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Thermal energy, heat transfer, and temperature
Transcript of Thermal energy, heat transfer, and temperature
Temperature is a measure of the average amount of kinetic energy (average speed) of the particles in a substance.
It can be measured in degrees Fahrenheit, Celsius, or Kelvin.
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 kinetic energy of all the particles in a substance!
It depends on three factors:
1. The number of particles in a substance (mass of the substance)
If you increase the temperature of a substance, it will have more 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
Heat is simply the transfer of thermal energy from one substance to another.
Thermal energy is ALWAYS transferred 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 taking place!
While all matter contains thermal energy, matter does NOT contain heat!
Heat is transferred 3 different ways.
A Prezi on thermal energy and heat transfer...
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 energy causes the slower particles to speed up.
Some metaphors - during conduction, imagine the particles are like...
Metals such as copper make good conductors.
Solids are usually much better conductors than liquids and gases due to the arrangement of their particles. (Particles are much closer together.)
Gases and liquids are usually poor conductors, making them good insulators.
Some solids, such as wood and foam are also poor conductors. This can be attributed to their density, and amount of air contained.
Insulators do NOT prevent heat transfer from taking place. They simply slow the process down. What are some other good insulators that you know?
All of these represent particles colliding with each other!
When particles collide, the faster particle transfers its energy to the slower particle. The faster particle slows down, and the slower particle speeds up. Eventually, they will move at the same speed.
In the process of convection, heat is transferred by the
mass movement of particles.
As particles gain energy, their speed 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. As 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. These can be very small to very large.
Convection is the main form of heat transfer
in liquids and gases.
Some metaphors for particles during convection...
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 as they gain/lose energy.
In the process of radiation, heat is transferred through electromagnetic waves.
Radiation transfers heat using transverse waves (electromagnetic energy) and does not need matter. The electromagnetic energy transforms into thermal energy when the waves come into contact with matter.
The Sun's rays travel 93 million miles through empty space!
Some examples of thermal radiation are microwaves, incandescent light bulbs, campfires and, of course, the Sun!
A good metaphor...
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!
...with a twist!
When the electromagnetic waves hit an object,
the waves transfer their energy to the object
by making the atoms and molecules move faster! (increases the temperature)
Light objects reflect most
of the sunlight. Less energy is transferred so they
will feel cooler.
Dark objects absorb more of the sunlight. More energy is transferred so they will feel warmer.
Even though this iceberg has a low temperature, it still has more thermal energy compared to a cup of hot chocolate because it has MANY more particles.
Conduction takes places when two substances are touching (two solids, a solid and a liquid, etc.)
Anytime you touch an object, conduction takes place. Heat either moves from you to the object (if it has a lower temp) or from the object to you (if it has a higher temp).
The faster particles then slow down as their energy is transferred. Eventually, after many collisions, all particles will be moving at the same average speed (same temperature).