Acids & Alkalis

The pH Scale
1. Used to measure how acidic or alkaline a solution is
2. The strongest acid has a pH of 0
3. The strongest alkali has a pH of 14
4. A neutral substance (eg. water) has a pH of 7
Indicator Dye
1. The dye in an indicator solution changes colour depending on whether it's above or below a certain pH.
2. Universal Indicator is a combination of dyes that produce the colours in the diagram to the right depending on the pH of a solution
  1. It's very useful for estimating the pH of a solution
Acids & Bases
1. Acids & Bases neutralise each other
2. An ACID is a substance with a pH of LESS than 7
  1. Acids for H+ ions in water
3. A BASE is a substance with a pH GREATER than 7
  1. An ALKALI is a base that DISSOLVES in water
    1. Alkalis form OH- ions in water
4. H+ ions make solutions acidic
  1. OH- ions make solutions alkaline
The reaction between acids and bases is called neutralisation
1. acid + base -> salt + water
2. H+ + OH- -> H2O
  1. H2O (Water) has a neutral pH so this shows that an acid and bases neutralise each other

Resource summary

	Created by Tom Johnson almost 10 years ago