Chapter One : Choosing Fuels Flashcards
Energy definition
The ability to do work
Thermochemistry definition
The study of heat changes in chemical reactions
Fuel definition
Is a substance that can be reacted with other substances leading to the release of energy that can be harnessed for a specific purpose
Fossil fuel definition
Are chemicals produced by the fossilisation of dead plant and animal matter, pressurised over millions of years leads to the formation of liquid crude oil
Thermochemical equation definition
A balanced stoichiometric equation that includes enthalpy change
Combustion of coal
C(s) + O2(g) -> CO2(g)
Combustion of oil (petrol)
2C8H18(l) + 25O2(g) ->16CO2(g) + 18H2O(g)
Combustion of natural gas
CH4(g) + 2O2(g) -> CO2(g) + 2H2O(g)
Types of energy
Kinetic- Sound, heat, mechanical, chemical, light
Potential - Gravitational, electrical, nuclear, elastic, magnetic, chemical
Law of Conservation of Energy
Energy is neither created nor destroyed, but simply changes from one form to another
The second law of energy
Though the quantity of energy in the universe may stay the same, the quality decreases
Efficiency formula
Efficiency = Energy obtained in desired form / Energy available before conversion
X 100
Efficency of energy changes
Light to chemical = <1% Chemical to heat = 85% Chemical to mechanical = 25%(car) or 50%(rocket) Chemical to electrical = 60-90% Heat to mechanical = 45% Mechanical to electrical = 95% Electrical to mechanical = 60-90% Electrical to heat = 99% Electrical to light = 4% Light to electrical = 5-15%
Non-renewable energy definition
Energy sources that are being used up faster than they can be produced
- Fossil fuels (coal, oil, gas) and nuclear fuels (uranium)
Renewable energy definition
Energy sources that can be produced faster than they are used. Sustainable sources of energy
- Biofuels, solar, wind, waves, tides
Coal facts
Very efficient fuel
Destructive distillation turns coal into useful energy
Petroleum facts
Contains many different hydrocarbons
Must be refined (fractional distillation)
Mostly octane
LPG facts (liquefied petroleum gas)
Made of propane and butane
Is liquefied under pressure and can be stored as a compact liquid but burns as a gaseous vapour
Natural gas facts
Made of mostly methane
Odourless
Efficiency of fossil fuels (decreasing order)
Natural gas Petrol Diesel Black coal Brown coal
Coal seam gas facts
Extracted by drilling into deep wells of underground coal deposits
Coal seams are filled with water and pumped to the surface, desorbs methane from coal and brings it to the surface
Biofuels definition
Are fuels that are derived from living or recently deceased plants
Biofuels facts
Plants absorb CO2 and H2O to create glucose and oxygen, glucose and can be converted to oils, proteins and complex carbs which can be made into biofuels
Why are biofuels carbon neutral?
When biofuels are formed they absorb CO2 but whenn biofuels are burnt they also release CO2 but they are relasing and absorbing the same amount meaning that they are carbon neutral
Formation of bioethanol
Fermentation of sugar from waste wheat starch and molasses.
C6H12O6 > 2C2H5OH + 2CO2
Advantages of bioethanol
Reduces emissions of greenhouse gases
Renewable
Disadvantages of bioethanol
Lower efficiency
Conflict in land use as it takes up arable land
Can breakdown rubber and plastic in vehicles
Sometimes will produce more CO2 than it absorbs
Needs a modified engine
Formation of biodiesel
Fatty acids are added to glycerol to produce water and a triglyceride
Triglyceride is added to methanol/alcohol to make biodiesel
Made in presence of catalyst KOH/NaOH
Advantages of biodiesel
Biodegradable Lower emissions of greenhouse gases Requires no engine modification Renewable Just as efficient as petrol and diesel
Disadvantages of biodiesel
Economically unfavourable
At low temperatures it gels
Conflict in land use and can take up arable land
Formation of biogas
Produced from bacterial breakdown of organic material in the absence of oxygen
Sewage treatment plants and landfill decompose anaerobically to produce methane
Advantages of biogas
Renewability
Productive use of wastes
Little environmental impact
Disadvantages of biogas
Energy inefficiency
Low supplies
Petrodiesel sources
Petroleum
Biodiesel sources
Cooking oil
Oil from algae
Methanol production from glycerol
Chemical structure or petrodiesel
Alkanes
Straight chained and branched (aliphatic)
Benzene rings (aromatic)
Chemical structure of biodiesel
Fatty acids to triglyceride to biodiesel
Combustion products of petrodiesel
Carbon dioxide/monoxide Water Soot SO2 Nitrogen oxides
Combustion products of biodiesel
Same as petrodiesel but lower in quantity
Increased nitrogen oxide emission
Viscosity of petrodiesel
Hygroscopic but seasonal blending allows for temp changes
Viscosity of biodiesel
Hygroscopic and gels at low temps
As there are dipole dipole bonds in the C=O groups
Environmental impact of petrodiesel
Non-renewable
Non-biodegradable
Spills in transportation
Combustion emissions in transport
Environmental impact of biodiesel
Renewable
Biodegradable
Issues with land use for biodiesel
Deforestation issues
Effect of fossil fuels on the environment
Increases greenhouse gases which increases greenhouse effect causing global warming
Reaction between sulfur dioxide and water causes acid rain
Sustainable energy definition
Providing the energy needs of todays generation without comprimising future generations to meet their own needs
