How to test for gases

• What are the four carbon gases tested in the video?

  Chlorine, oxygen, hydrogen, carbon dioxide
• What is the first step in testing for chlorine?

  Fill a test tube with the sample gas
• What happens to blue litmus paper when chlorine is present?

  It turns from blue to white
• Why might the blue litmus paper briefly turn red before turning white?

  Chlorine forms hydrochloric acid with water
• What safety precaution should be taken when testing for chlorine?

  Wear a mask or use a fume cupboard
• What is used to test for oxygen?

  A glowing splint
• What happens to a glowing splint in the presence of oxygen?

  It relights
• How is hydrogen tested?

  With a burning splint that makes a pop
• What causes the squeaky pop sound when testing for hydrogen?

  Hydrogen burns with oxygen to form water
• What is the test for carbon dioxide?

  Bubbling gas through lime water
• What happens to lime water when carbon dioxide is bubbled through it?

  It goes cloudy
• Why does lime water go cloudy when carbon dioxide is present?

  Calcium carbonate forms as a solid
• What are the results of the tests for the four gases?

  • Chlorine: Turns blue litmus paper white
  • Oxygen: Relights a glowing splint
  • Hydrogen: Produces a squeaky pop
  • Carbon dioxide: Causes lime water to go cloudy
• What is the chemical reaction when hydrogen burns?

  Hydrogen and oxygen form water
• What is the role of calcium hydroxide in the carbon dioxide test?

  It reacts to form calcium carbonate
• How does the presence of chlorine affect litmus paper differently than carbon dioxide?

  Chlorine bleaches it, carbon dioxide does not