Chemistry paper 2

• Crude oil

  • It is a finite resource found in the earths crust.
  • It is the remains of organisms that lived and died millions of years ago.
  • It is a complex mixture of hydrocarbons they are joined together in chains and rings.
  • It is an important source of fuel such as petrol, diesel and heavy fuel oil.
• Separating Crude Oil

  • Fractional distillation is used to separate crude oil into simpler, more useful mixtures.
  • This method can be used because different hydrocarbons have different boiling points.

  Fractional Distillation:

  • Heated crude oil enters a tall fractionating column, which is hot at the bottom and gets cooler towards the top.
  • Vapours from the oil rise through the column.
  • Vapours condense when they become cool enough.
  • Liquids are led out of the column at different heights.
• Cracking

  • Cracking is a reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules, some of which are unsaturated.
  • The starting hydrocarbons are alkanes and then the products of cracking are alkanes and alkenes.

  Catalytic Cracking = uses a high temperature and a catalyst

  Steam Cracking = uses a high temperature and no catalyst
• What is the general formula for an Alkane

  Cn H2n+2
• Alkanes

  
• Greenhouse Gases

  • the gases responsible for global warming e.g. water vapour, carbon dioxide, methane.
  • These gases absorb heat radiated from the earth then release  energy in all directions, which keeps the Earth warm.
• Greenhouse Effect

  1. The sun heats up the earth.
  2. Some energy escapes into space whilst the rest is kept in by the o-zone layer.
  3. Greenhouses gases absorb the infrared radiation and heat up the earth.
• Humans impact on the Greenhouse Effect

  • Farming cattle releases methane.
  • Burning fossil fuels in vehicles and power stations releases carbon dioxide.
  • Deforestation releases carbon dioxide and reduces the absorption of carbon dioxide through photosynthesis.
• Combustion

  Complete Combustion = occurs when there is a good supply of oxygen. It releases the maximum amount of energy and produces carbon dioxide and water.

  • Fuel + Oxygen --- Carbon Dioxide + Water

  Incomplete Combustion = occurs when there is a poor supply of oxygen. Less energy is released. Water is still produced from the hydrogen atoms. Can be dangerous as it may produce carbon monoxide which is a poisonous gas.

  • Fuel + Oxygen --- Carbon monoxide/ Carbon and Water
• Potable Water

  • Potable water is water that is safe for humans to drink.
  • It is not pure water because it almost always contains dissolved impurities.
  • For water to be potable it must have low levels of dissolved salts and microbes since they can be harmful and cause illness.
  • Most water in the UK is produced by naturally occurring fresh water by passing the water through filter beds to remove insoluble particles and sterilising the water to kill microbes.
• What things can you change to increase the rate of reaction?

  • Increase the surface area (solid)
  • Increase the concentration (solution)
  • Increase the pressure (gas)
  • Increase the temperature
  • Use a catalyst
• What is a Hydrocarbon?

  They are molecules made from only carbon and hydrogen atoms.
• What is an Alkane?

  They are Hydrocarbons that only contain single covalent bonds whilst Alkenes have at least one double bond.
• What is the test for an Alkene?

  • Alkenes will turn bromine water for orange to colourless.
  • This is because the bromine atoms bond to the alkene by breaking the double bond.
• Chromatography

  • Is used to separate mixtures of soluble substances.

  1. Spots of ink are placed on the pencil line.
  2. As the paper is lowered into the solvent, the dye travels up the paper.

  • Mobile phase = solvent moves up the paper carrying different substances with it.
  • Stationary phase = contained on paper and does not move.

  RF = distance moved from the start line/ distance moved by the solvent from the start line.
• Testing for gases

  Oxygen = glowing splint relights when being held inside

  Hydrogen = a lit splint is held near its mouth and ignites with a squeaky pop.

  Carbon dioxide = lime water turns milky or cloudy white.

  Chlorine = damp litmus paper is bleached white.