Energy in fuels

• Crude oil


  A finite (non-renewable) resource found in rocks, used to produce fuels and other important chemicals, made from fossilised remnants of ancient plankton
• Hydrocarbons


  • Molecules made up of only hydrogen and carbon atoms, differ in size which changes the properties
• Crude oil


  A mixture of lots of different hydrocarbons that are not chemically combined, majority of the compounds are hydrocarbons
• Fractional distillation


  Separates crude oil into simpler more useful mixtures: Refinery Gases, Bottled gas, Gasoline, Naphtha, Kerosene, Diesel, Fuel Oil, Lubricating Oil, Bitumen
• Fractional distillation


  Separates components based on their different boiling points
• Properties of hydrocarbons


  • Boiling point (longer chain = higher), Toxicity, Explosiveness, Flammability (longer chain = less), Viscosity (longer chain = higher)
• Burning hydrocarbons


  1. Burning with plenty of oxygen (releases energy, oxidises carbon and hydrogen to create CO2 and H2O)

  2. Burning with lack of oxygen (can create CO)
• Complete combustion


  Burning of hydrocarbons with good air supply, gives blue flame, produces only CO2 and H2O
• Incomplete combustion


  Alkanes burned without enough oxygen, gives orange smoky flame, produces CO2, H2O, pure carbon, hydrocarbons, CO. Produces soot
• Incomplete combustion


  More likely with longer chain alkanes as more oxygen is needed to combust completely
• Internal combustion engine


  • Combustion of alkanes powers cars, can produce impurities like nitrous oxides, unburned hydrocarbons, carbon monoxide
• Nitrous oxides from internal combustion engines

  React to form ozone at ground level, which irritates eyes and can cause lung damage
• Flue gases from chimneys

  Often contain sulfur dioxide, which dissolves in water to make sulfuric acid, causing acid rain that can destroy trees and vegetation
• Removing sulfur dioxide


  Reacting with calcium oxide or calcium carbonate, CaO + SO2 -> CaSO3
• Catalytic converters can remove unburned hydrocarbons and nitrous oxides from fuel
• Needed calories for a man = 2500 kj, needed calories for a woman = 2000 kj
• Power rating on fuel bills

  Calculated in kilowatts (kW)
• Energy transferred on fuel bills


  Measured in kilowatt hours [kWh], called units
• Calculating units used


  Units = power × time
• Calculating fuel bill cost

  Units × cost per unit
• Calculating enthalpy changes from temperature changes

  q = m × c × ΔT, where q is heat energy, m is mass, c is specific heat capacity, ΔT is temperature change
• The combustion of fuels is exothermic. It produces heat energy which is released into the surrounding environment.
• equation for Complete Combustion :

  fuel + oxygen = carbon dioxide + water + (heat energy)
• Word Equation Incomplete Combustion

  fuel + oxygen = carbon monoxide + water + (heat energy)
• carbon monoxide is a toxic gas that can cause headache’s, dizziness and death
• incomplete combustion makes an orange smoky flame

  complete combustion makes a blue flame
• incomplete combustion creates soot, which is carbon
• specific heat capacity of water :

  4.2 joules.
• specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1 degree
• the energy content of foods can be measured by burning foods under a calorimeter filled with a certain volume of water.
• Heat Energy = mass of water (g) X specific heat capacity (J/kg°C) x change in temperature (°C)