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Oils, earth and atmosphere summary

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Oils, earth and atmosphere summary

Oils, earth and atmosphere summary

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  • 1. Oils, Earth and atmosphere summary 2 May 2011
  • 2. Cracking hydrocarbons
    • Large hydrocarbon molecules are not very useful. They can be cracked into smaller molecules by heating them and passing them over a catalyst.
    • The process of cracking involves thermal decomposition and produces some unsaturated hydrocarbons.
    • The test for unsaturated hydrocarbons is that they will turn red bromine solution colourless.
    1
  • 3. Making polymers from alkanes
    • Plastics are long chain molecules which are produced form unsaturated hydrocarbons.
    • The small molecules used to create the long chains are called monomers.
    • Once joined together the long chain is called a polymer.
    • When a carbon to carbon double bond is broken and the molecules are linked we have an addition polymer.
    2
  • 4. The properties of plastics
    • The forces between molecules are called intermolecular forces. The strength of the force in a plastic depends on the monomer used to make the plastic.
    • If the force is weak the plastic softens when heated – these are called thermosoftening plastics.
    • If the force is strong the plastic does not soften when heated – these plastics are called themosetting plastics.
    3
  • 5. New and useful polymers
    • New polymers are being developed all the time – these designer plastics are made to perform in a specific way when used.
    • Certain polymers that respond to changes around them are called ‘smart polymers’ – they can regain their origins shape or respond to changes in light and temperature.
    4
  • 6. Extracting vegetable oils
    • Plants produce glucose during photosynthesis. The glucose can then be changed into other chemical such as vegetable oils.
    • The vegetable oil can be extracted by crushing the plant material (like seeds) or by distillation.
    • Vegetable oils are more healthy than animal fats because they contain carbon-carbon double bonds – they are unsaturated.
    • The test for unsaturation is adding bromine water which turns colourless if the oil is unsaturated but remain orange if it is saturated.
    5
  • 7. Cooking with vegetable oils
    • The boiling point of a liquid depends on the size of the forces between molecules.
    • The large size of vegetable oil molecules means that these oils boil at a much higher temperature than water.
    • The texture of cooked food depends on the temperature at which it is cooked. So for example potatoes cooked in water and oil have very different textures.
    • Unsaturated oils melt and boil at lower temperatures than saturated fats.
    • Hydrogenating oils (adding hydrogen to them to remove the carbon-carbon double bond) results in higher melting points and the oil is said to be hardened.
    6
  • 8. Everyday emulsions
    • Oil and water do not mix, however if the oil droplets can be made very small and spread out throughout the liquid we have an emulsion.
    • In order to make an emulsion an agent which will attract both water and oil molecules is called an emusifier.
    • Emulsions made from vegetable oils include salad dressing and ice cream.
    7
  • 9. Food additives
    • Chemicals are often added to foods for the following reasons
    • (1) to make it look more attractive
    • (2) to preserve the food
    • (3) to improve the texture
    • (4) to control the acidity (pH)
    • (5) to improve the flavour.
    • Additives can be detected by using a separating method such as chromatography or a mass spectrometer.
    8
  • 10. Vegetable oils as fuels
    • It is now possible to make fuels from vegetable material.
    • Biodiesel can be made from vegetable oils it is carbon neutral and free from sulphur however there is a huge need for food in the world so using oils in this way is not really a long term solution.
    • Ethanol can be made from sugar by allowing the sugar to ferment when yeast is added to the sugar solution.
    9
  • 11. Structure of the Earth
    • The Earth has a series of layers.
    • The solid crust is 6km to 70km thick .
    10
    • The mantle behaves like a solid but does flow slowly, it is very thick – about 3000km.
    • The Earth’s core is made up of a mixture of iron and nickel – the outer layer is liquid and the inner layer is solid.
  • 12. The restless Earth
    • The Earth’s lithosphere (outer shell) is cracked into a number of tectonic plates which are constantly moving.
    • The movement of the plates is caused by convection currents in the mantle. The mantle is semi liquid due to the heat produced by radioactive decay in the mantle.
    • Earthquakes and volcanoes occur where the tectonic plates meet. Earthquakes take place when the layers slip past each other but are difficult to predict.
    11
  • 13. The tectonic plates 12
  • 14. The Earth’s past atmosphere
    • The Earth’s atmosphere was formed originally by volcanic activity.
    • The gases present were carbon dioxide, methane and ammonia.
    • As pants formed they consumed the carbon dioxide and produced oxygen.
    • At the same time oxygen reacted with methane to form carbon dioxide and water vapour.
    13
  • 15. The Earth’s current atmosphere
    • The ammonia reacted with oxygen to form nitrogen and water vapour.
    • The Earths present atmosphere consists of 78% nitrogen, 21% oxygen, 0.9% argon (an inert noble gas) and 0.04% carbon dioxide.
    • The next slide shows how these changes took place over a long period of time.
    14
  • 16.
    • All positions are approximate
    4500 million Now 3000 million 2000 million 1000 million 500 million 200 million No gases H 2 and He Volcanoes Algae Plants CO 2 NH 3 CH 4 O 2 N 2 H 2 O The changing atmosphere
  • 17. The Carbon Cycle photosynthesis eaten by respiration respiration respiration Death of plants Death of animals and excretion CO 2 in air Plants contain carbon compounds Detritus feeders and microorganisms feed on dead matter Animals contain carbon compounds 15