Chemistry C1B

Oils, Earth and Atmosphere

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  • Created by: Amy GOuld
  • Created on: 05-06-10 17:55

Cracking Hydrocarbons

  • Fractions from crude oil can be broken down by Thermal Decomposition in a catalytic cracker. The fraction is vapourised and passed over a hot catalyst => molecules split apart.
  • Alkenes: unsaturated hydrocarbons, contain fewer hydrogen atoms than alkanes, but have the same number of carbon atoms.
    FORMULA = CnH2n
    More reactive than alkanes.
    When reacted with Bromine water, the solution ( orange-yellow ) turns colourless.
  • Alkanes: saturated hydrocarbons, no double bonds in this molecule.
    FORMULA: CnH2n+2
    When reacted with Bromine water, the colour of the solution does not change.
  • Bromine Water is used to test for unsaturation.

    C=C <<<< A Double Bond ( alkene )

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Making Polymers From alkenes and the properties of

  • Polymers are large molecules made from small molecules that have joined together; monomers.
  • Polymerisation: The reaction thats produces polymers.
  • Addition Polymerisation: When alkene molecules join together, the double bond is each molecule opens up, being replaced by single nods as molecules join together ( addition reaction ) .
  • Many plastics used such as bags, and bottles are made from alkenes.
  • Polymers have very long molecules in a tangled mess, with strong bonds holding the atoms together within the molecules.
  • Using different monomers = polymers produced have different properties.
  • Thermosoftening Plastics : Weak intermolecular forces between their molecules, so when they are heated, they become soft, and harden when cooled. This process can be repeated.
  • Thermosetting Plastics : When heated, chemical bonds form between the polymer molecules, the link in a giant network. When cooled, the bonds make the polymers unable to repeat this method of remoulding.
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Extracting Vegetable Oils and cooking with Vegetab

  • Seeds, nuts and fruit are rich in vegetable oils. The oils can be extracted by pressing follwed by removing water.
  • Some oils are extracted by distilling the plants mixed with water.
  • The molecules in vegetable oils have long hydrocarbon chains.
  • Those with C=C bonds are unsaturated, and with several double bonds, they are polyunsaturated.
  • Unsaturated oils react with bromine and iodine. Bromine water is used to test for unsaturated compounds.
  • The boiling points of vegetables are higher than water, so food is cooked at a higher temp in oil = cooking times speed up Flavour, colour and texture is changed.
  • Some oil is absorbed => increase in energy content.
  • Unsaturated oils can be reacted with hydrogen so some or all C=C bonds become single. ( addition reaction, Hydrogenation )
  • 60`C with a nickel catalyst. increases the melting points of oils =
    They will harden at room temp.
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Emulsions

  • Emulsions ar made from liquids that spearate from each other. They are made by shaking, stirring and beating liquids together => forms tiny droplets of the liquids.
  • Emuslifiers help keep the droplets to stay suspeneded to stop the liquids from separating -This is done due to different parts of their molecules are attracted to the different liquids.
  • Emulsions are opaque and usually thicker than what they are made from. Texture, appearance and ability to stick is improved. ( milk , sauces )
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Additives and Vegeatable oils as fuels

  • Additives = Used in food to improve appearance, taste and shelf life.
  • They may be natural or artificial additives, checked by chromatography.
  • Six Types ;
    Colours ( E1 caramel) ,
    Preservatives ( E2 sodium benzoate)
    Antioxidants (E3 Vitamin C)
    Emulsifiers (E4 Pectin)
    Acidity Regulators (E5 Pottassium Carbonate)
    Flavourings (E6, MSG)
  • E- NUMBERS are given to additives, approved for use in Europe, to identify them.
  • When oils are burn't, a lot of energy is produced.
  • They can be treated to remove some chemicals and then use them as fuel.
  • Biodiesel - Replaces some or all of the diesel produced from crude oil.
  • It is renewable as plants are grown to produce the oils, and the plant material can be left.
  • Biodiesel is less harmful than fossil fuels and the CO2 is removed from the air as plants grow. No sulfur dioxide is produced and it is more biodegradeable.
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Structure Of the Earth and Movements.

  • The Earth is made up of layers - The crust, mantle and core.
  • THE SURFACE - A thin, solid crust. 5km - 7km thick, it is thinnest under the oceans.
  • THE MANTLE - Under the crust, 3000km thick goes to almost halfways to the centre of the Earth. It is almost entirely solid, but can flow slowly.
  • THE CORE - Very dense, made of mainly nickel and iron. The outer core is liquid and inner is solid.
  • Scientists thought that mountains and valleys were formed by the Earth shrinking. The believes that the crust solidified as the Earth cooled down and the Earth continued to shrink => crust winkles.
  • The Earth's Litosphere is cracked (tectonic plates), the Earth's crust and upper part of the mantle.
  • The tectonic plates continue to move a few centimetres every year.
  • Mountains form, earthquakes and volcanoes occur at plate boundaries.
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The Earth's atmosphere in the past and its gases.

  • Scientists think that Earth was formed about 4.5 billion years ago.
  • The surface was covered with volcanoes that released CO2, N, and water vapour in the early atmosphere.
  • The water vapour condensed to form oceans as the Earth cooled down.
  • Algae and plants evolved over the next two billion years, using CO2 for photosynthesis to produce food and this relased oxygen.
  • As plant growth increased, CO2 decreased and O increased.
  • There was little or no O in the early atmosphere.
  • 2000 million years - the proportions of the gases in the atmosphere have been similar to how they are now.
    Nitrogen - 78%
    Oxygen - 21%
    CO2 - 0.04%
  • The noble gases, in Group 0 are the least reactive elements, Argon, Neon and Helium and present in the atmosphere, but in extremely small amounts (0.01%)
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The Carbon Cycle

  • Carbon dioxide moves in and out of the atmosphere and natural processes have kept this is balance for millions of years.
    The cycle maintains the level of CO2 in the atmosphere. (http://bioh.wikispaces.com/file/view/36-15-CarbonCycle-L.gif/31445429/36-15-CarbonCycle-L.gif)
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