Topic 4: Chemical Changes

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Metal oxides

metals + oxygen → metal oxides

oxidation reactions = the gain of oxygen by a substance during chemical reactions

reduction = loss of oxygen

magnesium + oxygen → magnesium oxide

2Mg(s) + O₂(g) → 2MgO(s)

Copper oxide + carbon → copper + carbon dioxide

2CuO(s) + C(s) → 2Cu(l) + CO₂(g)

- carbon is oxidised because it gains oxygen

- copper oxide is reduced because oxygen is removed from it

The reactivity series

- when metals react with other substances, metal atoms form positive ions

- reactivity of a metal is related to its tend ency to form positive ions

A more reactive metal can displace a less reactive metals from a compound