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What is a hydrocarbon
Any compound that’s formed from carbon and hydrogen only
What are alkanes
Saturated hydrocarbons
What are the first four alkanes in the homologous series
Methane, ethane, propane, butane
What is the chemical formula of alkanes
CnH2n+2
Properties of alkanes
Boiling point increases with chain length, shorter alkanes are more flammable and volatile, longer alkanes are more viscous
What is the main use for hydrocarbons
Fuels
What is complete combustion
When a hydrocarbon reacts with oxygen to form carbon dioxide and water releasing lots of energy in the process
What type of reaction is complete combustion
Exothermic
What order do you balance elements in a complete combustion equation
Carbons, hydrogens, oxygens
Properties depend on…
…length of hydrocarbons
What is crude oil
A mixture of different compounds mainly hydrocarbons.
How is crude oil formed
From remains of dead plants and animals mainly plankton that died millions of years ago and were buried in mud high pressure and temperatures underground
crude oil is a…
…finite resource
What is the process of Fractional distillation
1) crude oil heated so it evaporates and then entered in fractionating column
2) fractional column is hottest at bottom and coolest at the top
3)hot gas rises to column and gradually cools
4)different compounds in mixtures have different boiling points do condense at different temperatures and therefore different levels
What are petrochemicals
Substances from crude oil
What are petrochemicals used as
Feedstock
What are petrochemicals used to make
Solvents, lubricants, polymers, detergents
What is cracking
Process of breaking down longer hydrocarbons into smaller more useful hydrocarbons
What type of reaction is cracking
A thermal decomposition reaction
What is the process of steam cracking
Heat long chain hydrocarbon till its a gas, mix vapourised hydrocarbon with steam and then heat to very high temperature, causing long chain hydrocarbon to split into shorter ones
What is process of catalytic cracking
Heat long chain hydrocarbon till it’s a gas, pass hydrocarbon vapour over a hot powdered catalyst, as hydrocarbon contacts catalyst it splits into two smaller hydrocarbons
Cracking chemical reaction
Long chain HC —> small alkane + alkane
What can alkanes be used to produce
Polymers
What are alkenes
Unsaturated hydrocarbons
Alkenes are more ___ than alkanes
Reactive
What is test for alkenes
Bromine water, will decolourises when alkene solution is added
