Topic 8 - Fuels and Earth Sciences

hydrocarbons

contain solely hydrogen and carbon atoms

fractional distillation

Oil is heated to evaporate it

Vapours rise in a fractionating column

The column has a temperature gradient (hot at bottom, cool at top)

Each fraction condenses where it becomes cool enough and is piped out of the column

crude oil fractioning columns

Gases (domestic heating and cooking)

Petrol (fuel for cars)

Kerosene (fuel for aircraft)

Diesel (fuel for cars and trains)

Fuel oil (fuel for large ships)

Bitumen (surfacing roads and roofs)

trends as you go down the fractioning columns

Number of CH atoms increases

Boiling point increases

Viscosity increases

Flammability decreases

what is a homologous series

 series of compounds in which molecular formulae differ by CH2, have a gradual variation in physical properties (such as boiling points), have similar chemical properties.

products of complete combustion of alkanes

carbon dioxide and water vapour

products of incomplete combustion

carbon, carbon monoxide

how is sulfur dioxide produced from hydrocarbons

hydrocarbons contain impurities such as sulfur, this is then oxidised when burnt. the sulfur dioxide can dissolve in rainwater to form acid rain. this cnan damage buildings, trees, and soils

hydrogen as a fuel

doesnt produce ash or smoke, only produces water when burns. releases nearly 3 times as much energy as petrol. however, it is a gas, so needs to be stored at high pressures.

cracking

involves breaking down larger alkaes into smaller more useful alkanes and alkenes. this is done by heating them. there is a high demand for small alkanes, and these are less commonly found.

early atmosphere

carbon dioxide, water vapour, oxygen, small amounts of other gases

test for oxygen

glowing splint relights

greenhouse gas process

greenhouse gases abosrb heat radiated from the earth. the greenhouse gases then release energy in all directions, and this reduces the amount of heat radiating into space, keeping the earth warm

todays atmosphere

78% nitrogen, 21% oxygen, 1% other gases (argon, water vapour, carbon dioxide)