chem - fuels + health science (8)

• Crude oil is a complex mixture made up of largely hydrocarbons.
• Crude oil is a finite resource that contains molecules in which carbon atoms are in chains or rings and is an important source of useful substances (fuels + feedstock for the petrochemical industry).
• The process of fractional distillation involves heating the crude oil and feeding it into a fractionating column which has a temperature gradient.
• Long chain hydrocarbons with higher bps will condense at lower fractions in the column.
• Shorter chain hydrocarbons with lower bps will condense at higher fractions in the column.
• These fractions now hold liquid hydrocarbons which will be collected through pipes.
• Some hydrocarbons with very low bps will escape out of the top of the column.
• Some hydrocarbons with very high bps do not vaporise (bitumen), which leaves through the bottom.
• All different fractions are for different purposes: Gases are used for domestic heating and cooking, Petrol is used as fuel in cars, Kerosene is used as fuel for aircraft, Diesel oil is used as fuel for some cars and trains, Fuel oil is used as fuel for large ships, Bitumen is used for surfaces roads and roofs.
• The shorter the molecules, the less viscous, the lower the temperature the fraction evaps/condenses, the lower its bp, the more flammable it is, and the easier it is to ignite.
• A homologous series of compounds share the same general formula, differ by CH2 from neighbouring compounds, show a gradual variation in physical properties and similar chemical properties.
• In the complete combustion of hydrocarbon fuels, CO2 and H2O are produced – energy is given out.
• In the incomplete combustion of hydrocarbons, carbon and carbon monoxide are produced as there’s not enough oxygen.
• Carbon monoxide causes health problems and soot causes global dimming.
• Some fuels contain sulphur, when these are burnt in O2, sulphur can react to form sulphur dioxide.
• When sulphur dioxide dissolves in rain, acid rain is caused – damages limestone statues, reduces the growth of crops and lowers the pH of water killing fish.
• Nitrogen and oxygen from the air combine to produce nitrogen monoxide.
• When released from the vehicle exhaust systems, nitrogen monoxide combines with oxygen in the air to form nitrogen dioxide (pollutants).
• Hydrogen as fuel is only water and petrol is finite but expensive, difficult to store and is dangerous.
• Petrol, kerosene and diesel oil are non-renewable fossil fuels obtained from crude oil.
• Methane is a non-renewable fossil fuel found in natural gas.
• Hydrocarbons can be cracked to produce small, more useful molecules.
• The early atmosphere was made of mostly carbon dioxide, water vapour, methane, and ammonia due to volcano eruptions.
• Water vapour levels dropped because it condensed and formed oceans.
• Carbon dioxide dissolved in the newly formed oceans and carbonates were precipitated producing sediments and algae and plants took it away with photosynthesis.
• Oxygen increased due to algae and plants going through photosynthesis therefore releasing oxygen.
• The chemical test for O2 uses a glowing splint which relights in oxygen.