C4

• the PH scale

  • lower the PH of a solution, the more acidic it is
  • A neutral substance has ph 7
• How to measure the PH:

  • Indicator -a dye that changes colour depending on whether its above or below a certain PH.
  • A PH probe attached to a PH meter can also be used to measure pH electronically. the probe is placed in the solution you are measuring and the PH is given on a digital display as a numerical value, meaning its more accurate than an indicator
• Acids and bases netralise each other

  1. An acid is a substance that forms aqueous solutions with a pH of less than 7. Acids form H+ ions in water
  2. A base is a substance with a pH greater than 7
  3. An alkali is a base that dissolves in water to form a solution with a PH greater than 7. Alkalis form OH- ions in water

  the reaction between acids and bases is called neutralisation:

  acid + base = salt + water