4. ENERGY RESOURCES AND ENERGY TRANSFERS
A – Units:
4.1 – use the following units: kilogram (kg), joule (J), metre (m), metre/second (m/s), metre/second 2 (m/s2),
newton (N), seconds (s) and watt (W)
B – Energy Transfers:
4.2 – describe energy transfers involving energy stores
Energy can be stored in these 8 main stores:
o Kinetic – energy an object has because it’s moving
o Gravitational – energy an object has due to its position above the ground. An object gains gravitational energy
when lifted and loses it when it falls
o Chemical – energy found in fuels, food or batteries. This energy is transferred during chemical reaction
o Elastic – energy stored in a stretched spring or elastic band
o Magnetic – energy due to the force of attraction between two magnets
o Electrostatic – energy due to the force of attraction between two charges 8 KG of CEMENT
o Nuclear – energy contained within the nucleus of an atom
o Thermal – energy a substance has due to its temperature
Energy can be transferred through these 4 energy transfers:
o Heating – thermal energy can be transferred by conduction, convection, radiation
o Electrical – electricity can transfer energy from a power source (a cell), delivering it to components in a circuit
o Radiation – light and sound carry energy and can transfer this between two points
o Mechanical – when a force acts on a body e.g. collision HERM
4.3 – use the principle of conservation of energy
o Energy cannot be created or destroyed; it can only be transferred from one store to another
4.4 – know and use the relationship between efficiency, useful energy output and total energy output
useful energy output
o Efficiency = x 100
total energy input
o The efficiency of a system is a measure of how well energy is transferred in a system
o High efficiency = most of the energy transferred is useful
o Low efficiency = most of the energy transferred is wasted
o Measured in percentage
4.5 – describe a variety of everyday and scientific devices and situations, explaining the transfer of the input
energy in terms of the above relationship, including their representation by Sankey diagrams
Sankey diagrams:
o Arrows in Sankey diagrams represent the transfer of energy
o The end of the arrow pointing to the right represents the
useful energy
o The end that points down represents the wasted energy
o The width of each arrow is proportional to the amount of
energy going to each store
, 4. ENERGY RESOURCES AND ENERGY TRANSFERS
4.6 – describe how thermal energy transfer may take place by conduction, convection and radiation
Conduction:
o The process of transferring thermal energy by particle
collision (vibration/domino effect)
o Main method of thermal energy transfer in solids but works
in liquids too
o As a substance is heated up, the molecules vibrate more
hitting more nearby particles, making them vibrate too.
o This transfers heat energy from hot parts to cooler parts
o Metals are good conductors - electrons inside are free to
move transfers the heat from one end to the other faster
o Non-metals are poor conductors (insulators)
Convection:
o Main way that heat travels through liquids and gases
o It cannot occur in solids
o When a fluid (liquid or gas) is heated, the molecules push
each other apart, making the fluid expand. The hot fluid is
less dense than the surroundings. The hot fluid rises, and
the cooler fluid takes its place. Eventually, the hot fluid
cools, contracts and sinks down again. The resulting motion
is called a convection current (relies on change in density)
Radiation:
o Also known as infrared radiation which does not require a medium
o Radiation is the only way heat can travel through a vacuum (as conduction and convection require particles to
transfer heat)
4.7 – explain the role of convection in everyday phenomena
o Examples – radiators and pans of water boiling
o Convection can be helpful by distributing heat energy, such as in a radiator, to heat the whole room.
o Hot air rises away from it, creating a current of cool air to be heated.
4.8 – explain how emission and absorption of radiation are related to surface and temperature
o Light, shiny surfaces – good reflectors, bad absorbers of infrared radiation
o Dark, matt surfaces – poor reflectors, good absorbers of infrared radiation, best at emitting infrared radiation
o When placed next to a heat source, a dark object would heat up faster than a light one
4.9 – practical: investigate thermal energy transfer by conduction, convection and radiation
4.10 – explain ways of reducing unwanted energy transfer, such as insulation
o To reduce conduction: use materials with low thermal conductivity
o To reduce convection: stop the fluid moving
Insulation – clothes, blankets, foam cavity wall insulation:
o For when heat is wanted, insulating the loft of a house lowers the rate of cooling less heat is lost
o Insulation contains trapped air, which is a poor conductor of heat and also prevents heat transfer by convection
A – Units:
4.1 – use the following units: kilogram (kg), joule (J), metre (m), metre/second (m/s), metre/second 2 (m/s2),
newton (N), seconds (s) and watt (W)
B – Energy Transfers:
4.2 – describe energy transfers involving energy stores
Energy can be stored in these 8 main stores:
o Kinetic – energy an object has because it’s moving
o Gravitational – energy an object has due to its position above the ground. An object gains gravitational energy
when lifted and loses it when it falls
o Chemical – energy found in fuels, food or batteries. This energy is transferred during chemical reaction
o Elastic – energy stored in a stretched spring or elastic band
o Magnetic – energy due to the force of attraction between two magnets
o Electrostatic – energy due to the force of attraction between two charges 8 KG of CEMENT
o Nuclear – energy contained within the nucleus of an atom
o Thermal – energy a substance has due to its temperature
Energy can be transferred through these 4 energy transfers:
o Heating – thermal energy can be transferred by conduction, convection, radiation
o Electrical – electricity can transfer energy from a power source (a cell), delivering it to components in a circuit
o Radiation – light and sound carry energy and can transfer this between two points
o Mechanical – when a force acts on a body e.g. collision HERM
4.3 – use the principle of conservation of energy
o Energy cannot be created or destroyed; it can only be transferred from one store to another
4.4 – know and use the relationship between efficiency, useful energy output and total energy output
useful energy output
o Efficiency = x 100
total energy input
o The efficiency of a system is a measure of how well energy is transferred in a system
o High efficiency = most of the energy transferred is useful
o Low efficiency = most of the energy transferred is wasted
o Measured in percentage
4.5 – describe a variety of everyday and scientific devices and situations, explaining the transfer of the input
energy in terms of the above relationship, including their representation by Sankey diagrams
Sankey diagrams:
o Arrows in Sankey diagrams represent the transfer of energy
o The end of the arrow pointing to the right represents the
useful energy
o The end that points down represents the wasted energy
o The width of each arrow is proportional to the amount of
energy going to each store
, 4. ENERGY RESOURCES AND ENERGY TRANSFERS
4.6 – describe how thermal energy transfer may take place by conduction, convection and radiation
Conduction:
o The process of transferring thermal energy by particle
collision (vibration/domino effect)
o Main method of thermal energy transfer in solids but works
in liquids too
o As a substance is heated up, the molecules vibrate more
hitting more nearby particles, making them vibrate too.
o This transfers heat energy from hot parts to cooler parts
o Metals are good conductors - electrons inside are free to
move transfers the heat from one end to the other faster
o Non-metals are poor conductors (insulators)
Convection:
o Main way that heat travels through liquids and gases
o It cannot occur in solids
o When a fluid (liquid or gas) is heated, the molecules push
each other apart, making the fluid expand. The hot fluid is
less dense than the surroundings. The hot fluid rises, and
the cooler fluid takes its place. Eventually, the hot fluid
cools, contracts and sinks down again. The resulting motion
is called a convection current (relies on change in density)
Radiation:
o Also known as infrared radiation which does not require a medium
o Radiation is the only way heat can travel through a vacuum (as conduction and convection require particles to
transfer heat)
4.7 – explain the role of convection in everyday phenomena
o Examples – radiators and pans of water boiling
o Convection can be helpful by distributing heat energy, such as in a radiator, to heat the whole room.
o Hot air rises away from it, creating a current of cool air to be heated.
4.8 – explain how emission and absorption of radiation are related to surface and temperature
o Light, shiny surfaces – good reflectors, bad absorbers of infrared radiation
o Dark, matt surfaces – poor reflectors, good absorbers of infrared radiation, best at emitting infrared radiation
o When placed next to a heat source, a dark object would heat up faster than a light one
4.9 – practical: investigate thermal energy transfer by conduction, convection and radiation
4.10 – explain ways of reducing unwanted energy transfer, such as insulation
o To reduce conduction: use materials with low thermal conductivity
o To reduce convection: stop the fluid moving
Insulation – clothes, blankets, foam cavity wall insulation:
o For when heat is wanted, insulating the loft of a house lowers the rate of cooling less heat is lost
o Insulation contains trapped air, which is a poor conductor of heat and also prevents heat transfer by convection
