Put simply, an acid is any substance that has pH of less than 7. The pH scale is used to measure how acid or alkali a substance is:
- 0-3 = strong acid (UI turns red)
- 4-6 = weak acid (UI turns orange/yellow)
- 7 = neutral (UI turns green)
- 8-10 = weak alkali (UI turns blue)
- 11-14 = strong alkali (UI turns purple)
The pH of an acid is determined by the concentration of Hydrogen ions (H+) the substance has when in solution. All acids contain hydrogen ions when in solution; the higher the concentration of H+ ions, the lower the pH.
Fast Fact: Bee stings are acidic. They can be neutralised using baking powder which contains sodium hydrogen carbonate – a base.
Common Acids
| Name | Formula |
|---|---|
| Hydrochloric Acid | HCl |
| Sulphuric Acid | H2SO4 |
| Nitric Acid | HNO3 |
| Phosphoric Acid | H3PO4 |
| Ethanoic Acid (Vinegar) | CH3COOH |