hydrocarbons (alkanes and alkenes)

• hydrocarbons only contain...


  hydrogen and carbon atoms
• alkanes have ... bonds

  C-C single
• are alkanes saturated or unsaturated?

  they are saturated - they only contain single bonds
• alkanes are the simplest type of ... you can get

  hydrocarbon
• alkane general formula


  C(n) H(2n+2)
• alkanes are a ... series


  homogulous
• homogulous series


  a group of organic compounds that react in a similar way
• methane


  CH4

  
• ethane


  C2H6

  
• propane


  C3H8

  
• butane


  C4H10

  
• pentane


  C5H12

  
• hexane


  C6H14

  
• heptane


  C7H16

  
• octane


  C8H18

  
• nonane


  C9H20

  
• decane


  C10H22

  
• hydrocarbon properties change as...


  the chain gets longer
• the shorter the carbon chain is the ... the hydrocarbon is

  - less viscous

  - more volatile

  - more flammable
• short chained hydrocarbons have a ... boiling point


  lower
• why do short chained hydrocarbons have lower boiling points?

  because they have weaker intermolecular forces
• long chained hydrocarbons have a ... boiling point


  higher
• why do long chained hydrocarbons have higher boiling points?

  because they have stronger intermolecular forces
• the longer the carbon chain is the ... the hydrocarbon is

  - more viscous

  - less volatile

  - less flammable
• the properties of hydrocarbons affect how they're used for...

  fuels

  (e.g. short chain hydrocarbons with lower boiling points are used as 'bottled gases' - stores under pressure as liquids in bottles)
• complete combustion occurs when there's...

  plenty of oxygen
• complete combustion reaction


  hydrocarbon + oxygen --> carbon dioxide + water
• during combustion, both carbon and hydrogen from the hydrocarbon are...

  oxidised
• why are hydrocarbons used as fuels?

  due to the amount of energy released when they combust completely
• cracking


  the breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes
• steam cracking


  the process of breaking down long-chain hydrocarbons into shorter ones by mixing the vapour of hydrocarbons with steam and heating to very high temperatures
• catalytic cracking


  the breaking down of long-chain hydrocarbon molecules by the action of heat and catalysts into short-chain molecules for which there is greater demand
• why are short chain hydrocarbons more useful?

  they are flammable so make good fuels and are in higher demand
• alkenes have ... bonds

  C=C double bonds
• are alkenes saturated or unsaturated?

  unsaturated - they have a carbon to carbon double bond
• the C=C double bond in alkenes means...

  - that alkenes have two fewer hydrocarbons than alkanes while containing the same number of carbon atoms

  - the bond can open up to make a single bond, allowing the two carbon atoms to bond with other atoms and making them more reactive than alkanes
• alkene general formula


  C(n)H(2n)
• ethene


  C2H4

  
• propene


  C3H6

  
• butene


  C4H8