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1 1 KS3 SCIENCE - CHEMISTRY KS3 SCIENCE - CHEMISTRY Chemical Changes Chemical Changes

2 2 ABOUT CHEMICAL REACTIONS

3 3 A Chemical Reaction takes place between Reactants and leads to certain Products being formed A Chemical Reaction takes place between Reactants and leads to certain Products being formed FeFe SS SS FeFe + + In this case, Iron plus Sulphur heated together make Iron Sulphide In this case, Iron plus Sulphur heated together make Iron Sulphide

4 4 ABOUT CHEMICAL REACTIONS Apart from about 100 Elements, all other materials are Compounds, produced by chemical reactions Apart from about 100 Elements, all other materials are Compounds, produced by chemical reactions The Atoms of the elements Bond to form Molecules of the compound The Atoms of the elements Bond to form Molecules of the compound SS FeFe

5 5 ABOUT CHEMICAL REACTIONS Apart from about 100 Elements, all other materials are Compounds, produced by chemical reactions Apart from about 100 Elements, all other materials are Compounds, produced by chemical reactions In a chemical reaction there is no change in Mass In a chemical reaction there is no change in Mass

6 6 ABOUT CHEMICAL REACTIONS However, chemical reactions always take in or give out energy, usually heat However, chemical reactions always take in or give out energy, usually heat Apart from about 100 Elements, all other materials are Compounds, produced by chemical reactions Apart from about 100 Elements, all other materials are Compounds, produced by chemical reactions

7 7 ABOUT CHEMICAL REACTIONS Visible signs of reaction include gas coming off or colour changes Visible signs of reaction include gas coming off or colour changes Apart from about 100 Elements, all other materials are Compounds, produced by chemical reactions Apart from about 100 Elements, all other materials are Compounds, produced by chemical reactions

8 8 TYPES OF REACTIONS

9 9 Oxidation is when Oxygen combines with a substance to make the Oxide Oxidation is when Oxygen combines with a substance to make the Oxide Examples include Rusting to give Iron Oxide and Combustion to give Carbon Dioxide Examples include Rusting to give Iron Oxide and Combustion to give Carbon Dioxide

10 TYPES OF REACTIONS Reduction is the removal of Oxygen, e.g. smelting metal Reduction is the removal of Oxygen, e.g. smelting metal Neutralisation is the removal of Acidity or Alkalinity, e.g. for the stomach Neutralisation is the removal of Acidity or Alkalinity, e.g. for the stomach

11 TYPES OF REACTIONS Decomposition is the breaking down of a compound into its parts Decomposition is the breaking down of a compound into its parts This can be Thermal decomposition which is caused by heat This can be Thermal decomposition which is caused by heat

12 TYPES OF REACTIONS Decomposition is the breaking down of a compound into its parts Decomposition is the breaking down of a compound into its parts Or it can be Electrolysis, where the compound is broken down by electricity Or it can be Electrolysis, where the compound is broken down by electricity X X CELL

13 TYPES OF REACTIONS Reactions that give out heat are called Exothermic, those that take in heat are Endothermic Reactions that give out heat are called Exothermic, those that take in heat are Endothermic Exothermic Endothermic

14 TYPES OF REACTIONS A Displacement reaction occurs when a Metal “kicks out” a less reactive one and takes its place A Displacement reaction occurs when a Metal “kicks out” a less reactive one and takes its place OO OO SS OO Cu OO Zn OO OO SS OO OO Cu Copper Sulphate and Zinc becomes Zinc Sulphate and Copper Copper Sulphate and Zinc becomes Zinc Sulphate and Copper

15 COMMON REACTIONS

16 COMMON REACTIONS Fermentation is used to produce wine - this is a reaction that turns Sugars into Ethanol, giving off some Carbon Dioxide Fermentation is used to produce wine - this is a reaction that turns Sugars into Ethanol, giving off some Carbon Dioxide

17 COMMON REACTIONS To generate electricity we need Energy, and this often means combustion To generate electricity we need Energy, and this often means combustion Fossil Fuels are burned to create steam to drive Turbines Fossil Fuels are burned to create steam to drive Turbines

18 COMMON REACTIONS Internal Combustion Engines are used to power vehicles Internal Combustion Engines are used to power vehicles

19 COMMON REACTIONS Food “goes off” when Bacteria and Fungi grow on it, giving off bad, smelly chemicals Food “goes off” when Bacteria and Fungi grow on it, giving off bad, smelly chemicals