Acids and bases

• Acid


  A substance that has a hydrogen ion (H+) and a pH lower than 7
• Base


  A substance that has a hydroxide ion (OH-) and a pH higher than 7
• Alkali


  A base that dissolves in water
• Corrosive


  A corrosive substance can cause a material to corrode/dissolve
• pH scale


  Compares the different acids and bases
• Universal indicator


  Can be used with the pH scale to help identify the pH level of a substance
• pH 7 is neutral
• Stronger acids have a lower pH than weak acids
• Stronger bases have a higher pH than weak bases
• Neutralisation


  The reaction of an acid + base to form salt and water
• Neutralisation by titration


  1. Burette

  2. Conical flask

  3. HCl

  4. Sodium hydroxide

  5. Universal indicator
• Acid rain formation


  1. Sulphur dioxide (SO2) + nitrogen oxide (NO2) are formed by combustion of fossil fuels

  2. These gases mix and react with the water in the clouds to form acid

  3. The acid in the cloud can travel long distance and fall as acid rain
• Acid rain effect


  Damages plants/animals and corrodes metals and buildings
• To reduce acid rain formation


  Reduce use of fossil fuels
• Acid reactions


  1. Acid + metal - Salt + Hydrogen

  2. Acid + carbonate - Salt + water + carbon dioxide