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# Heat Transfer

Prezi for heat transfer unit focusing on conduction, convection, and radiation
by

## Jamie Dugan

on 5 May 2010

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#### Transcript of Heat Transfer

Heat Thermal Energy Temperature is a measure of the average amount of kinetic energy of the particles in a substance. It can be measured in degrees Celsius, or Kelvin. (Fahrenheit if you're American...but not scientists ;) Temperature Imagine cars represent the particles
(atoms and molecules) in a substance. Finding the temperature of that substance would be comparable to finding the average speed for all of the cars. Thermal energy is the total energy of
all the particles in an object!
Measured in Joules!!! It depends on three factors: 1. The number of particles in a substance If you increase the temperature of a substance,
you will increase the amount of thermal energy! 2. The temperature of the substance 3. The arrangement of the particles Since ALL matter has moving particles,
ALL matter has some amount of
thermal energy!! Heat is the movement of thermal energy from one substance to another. Heat ALWAYS flows in predictable ways from the substance with a higher temperature to the substance with a lower temperature. If they have equal temperatures, there will be NO heat transfer! While all matter contains thermal energy, matter does NOT contain heat!! Heat is transferred 3 different ways. Heat Transfer... Conduction Convection Radiation In the process of conduction, heat is transferred through the direct collision of particles. Fast-moving particles in the substance with a higher
temperature collide with slower-moving particles in the
substance with a lower temperature. The transfer of heat
causes those slower particles to speed up. Mosh Pit Pool Bumper Cars Some metaphors... Metals such as copper make good conductors.
Solids are generally better conductors than liquids
and gases because their particles are closer
together and have more frequent collisions. Gases and liquids are usually poor conductors, making them good insulators. Some solids, such as wood and foam are also poor conductors. Remember, insulators do NOT prevent heat transfer from taking place.
They simply slow the process down.
Examples: Coffee mug handles, wooden handles on pots
and pans, pot holders, wooden spoons All of these represent particles colliding with each other! In the process of convection, heat is transferred by the
mass movement of particles. As particles gain heat, their temperature increases. This causes the particles to move faster and take up more space. This causes the gas or liquid to become less
dense and float. Once the fluid cools, the particles
slow down and come closer together. This causes it
to become more dense and sink. Through the continuous rise and fall of matter,
convection currents are formed. Convection is the main form of heat transfer
in liquids and gases. Some metaphors... Flock of Birds School of Fish Both examples represent particles moving together in the same direction.

Just like fish and birds, atoms and molecules will move in the same direction as they move up and down in convection currents. In the process of radiation, heat is transferred through electromagnetic waves. Radiation is unlike conduction and convection in that it does not need matter to transfer heat. The sun's rays travel millions of miles through empty space! Some examples of radiation are microwaves,
campfires and, of course, the Sun! A good metaphor... Star Wars Darth Vader is able to affect this guy on the left without the use of any matter in between them, just like how the Sun can heat up the atmosphere with millions of miles of empty space! Any Questions?! These include infrared, microwaves, and UV rays ...with a twist!
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