energy

• gravity?

  invisible force that pulls objects towards eachother
• 4 steps of convection

  1. as a fluid is heated, the particles gain kinetic energy and spread apart
  2. this means the heated fluid is less dense, and so it rises above cooler fluid
  3. as the fluid cools down, it becomes more dense again and so sinks
  4. if this process occurs in a limited space, such as a container or room, it may created a convection current
• why are bio fuels not really carbon neutral in practice?

  • in order to grow the bio fuels we often have to clear land by deforestation
  • this means that the trees can no longer photosynthesise and absorb CO2
  • this process will also release large amounts of CO2 if burned
  • in addition, it usually requires a lot of energy to harvest, process and transport the bio fuels, which itself will produce a lot of CO2
• 3 disadvantages of fossil fuels

  1. finite resource so it will run out one day
  2. produce CO2 when burned, which is a greenhouse gas and contributes to global warming
  3. sometimes produce toxic gases when they are burned, such as sulphur dioxide and carbon monoxide
• electrostatic energy store?

  energy stored when repelling charges have been moved closer together or when attracting charges have been pulled further apart
• infrared radiation

  the hotter the object the more infrared radiation it will emit
• purpose of putting insulation in the gap of cavity walls


  minimise air convection currents
• 3 advantages of hydroelectricity

  1. renewable
  2. can increase or decrease energy output to match demand
  3. cheap to run once set up
• what is a non renewable energy resource?

  one that isn't being replenished and so has a limited supply (finite)
• 3 types of fossil fuels and their states

  1. coal- solid
  2. crude oil- liquid
  3. natural gas- gas
• closed system?

  a system which cannot gain or lose energy (or matter) to the outside world
• thermal conductivity in windows

  double glazed windows have a lower thermal conductivity, meaning less thermal energy transfers through them
• 7 renewable energy resources

  1. wind
  2. solar
  3. tidal
  4. bio fuels
  5. geothermal
  6. water waves
  7. hydroelectricity
• nuclear energy store?

  energy stored in the nucleus of an atom
• 2 common disadvantages between wind and solar power

  1. unreliable
  2. expensive to set up
• why are bio fuels carbon neutral (in theory)?

  they absorb the same amount of CO2 while growing as they release when theyr'e burned - so there is no net release of CO2