Topic 1 - Acids and indicators

INDICATORS

• Blue litmus paper turns red when wetted with acid.
• There are plenty of naturally occurring dyes which behave in a similar way to commercial indicators. Some examples are: 
  • red cabbage leaves
  • purple hollycock flowers
  • purple violet flowers
  • deep red or purple fruits (e.g. cherries, blackberries).

ACIDS

• We come across acids in everyday life. Some examples are:
  • ethanoic acid (often called acetic acid) – in vinegar
  • citric acid – in citrus fruits such as oranges and lemons
  • ascorbic acid – a scientific name for vitamin C
  • salicylic acid – a scientific name for aspirin
  • tartaric acid – used in baking
  • phosphoric acid – found in rust remover and cola drink.

In general, acids have…