Properties of hydrocarbons
Lajoy Tucker
Teacher
Contents
Properties of hydrocarbons
Hydrocarbons are compounds made of hydrogen and carbon atoms only.
Their properties depend on the length of their carbon chains – that is, the size of their molecules.
Property | Definition | Trend with Increasing Molecular Size (Chain Length) |
|---|---|---|
Boiling point | The temperature at which a substance changes from liquid to gas | Increases – larger molecules have stronger intermolecular forces and need more energy to evaporate |
Viscosity | How thick or sticky a liquid is | Increases – longer chains make the liquid flow more slowly |
Flammability | How easily a substance burns | Decreases – larger molecules are harder to ignite and burn less cleanly |
How These Properties Affect Fuel Use
Typical Use | Reason | |
|---|---|---|
Short-chain hydrocarbons (e.g. refinery gases, petrol) | Fuels for cooking, heating, and vehicles | Burn easily and cleanly, gases at room temperature |
Long-chain hydrocarbons (e.g. heavy oils, bitumen) | Lubricants, ship fuels, road surfacing | Viscous, hard to burn, high boiling points |
Practice Question
How do boiling point, viscosity, and flammability change as the size of hydrocarbon molecules increases?
Answer
Boiling point increases
Viscosity increases
Flammability decreases
Summary
Hydrocarbon properties depend on molecular size.
Larger molecules → higher boiling points, more viscous, less flammable.
Short-chain hydrocarbons are best as fuels
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