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8.1.1 State that thermal energy may be
completely converted to work in a single process, but that continuous conversion of this energy into work requires a cyclical process and the transfer of some energy from the system. |
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Definition
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| 8.1.2 Explain what is meant by degraded energy. |
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Definition
The second law of thermodynamics states that “it is impossible to take heat from a hot object and use
it without losing some heat to the surroundings”. Energy becoming more spread out is known as the
degradation of energy. It's energy that is unavailable for use. |
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| 8.1.4 Outline the principal mechanisms involved in the production of electrical power. |
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Definition
- A fuel is used to release thermal energy. The thermal energy is used to boil water to make steam, which in turn is used to turn turbine and the motion of the turbines generates electrical energy.
- A dynamo |
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| 8.2.1 Identify different world energy sources. |
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Definition
Directly and indirectly, the Sun is the prime energy source in the world. Below is a list of different sources and whether they emit CO2 or not.
- Coal, YES
- Oil, YES
- Gas, YES
- Nuclear, NO
- Waste, YES
- Solar, NO
- Wind, NO
- Hydro, NO
- Tidal, NO
- Pumped storage, NO
- Wave, NO
- Geothermal, NO
- Biofuels, YES |
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| 8.2.2 Outline and distinguish between renewable and non-renewable sources. |
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Definition
Renewable:
- Hydro
- Solar
- Wind
- Wave
- Tidal
- Bio
- Geothermal
Non-renewable:
- Coal
- Oil
- Natural gas
- Nuclear |
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| 8.2.3 Define the energy density of a fuel. |
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Definition
| The energy liberated per unit mass of fuel consumed. |
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| 8.2.4 Discuss how choice of fuel is influenced by its energy density. |
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Definition
| Affects transportation issues in particular: the greater the mass of fuel that needs to be transported, the greater the cost. |
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| 8.2.5 State the relative proportions of world use of the different energy sources that are available. |
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Definition
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| 8.2.6 Discuss the relative advantages and disadvantages of various energy sources. |
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Definition
| Mention environmental effects, cost, efficiency, reliability, and waste and other harmful effects. |
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| 8.3.1 Outline the historical and geographical reasons for the widespread use of fossil fuels. |
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Definition
| Easy access, high demand for energy, infrastructure |
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| 8.3.2 Discuss the energy density of fossil fuels with respect to the demands of power stations. |
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Definition
Efficiency:
coal - 35%
gas - 45%
oil - 38% |
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| 8.3.3 Discuss the relative advantages and disadvantages associated with the transportation and storage of fossil fuels. |
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Definition
Very high energy density, so easy to transport. Power plants can be built anywhere with transport links and water availability.
Pollution, non-renewable, require large amounts of fuel. |
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| 8.3.4 State the overall efficiency of power stations fuelled by different fossil fuels. |
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Definition
Efficiency:
coal - 35%
gas - 45%
oil - 38% |
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| 8.3.5 Describe the environmental problems associated with the recovery of fossil fuels and their use in power stations. |
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Definition
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Term
| 8.4.1 Describe how neutrons produced in a fission reaction may be used to initiate further fission reactions (chain reaction). |
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Definition
| A controlled amount neutrons collide with further nuclei. The chain reaction can only happen when critical mass is reached. In genera, the neutrons created by the fission reaction are moving too fast to make reactions likely. Before they can cause further reactions they have to be slowed down. |
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Term
| 8.4.2 Distinguish between controlled nuclear fission (power production) and uncontrolled nuclear fission (nuclear weapons). |
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Definition
In a nuclear power station it is important that the chain reaction is controlled. Only one neutron from each reaction can be allowed to make fission. The other neutrons are absorbed by control rods in the reactor.
In a nuclear weapon the chain reaction is not controlled. The fissionable material and a moderator are mixed together. |
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| 8.4.3 Describe what is meant by fuel enrichment. |
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Definition
| The process by which the percentage of useful matter is increased in a substance. |
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| 8.4.4 Describe the main energy transformations that take place in a nuclear power station. |
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Definition
| nuclear -> thermal -> KE of steam -> KE of turbine -> electrical |
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Term
| 8.4.5 Discuss the role of the moderator and the control rods in the production of controlled fission in a thermal fission reactor. |
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Definition
moderator: slows neutrons down to allow the chain reaction to take place
rods: absorb neutrons. This helps in controlling the chain reaction. |
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Term
| 8.4.6 Discuss the role of the heat exchanger in a fission reactor. |
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Definition
| allows the nuclear reactions to happen in a place that is sealed off from the rest of the environment. |
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Term
| 8.4.7 Describe how neutron capture by a nucleus of uranium-238 (238U) results in the production of a nucleus of plutonium-239 (239Pu). |
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Definition
| A U-238 nucleus captures a neutron to form U-239. This undergoes beta decay to Np-239 which further decays into Pu-239 |
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| 8.4.8 Describe the importance of plutonium-239 (239Pu) as a nuclear fuel. |
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Definition
| It's used as a fuel in other types of reactors. |
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| 8.4.9 Discuss safety issues and risks associated with the production of nuclear power. |
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Definition
• the possibility of thermal meltdown and how it might arise (natural disasters, problems with control rods, terrorist attack)
• problems associated with nuclear waste
• problems associated with the mining of uranium
• the possibility that a nuclear power programme may be used as a means to produce nuclear weapons. |
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| 8.4.10 Outline the problems associated with producing nuclear power using nuclear fusion. |
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Definition
| The problem of maintaining and confining a high‑temperature, high-density plasma. |
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Term
| 8.4.12 Distinguish between a photovoltaic cell and a solar heating panel. |
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Definition
Photovoltaic cell: converts radiation directly into potential difference.
Solar Heating panels: absorb solar radiation and use it to heat water. This water can be used domestically and saves energy by reducing the amount of fuel being used for heating. |
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| 8.4.13 Outline reasons for seasonal and regional variations in the solar power incident per unit area of the Earth’s surface. |
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Definition
| REgions at different latitudes receive different amounts of solar radiation due to different distances of travel through the Earth's atmosphere. The seasons affect this. |
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| 8.4.15 Distinguish between different hydroelectric schemes. |
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Definition
• water storage in lakes
• tidal water storage
• pump storage |
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| 8.4.16 Describe the main energy transformations that take place in hydroelectric schemes. |
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Definition
| gravitational PE -> KE of water -> KE of turbines -> electrical energy |
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Term
8.4.19 Determine the power that may be delivered by a wind generator, assuming that the wind kinetic energy is completely converted into mechanical kinetic energy, and
explain why this is impossible. |
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Definition
P = 1/2*A*ρ*v^3
All KE of incoming wind cannot be harnessed. |
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Term
8.4.21 Describe the principle of operation of an oscillating water column (OWC)
ocean-wave energy converter. |
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Definition
| Built on land. In-coming waves force air in and out of a turbine which generates electrical energy. The Wells turbine allows for electricity generation whichever direction the air is flowing in. |
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Term
| 8.4.22 Determine the power per unit length of a wave front, assuming a rectangular profile for the wave. |
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Definition
(ρvgA^2)/2
ρ - density
v - velocity
g - gravitational acceleration
A - amplitude |
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Term
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Definition
| Albedo is the term used to describe the ratio of reflection to absorption for an object. The Albedo for light surfaces is high. Snow reflects most of the radiation incident on it and has an Albedo of around 90%. The average Albedo for the earth is about 30%. |
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Term
| 8.5.3 State factors that determine a planet’s albedo. |
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Definition
• Land coverage i.e. land or water or snow
- daily variation due to weather
• Vegetation coverage
• Latitude
• Time of year (Because it affects the vegetation) |
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Term
| 8.5.4 Describe the greenhouse effect. |
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Definition
| Short wavelength radiation is received from the sun and causes the surface of the Earth to warm up. The Earth will then emit infra-red radiation (longer wavelengths than absorbed, because the earth is cooler). Some of this outgoing radiation is intercepted and absorbed by the greenhouse gases and after which it is re-radiated in all directions. |
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| 8.5.5 Identify the main greenhouse gases and their sources. |
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Definition
| The gases to be considered are CH4, H2O, CO2 and N2O. It is sufficient for students to know that each has natural and man-made origins. |
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| 8.5.6 Explain the molecular mechanisms by which greenhouse gases absorb infrared radiation. |
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Definition
| Resonance. The natural frequency of oscillation of the molecules of greenhouse gases is in the infrared region. |
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| 8.5.8 Outline the nature of black-body radiation. |
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Definition
| The radiation from a theoretical perfect emitter. Doesn't depend upon the emitting surface, but the temperature. |
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Term
8.5.9 Draw and annotate a graph of the emission spectra of black bodies at different
temperatures.
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Definition
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Term
| 8.5.10 State the Stefan–Boltzmann law and apply it to compare emission rates from different surfaces. |
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Definition
| The total energy radiated per unit surface area of a black body per unit time is directly proportional to the fourth power of the black body's thermodynamic temperature. |
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Term
| 8.5.11 Apply the concept of emissivity to compare the emission rates from the different surfaces. |
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Definition
ε =
Power emitted by object per unit area/
Power radiated by a black body at the same temperature |
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Term
| 8.5.12 Define surface heat capacity Cs. |
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Definition
| The surface heat capacity is the energy that is required to raise 1m^3 of the surface of a planet by 1K. |
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Term
8.5.13 Solve problems on the greenhouse
effect and the heating of planets using
a simple energy balance climate model. |
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Definition
| Students should appreciate that the change of a planet’s temperature over a period of time is given by:(incoming radiation intensity – outgoing radiation intensity) × time / surface heat capacity. Students should be aware of limitations of the model and suggest how it may be improved. |
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Term
| 8.6.1 Describe some possible models of global warming. |
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Definition
| Students must be aware that a range of models has been suggested to explain global warming, including changes in the composition of greenhouse gases in the atmosphere, increased solar flare activity, cyclical changes in the Earth’s orbit and volcanic activity. |
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| 8.6.2 State what is meant by the enhanced greenhouse effect. |
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Definition
| An increase in the greenhouse effect caused by human activities. |
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| 8.6.3 Identify the increased combustion of fossil fuels as the likely major cause of the enhanced greenhouse effect. |
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Definition
| Students should be aware that, although debatable, the generally accepted view of most scientists is that human activities, mainly related to burning of fossil fuels, have released extra carbon dioxide into the atmosphere. |
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| 8.6.4 Describe the evidence that links global warming to increased levels of greenhouse gases. |
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Definition
| For example, international ice core research produces evidence of atmospheric composition and mean global temperatures over thousands of years (ice cores up to 420,000 years have been drilled in the Russian Antarctic base, Vostok). |
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| 8.6.5 Outline some of the mechanisms that may increase the rate of global warming. |
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Definition
Students should know that:
• global warming reduces ice/snow cover, which in turn changes the albedo, to increase rate of heat absorption
• temperature increase reduces the solubility of CO2 in the sea and increases atmospheric concentrations
• deforestation reduces carbon fixation. |
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| 8.6.6 Define coefficient of volume expansion. |
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Definition
| Students should know that the coefficient of volume expansion is the fractional change in volume per degree change in temperature. |
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| 8.6.7 State that one possible effect of the enhanced greenhouse effect is a rise in mean sealevel. |
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Definition
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Term
| 8.6.8 Outline possible reasons for a predicted rise in mean sea-level. |
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Definition
Students should be aware that precise predictions are difficult to make due to factors such as:
• anomalous expansion of water
• different effects of ice melting on sea water compared to ice melting on land. |
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| 8.6.9 Identify climate change as an outcome of the enhanced greenhouse effect. |
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Definition
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| 8.6.11 Identify some possible solutions to reduce the enhanced greenhouse effect. |
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Definition
• greater efficiency of power production
• replacing the use of coal and oil with natural gas
• use of combined heating and power systems (CHP)
• increased use of renewable energy sources and nuclear power
• carbon dioxide capture and storage
• use of hybrid vehicles. |
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| 8.6.12 Discuss international efforts to reduce the enhanced greenhouse effect. |
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Definition
Intergovernmental Panel on Climate Change (IPCC)
• Kyoto Protocol
• Asia-Pacific Partnership on Clean Development and Climate (APPCDC). |
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