GCSE Science | Organic Chemistry

2 min read

Crude oil

  • crude oil can be burnt to produce energy but it is a finite resource
  • crude oil is a mixture of short hydrocarbons and long hydrocarbons
  • short hydrocarbons are more flammable, more runny, and more volatile
  • long hydrocarbons are less flammable, more viscous, and less volatile
  • longer hydrocarbons have stronger intermolecular forces

Fractional distillation

  • fractional distillation is used to seperate the short, medium and long hydrocarbons
  • vaporise the crude oil (heat) - so they turn into a steam/ vapour
  • allow the vaporised crude oil to enter the column
  • the column is hotter at the bottom and cooler at the top
  • the long hydrocarbons have higher boiling points so they will condense quickly and leave the column
  • the short hydrocarbons have lower boiling points so will rise more before they condense

Cracking

  • long hydrocarbons produced from fractional distillation are not as useful as short hydrocarbons
  • cracking breaks long chain hydrocarbons into short chain hydrocarbons
  • conditions: high temperature (600o C), aluminium oxide catalyst

Homologous series

  • each member has the same functional group and the same general formula
  • consecutive members differ by CH2

Alkanes

  • The general formula of alkanes is CnH2n+2
  • Monkeys eat peanut butter can be used to remember the names of the first four alkanes - methane ethane propane butane
  • alkanes are an example of a homologous series
    • each member of a homologous series shares the same functional group
    • each member of a homologous series has the same general formula
    • each consecutive member of a homologous series differs by an extra CH2

Complete combustion

  • excess O2
  • Hydrocarbon + O2 --> CO2 + H2O

Incomplete combustion

  • not enough O2
  • Hydrocarbon + O2 --> CO + H2O
  • Carbon monoxide (CO) is poisonous. It binds to the haemoglobin preventing the blood from carrying oxygen.

(Halogen) addition of alkenes

(Hydrogen) addition of alkenes

Polymers

  • a long chain molecule made up of many monomers

Addition polymerisation

  • alkene monomers
  • double bond breaks and opens up
  • each monomer joins together

Oxidiation of alcohols

Condensation polymerisation

  • di-ol and di-carboxylic acid monomers
  • H2O is removed from the pair of monomers
  • each monomer joins together

1 min read

GCSE Science | Lenses

What is the focal point? * the point at which rays or waves meet after reflection or refraction, or the point from which diverging rays or waves appear to proceed. What is focal length?
1 min read

GCSE Science | Concentration

* concentration = moles/ volume * concentraion: mol/dm3 * moles: mol * volume: cm3 * 1cm3 = 0.001dm3 (divide by 1000) Question 1 Question 2 Question 3 Volume of gases at room temperature and pressure * at room temperature
1 min read

GCSE Science | National Grid

National grid * electrical power is transferred at high voltages from power stations, and then transferred at lower voltages in each locality for domestic use Step-up transformers * increases the voltage * this allows the cables