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Amy Atteridge. Alkenes. Alkenes are hydrocarbons containing a ... in water or trichloroethane solvent forms an orange (yellow/brown) solution. ... Amy Atteridge ... – PowerPoint PPT presentation

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The origins of oil
  • Crude oil is formed from organic material of the
    remains of plant and animal organisms that lived
    millions of years ago.  These remains form
    sediments e.g. at the bottom of seas, and become
    buried under layers of sedimentary rock.
    They decay, without air (oxygen), under the
    action of heat and pressure to form crude oil
    over millions of years.
  • It is a fossil fuel because it is formed from
    once living organisms and the Sun is the original
    source of energy. It is a non-renewable and
    finite (limited reserves) energy resource because
    it takes millions of years to form and we burn it
    faster than it is formed! It is also known as a
    finite energy resource because it will eventually
    run out! We do not have unlimited oil reserves!
  • When the fossil fuels are burned the 'carbon', as
    carbon dioxide, is returned to the living
    environment, gets used up in photosynthesis, the
    plant material decays or is eaten by animals, so
    completing the carbon cycle.

  • Alkenes are hydrocarbons containing a double bond
    as well as single bonds. These are called
    unsaturated molecules because two atoms can join
    onto the bond when it opens up. The first two in
    the series are shown below. They are extremely
    reactive and important compounds in the chemical
    industry and are converted into very useful
    compounds e.g. plastics. They are made from
    cracking processes.

  • Hydrocarbons are colourless. Bromine dissolved in
    water or trichloroethane solvent forms an orange
    (yellow/brown) solution. When bromine solution is
    added to both an alkane and an alkene the result
    is quite different. The alkane solution remains
    orange - no reaction. However, the alkene
    decolourises the bromine as it forms a colourless
    dibromo-alkane compound - see equations.

Crude Oil
  • Crude oil is the term for "unprocessed" oil, the
    stuff that comes out of the ground. It is also
    known as petroleum. Crude oil is a fossil fuel,
    meaning that it was made naturally from decaying
    plants and animals living in ancient seas
    millions of years ago -- anywhere you find crude
    oil was once a sea bed. Crude oils vary in
    colour, from clear to tar-black, and in
    viscosity, from water to almost solid.

  • Crude oils are such a useful starting point for
    so many different substances because they contain
    hydrocarbons. Hydrocarbons are molecules that
    contain hydrogen and carbon and come in various
    lengths and structures, from straight chains to
    branching chains to rings.

what makes them exiting
  • There are two things that make hydrocarbons
    exciting to chemists
  • Hydrocarbons contain a lot of energy. Many of the
    things derived from crude oil like gasoline,
    diesel fuel, paraffin wax and so on take
    advantage of this energy.
  • Hydrocarbons can take on many different forms.
    The smallest hydrocarbon is methane (CH4), which
    is a gas that is a lighter than air. Longer
    chains with 5 or more carbons are liquids. Very
    long chains are solids like wax or tar. By
    chemically cross-linking hydrocarbon chains you
    can get everything from synthetic rubber to nylon
    to the plastic in tupperware. Hydrocarbon chains
    are very versatile!

What is it made of
  • On average, crude oils are made of the following
    elements or compounds
  • Carbon - 84
  • Hydrogen - 14
  • Sulfur - 1 to 3 (hydrogen sulfide, sulfides,
    disulfides, elemental sulfur)
  • Nitrogen - less than 1 (basic compounds with
    amine groups)
  • Oxygen - less than 1 (found in organic compounds
    such as carbon dioxide, phenols, ketones,
    carboxylic acids)
  • Metals - less than 1 (nickel, iron, vanadium,
    copper, arsenic)
  • Salts - less than 1 (sodium chloride, magnesium
    chloride, calcium chloride)

  • Crude oil is a mixture of many compounds, most of
    them hydrocarbons.
  • Hydrocarbon molecules vary a great deal as to how
    many atoms they contain. A molecule of methane -
    the main component of natural gas - consists of
    just one carbon atom and four hydrogen atoms
    while a molecule of polyethelene is a long chain
    of thousands of carbon and hydrogen atoms.

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