Thermal Energy & Heat Transfer

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Thermal Energy & Heat Transfer

  1. 1. Energy<br />ThermalEnergy<br />
  2. 2. Describe theenergytransfers in thefollowingitems<br />
  3. 3. Thermalenergy<br />Temperature and heat are two different thing<br />We use different units of measurement for these two things:<br />Temperature is measured in _______<br />Heat is measured in ________ <br />
  4. 4. Whatisheat?<br />Heat is a form of energy and is measured in Joules.<br />Scientists use the word "thermal" to mean "heat".It does not matter whether you say "heat energy" or "thermal energy“ they both mean the same thing.<br />
  5. 5. Whatistemperature<br />Temperature is a measure of how hot something isand is measured in °C (degree Celsius).<br />Heat is related to temperature but the two are not the same.<br />
  6. 6. Differencebetweenheat and temperature<br />
  7. 7. Differencebetweenheat and temperature<br />Imagine that you have a bucket full of water and a cup full of water both at 25 °C.<br />If you add the same amount of heat energy (for example 50,000J) to both you would find that the temperature of the cup of water increases by much more than the temperature of the bucket of water.<br />
  8. 8. Thermalenergy<br />To raise 2 different substances to the same heat, we need different amounts of heat energy<br />For example:<br />To heat 1kg of copper from 20°C to 21°C requires 390J, <br />To heat 1kg of aluminium from 20 to 21°C takes 910J. This is known as the SPECIFIC HEAT CAPACITY of a substance. <br />
  9. 9. Specificheatcapacity<br />The specific heat capacity of a substance is the amount of heat energy required to raise the temperature of the substance unit mass by a unit change in temperature. <br />The unit mass is usually 1kg, while the unit change in temperature is 1K or 1°C. The key formula is:<br />Energy = specific heat capacity × mass × change in temperature<br />
  10. 10. Specificheatcapacity<br />Calculatethefollowing:<br />How much energy is needed to increase the temperature of 500 g of lead from 20 ºC to 45 ºC? The specific heat capacity of lead is 128 J/kg/ºC.<br />
  11. 11. Heat transfer<br />Heat is transferred naturally from a substance with a higher temperature to a substance with a lower temperature.<br />
  12. 12. Heat Transfer <br />Complete the following definition using the words below:<br />___________ energy or heat is always transferred from a _________ place to a ___________ place. The amount of energy _____________ depends on how big the _______________ difference is<br />cooler thermal transferred <br /> hotter temperature<br />
  13. 13. Heat transfer<br />Draw arrows to show the direction of <br />energy transfer:<br />
  14. 14. Heat transfer<br />Heat can be transferred in three ways.<br />Conduction - by a substance which does not move (solids).<br />Convection - by  substance which moves (liquids and gasses).<br />Radiation - infra-red radiation is exchanged between all substances.<br />

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