Gases

• If the gas is more dense (CO2) to collect it you do the upward displacement of air. So the air is pushed upwards
• If the gas is less dense then air (H2) you can collect it by doing downwards displacement of air. So air has to move out of the tube
• If it is not soluble in water (O2) put the test tube over water so it can be collected
• AmmoniA turns damp red litmus paper blue because there are present of OH- ions
• Chlorine bleaches damp litmus paper because it is acidic. Also forms an acidic solution
• Test for carbonate ions

  Add hcl to CACO3 it should fizz. bubble gas through limewater. It should turn cloudy