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Early Atmosphere
1. Evolution of atmosphere
  1. Phase 1
    1. Volcanoes gave out Gases at the beginning
      1. 1) Earth's surface originally molten for millions of years and so any atmosphere 'boiled away into space'
      2. 2) Then a thin crust was formed when things cooled down but volcanoes kept erupting
      3. 3) Volcanoes gave out lots of gases which is how oceans were formed
        E.g. Carbon dioxide and water vapour
      4. 4) This theory suggests that the atmosphere was mostly carbon dioxide with little oxygen, like mars and venus
      5. 5) Oceans formed when water vapour condensed
  2. Phase 2
    1. A lot of CO2 dissolved into the water
    2. Then marine creatures formed and took in some CO2
      1. When they died they were buried under layers of sediment and the CO2 became locked up in carbonate rocks
    3. Plants started to evolve and take in CO2 and gave out oxygen
    4. This caused oxygen levels to gradually increase
  3. Phase 3
    1. The build up of oxygen killed off some organisms but allowed some to grow and flourish
    2. The oxygen created the ozone layer which blocked harmful rays from the sun and allowed even more complex organisms to evolve
    3. Very little CO2 left now (0.04%)
2. Today's atmosphere
  1. Even today our atmosphere is changing, but there are only theories why it is
    1. Human activity
      1. Burning fossil fuels
        releases CO2, and as the world grows more fossil fuels are burnt
      2. Deforestation
        Contributes to the increase of CO2 because the trees that take in CO2 are being chopped down.
        which means there is more CO2 left in the atmosphere
      3. Livestock farming
        releases large amounts of methane into the atmosphere.
        Animals produce this when they pass wind
    2. Volcanic activity
      1. sulphur dioxide gas reacts with sunlight, water, oxygen and dust to form volcanic smog
      2. CO2 is released through volcanic eruptions
    3. However evidence on evolution is limitted
      1. We've learnt a lot about the past atmosphere from Antarctic ice cores.
        Each year a layer of ice forms and bubbles of air get trapped inside it and is
      2. However because no one was there at that time to record it , it is difficult to be precise about how the atmosphere has changed
        so some of it is guess work
  2. Investigation!!!
Materials from the Earth
1. 3 different types of rocks
  1. Sedimentary Rocks
    1. Formed from layers of sediment laid down in lakes or seas
    2. Over millions of years the layers get buried under more layers and he weight pressing down squeezes out the water
    3. Fluids flowing through the pores deposit natural mineral cement
      1. e.g limestone and chalk, they're also fossils because the rock isn't formed at high temperatures
        Limestone is used for many purposes
        Used as a building material
        It is quarried out of the ground to make blocks to build with
        Limestone is virtually insoluble in plain water, but erode in acid rain
        When crushed up into chippings limestone can be used for road surfacing
        Limestone also is used for other building materials
        Powdered limestone heated in a kiln with powdered clay makes cement
        Mix the cement with sand, water and gravel to make concrete
        heat limestone with sand and sodium carbonate until it melts to make glass
        Positives and negatives of limestone
        Positives
        Provides housing, roads, dyes, paints and medicines
        It can neutralise acidic soil and the acidity of lakes and rivers caused by rain soil
        Used in power stations to neutralise sulphur dioxide
        Provides jobs
        Negitives
        Quarrying makes big holes which permantently change the landscape
        Creates noises and dust during processes in quiet areas
        Destroys habitats
        the limestone needs to be transported away in lorries, causing pollution and noise
        When disposed it creates unsightly tips
      2. They're both are easily broken away by wind, rain and waves, this is called erosion
  2. Metaphoric rocks
    1. formed under heat and pressure on sedimentary or igneous rocks over long periods of time
    2. As long as the rocks don't melt they are metaphoric, but if they melt into magma, they're gone (but may resurface as igneous later)
    3. E.g. Marble (formed from limestone or chalk), very high temps break down the limestone and it reforms as small crystals , making marble harder
  3. Igneous rocks
    1. Igneous rocks form when molten magma pushes up into the crust before cooling and solidifying and contain different minerals. there are 2 types
      1. Extrusive igneous rocks cool QUICKLY ABOVE GROUND, forming SMALL crystals
        E.g. Basalt, rhyolite
      2. Intrusive igneous rocks cool SLOWLY UNDERGROUND, forming BIG crystals
        E.g. granite and gabbro
2. Atoms and mass in chemical reactions
  1. Atoms aren't lost or made in chemical reactions
    1. Elements and compounds are made of atoms, and these are what take part in reactions
    2. During reactions things don't appear or disappear
    3. You still have the same atoms from the beginning of the reaction at the end, they're just arranged to give new products with new properties than the reactants
    4. Balanced symbol equations shows the atoms at the start and at the end (the reactants and the products), and how they are arranged
  2. The total before and after a reaction is unchanged
    1. If you do a reaction in a sealed container, the total ass before and after doesn't change
    2. This can be shown through a precipitate reaction
    3. A precipitation reaction when 2 solutions react and an insoluble solid forms
    4. Nothing should escape from the flask so the mass before and after the mass should be the same, no mass is lost or gained
3. Balancing equations
  1. You need to do this to show the change of properties from the reactants to the products, but since atoms cant disappear you need to numbers in front of the formulas where needed
    1. 1) Find the element that doesn't balance and put a number in that would work and see if you can balance it on the other side
    2. if it doesn't try another number and continue doing trial and error until you get it
    3. Don't forget the state symbols! (s) -solid, (l) -liquid, (g )-gas, (aq) - Dissolved in water

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