Chapter 18 - Fuels and Crude Oil

1) Millions of years ago, tiny sea creatures sank to the seabed after death 2) They were covered by mud and sand 3) Heat from Earth + pressure from the compressing rocks acted on the organisms producing fossil fuels 4) E.g. crude oil & natural gas

• Fossil fuels are formed form decayed plants and animals from millions of years ago • Mainly organic compounds containing only carbon & hydrogen (aka hydrocarbons) • Fossil fuels are burnt in presence of O2 to form CO2 + H2O + thermal energy • Exothermic/Combustion reaction • Thermal energy converted to other forms of energy

• Fossil fuel consisting mainly methane • Odourless & colourless • When methane is burnt in excess O2, CO2 + H2O is produced • Cleanest gas • Liquefied for transport to become LNG as it does not burn easy = X danger • Additive THT added for pungent smell to detect gas leak

• Contains mixture of hydrocarbons • Found beneath land (underground deposits) /ocean floor, thousands of metres below Earth’s surface • Extracted crude oil has different types of hydrocarbons separated into groups based on its properties • e.g. burns under same conditions = 1 group • e.g. used as starting materials to synthesise chemicals = a few groups

Natural gas and crude oil are considered non renewable sources of energy. Limited amounts of these sources + can’t be replaced fast enough to keep up with our rate of use

Oil refineries

They use fractional distillation to separate crude oils into various fractions because of the hydrocarbons present in crude oil have different boiling points and are miscible

useful fractions

Lower boiling points = higher/closer to the top collected at top most outlet) Higher boiling points = lower/closer to the bottom (collected at bottom outlet)

1 to 70

Higher bp = more carbon atoms Lower bp = less carbon atoms

Lower bp = less viscous + burn more easily Higher bp = more viscous + burn less easily

1) Crude oil is heated in a furnace to 400°C 2) Boiling occurs and liquid changes into vapour 3) Vapour is passed into the fractionating column 4) Column is hottest at the bottom and gets cooler towards the top - Fractions with higher bp condense at higher temperature, collected at lower levels - Fractions with lower bp rise further up the column before they condense and are collected

Boiling point increases as no. of carbon atoms in hydrocarbons increases

1) 90% used for fuels to - generate thermal + electrical energy - power motor vehicles and industrial activities 2) 10% used as petrochemical feedstock - manufacture of plastics, detergents, medicines, fertilisers, pesticides, synthetic rubber

• Supply is limited • Important as chemical feedstock for manufacture of daily products • Waste to just ‘burn’ away as fuel • Compete for limited supply • To last longer both fuel and chemical feedstock, we need to conserve

1) Reduce the use of crude oil by - reducing number of motor vehicles on the road - driving smaller cars that consume less fuel - take public transport 2) Use alternative sources of energy - alternative fuels - solar/nuclear energy 3) Improve design of power stations and vehicles such that they use crude oil more efficiently (e.g. electric vehicles)

Nuclear plants use fuels such as plutonium and uranium. However, there can be harmful radiation leaking into the environment from the nuclear plant

Carbon dioxide (CO₂)

Sulfur dioxide (SO₂)

Because they are currently the most economical and convenient energy sources

Alternative renewable energy sources to crude oil and natural gas

Because sugarcane can be regrown quickly and repeatedly after harvest and it is an alternative to fossil fuels

Crushing → Acid/alkali treatment → Fermentation → Fractional distillation