Sorry, we wont be talking about the NBA champs

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• Sorry, we wont be talking about the NBA champs!

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• matter is made up of atoms and molecules and
  energy causes the atoms and molecules to always
  be in motion - bumping into each other or
  vibrating back and forth
• the motion of atoms and molecules creates a form
  of energy called heat or thermal energy which is
  present in all matter

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• many different types of energy can be converted
  into heat energy
• light, electrical, mechanical, chemical, nuclear,
  sound and thermal energy itself can each cause a
  substance to heat up by increasing the speed of
  its molecules

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• Mechanical Equivalent of Heat
• 1 calorie 4.184 joules
• remember a joule is a unit of energy

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• put energy into a system and it heats up
• take energy away and it cools
• for example, when we are cold, we can jump up and
  down to get warmer

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• examples of various types of energy being
  converted into thermal energy (heat)
• (1) Mechanical energy is converted into thermal
  energy whenever you bounce a ball
• Each time the ball hits the ground, some of the
  energy of the ball's motion is converted into
  heating up the ball, causing it to slow down at
  each bounce

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A thermal infrared image of a ball before (left)
and after (right) being bounced.
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• (2) Thermal energy can be transferred to other
  objects causing them to heat up
• When you heat up a pan of water, the heat from
  the stove causes the molecules in the pan to
  vibrate faster causing the pan to heat up. The
  heat from the pan causes water molecules to move
  faster and heat up. So, when you heat something
  up, you are just making its molecules move
  faster.

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• 3) Electrical energy is converted into thermal
  energy when you use objects such as heating pads,
  electrical stove elements, toasters, hair dryers,
  or light bulbs

A thermal infrared image of a hair dryer and a
fluorescent light bulb
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• 4) Chemical energy from the foods we eat is
  converted into heating our bodies
• not the best for you but still makes our
  point here

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• (5) Light (radiant energy) from the sun is
  converted to heat as the sun's rays warm the
  earth's surface

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• (6) Energy from friction creates heat
• For example when you rub your hands, sharpen a
  pencil, make a skid mark with your bike, or use
  the brakes on your car, friction generates heat

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A thermal infrared image of a pencil after being
sharpened (left) and of hot brakes in a car
(right). Notice the hot tip of the pencil
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• the more energy that goes into a system, the more
  active its molecules are
• the faster molecules move, the more heat or
  thermal energy they create
• so, the amount of heat a substance has is
  determined by how fast its molecules are moving,
  which in turn depends on how much energy is put
  into it

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• CONDUCTION
• occurs when two object at different temperatures
  are in contact with each other
• heat flows from the warmer to the cooler object
  until they are both at the same temperature
• metals are better conductors than liquids and
  liquids are better conductors than gases
• metals are very good conductors of heat, while
  air is very poor conductor of heat

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CONDUCTION
A thermal infrared image of a coffee cup filled
with a hot liquid. Notice the rings of color
showing heat traveling from the hot liquid
through the metal cup. You can see this in the
metal spoon as well. This is a good example of
conduction.
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• Heat Conduction
• H kA (T2 - T1)/L                  
  (joules/second)

T2                                            
 T1                     k thermal
conductivity   J/s-m-C
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Heat Conduction
Steel  k 14  J/s-m-CHow much energy is
conducted in 40 seconds?------------------------
--H kA (T2 - T1)/L H 14 (2)(475)/10   
1330 J/sQ Ht 1330 (40)    5.32 x 104 J
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• ha ha, you thought you were stuck having to do
  more calculations!
• I got ya!
• but there will be more throughout the trimester
  (sorry, I cant help it)

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• CONVECTION
• occurs when warmer areas of a liquid or gas rise
  to cooler areas in the liquid or gas
• as this happens, cooler liquid or gas takes the
  place of the warmer areas which have risen higher
  
• "Hot air rises and cool air falls to take its
  place" - this is a description of convection in
  our atmosphere

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CONVECTION
This thermal infrared image shows hot oil boiling
in a pan. The oil is transfering heat out of the
pan by convection. Notice the hot (yellow)
centers of rising hot oil and the cooler outlines
of the sinking oil
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CONVECTION
Hot water rises, cools,and falls.
Air above warmer groundrises.
Heated air rises, cools, thenfalls.  Air near
heater isreplaced by cooler air, andthe cycle
repeats.
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• RADIATION
• method of heat transfer that does not rely upon
  any contact between the heat source and the
  heated object
• radiation is a form of energy transport
  consisting of electromagnetic waves traveling at
  the speed of light
• no mass is exchanged and no medium is required

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• objects emit radiation when high energy electrons
  in a higher atomic level fall down to lower
  energy levels
• the energy lost is emitted as light or
  electromagnetic radiation
• energy that is absorbed by an atom causes its
  electrons to "jump" up to higher energy levels
• all objects absorb and emit radiation

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RADIATION
A thermal infrared image of the center of our
galaxy. This heat from numerous stars and
interstellar clouds traveled about 24,000 light
years (about 150,000,000,000,000,000 miles!)
through space by radiation to reach our infrared
telescopes.
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