Conservation and dissipation of energy

• how can energy be moved


  transferred usefully, stored or dissipated
• what is an open system 


  they're able to exchange energy and matter with their surroundings eg boiling water in a pan - heat energy leaves in a form of steam
• what is a closed system 


  a system that is unable to exchange energy and matter with their surroundings - putting coffee in a thermos and closing the lid so heat energy is unable to leave
• how to reduce energy waste in a motor


  lubrication
• how does lubrication work to reduce energy waste


  oil in a motor - reduces friction - so less energy is lost as heat through friction
• how to reduce energy waste in windows

  double glazing
• how does double glazing work to reduce energy waste 


  less useful thermal energy is lost
• how is thermal conductivity related to rate of energy transfer


  the higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material
• how is the rate of cooling of a material effected by its thickness

  the thicker the material - the less energy will be transferred by conduction
• how is the rate of cooling of a building affected by its thermal conductivity

  the higher the thermal conductivity - heat is allowed to travel through the material more easily - higher the rate of energy transfer by conduction across the material
• how can the efficiency of a system be increased


  reducing waste output (lubrication, thermal insulation etc)

  recycling waste output (absorbing thermal waste and recycling as input energy)