How the physical properties of hydrocarbons change with molecule size
2 marks · NormalState how the boiling point and viscosity of hydrocarbons change as the length of their carbon chain increases.
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Also accept: Boiling point increases, viscosity increases; Both boiling point and viscosity increase as molecules get larger
Common mistakes: Saying boiling point decreases; Saying viscosity decreases
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Marking points
B1 · 1 mark · States that boiling point increases as carbon chain length increases.
B2 · 1 mark · States that viscosity increases as carbon chain length increases.
Worked solution
As the carbon chain length increases:
- The boiling point of hydrocarbons increases.
- The viscosity of hydrocarbons also increases; they flow less easily.