Exams Flashcards
What is the deal with recycling
The recycling of materials includes breaking down waste material to more useful products. The recycling of materials is becoming more increasingly important as the metal ores are finite and the non-renewable recourses must be preserved for future generation. The recycling of lead and aluminium is roughly 50% from scrap.
What are the benefits of recycling material
The material preserves finite recourses. Metal is expensive to creates large amounts of material, damages environment. Metal reduces emissions of soot, carbon monoxide, nitrogen oxide, and nitrogen oxides in metal production. Lowers greenhouse emissions reduces energy used associated with petroleum. Recycling used from solvent mostly from non-renewable energy. Waste materials are produced in production and can harm environment. Reduces landfill as metal in landfill is not reused.
What are the two types of recycling polymers methods.
Two methods of recycling polymers involve feedstock recycling and mechanical recycling. Mechanical recycling involves the physical break down of molecules, through melting, granulation and shredding. Whereas, feedstock recycling involves the creation of monomers in polymerisation of fuels. Conserves the petroleum that is finite. Conserves the use of less energy synthesising material and in landfill reduction. Moreover, plastic polymers are 100% useable and reused until structural integrity fails. The reduction is harder to recycle, they do not melt after prolonged heating they are shredded into smaller pieces into filler materials.
Disadvantages of recycling
Disadvantages involves collection, separation and repurposing of material.
Advantage of composite material
The materials are stronger and can be used to improved that is not in present in individual components. They can be designed for a particular use as matrix and reinforcement. Most composite can be moulded into complex shapes.
Describe the recycling of composites.
The reclycing is difficult as cross links, and cannot be reshaped. Involves grinding material to small pieces which can be used as filler or melt the or combust matrix and retain fibres. Prylosis is used to recover expensive carbon fibres. Carbon fibres retain more than 90% of original mechanical matrix.
Explain the importance of renewable energy
There is over 80% of the global energy which is derived from fossil fuels not even 10% is derived from renewable energy sources. Renewable energy sources are important because they do not exceed any emissions, namely, wind power and solar power. Biofuel emits significantly less than fossil fuels. The only catch fossil fuels are required for bio crops, biofuels and wind turbines. Carbon dioxide methane and nitrous oxides are all produced in extraction of fossil fuels.
Advantages of fossil fuels
Advantages
Currently fossil fuels are abundant and accessible
Fossil fuels have high energy density and large quantities of energy are released in the combustion of these materials
Extraction of fossil fuels is relatively easy and inexpensive
Fossil fuels are feedstock for thousands of commercially available products that are used in everyday living
Disadvantages of fossil fuels
Carbon dioxide (greenhouse gas) is released in the combustion of fossil fuels Sulphur oxides (SOx) and nitrogen oxides (NOx) are released when coal and oil undergo combustion. These gases contribute to acid rain and smog. Particular matter (PM) is released into the atmosphere in the extraction of coal and these materials are major contributors to global air pollution Fossil fuels are non-renewable and cannot be replaced once they are consumed.
Fossil fuel feedstocks
Petroleum comprises most of the feedstock for fossil fuels 20% of all petroleum extraction is used for feed stock annually with over 5000 consumer goods. Including, alkenes as manufacture of polymers larger alkenes as lubricants, asphalt for road production and aromatic compounds as manufacture of polymers/solvents. Natural gas is also used as a feedstock for nitrogen fertilisers, hydrogen gas and methanol.
Advantages of wind power
Wind is an inexhaustible recourse of renewable energy with zero emissions of greenhouse gases during operation.
Currently wind power is one of the most cost-effective renewable energy technologies
Wind turbines do not require the use of water whereas steam turbines (used in power stations where fossil fuels are combusted) require large amounts of water.
Disadvantages of wind power
Wind turbines cannot provide a sustainable source of energy for domestic use in the absence of wind (can be unreliable.)
The best locations for wind turbines are often great distances from the users of electricity meaning that the power transmitted (inefficiently) over long distances
Wind turbines create noise pollution, have been describes as unsightly, and have been implicated in the death of birds and bats.
Whats the deal with wind power
Kinetic energy is converted to electrical energy by wind turbines. The large blades capture wind energy and turn it to electrical energy. The wind turbines are grouped together to form wind farms that are collectively used to form generate electricity for homes and businesses. Currently there are 16 wind farms in Australia.
Biofuel generations
Generation Description Examples
First Produced directly from food crops Bioethanol, biodiesel
Second Product from non-food crops such as wood, food crop waste, and organic waste Biogas (50-80% methane)
Third Produced in chemical processes carried out by genetically engineered algae. Biodiesel, butanol, gasoline, methane, and bioethanol
Advantages of biofuel
Advantages
Combustion of biofuels produces fewer greenhouse gases.
Biofuels crops remove carbon dioxide from the atmosphere during photosynthesis
Waste material can be used to produce biofuels which reduce emissions of greenhouse gases from waste and landfill.
Biofuel crops can be grown every year creating a renewable fuel source which has greater security in the future.
Disadvantages of biofuel
Disadvantages
Greenhouse gases are emitted in the fertilising, harvesting, refining and transporting of biofuel crops.
Biofuel crops occupy land that could be used for growing crops. This could lead to higher food prices in future.
The growth of biofuel crops requires a large amount of water which will contribute to water shortages in future.
The demand for palm oil has caused deforestation in some areas of the world.
Advantages of solar cells
Solar cells require very little maintenance once installed properly.
Solar cells can be engineered to any size to suit a variety of applications from charging a phone to powering a building.
The sun provides an inexhaustible amount of renewable energy that can be converted into electrical energy in all parts of the planet.
Conversion of electromagnetic radiation (light) into electric current does not involve any greenhouse gas emissions.
Disadvantages of solar cells
Power output of solar cells decrease in the absence of sunlight (at night) and in periods of high cloud cover
Solar cells in solar panels are fixed in a position that is not always facing the sun.
Currently solar cells have low energy efficiency (~20%) but advances in nanoscience and technology are improving the efficiency of solar cells every year.
80% of solar cells are made from high purity silicon which is an expensive raw material which greatly reduces the cost-effectiveness of solar cells.
How are biodiesel made
Biodiesel are esters compared with fatty acids with low molar mass alcohols such as ethanol or methanol. The ester is made in a process called transesterification involving the fatty acid and the low molar mass alcohol to form the biodiesel. It can be used in its pure form or combined with another diesel to create a combination which contributes to less fuel used annually. Moreover, the biodiesel emits less carbon dioxide than regular diesel. Oil seed crops are main sources of biofuel production
What is the deal with calorimetry
Calorimetry is a technique to measure the amount of heat formed in a reaction. The larger the carbon change in a homologous series is the more energy is released per mole in a complete reaction of oxygen. Calorimetry is used to measure the energy released per mole of simple hydrocarbons and alcohols. The molar enthalpy. The bond formation of water and carbon dioxide is exothermic.
What is energy density
Energy density is the fuel contained per unit of volume. Mixtures do not usually have a molar enthalpy as they have different molecules within them. The energy density is expressed per unit of volume. Kilojoules per litre. Specific heat multiplied by fuel density.
