1. Chapter 28 Acids & Bases 2 Revision: Chapter 24 Acids & Bases Acids are substances that turn litmus from blue to red. Bases are substances that turn litmus from red to blue. pH Scale is a measure of how acidic or basic a substance is. It is a scale from 0-14. pH 7 is neutral, 0-6 is acidic and 8-14 is basic Universal indicator is a mixture of indicators.

2. Common Acids Hydrochloric Acid (HCl) Sulphuric Acid (H 2 SO 4 ) Both are strong acids Examples of weak acids are citric acid or acetic acid. Common Bases Sodium Hydroxide (NaOH) (Caustic Soda) Calcium Hydroxide (Ca(OH 2 ) (limewater) (Test for carbon dioxide turns milky) These are strong bases. Examples of weak bases are toothpaste

3. Reaction of an Acid with a Base is called Neutralisation Indigestion: antacid + indigestion = neutralisation Examples of neutralisation: Toothpaste + plaque on teeth = neutralisation Bee sting + baking soda = neutralisation Wasp sting + vinegar = neutralisation Dock leaves + acid sting from nettle = neutralisation Formation of Salts Acid + Base = Salt + Water HCl + NaoH = NaCl + H 2 O

4. A salt is formed when the hydrogen in an acid is replaced by a metal There are lots of different salts e.g. sodium chloride NaCl, potassium chloride KCl Acids with Limestone

15. Summary