organic chemistry

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what is a hydrocarbon
a compound formed from only carbon and hydrogen
what is the word for hydrocarbons with single bonds
saturated
what are alkanes
most simple type of hydrocarbon
alkanes are saturated compounds - every carbon atom has 4 single covalent bonds
general formula for alkanes
CnH2n+2
n= number of carbon atoms
what is the order of alkanes
methane (CH4)
2. ethane(C2H6)
3. propane(C3H8)
4. butane(C4H10)
homologous series definition
group of compounds with similar chemical properties due to having the same general formula
word equation for combustion
hydrocarbon + oxygen —> carbon dioxide + water
what happens to alkanes as the chain length increases
becomes more viscous (thick + sticky)
becomes less volatile (evaporates less easily)
is less flammable
a higher melting and boiling point
what happens to alkanes as their chain lengths are small
becomes less viscous (not thick + sticky)
becomes more volatile (evaporates easier)
is more flammable
lower melting and boiling point
what is cracking
when larger chain hydrocarbons are broke up into smaller more useful hydrocarbons
what are smaller chain hydro carbons more useful
they are used for fuel while large chain hydrocarbons are sticky, viscous + useless
what type of reaction is cracking
thermal decomposition reaction - using heat to break larger chain hydrocarbons apart
what is catalytic cracking
long chain alkane are heated until vaporised into a gas
they are past over a hot powdered aluminium oxide catalyst
this breaks the long chain catalyst into a small chain alkane and an alkene
what is steam cracking
no catalyst involved
the vaporised long chain alkane is mixed with steam at very high temperatures
what are alkenes
hydrocarbons with a double bond between two carbon atoms
what will cracking always produce
one alkane and one alkene - there aren’t enough hydrogen atoms to make two alkanes
what is a word to describe alkenes
unsaturated
are alkenes more or less reactive than alkanes
more reactive as they have double bonds
test for alkenes
bromine water test
bromine is orange but when it’s mixed with alkenes all of it will react + turn colourless
this is how to tell the difference between alkenes and alkanes - alkanes aren’t reactive enough + bromine stays orange
how are polymers held together
strong covalent bonds between atoms
weak inter-molecular forces between molecules
types of reactions that form polymers
condensation + addition
what two elements are alkanes made from
hydrogen and carbon
two types of cracking
catalytic and steam
what catalyst is needed for a addition reaction between an alkene and hydrogen
nickle
explain the combustion of hydrocarbons
exothermic reaction - hydrocarbons react with oxygen
complete combustion produces carbon dioxide and water
incomplete combustion produces carbon monoxide and water
what type of reaction is cracking
thermal decomposition
combustion of alkenes
burn with smoky flames due to incomplete combustion
what is an addition reaction
lots of small molecules (monomers) join together to form large molecules (polymers)
what happens when you react an alkene with hydrogen
produces an alkane
what happens when you react an alkene with water
produces an alcohol
what happens when you react a alkene with a halogen
produces a halogenoalkane
how do alkenes join together
addition polymerisation
what is an alcohol
an organic compound that contains an -OH functional group
general formula for alcohols
Cn H2n + 1
properties of alcohols
flammable
soluble
oxidised to form carboxylic acids
what does the oxidation of alcohols lead to
carboxylic acid
why are alcohols flammable
undergo complete combustion
uses of alcohol
fuels - they're flammable
solvents
drinks
uses of ethanol
feed stock - produces other organic compounds
bio fuel
alcoholic drinks
how is ethanol produced
ethene + steam