chapter 10 heat energy

• What is temperature?

  Temperature is a measurement of how hot an object is 

  measured using a thermometer
• Transferring of heat energy

  heat energy is transferred from the hotter object to the colder object 

  temperature will change until the two objects reaches the same temperature 
• Expansion and contraction:

  • When a substance is heated, it expands
  • When a substance is cooled, it contracts
• Expansion in liquids:

  • Oceans absorb heat energy from the earth's atmosphere, causing them to expand and sea levels to rise
  • The rise in sea levels leads to more coastal land being washed away
• Bimetallic strips:

  • Made up of two metals that expand at different rates
  • Brass expands and contracts more than steel
  • A thermostat helps to keep the temperature constant
• Hot air balloon:

  • When air in a hot air balloon is heated, its volume increases
  • The mass remains constant as the number of air particles stays the same
  • Since the volume increases, the density decreases
  • The hotter and less dense air rises, causing the balloon to float
• When the boy sucks the straw, the air pressure inside the straw decreases and becomes lower than the surrounding atmospheric pressure, The higher atmospheric pressure pushes the liquid up the straw 
• Conduction


  Transfer of heat energy without the physical movement of the medium

  -metal is a better conductor of heat compared to paper so it conducts heat away from our hand more quickly and the metal feels colder

  -solids are better conductors of heat than fluids due to close arrangement of particles compared to liquid and gases and enables the transfer of heat energy to occur more quickly

  
  

  words to describe:

  conduction
• Factors affecting conduction


  • Type of material used
• Convection


  Transfer of heat energy from one place to another by the physical movement of a medium
• Convection in liquids


  Water gains heat, expands, volume increases, density decreases, hotter and less dense water rises, cooler and denser water sinks, heat energy is evenly distributed
• Convection in gases


  Air above the candle heats up, expands, becomes less dense, rises, cooler air moves down to replace the hotter air
• Radiation


  Transfer of energy from a hotter body to a cooler body without the need of a medium

  
  

  words used:

  absorption / emitter
• Radiation


  • Some energy is reflected back, greenhouse gases absorb and release energy back to the atmosphere
• Factors affecting radiation


  • Temperature of object
  • Surface area of object
  • Type of surface (dull and rough are better absorbers of heat and emitters than shiny and smooth)
• How does an air conditioner work?


  Warm air is less dense and collects under the ceiling, air con cools the warm air, it becomes denser and sinks to the bottom