Energy Resources and Energy Transfer
13.1 Thermal Energy Transfer
F/H	When  different  parts  of  a  substance  are  at  different temperatures,  energy  is  transferred  by  the substance from places where the temperature is higher to places where the temperature is lower.
F/H	Transfer of energy by a substance, without the substance itself moving, is called conduction. Metals are very good conductors. Non-metals are usually poor conductors (insulators). Gases are very poor conductors.
F/H	Liquids and gases can flow and so can carry energy from places where the temperature is higher to places where the temperature is lower.
F/H	Transfer of energy by liquids or gases moving in this way is called convection.
F/H	Energy is continually being transferred to and from all objects by radiation, even through empty space (a vacuum). Hot bodies emit mainly infra red radiation.
F/H	The hotter an object is, the more energy it radiates. Dark, matt surfaces emit more radiation than light, shiny surfaces at the same temperature.
F/H	Dark, matt surfaces are good absorbers (poor reflectors) of radiation. Light, shiny surfaces are good reflectors (poor absorbers) of radiation.
F/H	Candidates should be able:
F/H	* to describe various ways in which heat energy is transferred from buildings;
F/H	* to describe and explain ways in which the rates of these energy transfers can be reduced.
H	Candidates should be able, when given appropriate information, to evaluate the effectiveness and cost-effectiveness of methods used to reduce energy consumption in buildings.
H	Conduction occurs in metals because the hotter the metal is the more kinetic energy its free electrons have and the faster they diffuse through the metal. The more vigorous movement of the electrons in the hot region of the metal is also transferred, via collisions, to adjacent electrons which, in turn, transfer energy to the electrons adjacent to them, and so on.
H	Convection currents occur in liquids and gases because their particles move faster when they are hot causing the liquid or gas to expand. Warm regions are then less dense than cold regions. The warm regions rise up through the colder regions and colder regions replace the warmer regions.
H	Thermal radiation is the transfer of energy by waves.  Particles of matter are not involved.
13.2 Efficiency
F/H	Whenever energy is transferred, only part of it is transferred to where it is wanted and in the form it is wanted (usefully transferred). The rest of the energy is transferred in some non-useful way and so wasted.
F/H	Candidates should be able to describe the intended energy transfers and the main energy wastages which occur when using a range of everyday devices.
F/H	The energy which is 'wasted' during energy transfers and the energy which is usefully transferred both end up being transferred to the surroundings which become warmer.
F/H	The energy becomes increasingly spread out and becomes increasingly more difficult to use for further useful energy transfers.
F/H	The fraction of the energy supplied to a device which is usefully transferred is called the efficiency of the device.
F/H	Candidates should be able, when provided with appropriate information, to evaluate methods of reducing wasteful transfers of energy.
H	Candidates should be able to use [but will not be expected to recall] the relationship:
H	efficiency = use energy transferred by device / total energy supplied to device
H	[This relationship will be provided when required.]
13.3 Energy Resources
F	Coal, oil, gas and wood are all fuels.  They release energy when they are burned.
F	The Earth's supply of the fossil fuels (coal, oil and gas) and of nuclear fuels is limited. Once they are used up they cannot be replaced. They are non-renewable energy resources.
F	Most of the energy used by humans comes from non-renewable fuels, mainly from fossil fuels. The more economical people are with these fuels, the longer they will last.
F	More trees can be grown to replace trees that are cut down to provide wood for fuel. Wood is a renewable energy resource.
F/H	Renewable energy resources include sunlight, the wind, the waves, running water and the tides. These energy resources will not run out.
F/H	Electricity is a very convenient and widely used energy source. It is generated in power stations using some other energy resource.
F/H	In most power stations, energy from fuel is used to heat water. In Britain, many power stations burn fossil fuels. Other power stations use nuclear fuel, mainly uranium and plutonium. The steam which is produced is used to drive turbines. The turbines then drive generators which produce electricity.
F/H	Electricity can also be generated from renewable energy resources.  Energy from renewable resource can be used to drive turbines directly. The resources used in this way include:
F/H	* the wind;
F/H	* the rise and fall of water due to waves;
F/H	* the flow of water from a higher level to a lower level from behind tidal barrages or the dams of hydro electric schemes.
F/H	The steam needed to drive turbines can be produced by pumping water through hot rocks below the surface of the Earth. The energy which makes the rocks hot is constantly being released by radioactive elements, including uranium, as they decay. This happens much more slowly than in a nuclear reactor.
F/H	Electricity can be produced directly from the Sun's radiation using solar cells.
F/H	Candidates should be able, to describe:
F/H	* one specific environmental problem in each case associated with generating electricity using specific fossil fuels, using nuclear fuel, and using large-scale wind, tide and hydro-electricity schemes;
F/H	* the extent to which, if at all, these environmental problems can be reduced;
F/H	* how reliable these different energy resources are and how quickly different power stations can start and stop generating electricity;
F/H	* situations where, despite the high cost per Unit, solar cells are the best way of generating electricity.
H	Candidates should be able  to identify and evaluate the  financial  and environmental  costs of using various energy resources to generate electricity and to evaluate these costs against the benefits to society, taking into consideration:
H	* the factors listed above;
H	* that though there are no fuel costs with renewables, the energy is dilute so that the capital cost of the generating equipment is high;
H	* that though the fuel costs for nuclear power stations are low, the cost of building the power stations, and of de-commissioning them at the end of their useful life, is high;
H	* the need to match supply and demand;
H	* any additional information, including quantitative information, with which they are provided.
13.4 Work, Power and Energy
F/H	Energy is measured in joules (J).
F/H	When a force moves an object, energy is transferred and work is done:
F/H	The amount of work done, force and distance are related as shown: work done = force x distance
F/H	Power  is a  measure of  how fast  energy is  transferred.  The greater  the power,  the more  energy is transferred in a given time.
F/H	Candidates should be able to use [but will not be expected to recall] the relationship:
F/H	power = energy / time OR power = work done / time This relationship will be provided when required.]
F/H	Gravitational potential energy is the energy stored in an object because of the height to which the object has been lifted against the force of gravity.
F/H	On Earth the gravitational field strength is about 10 N/kg.
F/H	Candidates should be able to use [but will not be expected to recall] the relationship:
F/H	GPE = mass x g x height    [This relationship will be provided when required.]
F/H	Elastic potential energy is the energy stored in an elastic object when work is done on the object to change its shape.
F/H	Kinetic energy is the energy an object has because of its movement.
F/H	An object has more kinetic energy:
F/H	* the greater its mass;
F/H	* the greater its speed.
H	Candidates should be able to use [but will not be expected to recall] the relationships:
H	kinetic energy   =  1 /2  x  mass  x [speed]2
H	(joule, J)       (kilogram, kg)  [(metre/second)2, [m/s]2]
H	[These relationships will be provided when required.]