Breaking all of the O–H covalent bonds in 18 g of water needs 928 kJ of energy. Boiling 18 g of water at 100 ∘C100\,^\circ\mathrm{C}100∘C needs 41 kJ of energy.
Which conclusion is best supported by these data?
Boiling breaks about 4% of the O–H bonds, and the other bonds stay intact
O–H covalent bonds are weaker than the forces between water molecules
Steam is a mixture of hydrogen and oxygen formed as the O–H bonds break
Boiling only overcomes the much weaker forces between the water molecules
53 exam-style questions on Edexcel GCSE Chemistry 2.4 Covalent bonding, covering 2.4.1 Covalent bonding and simple molecules. Each one has a worked solution and a mark scheme showing where the marks go.