HEAT

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HEAT
Heat is the transfer of thermal energy between
objects. Heat always flows from warmer objects
to cooler objects.
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How Ice Cools Water
Water Temperature 25 oC
Water Temperature 21 oC
Water Temperature 18 oC
Water Temperature 15 oC
Water Temperature 12 oC
Water Temperature 10 oC
Thermal Energy
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Temperature
Temperature is the measure of how fast molecules
of a substance are moving. The faster the
molecules move, the higher the temperature. Even
in solid objects, the molecules are moving, its
just that they are vibrating in place.
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Thermometer
100 90 80 70 60 50 40 30 20 10 0 -10
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Thermometer
100 90 80 70 60 50 40 30 20 10 0 -10
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Temperature Scales
Water Boils
212 100 32 0

• The two temperature scales that are most commonly
  used are
• Fahrenheit
• Celsius (Centigrade)
• Another scale, the Kelvin scale, is also used
  commonly in the scientific community.

Fahrenheit
Celsius
Water Freezes
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Conductors
Conductors are materials that allow heat to
transfer easily. Conductors are usually made
from materials that have atoms or molecules that
are relatively close together. This allows the
heat to jump from one molecule to the next.
Materials such as metals are good conductors.
HEAT
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Insulators
Insulators are materials that do no allow heat to
transfer easily. Insulators are usually made
from materials that have atoms or molecules that
are relatively far apart. Materials such as
plastic, rubber, wood, gases (air) are good
insulators.
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Gas
Heat
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Gas
Heat
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Heat Transfer
As mentioned before, thermal energy always goes
from the warmer object to the cooler object.
This can happen in three ways A) Conduction
B) Convection C) Radiation
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Conduction
Conduction is the transfer of thermal energy
through the direct contact of particles. One
particles gains thermal energy and then transfers
it to the particles closest to it. The closer
the particles are to each other, the better the
transfer of thermal energy.
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HEAT
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Convection
Convection is the transfer of thermal energy
through the movement of fluids. As a fluid gets
warmer, its density gets lower. As a result, the
warmer fluid is pushed up and rises (hot air
balloons work because of this principle). As it
rises, it carries it thermal energy along with
it, passing it to other particles as it travels.
When it loses thermal energy, the density
increases, causing it to sink and repeat the
cycle once again.
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Convection Current
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Convection Under the Earths Surface
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Radiation
Radiation is the transfer of thermal energy
through the electromagnitic waves. Unlike
conduction and convection, radiation does not
need something (a medium) to transfer heat. The
Sun, 93,000,000 miles from Earth, has no direct
contact with Earth and nothing known flows
between the Earth and the Sun. The only way the
Earth can receive its energy from the Sun is
radiation.
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Heat Transfer in the Atmosphere
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Thermal Expansion
As an object gets warmer, its molecules move
farther apart and the object expands. Also, the
when an object cools, its molecules get closer
together, and the object shrinks or contracts.
IMPORTANT Water is an exception to the
contraction rule. As water cools, it contracts
until it reaches 4 oC. Below 4 oC, water
expands!
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Water
The shape of water molecules and their
arrangement when they become solid causes water
to expand as it freezes.
Gas
Liquid
Solid
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Tracks put down straight in February!
As seen in August!