organic chem

• What is crude oil?

  A mixture of hydrocarbons
• What is crude oil formed from?

  The remains of ancient biomass (mostly plankton) that was buried in mud
• What is a finite resource?

  One that will run out
• Why is crude oil a finite resource?

  Because it takes longer to form than the rate at which we are using it up
• What is a hydrocarbon?

  A compound made of atoms of carbon and hydrogen only
• What is a general formula?


  A mathematical formula which allows you to work out the chemical formula of a substance
• What is an alkane?


  A hydrocarbon with only single bonds
• Name the first six alkanes

  Methane, ethane, propane, butane, pentane, hexane
• What is the general formula for alkanes?


  CnH2n+2 (the n and 2n are small)
• How does boiling point change with the length of an alkane?

  The longer the alkane, the higher its boiling point
• How does viscosity change with the length of an alkane?


  The longer the alkane, the more viscous (the thicker) it is
• How does flammability change with the length of an alkane?


  The longer the alkane, the less flammable it is
• What is fractional distillation?

  A process used to separate mixtures of substances with different boiling points
• What are the steps involved in fractional distillation?

  Crude oil is vaporised, different molecules rise up the fractionating column and cool down. Condense at different points on the column.
• Why is fractional distillation important?


  Because the different fractions have different uses
• What is a fuel?

  A substance which when reacted with oxygen releases energy
• Name five fuels we obtain from crude oil

  Petrol, diesel oil, kerosene, fuel oil and liquefied petroleum gases
• What other uses are there for products of fractional distillation?

  Solvents, lubricants, polymers and detergents
• What is combustion?


  The reaction of a fuel with oxygen
• What are the products of complete combustion?

  Carbon dioxide and water
• When does incomplete combustion occur?

  When there is not enough oxygen present
• What is formed in incomplete combustion

  Carbon monoxide
• Why is carbon monoxide dangerous

  It is toxic, taken up by red blood cells in preference to oxygen.
• What is cracking?


  The process of breaking down a long hydrocarbon into smaller hydrocarbons
• What are the products of cracking?

  Short alkanes and alkenes
• Why is cracking important?

  Because smaller hydrocarbons are more useful than longer ones
• What are alkenes


  A different type of hydrocarbon which is more reactive than an alkane
• What are alkenes used for?

  As a starting material to make more useful chemicals
• How do you test for an alkene?

  React it with bromine water
• What is the colour change when an alkene reacts with bromine water?

  Turns from orange to colourless
• What is an alkene?


  A hydrocarbon with a double bond
• What is the general formula for alkenes?

  CnH2n
• What does unsaturated means?

  Contains double bonds (which could become C-H bonds)
• What are the first four alkenes?

  Ethene, propene, butene, pentene
• What are the three reactions of alkenes?

  Combustion, substitution, addition
• How is the combustion of alkenes different to combustion of alkanes?

  Alkenes usually react by incomplete combustion so burn with smoky flames
• Why is the reactions of alkenes with halogens known as an "addition" reaction?


  Because new atoms are being added to the molecule by breaking the double bond
• What do members of a homologous series have in common?

  Same general formula, differ by CH2 for neighbouring compounds in the series, boiling points increase with chain length, have similar chemical properties and reactions.
• How is sulphur dioxide produced?

  Sulphur impurities in fuels form it when the fuel is burnt
• What happens when the sulphur dioxide dissolves in rain water?

  Acid rain is formed