Crude oils and fuels

AQA GCSE Science & Additional Science

Chemistry 1 Topic 4

Hodder Education Revision Lessons

Crude oil and fuelsCrude oils and fuels

Click to continue


Chemistry 1 Topic 4

Overview — crude oil

• Crude oil is derived from an ancient biomass found in rocks. • Many useful materials can be produced from crude oil. • Crude oil can be fractionally distilled. Some of the fractions

can be used as fuels.

Click to continue

What useful materials can be made from crude oil?


Chemistry 1 Topic 4

Overview — biofuels

• Biofuels are produced from plant material. • There are advantages and disadvantages to their use as

fuels. • Fuels can come from renewable or non-renewable resources.

Click to continue

What are the advantages and disadvantages of biofuels?


Chemistry 1 Topic 4

Crude oil

Crude oil is a mixture of a large number of compounds.

A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged.

It is possible to separate the substances in a mixture by physical methods, including distillation.

Click to continue

Why does crude oil have so many different compounds in it?


Chemistry 1 Topic 4

Hydrocarbons 1Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only (hydrocarbons).

Most of these are saturated hydrocarbons called alkanes, which have the general formula CnH2n+2.

Click to continue

What would a model of ethane (two carbons) look like?

A molecular model of methane and its structural formula


Chemistry 1 Topic 4

Hydrocarbons 2

The many hydrocarbons in crude oil may be separated into fractions by evaporating the oil and allowing it to condense at a number of different temperatures.

Each fraction contains molecules with a similar number of carbon atoms.

This process is called fractional distillation.

Click to continue


Chemistry 1 Topic 4

Fractional distillation

Explain how the fractionating column works.

Click to continue


Chemistry 1 Topic 4

Properties 1Some properties of hydrocarbons depend on the size of their molecules. Look at the table below and on the next slide. What patterns do you notice?

Click to continue

Fraction

Carbon atoms

in the molecule Description

Boiling

point (C) Flammability Uses

Petroleum

gas

1–4 Colourless gas Less than 40 Explodes if

mixed with air

and lit

Used as a fuel in

the refinery

Bottled and sold

as LPG

Naphtha 5–10 Yellowish liquid,

flows easily

25–175 Evaporates

easily, vapour

mixed with air

is explosive

Petrol

Used for making

other chemicals

Kerosene 10–14 Yellowish liquid,

flows like water

150–260 Burns when

heated

Aircraft fuel


Chemistry 1 Topic 4

Properties 2

Click to continue

Fraction

Carbon

atoms in

molecule Description

Boiling

point (C) Flammability Uses

Light gas

oil

14–20 Yellow liquid,

thicker than

water

235–360 Only burns when

soaked onto a wick

or other material

Diesel fuel

Heavy gas

oil

20–50 Yellow brown

liquid


soaked onto a wick

— very smoky

Used in the

catalytic cracker

Lubricants

(car engine

oils)

50–60 Thick brown

syrup-like liquid


hot and soaked

onto a wick

Grease for

lubrication

Catalytic cracker

Fuel oil 60–80 Thick brown

sticky liquid

Above 490 Only burns when

hot and soaked

onto a wick

Fuel oil for power

stations and

ships

Bitumen More than 80 Black semi-solid Above 580 Only burns if very

hot

Road and roof

surfaces


Chemistry 1 Topic 4

Hydrocarbon fuels 1

Most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur.

The gases released into the atmosphere when a fuel burns may include carbon dioxide, water (vapour), carbon monoxide, sulfur dioxide and oxides of nitrogen.

Solid particles (particulates) may also be released.

Click to continue

What problems do carbon dioxide, sulfur dioxide and particulates cause? (Answers on the next slide.)


Chemistry 1 Topic 4

Hydrocarbon fuels 2The combustion of hydrocarbon fuels releases heat.

During combustion, the carbon and hydrogen in the fuels are oxidised.

Click to continue

• Sulfur dioxide causes acid rain.• Carbon dioxide causes global warming.• Solid particles cause global dimming.

How can these effects be reduced? (Answers on the next slide.)


Chemistry 1 Topic 4

Hydrocarbon fuels 3

Sulfur can be removed from fuels before they are burned, for example in vehicles.

Sulfur dioxide can be removed from the waste gases after combustion, for example in power stations using scrubbers.

Catalytic converters in the exhausts of vehicles reduce the release of nitrogen oxides.

Click to continue


Chemistry 1 Topic 4

BiofuelsBiofuels, including biodiesel and ethanol, are produced from plant material, e.g palm oil. There are economic, ethical and environmental issues surrounding their use.

Sh

ari

ff C

he’L

ah

/Foto

lia

What are the issues with biofuels?

Click to continue

Documents

Crude oils and fuels