(b) energy transfers

different energy stores (4.2)

chemical, kinetic, gravitational (potential), elastic (potential), internal (thermal), magnetic, electrostatic, nuclear

chemical energy store (4.2)

the energy stored in chemical bonds, such as those between molecules

kinetic energy store (4.2)

the energy of a moving object

gravitational energy store (4.2)

the energy of an object at heigh

elastic energy store (4.2)

the energy stored when an object is stretched or squashed

thermal energy store (4.2)

the total kinetic and potential energy of the particles in an object. in hotter objects, the particles have more internal energy and therefore vibrate faster

magnetic energy store (4.2)

the energy stored when either:

repelling poles have been pushed closer together

or

attracting poles have been pulled further apart

electrostatic energy store (4.2)

the energy stored when either:

repelling charges have been moved closer together

or

attracting charges have been pulled further apart

nuclear energy store (4.2)

the energy stored in the nucleus of an atom

energy transfers (4.2)

mechanically, electrically, by heating, by radiation

transfer mechanically (4.2)

a force moving an object through a distance

transfer electrically (4.2)

charges moving due to a potential difference (a measure of the energy given to the charge carriers in a circuit)

transfer by heating (4.2)

due to temperature difference caused electrically or by chemical reaction

transfer by radiation (light and sound) (4.2)

energy transferred as a wave

principle of conservation of energy (4.3)

no energy can ever be created or destroyed, only transferred, stored or dissipated

relationship between efficiency, useful energy output and total energy output (4.4)

efficiency = ( useful energy output / total energy output ) × 100%

conduction (4.6)

a conductor is a material that transfers energy by heating quickly

metals are especially good conductors because the delocalised electrons in the metal can collide with the atoms, helping to transfer the vibrations through the material, therefore transferring the heat better

convection (4.6 / 4.7)

when a fluid is heated:

• the molecules push each other apart so the fluid expands, making the hot fluid less dense than its surroundings

• the hot fluid rises, letting the cooler surrounding fluid to take its place

• the hot fluid eventually cools down and sinks as the cooler fluid heats up and rises to take its place

• this motion is called a convection current

sea breezes (4.6 / 4.7)

during the daytime, the land warms up quickly, whereas the sea warms up more slowly (since solids are much more effective conductors than liquids)

this causes the air nearer the land to heat up quickly and rise, so the cooler air nearer the sea takes its place, causing a sea breeze

during the nighttime, the land cools down quickly, whereas the sea cools down more slowly

this causes the air nearer the sea to heat up quickly and rise, so the cooler air nearer the land takes its place, causing a land breeze

radiation (4.6 / 4.8)

GAHHh

investigate thermal energy transfer by conduction, convection and radiation (4.9)

ways of reducing unwanted energy transfer