 An acid is a substance that produces hydrogen ions (H + ) when in solution with water  Water (H 2 O) is made up of even amounts of H + and OH - ions. Water is NEUTRAL because of this. When an acid dissolves in water, this changes the amount of H + ions.  Examples of acids include hydrochloric acid, citric acid, acetic acid (vinegar)

 The more H + ions it produces, the more acidic the solution  Strong acids are very dangerous. They have a high H + concentration.  Weak acids are less dangerous. They have a low H + concentration

 Acids occur naturally in many fruits  Sore muscles and sour milk are cause by the same acid (lactic acid)  Acids add a tangy, sour flavours to foods and drinks  Some are deadly!

 A base is a substance that produces hydroxide ions (OH - ) when in solution with water.  When a base is added to water it increases the amount of OH - ions  Another word for basic is alkaline  Example: Sodium hydroxide (NaOH)

 The more OH - ions it produces, the more basic (alkaline) the solution  Strong bases are as dangerous as strong acids. They have a high OH - concentration.  Similarly, weak bases are like weak acids with a low OH - concentration

 Bases are bitter-tasting compounds  They have a slippery feel  Bases are in most soaps, drain and window cleaners.  They can be found in many pharmaceutical drugs  Some bases are deadly!

 pH means “power of the hydrogen ion”  A pH scale is a measure of the acidity of a solution  In pH the “p” is always lower case, even at the start of a sentence.

 The pH scale has a useful range of numbers between 0 and 14.  A solution with a pH of 7 is neutral (like water)  Below pH 7, a solution is acidic  Above pH 7, it is basic

 Paper tests like litmus paper and pH paper

 Tests the voltage of the electrolyte  Converts the voltage to pH  Very cheap, accurate  Must be calibrated with a buffer solution

 Indicators are dyes that can be added that will change color in the presence of an acid or base.  Some indicators only work in a specific range of pH  Once the drops are added, the sample is ruined  Some dyes are natural, like radish skin or red cabbage

 When an acid and a base react together their pH becomes neutral. Acid + base  salt + water Ex: HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l)  This is a double displacement!

Neutralisation Reaction: Acid+Base  Salt+Water Ex:HCl+NaOH  NaCl+ H 2 O  The acid and base neutralise each other creating a salt and water  Must be equal concentrations of acid and base

HNO 3 + KOH KNO 3 + H 2 O HF + NaOHNaF + H 2 O HCl + Ca(OH) 2 CaCl 2 + H 2 O22 acid + base salt + water

1. Ba(OH) 2 + H 3 PO 4  2. HC 2 H 3 O 2 + NaOH  3. H 2 SO 4 + KOH  4. H 2 CO 3 + NaOH  5. Na 2 CO 3 + HCl 