Unit 7 and 8 Chemistry

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Oxidisation = A reaction where oxygen is added. Reduction = A reaction where oxygen is removed.
Incomplete combustion = there isnt enough oxygen for the atoms to burn or form CO2.
Cracking is an example of a thermal decompositi-on reaction
Cracking breaks longer chain molecules to smaller ALKANE and ALKENE molecules.
High demand for short chain but low demand for long chain.
1. Heat crude oil until it evaporates and turns into gas.
- 2. Pass the vapour over a hot catalyst. At temp between 400-700 degrees.
  - Temp varies depending the length of hydrocarbon desired.
    - 3. The long chain molecule splits apart (CRACKS) giving you the desired product
      - Then separate the 2 products using fractional distillation.
When a hydrocarbon chain is cracked, we get an ALKANE nd an ALKENE.
The test for an ALKENE (double bond) is to add either Bromine water, or Potassium Permanganate,
- ALKANE will keep its colour but ALKENE will go colourless.
CHLORINE = Chlorine bleaches damp litmus paper turning it white.
OXYGEN = Put a glowing splint into a test tube with oxygen. If present the splint will relight.
C02 = Bubble CO2 with an aqueous solution of calcium hydroxide (limewater) and solution will go cloudy.
HYDROGEN= Hold a lit splint at the open end of test tube containing hydrogen, and there will be a squeaky pop.