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Heat Transfer
Three Methods of Heat
Transfer
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Heat always goes from hot to cold.
Heat is movement of energy from a warmer
object to a cooler object.
Radiation
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Heat transfer by radiation takes place with no direct
contact between a heat source and an object.
Will transfer through the vacuum of space. Matter is not
required. Travels as electro-magnetic waves.
Other familiar forms of radiation include the heat you
feel around a flame or open fire. Radiation enables
sunlight to warm Earth’s surface.
Conduction
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What happens as a metal
spoon heats up in a pot of
soup?
The heat is transported from
the hot soup and the pot to
the particles in the spoon.
The particles near the bottom
of the spoon vibrates faster as
they are heated, so they bump
into other particles as they
travel through the handle of
the spoon and pot.
Soon the handle will be too
hot to hold!
The transfer of heat from one
substance to another by direct
contact of particles of matter.
Usually associated with solids.
Convection
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Conduction heats up the spoon, but how does the
soup inside the pot heat up? Heat transfer involving
the movement of fluids- liquids and gases- it is
called convection.
During convection, heat particles of fluids begin to
flow transferring heat energy from one part of the
fluid to another.
Convection and Density
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The warmer particles are
moving faster, they
spread out more.
So they are less dense
and rise.
After giving their energy
to the cooler fluid at the
top, they are now cooler
and more dense. More
dense fluids sink.
Convection Currents Diagram
Convection Currents
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The heating and cooling of the fluid, changes in
the fluid’s density, and the force of gravity
combine to place the currents in motion.
Convection currents continue as long as heat is
added without heat the currents will stop when
all of the material has reached the same
temperature. However, heat from the Earth’s
mantle and core causes the currents to form in
the asthenosphere.
Radiation Conduction
Convection Song
Key Terms!
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Heat Transfer- The movement of energy from a
warmer object to a cooler object.
Radiation- The direct transfer of energy through
empty space by electromagnetic waves.
Conduction- The transfer of heat from one
substance to another by direct contact of particles
of matter.
Convection- The transfer of heat by movements
of a fluid.
Density- The amount in a given space; mass per
unit volume.
Convection Currents- The movement of a fluid,
caused by differences in temperature, that transfers
heat from one part of the fluid to another.
Temperature
Temperature
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a measure of the average
kinetic energy (motion) of
the particles in an object;
how fast the particles are
moving.
The faster they are moving,
the higher the temperature.
The slower they are moving,
the colder the temperature.
Always goes from hot to
cold.
Stops at thermal
equilibrium.
Three Temperature Scales
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We use three
scales to
measure
temperature.
Fahrenheit
Celsius
Kelvin
Fahrenheit (°F)
– Used in the USA
– Based on the lowest
temperature that
Dr. Fahrenheit could
achieve (mixture of
ice, salt, and
alcohol)
– 180 degrees
between freezing
and boiling points of
water
Celsius scale: (°C)
– Created by Anders Celsius
– Also called the centigrade
scale
– Based on freezing/boiling
points of water
– Used by most of the world
and by scientists
– Considered by some to be
an SI unit
– 100 degrees between
freezing/boiling points of
water
Kelvin scale: (K)
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Kelvins, not degrees Kelvin
Based on absolute zero,
the coldest possible
temperature. This is the
point where all the motion
of the particles has
stopped. Believed to be
impossible to achieve.
Has no negative numbers
Official SI unit
Same size as Celsius
degrees, just starts at a
different place
Used by scientists only