EDEXCEL CHEMISTRY PAPER 2

• Groups on the periodic table

  • Alkaline metals (group 1)
  • Alkaline earth metals or alkali metals (group 2)
  • Halogens (group 7)
  • Noble gases (group 8)
  • Transition metals (middle)
• Noble gases


  Have a full outer shell, are very unreactive, have many uses like helium in balloons and neon in lights
• Halogens


  Go around as diatomic molecules, are highly reactive as they only want to gain one electron, most reactive ones at the top
• More reactive element


  Displaces less reactive element in a compound
• Halogens


  Mostly used for sterilizing, like chlorine in swimming pools
• Alkaline metals


  React very violently with water, produce flames and colours used in fireworks, need to be kept in oil
• Reaction of alkaline metals

  1. Metal reacts with oxygen to form metal oxide

  2. Metal reacts with water to form metal hydroxide (alkaline)

  3. Reaction is exothermic and releases hydrogen gas
• Alkaline metals


  • Most reactive at the bottom, least reactive at the top
  • Have low melting/boiling point at the bottom, higher at the top
• Alkaline metals


  Want to lose an electron, most reactive at the bottom due to more shielding
• Measuring rate of reaction

  1. Can measure volume of gas produced over time or mass lost over time

  2. To find rate at a point, draw a tangent and calculate the gradient
• Rate of reaction is faster at the start compared to later in the reaction
• Following reaction by color change

  Reaction between sodium iodosulfate and hydrochloric acid, need to be careful with safety
• Collecting gas


  Can use an inverted measuring cylinder, need to be careful about gas already present
• Particle size


  Powder has more surface area than lump, so faster rate of reaction
• Catalyst


  Lowers the activation energy, making the reaction easier to happen
• Endothermic reaction


  Takes in energy, products have higher energy than reactants
• Exothermic reaction


  Gives out energy, products have lower energy than reactants
• Activation energy


  The hump a reaction has to get over to occur
• Catalyst


  Lowers the activation energy, making the reaction more likely to occur
• Endothermic reaction


  Feels like it gets colder, takes in energy
• Exothermic reaction


  Feels like it gets hotter, gives out energy
• Endothermic reaction


  Reactants have lower energy than products
• Exothermic reaction


  Reactants have higher energy than products
• Endothermic reaction


  • Electrolysis
• Exothermic reactions


  • Burning
  • Neutralization
• Calculating energy change of a reaction

  1. Write balanced equation

  2. List bonds broken and formed

  3. Calculate energy of reactants and products

  4. Subtract to get energy change
• Hydrocarbon


  Compound made up of only hydrogen and carbon
• Crude oil


  Mixture of different length hydrocarbons
• Fractional distillation of crude oil

  1. Heat crude oil until gaseous

  2. Condense in tower, longer hydrocarbons at bottom, shorter at top
• Fractional distillation products


  • Gases at top (flammable, not viscous)
  • Petrol, naphtha, kerosene in middle
  • Diesel, fuel oil at bottom (less flammable, more viscous)
• Cracking long hydrocarbons


  Use heat and catalyst to break down long hydrocarbons into shorter alkanes and alkenes
• Complete combustion


  Hydrocarbon + oxygen -> water + carbon dioxide
• Incomplete combustion


  Insufficient oxygen -> water, carbon dioxide, carbon monoxide, soot
• Main greenhouse gases


  • Carbon dioxide
  • Water vapor
  • Methane
• Greenhouse gases


  Absorb infrared radiation, trapping heat in atmosphere and causing global warming
• Levels of carbon dioxide in atmosphere increasing, contributing to global warming
• Global warming causing melting of ice caps, increased flooding, and changes to animal/plant habitats
• Carbon footprint


  Amount of carbon emissions from daily activities
• Predictions show carbon dioxide levels and global warming will continue to increase unless action is taken
• Acid rain


  Caused by sulfur dioxide dissolving in clouds and falling as acidic precipitation