Internal energy

• Explain why people often install loft insulation before installing double glazing or cavity wall insulation.

  It’s cheaper and has shorter payback time
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  The homeowner installs an electrically heated mirror into the shower room. When a person has a shower, the heated mirror does not become misty but stays clear. Why does the mirror stay clear?

  The mirror is warm so condensation is reduced
• What are convection currents?

  currents of moving liquids transferring energy
• Explain, in terms of the particles in the metal, how heat energy is transferred through the base of the saucepan.

  Ions gain energy electrons transfer energy by collision with ions

   

   
• Energy is transferred through the water by convection currents. Explain what happens to cause a convection current in the water.

  As heat energy is transferred through the saucepan, the water particles at the bottom move faster

  water expands and warm water rises
• Some energy is transferred from the hotplate to the air by thermal radiation. What is meant by thermal radiation?

  transfer of energy by waves
• One kilogram of a gas has a much larger volume than one kilogram of a solid. Explain why

  there are strong forces between the particles in a solid holding the particles close together holding the particles in a fixed pattern so they’re spread out
• Suggest one advantage of having no insulation around the chimney.


  Energy transfers to rooms in the house
• Heating


  Increases the internal energy of the particles

  
• Cooling


  Reduces the internal energy of the particles

  
• Internal energy

  Energy inside a system stored by the particles within the system.

  This includes any potential energy and the kinetic energy possessed by the particles

  
• Potential energy possessed by particles


  the energy due to the attractive forces holding particles close to each other. This is highest in a solid, zero in gases.

  
• Kinetic energy


  the energy possessed by particles because of their movement - lowest in solids, highest in gases

  
• Latent heat of fusion


  The energy being put into (or taken out of) the system during the time the solid melts (or liquid freezes). During this period of heating (cooling) the temperature of the system does not increase (or decrease) despite energy being put in (or taken out). The energy is being used to break (or make) the attractive forces between the particles as a solid.

  
• Latent heat of vaporisation


  The energy being put into (or taken out of) the system during the time the liquid boils (or gas condenses). During this period of heating (cooling) the temperature of the system does not increase (or decrease) despite energy being put in (or taken out). The energy is being used to break (or make) the attractive forces between the particles as a liquid.

  
• Specific heat capactiy

  the amount of heat needed to raise one kilogram of a substance by one Celsius degree. This varies according to the material and its state - for example water has a higher specific heat capacity than ice or steam, and than oil