Simple molecular structures

2 marks · Normal

State two characteristic physical properties of substances with simple molecular structures and explain why they have these properties.

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Must show: low melting/boiling points due to weak intermolecular forces, do not conduct electricity as molecules have no free ions or electrons

Also accept: low melting/boiling point due to weak intermolecular forces; poor electrical conductivity because there are no mobile charged particles

Common mistakes: saying covalent bonds break on melting/boiling; confusing with giant covalent structures

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Marking points

B1 · 1 mark · Award 1 mark for stating a correct property: low melting/boiling point OR do not conduct electricity.

B2 · 1 mark · Award 1 mark for correct explanation: due to weak intermolecular forces OR molecules have no free ions or electrons.

Worked solution

Substances with simple molecular structures usually have low melting and boiling points because only weak intermolecular forces need to be overcome, not the strong covalent bonds in molecules.

They do not conduct electricity because their molecules do not contain free ions or electrons to carry charge.