Chemistry - C1.7

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The Structure of the Earth and it's Atmosphere

  • The Earth has a layered structure, including the core, mantle and crust.
  • The crust and uppermantle are cracked into tectonic plates. They move slowly, and when they meet, they can cause volcanoes and earthquakes.
  • The crust is the outermost layer, and is relatively thin and rocky. ( Between 10km and 100km in different areas. )
  • The mantle is the next layer and has the properties of a solid, but flows slowly like a liquid.
  • The core is in the centre, and is made from liquid nickel and iron. The outer core is solid and in the inner core is liquid.
  • The Earth's crust, atmosphere, and oceans are the only resources we need to survive as humans.
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The Atmosphere

  • The Earth's early atmosphere was similar to that of Mars today. It was mostly Carbon Dioxide with traits of Oxygen and Nitrogen.
  • Today, the Earth's atmosphere is mainly Nitrogen ( 78% ) and Oxygen ( 21% ) with traits of Carbon Dioxide and Water Vapour.
  • The amount of CO2 has decreased because of photosynthesis, dissolving in ocean, through decay, coal, oil and natural gas, carbonate rocks, and shell creatures.
  • However, the amount of CO2 increases through burning fossil fuels, deforestation ( which prevents photosynthesis ), human respiration, volcanic gases, and decay.
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Theories about Life

  • earth is the only planet in the solar system where there is life, as it has all the conditions that living things need
  • Mercury and Venus are near the sun and too hot for life to exist
  • Mars and the outer planets are far away from the sun, and are too cold for life to exist
  • primitive forms of life appeared about 3400 million years ago
  • there is uncertainty about how life began because there is no evidence
  • one theory is that lightening provided the energy to split molecules with the fragments recombining to form new compounds including amino acids and other carbon compounds needed to make DNA
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Miller and Urey Experiment

  • Miller and Urey conducted an experiment for how life began on earth
  • they used electric speaks to force methane, ammonia, carbon dioxide and hydrogen to separate apart
  • the electric sparks represent lightening
  • the gas compounds separated out and then formed new compounds
  • these then condensed ( this represents rain ) so that they could test what new compounds were made
  • this water then flowed to the water flask ( which represented the ocean ) which was then heated up to it's boiling point so it could turn into water vapour and rise into the gas chamber
  • they left the flask for 1 week and then tested the flask contents , and they found amino acids and DNA molecules
  • amino acids and molecules that make up DNA are important because they are essential for life
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Fractional Distillation of Air

  • air is filtered to remove dust
  • water vapour condenses and is removed using absorbent filters
  • carbon dioxide freezes at -79°C and is removed
  • the remaining air is cooled in stages to 200°C, where it is a liquid
  • the liquid is then allowed to warm, and nitrogen boils off first at -196°C and oxygen boils off at -183°C
  • argon boils off at -186°C
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Uses of Components of Air

OXYGEN - steel making, oxyl-acetylene welding, breathing equipment, aerating sewage

NITROGEN - inert atmosphere for food ( stops it going off ), liquid nitrogen is used for cooking medical tissue

ARGON - inert atmosphere for light bulbs

CARBON DIOXIDE - carbonating fizzy drinks, stage effects, fire extinguishers

HELIUM - party balloons

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Tectonic Theory

  • A Wegener was a scientist who developed the idea that billions of years ago, the continents as we know them today were once stuck together, in a giant continent called Pangea. This theory is called continental drift.
  • the evidence he found for this was that a specific animal fossil was found on both South America and Africa, and also, these two continents look as though they fit together like a jigsaw
  • at the time, this theory was not accepted, and people thought that there was a land bridge that has now sunk underwater that allowed these animals to roam in both continents
  • he proposed that the movement of the crust was responsible for the separation of the land
  • we now know that the Earth's lithosphe is cracked into tectonic plates. We know that they move because of intense heat caused by radioactive decay in the core, which causes hot molten rock to rise to the surface, and the colder rock at the top fall to the bottom. These movements are known as convection currents.
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Predicting Earthquakes and Volcanic Eruptions

  • to predict an earthquake, we can:
  • monitoring small earthquakes ( these can be pre-shocks ) ( using seismometers )
  • monitor to see if water levels in wells fall
  • monitor to see if animals act strangely
  • to predict a volcanic eruption we can:
  • monitor the temperature of the volcano, if the temperature increases, it may be due to magma moving underground
  • monitor the ground level around the volcano, if the ground level rises, it could be due to a build up of magma
  • monitor the amount of sulphur dioxide that is released, if more SO2 is released, an eruption may occur
  • however, predictions are difficult to get accurate because:
  • we cannot know exactly when
  • we cannot know exactly where
  • we cannot know exactly how much damage will be caused
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