TOPIC 5TOPIC 5

FuelsFuels

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

FuelsFuels

Common fuelsCommon fuelsMost 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.

Combustion of HydrocarbonsCombustion of Hydrocarbons

Combustion of Methane gas

Water vapour from the burning methane gas condenses here

Carbon dioxide is collected in the tube here. The test for CO2 is that it turns limewater Milky(or chalky)

All Hydrocarbons burn to give CO2 and H2O

Any substance that contains Carbon and Hydrogen gives CO2 and H2O when burned

Fossil FuelsFossil FuelsFossil Fuels formed from living things millions of years ago. There are three main Fossil Fuels

Coal was formed by the decay of vegetation which was subjected to heat and pressure over a very long period of time.

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.

Alternative sources of energy which are Renewable must be found eg Solar, Wind Tide and Wave Power.

Coal Oil GasOil was formed by dead sea creatures falling to the sea-bed where they were subjected to chemical change by bacteria.

Distillation of Crude OilDistillation of Crude Oil

Crude OilCrude 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

Air PollutionWhen 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 MonoxideC + O2 CO

The test for CO2 is that it turns limewater milky(chalky)

CO is an odourless, poisonous gas which prevents the blood absorbing Oxygen is therefore extremely dangerous

CO2 extinguishes fires, whereas CO burns with a blue flame. CO is neutral whereas, CO2 is Acidic

Pollution from CarsPollution from CarsThe main pollutants from car exhausts are Unburned HydrocarbonsCarbon MonoxideOxides of Nitrogen

occurs in the SparkPlugs 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