Metals react with oxygen
Metal + oxygen → metal oxide. Magnesium burns with a bright white flame to form white magnesium oxide. Copper turns black as copper oxide forms.
Lesson 4.1 · AQA Combined Science
Metals and oxygen
Two words to remember
Oxidation is gain of oxygen. Reduction is loss of oxygen. In 2CuO + C → 2Cu + CO₂, copper oxide loses oxygen and is reduced. Carbon gains oxygen and is oxidised.
Explain the mass change
A metal gains mass when it reacts with oxygen because oxygen atoms from the air join the metal. Total mass is conserved when the oxygen is counted. The balanced magnesium equation is 2Mg + O₂ → 2MgO.
Remember
Gain oxygen = oxidation. Lose oxygen = reduction.
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