Heat transfer


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  • Data Harvest, data logging looking at the change in temp of a small red hot object compared with a large object heated to a relatively low temperature. Temperature of an object will be how hot it is and effectively the direction that heat energy will move. If something is hot it does not necessarily have a lot of energy. What does heat energy depend on?
  • The total amount of movement of all particles is a representation of the amount of heat energy, the average movement of particles is its temperature. If a substance has relatively a large amount of particles but they don’t vibrate much, what could be said about the substance? A lot of heat energy but a low temperature (Iceberg)
  • The weather and the waves are natural occurring processes that are driven by convection currents - these processes keep eco-systems balanced and provide the movement of essential factors (such as change in climate through temperature alterations) for survival. A high or low pressure system is generated by the difference in temperature between the Sun’s transfer of heat energy at the equator compared to the lower heat energy at the colder poles. This difference along with the rotation of the Earth and distribution of land mass causes a variation in weather and a transfer of energy from the resulting winds into the ocean.
  • 1 ton of bricks or 1 ton of feathers? Physically, what would be very different between one ton of bricks compared with feathers? One metric ton of either feathers or bricks will have an identical mass of 1,000 kilograms (one metric ton). However, a metric ton of feathers will occupy a volume of almost 400 million cm3(about the size of four tractor trailer trucks), while a metric ton of bricks will occupy only one-half million cm3 (about the size of a large-screen TV). The bricks are denser than the feathers because their mass is packed into a smaller volume.
  • Particles in a liquid and gas are not bound by the bonds of the particle beside them, they can move around freely. When the particles are heated how will there movement change? Faster, collide more, want more space, expand. Less dense, rise up and bring the heat energy with them. http://www.flashscience.com/heat/expansion.htm
  • Think! Density is the same as compactability!
  • Which one is ireland?
  • Keep the heat in! Stop heat transfer, Neoprene traps the water and the body heat passes into the pockets warming the water which is poor at transferring the heat away into the surrounds (hot to cold, direction of heat transfer)
  • each particle is kept in place as the bonds between particles are strong and one particle will always be surrounded by the same neighbouring particles... hence a solid cannot flow, convection currents cannot be the process by which heat energy transfers.
  • Winter time in NZ - Bear Grills, sleeping inside a snow cave he carved out of the deep snow, its all about cutting down conduction away from the body, trapping bad conductors, good insulators, air!
  • What is the one source of heat energy that our planet relies upon? How does the heat from the Sun get to the Earth? Luminous ether theory... even Einstein did not question its existence
  • This is another form of energy transfer due to electric and magnetic pulses interacting as a wave moving away from a source, similar to light and it has many of the same characteristic of light - Travels at 300,000 m/s, can be reflected and only moves in a straight line, does not require any of the three states of matter to travel through (i.e. space or a vacuum). It is a part of the electromagnetic spectrum which the visible light spectrum is only a small portion of. We cannot sense this ‘light’ with our eyes although some cameras (night vision goggles) can detect it. It is sometimes referred to as infra-red radiation. It’s wavelength is just slightly longer than the colour red on the visible spectrum and all objects will either emit or absorb heat radiation depending on the surrounding temperature.
  • The greenhouse Gases,
  • Heat transfer

    1. 1. Heat Energy Transfer <ul><li>GCSE Physics </li></ul>
    2. 2. Textbook reference <ul><li>CCEA Physics, Page 17 – 25 </li></ul><ul><li>Key words list , what do you think the words and phrases mean? </li></ul><ul><li>You don’t want to get confused… like President Bush! </li></ul>
    3. 3. Learning Intentions <ul><li>State the three types of heat energy transfer </li></ul><ul><li>Recall in detail how the three types of heat energy transfer occur. </li></ul>
    4. 4. Don’t let the cold in!!!
    5. 5. Heat Transfer <ul><li>Heat Flow </li></ul><ul><li>Objects get hot if heat energy ( thermal energy) passes into them.  We know they get hot because the temperature rises.  It is important that we know the difference between temperature and heat: </li></ul><ul><li>Temperature - the measure of how hot something is, measured in degrees Celsius; </li></ul><ul><li>Heat - a flow of energy from a hot object to a cold object.  Heat is measured in joules (J). </li></ul>
    6. 6. Particle motion in a substance
    7. 7. Heat Flow <ul><li>Heat always flows from hot to cold .   Heat does not flow from a cold object to a hot object.  For example the heat from a hotplate passes into a cold pan to heat up the water in the pan. </li></ul><ul><li>The greater the temperature difference between the hot object and the cold object, the greater is the flow of heat . </li></ul>HOT HEAT COLD
    8. 8. Types of Heat Energy Transfer <ul><li>Page 17 </li></ul><ul><li>The three ways in which heat can move (types of heat energy transfer) are… </li></ul><ul><li>Conduction </li></ul><ul><li>Convection </li></ul><ul><li>Radiation </li></ul>
    9. 9. Convection
    10. 10. Which weighs more?
    11. 11. Convection <ul><li>Structure of a Liquid and a Gas </li></ul>Both states of matter flow and carry the heat energy with them.
    12. 12. What causes the convection currents? Particles move feely Gain heat energy Move faster and spread out Volume becomes less dense Rises and bringing the heat energy
    13. 13. Change in Density  The movement of hotter areas in a liquid can be seen using potassium permanganate as a dye: H E A T This cycle is called a convection current.  Can you explain how the convection current moves using the idea of density ? The diagrams on the left will help you.
    14. 14. Question Time <ul><li>CCEA Physics </li></ul><ul><li>Attempt Q 33 pg 24 and Q 5a pg 30 </li></ul>
    15. 16. Conduction
    16. 17. Conduction <ul><li>Structure of a Solid (cannot flow) </li></ul>
    17. 18. Conduction in Solids
    18. 19.
    19. 21. Radiation
    20. 22. Application of Heat transfer <ul><li>Trapping layers of air in between bed sheets </li></ul><ul><li>Skin cancer </li></ul><ul><li>Cooking utensils </li></ul><ul><li>A greenhouse </li></ul><ul><li>Table mats, handles of cooking appliances </li></ul><ul><li>Air con is usually placed at the top of a room </li></ul><ul><li>A heating coil of a kettle is at the bottom </li></ul><ul><li>Formation of land and sea breezes </li></ul><ul><li>Silver Teapots and pans </li></ul><ul><li>Different hot and cold touch sensations from objects </li></ul><ul><li>Colour and texture of clothing </li></ul>Conduction, Convection or Radiation??
    21. 23. Newspaper Headlines!
    22. 26. Greenhouse Gases… <ul><li>Water Vapour </li></ul><ul><li>Carbon Dioxide </li></ul><ul><li>Methane </li></ul><ul><li>Halocarbons </li></ul>
    23. 28. Questions <ul><li>Text Book pg 29 </li></ul><ul><li>Questions 4 – 7 </li></ul>
    24. 29. The internet can help! <ul><li>http://www.bbc.co.uk/climate/evidence/ </li></ul><ul><li>Evidence </li></ul><ul><li>Impacts </li></ul><ul><li>Adaptation </li></ul>
    25. 30. Reducing the runaway greenhouse effect <ul><li>http://www.bbc.co.uk/climate/adaptation/jack.shtml </li></ul><ul><li>Life at Home </li></ul><ul><li>Copy down what we can do to help slow this down! </li></ul>