• Insert a lit splint into a test tube of gas
• If hydrogen is present, you hear a squeaky pop

💡 The pop is caused by hydrogen reacting with oxygen in the air to form water.

Test for oxygen

✅ Glowing splint test

• Insert a glowing splint (not burning) into the test tube
• If oxygen is present, the splint relights

💡 Oxygen supports combustion, so the splint flares up again.

Test for carbon dioxide

✅ Limewater test

• Bubble the gas through limewater (calcium hydroxide solution)
• If carbon dioxide is present, the limewater turns cloudy/milky

💡 The cloudiness is caused by the formation of calcium carbonate.

Test for chlorine

✅ Damp litmus paper test

• Hold damp blue litmus paper near the gas
• If chlorine is present, the paper turns red, then is bleached white

💡 Chlorine is an acidic gas and also acts as a bleaching agent.

Gas test summary table