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Title
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Thermal Energy
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Type
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Primary: Mission Briefing Article
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Operation
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Infinite Potential
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Mission:
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Mission 2: Waves of Change
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Print Page
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38,40
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Subjects
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Physical science | Heat | Conduction | Convection | Kinetic molecular theory | Radiation | Temperature | Science
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Grades
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5 | 6 | 7 | 8
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Keywords
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thermal energy, hot, heat, cold, temperature, transfer, transform, conduction, convection, radiation, volume, conductor, insulator, conduct, refrigeration, conduct, convect, radiate, insulate, refrigerate, sublimation, melt, evaporation, evaporate, freeze, freezing, condensation, condensate, solid, liquid, gas, deposition
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Duration
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00:15:00 (HH:MM:SS)
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Audience
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Teachers | Elementary Grades | Junior High
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Created On
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3/30/2009
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Copyright
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Sun photo (pg.38) NASA; Ice cube photo (pg.40): Darren Hester/OpenPhoto.net - SA by 2.0
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From: Infinite Potential Mission 2: Waves of Change (pp: 38,40) |
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Thermal Energy Thermal energy is the total energy content of a system. Learn how it can be transferred or transformed between substances by convection, conduction or radiation in this article. |
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Heat and Temperature
The words hot and cold refer to how we perceive an object’s thermal energy. Thermal energy is the total energy content of a system. Often, it is measured in terms
of particle vibration and movement. Particles that move or vibrate faster have greater
thermal energy than particles that move at slower speeds.
Temperature is a measure of the concentration of thermal energy, not the
total amount of thermal energy in a system. Although the terms are often incorrectly
interchanged, do not confuse thermal energy with temperature.
Like other types of energy, thermal energy can be transferred and transformed. In
all cases, thermal energy moves from areas of high concentration to areas of low
concentration. This flow of thermal energy between substances is often referred
to as heat.
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Compare a mug of hot tea and a swimming pool. The tea’s temperature is 82ºC (180ºF).
The swimming pool’s temperature is 25ºC (77ºF). Although the measured temperature
of the tea is higher, the pool’s total content of thermal energy is greater. That
is because there are many more moving particles in the pool. Even though the particles
in the pool are slower moving, their numbers account for a much greater amount of
thermal energy.
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Thermal energy can be transferred by conduction, convection, and radiation.
If you put a spoon in hot soup, over time, thermal energy transfers from the hot
soup, through the spoon to your hand. This is conduction. Convection
within Earth transfers energy to the surface. These transfers drive geological processes
that can result in earthquakes and tsunamis. As magma circulates, thermal energy
is transferred from the core to the surface. If you have ever stood in the sun on
a hot summer day, you have felt the thermal energy transferred from the sun to your
skin by radiation. |
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Conduction, Convection and Radiation
Thermal energy is transferred or transformed between substances by conduction,
convection, or radiation. The process that transfers thermal energy
between atoms and molecules that are in direct contact is called conduction.
Convection transfers thermal energy through the movement of matter and occurs in
materials that are capable of flowing, such as liquids and gases. Colder liquids
and gases are more dense and therefore fall due to gravity, displacing warmer material,
which rises. This movement forms a convection cycle.
Radiation is the transfer of thermal energy through electromagnetic waves. The flow
of energy from the sun to the planets is an example of radiation. |
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Conductors and Insulators
Thermal energy transfers within a system are regulated by the property of conduction.
Good conductors are substances that easily transfer energy. The metal of
a soda can is a good conductor. It feels cold because the thermal energy easily
transfers from your hand to the can.
Insulators do not easily conduct energy. A plastic cooler is a thermal insulator.
This property means that thermal energy cannot be easily transferred into or out
of the cooler.
Cold
Cold is a word used to describe a condition of low temperature. It is critical when
talking about cooling and refrigeration. Cooling objects with refrigeration involves
putting them into an unbalanced system. The unbalanced system promotes a transfer
of thermal energy away from the substances you want to cool. |
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Your body has its own cooling system. Along with many other mammals, you
have glands all over your body that produce sweat on your skin when you get hot.
As this liquid covers your skin, it starts evaporating into the surrounding air.
When substances change phase from liquid to gas, they absorb thermal energy from
their local environment. Because your skin is part of the local environment, thermal
energy is removed from your skin, making it cooler.
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Air conditioners also create this imbalance When you enter an air-conditioned room,
your temperature is immediately out of balance with the room. This causes your body
to release its thermal energy to the surroundings. The constant loss of your thermal
energy to the surrounding air causes you to feel cooler. |
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