SC22

• Alkanes are made of carbon atoms which all form single bonds to other carbon atoms and so are saturated.

  They are hydrocarbons as they consist of carbon and hydrogen only
• Alkenes contain a double carbon=carbon (C=C) functional group and so are unsaturated.

  They are hydrocarbons as they consist of carbon and hydrogen only
• Test for Unsaturation:

  • add bromine water
  • if there is a double carbon bond then an addition reaction occurs
  • alkenes will react in similar ways
  • ethene ---> 1,2-dibromoethane
• Bromine Water Test:

  • In the presence of an alkene, bromine water will change from orange to colourless
  • In the presence of an alkane, bromine water will remain orange
• All hydrocarbons can combust (burn in oxygen) to release energy.

  Complete combustion means the only products are water and carbon dioxide
• Functional Group - an atom or group of atoms that is responsible for the characteristic reactions of particular compounds