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Thermal Energy

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Thermal Energy 11/1/2011 What is thermal energy? Thermal energy is also known as heat and is the kinetic energy of all the molecules in a material. – PowerPoint PPT presentation

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Title: Thermal Energy


1
Thermal Energy
  • 11/1/2011

2
What is thermal energy?
  • Thermal energy is also known as heat and is the
    kinetic energy of all the molecules in a
    material.
  • If molecules are moving fast
  • (1) Do they have more or less kinetic energy?
  • (2) Does the material have more or less thermal
    energy?
  • (3) Do you predict it will be a high or low
    temperature?

3
Temperature
  • Temperature is a number related to the average
    kinetic energy of the molecules of a substance.
  • Heat, however, IS the energy in a substance and
    is measured in Joules, just like all the kinds of
    energy we have been talking about.
  • http//phet.colorado.edu/en/simulation/gas-propert
    ies
  • What happens to the molecules in a gas when you
    add more energy or heat to the gas? Describe
    what you see in the simulation.

4
Heat
  • Heat is thermal energy that is transferred
    between two bodies due to a difference in
    temperature. If one object is higher temperature
    than the other, heat will flow from high to low
    temperature.
  • Heat transfer is the process of increasing the
    kinetic energy of a materials particles from a
    material of high temperature to one of lower
    temperature.

5
Three kinds of thermal energy transfer
  • Conduction
  • Convection
  • Radiation

6
Conduction
  • Conduction is the transfer of heat by direct
    contact (mostly with solid objects).
  • Molecules in one material can increase the energy
    of molecules in the other material.
  • Materials that allow heat to flow through them
    are called conductors (metals are good
    conductors).
  • Materials that do not conduct heat well, such as
    plastic and wood, are called insulators.

7
Convection
  • Convection is the transfer of heat by the
    movement of the medium itself and occurs in
    liquids and gases but not in solids.
  • Hot areas of the material flow and mix with cool
    areas (like in air conditioning).
  • Convection transfers heat over a distance faster
    than conduction but cannot transfer to solid
    objects.

8
Radiation
  • Radiation is the transfer of heat in the form of
    waves through space.
  • Hot objects give off infrared electromagnetic
    radiation, which can be absorbed in another
    object and heat it up.
  • Transfer of heat by radiation moves at the speed
    of light and can go great distances, for example
    from the Sun to the Earth.

9
Exit Slip (turn in!)
  • What is thermal energy?
  • If you add heat to air in a balloon by putting it
    over a candle, what kind of heat transfer are you
    using?
  • For that balloon, what do you think would happen
    to the air molecules inside?
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