Fuels

• What is a fuel?

  a substance which burns to release energy
• Draw and label the fire triangle

  Left - oxygen, right - heat, bottom - fuel
• What is another name for burning?

  Combustion
• What is the word used for a chemical reaction which releases energy? (ie combustion)

  Exothermic means heat energy is released
• Give examples of fossil fuels

  Coal, crude oil, gas
• Explain how crude oil is formed

  Remains of plants and marine animals fall to the ocean floor. Over millions of years, and with heat and pressure, the remains become oil.
• What types of molecules are found in crude oil?

  Hydrocarbons (contain carbon and hydrogen only)
• Crude oil can be separated into fractions by fractional distillation.

  Briefly explain how this works.

  The hydrocarbons in crude oil are separated because they have different boiling points. Larger molecules have higher boiling points
• What is a hydrocarbon?

  Hydrocarbons are molecules which contain carbon and hydrogen only
• Name the first 8 alkanes

  Methane

  Ethane

  Propane

  Butane

  Pentane

  Hexane

  Heptane

  Octane
• What is the shape of a methane molecule?

  Tetrahedral
• Draw ethane

  C2H6 ( 2 C's and 6 H's)
• Draw butane

  C4H10 (4 C's and 10 H's)
• Draw hexane

  C6H14 (6 C's and 14 H's)
• Name the two products which are always formed when a hydrocarbon burns (combusts)

  Carbon dioxide and water
• Write the word equation for combustion of methane

  Methane + oxygen -> carbon dioxide + water
• What is the test for carbon dioxide?

  Add limewater
• What is the colour change?

  If carbon dioxide is present, the limewater will go from colourless to cloudy
• What is a test for water?

  It freezes at 0 degrees C and boils at 100 degrees C

  Cobalt chloride paper goes from blue to pink
• Ethanol is an example of a biofuel. What is the name of the reaction used to form ethanol from glucose?

  fermentation
• Describe the process of fermentation and write the word equation for the conversion of glucose into ethanol (fermentation)

  Glucose -> ethanol + carbon dioxide
• When a biofuel such as ethanol burns it still produces ethanol. Explain why biofuels can be considered carbon neutral.

  When you grow the plants required to make ethanol, they take in carbon dioxide from the atmosphere (photosynthesis)

  HOWEVER - it is not always as straightforward as this because the process of transporting the fuel, making fertiliser to grow the plants etc all release CO2 into the atmosphere
• Give 4 examples of fossil fuels

  Coal, natural gas, crude oil, peat
• What is crude oil?

  A mixture of hydrocarbons
• What can we do to useful substances from crude oil?

  (Petrol and diesel) are fuels that can be burned to release energy
• What is a hydrocarbon?

  A molecule containing only hydrogen and carbon
• Explain the simplest family of hydrocarbons

  The are called alkanes
• Name the first 8 alkanes

  Methane

  Ethane

  Propane

  Butane

  Pentane

  Hexane

  Heptane

  Octane
• Describe the shape of a methane molecule

  Tetrahedral
• Write the molecular formula and draw the first 8 alkanes

  Methane - CH2

  Ethane - C2H6

  Propane - C3H8

  Butane - C4H10

  Pentane - C5H12

  Hexane - C6H14

  Heptane - C7H16

  Octane - C8H18
• Describe a combustion reaction and word equation

  Hydrocarbons burning to produce carbon dioxide and water

  Hydrocarbons + oxygen -> carbon dioxide + water
• What is limewater/what is it used to test for?

  Limewater is used to test for carbon dioxide because carbon dioxide turns limewater milky
• What is a chemical test for water?

  Water is the only liquid which freezes at 0 degrees C and boils at 100 degrees C

  Water will turn cobalt chloride paper from blue to pink
• What is biomass

  Biomass can be used as an alternative to fossil fuels
• Give examples of biomass

  —
• What is ethanol an example of?

  Ethanol is an example of a biofuel and can be produced by the process of fermentation
• What happens when bioethanol is burned (as a fuel)?

  When bioethanol is burned as a fuel it releases carbon dioxide
• Why are biofuels considered "carbon neutral"?

  The CO2 they emit is balanced by the CO2 taken up by plants when they are produced
• Describe the process of fermentation

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• Complete the word equation for the conversion of glucose into alcohol

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