2. TOPIC 5 Fuels

3. 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 Fuels

4. 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 CH 4.Methane makes up 96% of Natural Gas.

5. Combustion 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 CO 2 is that it turns limewater Milky(or chalky) All Hydrocarbons burn to give CO 2 and H 2 O Any substance that contains Carbon and Hydrogen gives CO 2 and H 2 O when burned

6. Fossil Fuels Fossil 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. CoalOilGas Oil was formed by dead sea creatures falling to the sea-bed where they were subjected to chemical change by bacteria.

7. 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

8. Air Pollution When Carbon burns in plentiful supply of air it produces CO 2 C + O 2 CO 2 When Carbon burns in an insufficient supply of oxygen it produces` Carbon Monoxide C + O 2 CO The test for CO 2 is that it turns limewater milky(chalky) CO is an odourless, poisonous gas which prevents the blood absorbing Oxygen is therefore extremely dangerous CO 2 extinguishes fires, whereas CO burns with a blue flame. CO is neutral whereas, CO 2 is Acidic

9. 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 CO 2 and N 2. Catalytic converters are metal honeycombs coated in Platinum Sulphur from petrol produces the acidic gas Sulphur Dioxide(also a pollutant)when burned