chemical reactions

• state symbols


  (s) means solid

  (l) means liquid (not the same as dissolved in water)

  (g) means gas

  (aq) means aqueous (dissolved in water)
• chemical changes

  • non-reversible colour change
  • light or heat is absorbed or produced
  • formation of a precipitate (insoluble solid)
  • formation of a gas shown by bubbles
• test for gases: hydrogen test


  a lit wooden splint makes a popping sound in a test tube of hydrogen gas.
• test for gases: oxygen test


  a glowing wooden splint relights in a test tube of oxygen gas
• test for gases: carbon dioxide test


  limewater turns cloudy white with bubbles visible