Earth Materials

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The number of atoms present affects the boiling point of the compound.

This means that each molecule has a different boiling point.

Slide 29

The molecules with the least number of carbon atoms in them have the lowest boiling point.

Methane CH4 Boiling Point = - 163 Celsius

Ethane C2H6 Boiling Point = - 87 Celsius

Propane C3H8 Boiling Point = - 43 Celsius

Butane C4H10 Boiling Point = - 0.5 Celsius

Slide 30

Methane = -163

Ethane = - 87

Propane = - 43

Butane = - 0.5

The boiling point increases as the length of the carbon chain gets bigger.

Having different boiling points means that the molecules can be separated into simpler mixtures by:

Fractional Distillation.

Slide 31

Reminder!

Distillation is a separation technique using the fact that different compounds boil at different temperatures (they have different boiling points.) Remember separating pure water from Inky water in year 7?

When a mixture of different compounds is heated, the ones with the lowest boiling point will evaporate first.

Later vapour is condensed back into liquid.

Slide 32

There are many Hydrocarbon compounds in Crude Oil and this complex mixture is separated into a simpler mixture.

This simper mixture is made up of Fractions, groups of Hydrocarbons with similar carbon chain lengths.

The Crude Oil is first heated to make it Evaporate, then it is allowed to cool at different temperatures, so that different Fractions Condense at different points.

This process is called Fractional Distillation.

Slide 33

Hot Crude Oil in

LPG for calor gas stoves

Petrol for fuel

Naphtha for chemicals

Paraffin for aeroplanes

Diesel for Fuel

Fuel Oil for heating

Bitumen for Roads

Lubricating Oil for machines

350OC

40OC

Temperature decreasing

Average carbon atoms = 3

Average carbon atoms = 8

Average carbon atoms = 10

Average carbon atoms = 12

Average carbon atoms = 20

Average carbon atoms = 40

Average carbon atoms = 80

Average carbon atoms = 120

Slide 34

The larger the molecule,

(the more Carbons atoms there are) :

The more Viscous it is (the less easily it flows).

The less easily it ignites (the less Flammable it is).

The less Volatile it is (the harder it is to turn from a liquid into a vapour).

The higher its Boiling Point is.

All these points mean that large Hydrocarbons are less use as fuels than smaller Hydrocarbons.