paper 2

• Electrons

  Exist in shells around the nucleus
• Electron configuration of atoms

  • 2 on the first shell
  • 8 on the second and third shells
  • 2 on the fourth shell
• Calcium atom has 20 electrons in total
• Transition metals have a complex electron configuration
• Electron configuration of magnesium

  2 8 2
• Metals

  Atoms to the left of the staircase on the periodic table, they donate electrons to gain an empty outer shell
• Non-metals

  Atoms to the right of the staircase on the periodic table, they accept electrons to gain a full outer shell
• Group

  The column an atom is in on the periodic table, it tells you how many electrons are in the outer shell
• Groups on the periodic table

  • Group 1 (alkali metals)
  • Group 7 (halogens)
  • Group 0 (noble gases)
• Alkali metals

  Group 1 atoms, they have one electron in their outer shell which they readily donate
• As you go down group 1


  The outer electron is further from the nucleus, so it is more readily donated
• Halogens

  Group 7 atoms, they have 7 electrons in their outer shell and need 1 more to gain a full shell
• As you go down group 7

  Electrons are further from the nucleus, so they are less readily accepted
• Noble gases

  Group 0 atoms, they already have a full or empty outer shell so they are very unreactive
• Ions

  Atoms that have lost or gained electrons, they are positively or negatively charged
• Ion charges

  • Group 1 ions are 1+
  • Group 2 ions are 2+
  • Group 7 ions are 1-
  • Group 6 ions are 2-
• Transition metals


  Can form ions with different charges depending on how many electrons they donate
• Rate of reaction

  The change in a quantity (e.g. mass, volume of gas) divided by the change in time
• Measuring rate of reaction

  1. Reacting hydrochloric acid and sodium thiosulfate

  2. Measuring time until solution becomes cloudy

  3. Repeating at different temperatures
• Rate graph

  Starts off steep, then levels out as reaction reaches completion
• Tangent on rate graph


  Used to calculate rate at a specific time
• Factors that increase reaction rate

  • Increasing concentration of reactants
  • Increasing pressure of gas reactants
  • Increasing surface area of solid reactants
  • Increasing temperature
  • Adding a catalyst
• Reversible reactions


  Reactions where the products can reform the original reactants
• Equilibrium

  In a closed system, the point where the forward and reverse reaction rates are equal
• Increasing pressure


  Favours the forward reaction in an equilibrium
• Increasing temperature

  Favours the endothermic (reverse) reaction in an equilibrium
• Exothermic reaction

  A reaction that releases more energy than it absorbs
• Endothermic reaction


  A reaction that absorbs more energy than it releases
• Activation energy

  The minimum energy needed to start a reaction
• Bonds require a specific amount of energy to break or form
• Calculating net energy change

  1. Sum energy needed to break reactant bonds

  2. Subtract energy released when product bonds form
• Organic compounds

  Compounds with a carbon backbone
• Alkanes


  Organic compounds made of single-bonded carbon chains with hydrogen atoms
• Fractional distillation of crude oil

  1. Heat crude oil to evaporate

  2. Vapours condense at different heights based on boiling points

  3. Collect different fractions (LPG, petrol, kerosene, diesel, heavy fuel oil)
• LPG contains alkanes up to 4 carbon atoms long
• Alkanes


  Hydrocarbons with single carbon-carbon bonds
• Alkanes


  • Longer alkanes have higher boiling points
  • Shorter alkanes remain as gas even at the top
• LPG

  Liquid petroleum gases, a range of short-chain alkanes up to 4 carbons long
• Petrol


  The next longest fraction after LPG, used in cars
• Kerosene

  Used for jet fuel