Describe, with one balanced equation each, how metals react with (a) oxygen, (b) water, (c) dilute acids and (d) bases. What is special about aluminium oxide?

1. 1 · Open. Metals are electropositive: they lose electrons, so they react with oxygen, water, acids and some bases.
2. 2 · Oxygen. They form basic oxides: 4Na + O₂ → 2Na₂O; 2Mg + O₂ → 2MgO.
3. 3 · Water. They give a hydroxide or oxide and hydrogen: 2Na + 2H₂O → 2NaOH + H₂ (cold water); 3Fe + 4H₂O → Fe₃O₄ + 4H₂ (steam).
4. 4 · Dilute acids. They give salt + hydrogen: Mg + 2HCl → MgCl₂ + H₂.
5. 5 · Bases. Zinc and tin give a salt and hydrogen: Zn + 2NaOH → Na₂ZnO₂ + H₂.
6. 6 · Aluminium oxide. It is amphoteric: Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O and Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O.
7. 7 · Real life. Sodium is stored under kerosene because it reacts with air and water.
8. 8 · Close in one line. So the more reactive a metal, the more easily it reacts, as sodium does with cold water.

Scoring tip: Balance every equation and write 'steam' or (g) for iron and aluminium. Examiners check both.