Carbon Based Fuels Flashcards
What is a fuel?
Releases energy in combustion reactions with oxygen due to high carbon content.
Stores chemical energy that’s released as heat energy.
How is energy measured?
SI unit Joules (J)
What factor determines the amount of energy produced by a fuel?
The type of fuel combusted.
What are fossil fuels?
Derived from fossils remains of living organisms (plants/animals)
Where are fossil fuels found?
In the earth’s crust
How are fossil fuels formed?
Decompositions under anaerobic, intense heat and pressure conditions that alter chemical structure over millions of years.
Why can fossil fuels be used as a fuel?
Contain high amount of carbon and hydrogen for release of energy.
Prime global energy source
Define “non-renewable”
Cannot be replaced at the same rate via natural processes as they are consumed.
What is coal?
- most abundant fossil fuel
- mined in the ground
- combusted for electricity
What material is coal made from?
Wood and plant material
How is coal formed?
Carbon increases and oxygen/hydrogen decreases as the material decomposes.
AKA amount of H20
What are the factors determining energy potential of coal?
The longer coal is left and decomposes, the greater proportion of carbon thus greater energy potential.
What is the difference between black and brown coal?
Black coal has a higher energy potential because it has a higher carbon percentage than brown coal.
What compounds is in Natural Gas?
Methane (90%) Ethane, Propane, CO2 and Nitrogen
Where is Coal Seam Gas found?
Deposits of the earth’s crusts
- gas reservoirs between layers of rocks
How is Coal Seam Gas extracted?
Drilling and fracking
- Harmful impact on the environment
What is Fracking?
Inject liquid at high pressure into the coal to force open fissures.
How is coal seam gas formed?
Through remains of plants and animals
What is Crude Oil?
Viscous and black mixture of hydrocarbons (mostly alkanes)
- cannot be used in natural form
What are Crude Oil sources like in Australia?
Likely to be exhausted by the end of the century
What is fractional distillation?
Separates crude oils into different fuels on the basis of boiling points
What is petrol?
Mixture of hydrocarbons, predominantly Octane
What are the environmental constraints of these non-renewable sources?
- drilling and mining disrupt natural landscape and water table if oil spills occur.
- fuel combustion produces CO2 contributing to greenhouse gas effect
What is a concern regarding coal and crude oil?
Often contaminated with sulfur and nitrogen compounds
- can cause acid rain through SO2 (pH less than 4.5)
- damaging impact
What does renewable mean?
capable of being replaced in a relatively short period of time via natural processes
What are biofuels?
Derived from organic matter
Renewable
Smaller environmental impact
What organic matter are Biofuels derived from?
- sugar cane
- soya beans
- wheat
- vegetable oils
What is the reaction of Biofuels?
Still undergo combustion and produce CO2
What is Bioethanol?
- main biofuel
Produced via anaerobic fermentation of glucose in organic matter by yeast
What is E10?
Blend of 10% bioethanol and 90% petrol
What is the chemical formula for the fermentation of glucose?
What is the name of this fuel?
Bioethanol
What type of reaction is the fermentation of glucose?
Exothermic
What is an exothermic reaction?
Produces energy
What is required following the fermentation of glucose to produce bioethanol?
- ethanol in a solution
- distillation required to remove water and produce pure ethanol
- pH and temp carefully controlled
- temp below 78 degrees
What is the chemical equation for the distillation of ethanol?
What are examples of sources of glucose?
- sugarcane
- soya beans
- corn
What is Biogas?
- organic matter decays in an anaerobic environment
- generated through action of microorganisms (bacteria) on organic molecules
- has collected and used for fuel
Where can biogas be sourced?
Compost bins, piggeries
What is the chemical composition of biogas?
50-85% Methane and 20 - 25% Carbon Dioxide
How is biodiesel produced?
- reaction between vegetable oil/animal fats and small alcohol molecule
- methyl esters
What is the reaction that produces biodiesel?
Transesterification
- produced from methanol and long chain fatty acids ( carboxylic acids)
- no. of C atoms and type of C and C bond in fatty acids vary
What are animal fats and plants made from?
- compounds called triglycerides
- eg. canola
Draw the chemical structure of a methyl ester
What does the transesterification process involve?
Triglycerides + alcohol + catalyst (KOH) to produce 3 molecules of biodiesel (methyl ester) and glycerol
Draw the Chemical Structure of a transesterification reaction
Combustion of biofuels in terms of Carbon output
Carbon neutral as CO2 absorbed by plants during photosynthesis is equal to CO2 released
- must however consider transport and harvest machinery
Environmental and sustainability considerations
- land/water supplies limited in some countries and biofuel production should not reduce availability of food/water
- to decrease greenhouse gas emissions immense land for growing needed
Why is food essential?
Essential for survival, provides nutrients for energy, growth and repair/regulation of body processes.
What is the purpose of food metabolism?
Gives us molecules critical for biological functioning and energy for all reactions to survive.
Where is energy stored in food?
Stored in the chemical bonds
What is energy content?
Energy typically available for the body to use resulting from digestion and absorption of fuels.
What factors influence energy content values?
- specific composition of food
- metabolic factors
What is glucose?
Simple carbohydrate and primary source of energy
How is glucose produced?
Via photosynthesis by plants
How does glucose release energy?
Reacts in cells through cellular respiration to release energy?
Is photosynthesis an endothermic or exothermic process?
Endothermic
What is photosynthesis?
Plants, algae and bacteria convert light energy from the sun into chemical energy in the form of organic compounds.
What is the chemical equation for photosynthesis?
How is sunlight absorbed in a photosynthesis reaction?
Sunlight absorbed by green pigment “chlorophyll”
What are the conditions for photosynthesis to occur?
Heat
Is cellular respiration an exothermic or endothermic reaction?
Exothermic
What is cellular respiration?
Process that occurs in all living things where organisms convert glucose into energy
What is the energy produced in cellular respiration used for?
Energy is for important cellular processes such as growth.
How does cellular respiration occur in animals?
Glucose is absorbed into the bloodstream and transported to cells
Where is glucose obtained from in animals?
Carbohydrates in food are broken down through digestion to produce glucose.
What is the chemical equation for cellular respiration?
What is thermochemistry?
Study of heat changes in chemical reactions
What are chemical reactions?
Absorb and release energy generally in the form of heat.
What is chemical energy/enthalpy?
All substances contain chemical energy (energy in bonds)
