#### Key Terms for this topic (Tier 3 vocabulary)

Gravitational potential – electrostatic – closed system – work done – conservation of energy – kinetic – specific heat capacity – conduction – convection – thermal radiation – efficiency – geothermal – hydroelectric.

Energy

Are you ready for your assessment in this topic? Try out this simple quiz. #### What everyone needs to know:

You need to know the main types of energy stores such as kinetic, thermal and gravitational potential. Within a system, you need to be able to describe energy transfers such as chemical to thermal.

Note that energy can be transferred or dissipated but it cannot be created or destroyed.

You need to be able to calculate changes in energy due to heating, work done by forces and the work done when current flows through a conductor. You need to calculate the change in energy for:

A moving object (kinetic energy): Ek = ½ m v2

A stretched spring (elastic potential): Ee = ½ k e2

Lifting from ground level (change in GPE): Ep = m g h

Heat energy transfer can be measured by using the temperature change of a substance and its specific heat capacity (the measure of how much energy is needed to change its temperature). ΔE = m c ΔΘ

Change in energy = mass x specific heat capacity x change in temperature.

Required Practical 14 – Using the above formula, work out the specific heat capacity of a substance.

Power is the rate at which work is done, it is simply the work done in joules (or energy transferred) divided by the time taken in seconds. P=E/t

Finally, efficiency. This is a measure of how much of the energy put into s system is transferred into a useful store.

Efficiency = useful output/total input

This topic needs you to understand the main sources of energy used today. There are fossil fuels (coal, gas, oil), nuclear fuels and renewable sources such as wind, hydroelectric, geothermal, tidal, waves and solar.

Renewable energy sources are being replaced as we use them (eg more sunlight is arriving from the sun or if you plant more trees than you cut down and burn).

You need to be able to describe the sources, say if they are renewable or non-renewable (nuclear is non-renewable by the way), compare outputs, efficiency and pollution etc and discuss reliability. You may have graphs and data to interpret.

Patterns in usage (half time of the FA cup final, millions of kettles go on), describing the environmental effects and why people may be opposed to wind farms or nuclear power stations.

#### Extra topics needed for the Higher papers:

Students sitting the higher paper need to describe ways of increasing the efficiency such as lubrication to overcome friction and prevent energy being wasted as heat.