1. Fuels A Fuel is a substance that produces Energy when burned.
A good fuel releases it’s energy over a longer period of time
A reaction in which energy is released is called an Exothermic reaction( a reaction in which heat is taken in called an Endothermic reaction).
Another word for burning is Combustion ie.we combine the element with Oxygen gas

2. Common fuels Most common household fuels contain the element Carbon.
Fuels that contain carbon and hydrogen only are called Hydrocarbons.
The simplest hydrocarbon is methane formula CH4.Methane makes up 96% of Natural Gas.

3. Combustion of Hydrocarbons
Carbon dioxide is collected in the tube here. The test for CO2 is that it turns limewater Milky(or chalky)
Combustion of Methane gas
Water vapour from the burning methane gas condenses here
All Hydrocarbons burn to give CO2 and H2O
In fact any substance that contains Carbon and Hydrogen gives CO2 and H2O when burned

4. Fossil Fuels
Fossil Fuels are formed from Living things millions of years ago. There are three main Fossil Fuels:
Coal, Oil and Gas
Gas was formed in much the same way as Oil.It is often collected when drilling for Oil.
Fossil Fuels are Finite Fuels ie.They will run out in the future and cannot be regenerated
Coal: This was formed by the decay of Vegetation which was subjected to heat and pressure over a very long period of time
Oil: This was formed by dead sea creatures falling to the sea-bed where they were subjected to chemical change by Bacteria
Alternative sources of Energy which are Renewable must be found eg. Solar, Wind Tide and Wave Power

5. Distillation of Crude Oil
Crude Oil is a mixture of Substances called Fractions.
To separate the fractions we heat them until they boil off. This is known as Fractional Distillation
The smaller fractions ie short carbon chains have smaller Boiling Pts. and boil off first.
The smaller fractions are more flammable, lighter in colour and less Viscous than the longer chain Fractions
A Fractionating Tower

6. Air Pollution
When Carbon burns in plentiful supply of air it produces CO2
C + O2
CO2
When Carbon burns in an insufficient supply of oxygen it produces ` Carbon Monoxide
C + O2 CO
CO is an odourless, poisonous gas which prevents the blood absorbing Oxygen is therefore extremely dangerous
The test for CO2 is that it turns limewater milky(chalky)
CO2 extinguishes fires, whereas CO burns with a blue flame. CO is neutral whereas, CO2 is Acidic

7. Pollution from Cars The main pollutants from car exhausts are
Unburned Hydrocarbons
Carbon Monoxide
Oxides of Nitrogen occurs in the Spark Plugs of petrol cars (not Diesel since they do not have spark plugs)
Cars have Catalytic Converters fitted to change these to harmless gases CO2 and N2. Catalytic converters are metal honeycombs coated in Platinum
Sulphur from petrol produces the acidic gas Sulphur Dioxide(also a pollutant)when burned