P2

• Different energy stores

  Kinetic

  Thermal

  Magnetic

  Chemical

  Electrostatic

  Gravitational potential

  Elastic

  Nuclear
• Different ways energy can be transferred

  Mechanically

  Electrically

  Through heating

  Via infrared radiation

  Via light or sound waves
• An open system

  Can gain or lose energy to the outside world
• When you burn fuel, energy is transferred from the fuel's chemical energy store to the thermal energy store of the surroundings.
• When you throw a ball up in the air, it moves through a gravitational field. The reason it slows down as it rises is because energy from it's kinetic energy store is being transferred to its:

  Gravitational potential energy store
• As an object falls, energy is transferred from its gravitational potential energy store, to its kinetic energy store.
• Conservation of energy law

  Energy cannot be destroyed nor created. It can only be transferred from one form to another.
• Example 1: A coal fire (A fire burns fuel such as coal to produce heat)

  Coal has a large store of chemical energy (energy within chemical bonds). When coal is burned the chemical energy is transferred by heating to the thermal energy store of the coal. Hot coals and flames transfer energy to the surroundings by heating and radiation.
• Example 2: A car breaking

  The moving car has kinetic energy. The brakes mechanically do work on the car to slow it down. The kinetic energy of the car decreases and the thermal energy store of the brakes increases.
• Example 3: An archer firing a bow and arrow

  As the string of the bow is pulled back chemical energy in the archers muscles is transferred mechanically to the elastic potential of the bow. When the archer releases the string of the bow, the elastic potential energy of the string is transferred mechanically to the kinetic energy store of the arrow.
• Conduction

  1. One end of a solid object is heated

  2. Energy is transferred to the kinetic energy stores of the particles in that end

  3. Particles vibrate faster

  4. Particles collide with their neighbouring particles more often

  5. Collisions transfer kinetic energy

  6. Neighbours also vibrate faster and collide more often with their neighbours

  7. Process repeats over and over again

  8. Energy is effectively passed along the object from one particle to the next
• In conduction the heat is spread out evenly so we say each particle has around the same temperature.
• A fluid is a substance in which the particles are free to move around. They include both liquids and gases. 
• Convection

  As a fluid is heated the particles gain kinetic energy and spread further apart. This causes the fluid to become less dense and so it will rise above any cooler fluid that hasn't been heated (because that fluid is more dense). As the fluid cools down it will become more dense again, and so sink back down. If this process takes place in a limited space, like a container or a room, it can create a convection current.
• Warm fluids rise because they are less dense than cooler fluids
• Power is the rate at which energy is transferred, or the rate at which work is done.
• The terms 'Work' or 'work done' refer to the energy transfer that occurs when a force is used to move an object by a certain distance
• What happens to 'dissipated' energy?

  It is lost to the surroundings
• An open system can exchange energy and matter with its surroundings. A closed system cannot exchange energy or matter with the surroundings.
• What is the main energy transfer of a marathon runner?

  Chemical -> Kinetic
• What helps to reduce heat loss by convection in a home?


  Foam seals around doors and windows
• What helps to reduce heat loss by conduction in a home?

  Double glazed windows

  Cavity walls

  Walls made of material with low thermal conductivity
• What is the purpose of putting insulating foam in cavity walls?


  To minimise air convection currents
• Single glazed windows only have one pane of glass, whereas double glazed windows have two panes of glass. In both cases, the panes of glass reduce heat loss by convection.

  The added benefit of double glazing is that there is a small air gap between the two panes of glass, which minimises conduction (as air is a poor conductor of heat).
• Friction

  The resistance that an object encounters when moving across a solid, or moving through a liquid
• Fast moving vehicles like cars and planes have a streamlined shape to reduce friction from air resistance. This allows them to use less fuel.
• Why does cavity wall insulation contain pockets of trapped air?

  Air is a good insulator
• How much thermal energy is produced?

  22

  
• Calculate the useful energy output of the bulb

  30

  
• Renewable energy sources:

  Wind

  Solar

  Geothermal

  Hydroelectricity

  Biofuels

  Tidal

  Water waves
• Non renewable energy resources:

  Fossil fuels - coal, natural gas, crude oil

  Nuclear energy
• Vehicles like cars mostly run on petrol or diesel, both of which are found in crude oil.

  However, electric cars are becoming more common, which is great as electricity can be generated from renewable energy resources. 
• Explain the difference between renewable and non renewable energy resources

  A renewable energy resource is one that is being replenished as quickly as it is used. For example solar energy is renewable because new sunlight is always being generated by the sun - we don't use it up. 

  A non-renewable energy resource on the other hand is one that isn't being replenished and so has a limited supply. For example fossil fuels like coal are non-renewable because they're not being replenished and at some point coal could run out. 
• Fossil fuels may be burned to provide heat for things such as:

  Cooking

  Power engines

  Generate electricity
• Pros and cons of fossil fuels

  Pros - Cheap, can be used in any conditions, most of our current infrastructure is designed for the use of fossil fuels

  Cons - Limited resource so will run out one day, produce carbon dioxide when burned, can produce toxic gases
• Nuclear energy is energy obtained via nuclear reactions, such as nuclear fission reactions in nuclear power stations.

  This energy can be used to generate electricity, which can then be transmitted to homes and factories across the country. 
• Pros and cons on nuclear energy

  Pros - do not produce any pollutants, can be used in any conditions, very unlikely to run out for a long time

  Cons- technically a finite resource, produce radioactive waste which is harmful for thousands of years, quite expensive, small chance of nuclear meltdown
• Wind power is generated by wind turbines which have blades that spin due to the wind. This spinning action turns a generator which produces electricity. 
• Wind turbines convert the kinetic energy from the wind into electrical energy.
• Solar power is generated by solar cells or solar panels which can generate electricity directly from sunlight.