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					          Thermal Energy


Chapter 6 Section 1
Temperature & Heat
      Part 1
Warm Up:
• To shape metal into a horseshoe, the metal is
  heated in a fire. Why will a horseshoe bend
  when it’s very hot, but not after it cools?
       What was different ?
• There was            • Matter is
  more motion in         always in
  the hot water          motion

                       • Particles of
                         gases,
                         liquids, and
                         solids all
• The energy of
                           move
motion is Kinetic
Energy
                Heat
Heat is related to
temperature:

The Temperature of
an object is the
measurement of the
average kinetic energy
(KE) of particles
    What do Temperature Scales
            Measure?
• Fahrenheit: used in US
• Celsius: used in other countries
• Kelvin: SI unit
   0 K = -273°C
   0°C = 273 K
           Thermal Energy
• Thermal Energy (Q) is the sum of the
  kinetic energy + the potential energy of all
  the particles in an object:
             Q = KE + PE
          Thermodynamics
• First Law of           –Energy is
  Thermodynamics:         CONSERVED
  the increase in
  thermal energy of a
  system equals the
  work done on the
  system plus the heat
  transferred to the
  system
           Open Systems
• In an open system, heat flows across the
  boundary, or work is done across the
  boundary.
• What are examples of open systems?
          Closed Systems




• In a closed system, no heat flows across
  the boundary and no work is done across
  the boundary.
• What are examples of closed systems?
Thermodynamics
• Second Law of
  Thermodynamics:
  Heat flows from
  warmer objects to
  cooler objects
  Heat cannot flow from
  a cooler object to a
  warmer object unless
  work is done
   How do solids transfer heat?
• Conduction: the
  transfer of thermal
  energy by collisions
  between particles in
  matter.

• Particles in solids
  vibrate and collide
  with each other
                         • List 3 examples
                           of conduction
                         Convection
                                       • Convection is the
                                         transfer of thermal
                                         energy in a gas or
                                         liquid by the
                                         movement of warmer
                                         and cooler fluid from
                                         place to place.
Knowing this, what will happen to a piece of ice floating at the top of a
warm glass of water?
What will happen to a piece of ice at the bottom of a glass of water?

• List 3 examples of convection
                  Radiation
• Radiation is the transfer of
  energy by electromagnetic
  waves. These waves
  travel in the empty spaces
  between particles until their
  energy is absorbed by a
  particle.

• Would radiation pass
                                  • List 3 examples
  through a solid or a gas
                                    of heat radiation.
  more easily?

				
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posted:9/9/2012
language:English
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