Alkanes and Alkenes

hydrocarbons

compounds made from only carbon and hydrogen atoms

alkanes

homologous series of saturated hydrocarbons

homologous series

a group of chemicals which have similar chemical properties and can be represented by a general formula.

saturated meaning

has the maximum amount of hydrogen atoms for each carbon atom i.e doesn’t have a double bond

general formula for alkanes

CnH2n+2

1 carbon atom alkane

methane

2 carbon atom alkane

ethane

3 carbon atom alkane

propane

4 carbon atom alkane

butane

anagram for alkanes

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cracking

a method used to break longer chain alkanes into shorter chains which are more in demand

this will always make one shorter alkane and 1 alkene

types of cracking

thermal cracking - using heat

catalytic cracking - using catalysts

alkenes

a homologous series of unsaturated hydrocarbons

general formula for alkenes

CnH2n

unsaturated

a molecule containing carbon-carbon double bond

2 carbon atom alkene

ethene

3 carbon atom alkene

propene

4 carbon atom alkene

butene

5 carbon atom alkene

pentene

when do alkenes go under complete combustion

when there is a plentiful supply of oxygen

complete combustion of alkene symbol equation

C2H4 + 3O2 = 2CO2 + 2H2O

Test to distinguish alkenes and alkanes

Add bromine water, if alkenes are present the ln solution will go from orange to colourless, if alkanes are present then it wont turn colour

polymer

very large molecules made from many small molecules joined together in repeating units

monomer

small molecules that join together to make polymers

polymerisation

formation of polymers - small monomers joining together

additional polymerisation

process where many unsaturated monomers join together to make a saturated polymer

thermosetting

melt/soften on heating as chains are not joined together

thermosoftening

do not melt/sofetn on heat as chains are joined together

repeating unit in polymerisation