Crude Oil & Fuels 9th May - 12th July

Contain mixture of molecules > hydrocarbons (only contain hydrogen & carbon)

Different sized hydrocarbons have different boiling points > can be seperated via fractional distillation

 Lower boiling points = less energy to break = smaller molecules = weak intermollecular forces = more flammable = less viscious

Higher boiling points = more energy to break = larger molecules = stronger intermollecular forces = more flammable = more viscious

> Sun gives tiny sea creature energy 

> Creatures die & sink to sea bed

> Become buried under sand & non-porous rock

150 million years later

> Don't decay normally as bacteria feeding on them have little          oxygen

> Pressure & temperature increase = OIL

Alkane molecules have 'backbone' of carbon atoms > surrounded by hydrogen atoms

Carbon atoms always have 4 bonds .... Hydrogen only have 1

Alkanes will always have at least one double bond between carbon atoms (makes more reactive)

hydrocarbon + oxygen > carbon dioxide + water

Complete combustion needs a pleantiful supply of oxygen so elements can react fully with the oxygen

• Hydrogen oxidises to become water
• Carbon oxidises to becomes carbon dioxide

Fuel > a substance that reacts with oxygen to release useful energy

Occurs when suppy of air or oxygen poor

• hydrogen oxidises to water
• carbon remains as carbon (soot)
• some carbon forms carbon monoxide

hydrocarbon + oxygen > carbon monoxide + carbon + water

Carbon monoxide is poisonous as it binds with the haemoglobin in our red blood cells limiting the amount of oxygen they can carry

Allows large hydrocarbons to be broken into smaller hydrocarbons > more useful

Can be done my either:

• heating to 600-700'
• passed over a catalyst (silica or alumina)

Process breaks covalent bonds > causes thermal decomposition reactions

• Smaller hydrocarbons are used as fuels
• Larger hydrocarbons are used as polymers in plastic manufacturers

Saturated hyrdocarbons (single bonds & unreactive unless with air)

Formula > Cn H2n + 2

Nb. carbon always have 4 bonds, hydrogen 1

Examples:

• methane
• ethane
• propane
• butane
• pentane

Always have a double carbon bond (more reactive than alkanes)

Formula > CnH2n

Test:
Bromine water is orange > beomes colourless when shaken with an  alkene (addiction reaction)

Eg. ethene + bromine > dibromoethane

Other addiction reactions

• if hydrogen is added to a C=C bond it has a saturating affect turning the alkene to an alkane
• if steam is added to an alkene an alcahol is made

> Oil refineries use steel vessels (crackers) to heat & vaporise hydrocarbons

> Vapour is passed on or mixed with a hot catalyst with steam & heated

> The hydrocarbons are then cracked (thermal decoposition takes place)

Making a desirable product in a chemical reaction with as little waste product as possible

High atom economy = sustainable reaction

atom economy = (formula mass of desire product / formula mass of all products) x100 %