Unit One - Energy

• System


  a group of objects or a single object.
• What happens when a system is changed

  there are also changes in the way some or all the energy is stored
• 8 energy stores


  kinetic, nuclear, magnetic, thermal, electrostatic, gravitational potential, elastic potential, chemical
• how is energy transferred


  mechanically, electrically, by heating and radiation
• closed system


  systems where either matter or energy cannot leave or enter.
• net change in a closed system is

  0
• describe the changes involved in energy stores when an object is projected upwards e.g. a person

  chemical energy from the arm to kinetic energy of the object and arm. the object's kinetic energy will transfer to GPE as it decelerates
• describe the changes involved in energy stores when a moving object hits an obstacle

  kinetic energy transfers to the car's elastic potential and thermal energy stores. some energy will also be transferred to the surroundings via sound wave
• describe the changes involved in energy stores when an object is accelerated by a constant force e.g. gravity

  gravitational potential energy transfers to kinetic energy
• describe the changes involved in energy stores when a vehicle is slowing down

  kinetic energy transfers to the surroundings as thermal energy and a small amount of sound waves via friction in the brakes
• describe the changes involved in energy stores when bringing water to boil in an electric kettle

  electrical energy transfers to the thermal energy stores of the kettle's heating element which transfers thermal energy to the water molecules
• what does the elastic potential energy equation presume

  the limit of proportionality has not been exceeded
• spring constant units


  N/m
• define specific heat capacity


  the amount of energy required to raise the temperature of 1kg of a substance by 1 degree Celsius
• define power


  rate at which energy is being transferred or the rate at which work is done
• an energy transfer of 1 joule per second is equal to what?

  power of 1W
• conservation of energy principle


  Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed
• use an example to describe energy transfer within a closed system where there is no net change to overall energy


  cold spoon dropped into an insulated flask of hot soup. the flask is a perfect insulator so the spoon and soup form a closed system. Thermal energy is transferred from the soup to the spoon . Energy transfers have occured within the closed system but no energy has left the system so no net change.
• use an example to describe energy transfer where some energy dissipates of is 'wasted'

  when using a phone chemical energy is transferred to electrical energy, however, some energy is lost through thermal energy
• how can you reduce 'wasted' energy in a system where there is friction ?

  lubricant or oil
• how can you reduce 'wasted' energy in a system where thermal energy is being dissipated ?

  thermal insulation
• how do double glazed windows work?

  vacuum between the glass panes prevents heat loss via conduction
• describe a way of preventing heat loss from a building

  thick walls of a low thermal conductivity
• describe thermal conductivity


  the higher the rate of thermal conductivity the higher the rate of energy transfer by conduction across the material
• define renewable energy resource


  an energy resource that can be replenished as it is used
• list 3 fossil fuels

  coal, oil & gas
• list 2 nuclear fuels

  uranium and plutonium
• what are fossil fuels?

  natural resources that form underground over millions of years
• define nuclear fuel


  substance used in nuclear reactors that release energy due to nuclear fission
• define biofuel


  any fuel taken from living or recently living material such as animal waste
• define geothermal


  energy released by radioactive substances deep within earth
• biofuel fits into what two categories?

  carbon neutral and renewable
• define carbon neutral


  a biofuel from a living organism that takes in as much carbon dioxide from the atmosphere as it releases when burnt
• from the energy sources studied, which are non-renewable

  fossil fuels, nuclear
• use of geothermal energy

  heat buildings by passing water pipes through ground source heat and pumping it around the building
• 2 advantages of nuclear energy (vs renewable)

  - no greenhouse gases

  - higher energy transfer per kilogram
• 2 disadvantages of nuclear energy (vs renewable)

  - used fuel rods contain radioactive waste

  - an explosion could release radioactive material over a wide area
• 3 negative environmental impacts of wind turbines

  - ruins a picturesque landscape

  - noise pollution

  - kill wildlife e.g. birds
• negative environmental impact of hydro-electricity

  habitats are often flooded to create dams
• why do countries not only rely on renewable energy sources?

  renewable energy resources are not currently able to meet the world's demand for energy