1. Topic 1
Chemical Reactions

2. What is a chemical reaction?
A chemical reaction can be defined as the process in which changes occur in matter to produce new substances.
These chemical changes happen all around us.

3. Everyday Chemical Reactions
Cars rusting
Frying an egg
Coal burning
Manufacture of medicines
Digestion of our food

4. In a chemical reaction a new substance is always formed.
The starting chemicals in reactions are called reactants and the new substances formed are called products.
Reactants  Products

5. Signs of a chemical reaction are:
A colour change
The appearance of a solid (precipitate)
A fizzing as a gas forms (effervescence)
A temperature change

6. 1. Precipitation Reaction
Aim: To investigate what happens when sodium carbonate solution is added to cobalt (II) chloride solution.
Method:
5ml sodium carbonate solution
5ml cobalt chloride solution +

7. Result:
Conclusion: On adding two solutions together, a solid may be formed. This is called precipitation.

8. Precipitation is the reaction in which a precipitate is formed.
Precipitate When two liquids are mixed an insoluble solid that appears is called a precipitate.
See pg 5 of data booklet