Chemistry Unit 2

Chemistry Unit 2

1. The Earth's Structure

   • The Earth' surface is made of large plates of rock
     • Earths structure
   • The Earth's surface is made up of large plates of rock
     • Tectonic plates
   • Seismic waves can tell us what's below the crust
     • Difficult to study th Earth structure when you can't get at it directly
       • Seismic waves are used to study Earth's structure
         • These are produced by earthquakes or by setting of man made explosions
           • By measuring where it happened and the time it takes for the waves to travel through the Earth and can draw conclusions about the structure of the Earth
   • P-waves
     • Travel faster throgh the middle of the core suggesting it is solid
   • S-waves
     • Travel through the mantle which is solid, not deceted in be liquid

2. Plate Tectonics

   • Alfred Wegener hypothesised that Africa and South America were once connected and had previously been one continat
     • The theory of 'continental drift' about 300 million years ago. He called it Pangaea.
       • Pangaea brake into different pieces and these pieces slowly drifted apart
         • The theory was not excepted at first but it was proved by the mid-Atlantic ridge

3. Volcanic eruptions

   • Volcanoes are formed by molten rock
   • Oceanic and continental crust colliding causes volcanoes
   • Volcanic activity forms igneous rock
     • Igneous rock is made when any sort of molten rock cools down and solidifies
     • Iron-rich basalt = runny+safe
     • Silica-rich rhyolite = thick+explosive

4. The there different types of rock

   • Sedimentary rock
     • Layers of rock are laid down in lacks and seas over millions of years so the layers get buried under other rocks. the weight squeezes out all of the water from the rocks.
     • Limestone is a sedimentary rock formed from seashells
       • CaCO3 (s) -> CaO(s) + CO2(g)
         • Calcium carbonate-->calcium oxide + carbon dioxide
   • Metamorphic rocks are formed from other rocks
     • Formed by the action of heat and pressure on sedimentary over a long period of time
       • So long as the rock does not melt they're classed metamorphic
         • If it melts it is called magma
     • Marble is a metamorphic rock formed from limestone
   • Igneous in 'volcanic eruptions'

5. Construction Materials

   • Aluminium and iron are extracted from the ground as ores
   • Glass is made by melting limestone sand and soda together
   • Bricks are made from clay
     • Clay is molded into bricks then fired at a high temperature
   • Limestone and clay are heated to make cement
     • These two are put in a kiln to make serment
       • Reinforced concrete is steel support plus concrete

6. Extracting pure copper

   • Electrolysis is used to obtain very pure copper
     • Reduction
       • The gain of electrons or the removal of oxygen
       • Cu2+ + 2e- --> Cu
     • Oxidation
       • The loss of electrons or the addition of oxygen
       • Cu --> Cu2+ + 2e-
   • Recycling copper saves money and resources
     • It's cheaper to recycle copper then it is to mine and extract new copper from from its ore

7. Alloys

   • An alloy is a mixture of a metal and other elements
     • Steel is an alloy of iron and carbon
       • Lots of things are made of steel
         • girders
         • bridges
         • engine parts
         • cutlery
         • washing machine
         • saucepans
         • ships
         • drill bits
         • cars
   • Brass, bronze, solder and amalgam are also alloys
     • Brass
       • copper + zinc --> brass
     • Bronze
       • copper + tin --> bronze
     • Solder
       • lead + tin --> solder
     • Amalgam
       • contains mercury

8. Building Cars

   • Iron and steel corrode much more than aluminium
     • iron + oxygen + water --> hydrated iron (III) oxide
     • Aluminium doesn't corrode when it's wet
       • When aluminium reacts with oxygen it forms aluminium oxide.
         • A protective layer of aluminium oxide sticks to the aluminium below and stops any further reaction taking place
   • Car bodies
     • Aluminium has two big advantages over steel
       • It has a lower density so it is lighter
       • Aluminium corrodes less and so and it has a longer life time
     • You need various materials to build different bits of a car
       • Steel
         • Bodywork
       • Aluminium
         • engine parts
       • Glass
         • Windscreen and windows
       • Plastics
         • Internal covering for doors and dashboards
         • covering electrical wires
       • Fibres
         • Seats and flooring
       • Recycling cars is important
         • It saves...
           • natural resources
           • money
           • landfill sight size
         • 85% (rising to 95%) of scrap metal from cars is recycled

9. Acids and Bases

   • An indicator is a dye that changes colour
     • The dye in the indicator changes colour depending on the pH of a substance
       • Universal indicator is a combination of dyes. It changes colour gradually as the pH changes
         • Some indicators change colour suddenly at a particular pH
           • Phenolphthalein changes suddenly from colourless to pink as the pH rises above 8
           • The pH scale
   • Acids and bases neutralise each other
     • Acids form H+ ions in water
     • Alkalies form OH- ions in water
     • acid + base --> salt + water
       • H+ + OH- --> H2O

10. Reactions

    • Metal oxides and metal hydroxides are bases
      • Acid + Metal Oxide --> Salt + Water
        • Acid + Metal Hydroxide --> Salt + Water
    • Acids and carbonates produce carbon dioxide
      • Acid + Carbonates --> Salt + Water + Carbon Dioxide
    • Acids and ammonia produce ammonium salts
      • Acid + Ammonia --> Ammonium salt

11. Fertilisers

    • Fertilisers provide plants with the essential for growth
      • Fertilisers contain nitrogen, phosphorus and potassium
        • If plants don't got enough of these elements, their growth and life processes are affected
    • Fertilisers are really useful-but they can cause big problems
      • Fertilisers damage lakes and rivers-eutrophication
        • When rain washes fertiliser runs of the plants into rivers and lakes
          • Algae in the water multiply rapidly creating an algae bloom. This blocks of light to the river parts and kills them as they can't photosynthesise
            • Aerobic bacteria feeds on the plant and multiply. This uses up all the oxygen
              • Because of this everything in the water dies

12. Preparing Fertilisers

    • Preparing fertiliser in the lab
      • Synthetic fertilisers are prepared in the lab by the reaction of an acid with an alkali. A quantity of alkali is placed in a beaker and a solution of acid is run in until the solution is neutral. This can be measured with a pH meter or by removing samples for testing with universal indicator.
        • The neutral solution of salt is evaporated until crystals form. These are filtered out, washed and dried in a warm oven.
    • Percentage yield compares actual with predicted yield
      • Percentage yield is always between 0 and 100%
        • 100% yield means that you got all the product you expected to get
          • 0% yield means that no product was made

13. The Haber Process

    • The haber process is a reversible reaction
      • N2 + 3H2 --> 2NH3
      • Pressure : High (200 atmospheres)
      • Temperature : 450'C
      • Catalyst : Iron
      • The Haber Process
      • The iron catalyst speeds up the reaction and keeps costs down
        • Without the catalyst the temperature would have to be raised even further to get a quick enough reaction

14. Minimising the costs of production

    • Production cost depends on several different factors
      • Price of energy
        • Must keep energy bills as low as possible
      • Cost of raw materials
        • recycle matirials
      • Labour costs (wages)
        • Every has to be paid
      • Plant cost
        • Equipment
        • Running costs
      • Rate of production
        • Faster reaction means less running cost

15. Salt

    • Salt is mined from underneath Cheshire
      • Rock salt mixture of salt and impurities
        • Electrolysis
    • Cathode: 2H+ + 2e- --> H2
    • Anode: 2Cl- - 2e- --> Cl2

Images and files in the map