1. Elements, compounds and mixtures
A mixture consists of 2 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

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

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

4. Fractional distillation
The many hydrocarbons in crude oil maybe separated into fractions by evaporating the oil and allowing it to condense at a number of different temperatures.
Each fraction contains molecules with similar number of carbon atoms.
This process is called fractional distillation

5. Properties of hydrocarbons
Small hydrocarbon
Large hydrocarbon
Boiling point
Low
Higher
Viscosity
Runny
Thicker
Flammability
Very
Harder to burn
Example
Petrol
Diesel

6. Burning fuels
The gases released into the atmosphere when a fuel burns may include carbon dioxide, water (vapour), carbon monoxide, sulphur dioxide, oxides of nitrogen and solid particles called particulates which may contain soot and unburnt fuels
The products of combustion relate to what elements were present in the fuel and whether the complete combustion took place

7. Effects of burning fuels
Sulphur dioxide and oxides of nitrogen cause acid rain
Carbon dioxide causes global warming
Solid particulates cause global dimming

8. Summary of air pollutants
What are the causes and effects of these air pollutants?
pollutant
cause
effect
combustion and respiration
adds to the greenhouse effect
carbon dioxide
high temperature combustion
nitric oxides
acid rain and smog
carbon monoxide
incomplete combustion
lowers blood’s ability to carry oxygen
Teacher notes
This slide can be used as a plenary or revision exercise on the causes and effects of the major air pollutants. Students could be asked to complete the table in their books or on mini-whiteboards before the information is revealed on the IWB.
sulfur dioxide
burning coal
acid rain
burning wood and fossil fuels
Global dimming
particulates

9. Reducing effects of burning fuels
Sulfur can be removed from fuels before they are burned
Sulfur dioxide can be removed from waste gases after combustion
There are economic, ethical and environmental reasons for using biofuels

10. Cracking in the lab
Hydrocarbons can be cracked to produce smaller more useful molecules.
This process involves heating the hydrocarbons to vaporise them
The vapours are either passed over a hot catalyst or mixed with steam and heated to a very high temperature so that thermal decomposition reactions then occur

11. Products of cracking
The products of cracking include alkanes and unsaturated hydrocarbons called alkenes

12. Alkenes Alkenes are unsaturated hydrocarbon molecules: contain at
least one C=C double bond
Alkenes have the general formula CnH2n
Alkenes react with bromine water, turning it from orange to colourless