GCSE Chemistry · AQA 8462 · Topic 4.4
Chemical changes
Key points
- Metals react with oxygen to form metal oxides (oxidation). The reactivity series places metals in order using their reactions with water and acids.
- Metals less reactive than carbon are extracted by reduction with carbon; more reactive metals are extracted by electrolysis.
- Oxidation is gain of oxygen or (Higher) loss of electrons; reduction is loss of oxygen or gain of electrons.
- Acids react with metals, alkalis, bases and carbonates to make salts. Soluble salts are made by reacting an acid with an insoluble base, filtering and crystallising.
- pH measures acidity: below 7 acidic, 7 neutral, above 7 alkaline. Neutralisation is .
- Electrolysis splits ionic compounds that are molten or dissolved: positive ions go to the cathode and negative ions to the anode.
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Chemical changes are about what happens when metals, acids and ionic compounds react. This topic explains how we get metals out of their ores, how acids react to make salts, and how electricity can split compounds apart.
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