Transcript Power point on Heat Transfer

The Movement of Heat
Chapter 4
Lesson 19
TCAP Coach
Objectives
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SPI: 0507.10.2 Use data from an investigation to
determine the method by which heat energy is
transferred from one object or material to
another.
The Movement of Heat
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You feel the warmth of the sun on your skin.
On a hot day at the beach, the sand feels hot on
your feet. On a cold day, the air in your room is
warmer near the ceiling than near the floor.
All these things happen because of the
movement of heat.
In this lesson, you will learn about the different
ways that heat energy can travel.
Understanding Heat Energy
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As you have learned, all matter is made up of tiny
particles that are always moving.
Heat is the energy of these moving particles.
That means heat is kinetic energy.
Your body is warm because tiny particles in it move all
the time.
When you move and exercise, the particles that make
up your body move a bit faster. That makes your body
warmer.
The faster the particles in an object move, the warmer
the object will be.
Understanding Heat Energy
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Heat always flows from a warmer material to a
cooler material.
An object becomes hotter if the particles in it
start to move faster.
There are three ways this can happen.
They are called conduction, convection, and
radiation.
Conduction
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Picture yourself walking barefoot along a beach on a
hot summer day. After walking through the sand for
just a little while, your feet feel hot. Heat moves from
hot sand to the bottoms of your feet by conduction.
Conduction is the transfer of heat between objects
that touch each other.
When two materials have different temperatures, heat
energy moves from the warmer one to the cooler one.
In other words, the heat moves from the hot sand to
the cooler bottoms of your feet.
Conduction
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When sand gets hot, the particles that make it up
move or vibrate very fast. They have a lot of energy.
When you walk the particles of your skin touch the
sand. The particles in the hot sand bump against the
particles that make up your feet.
When this happens, the sand particles transfer some
energy to your skin. Now your hand has more
energy than it had before and it feels hotter.
Conduction
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Since the sand gave away some heat energy to
your feet, the sand is a tiny bit cooler than it was
before you walked on it.
The sand transfers energy to your skin until the
temperatures of both the sand and your skin are
the same.
If your foot stayed in contact with the sand,
soon they both would have the same
temperature.
Conduction
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Heating a pot of water on an electric stove is
another example of conduction.
Heat moves from the hot coils of the stove to
the metal of the pot touching them.
As the bottom of the pot gets hot, heat moves
from the bottom of the pot to the cold water
that is touching the bottom of the pot.
Conduction
Convection
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How does water in a pot on a stove get hot all over?
Remember, the water at the bottom of the pot is
heated by conduction. Some heat moves through
the rest of the water by conduction, as particles
bump into each other and transfer energy.
But the water is also heated by convection.
Convection is the transfer of energy through a
liquid or gas by means of currents.
Convection
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Think again about the pot of water on the stove.
The water on the bottom of the pot is in contact
with the metal of the hot pot, so conduction
occurs. This bottom layer of water heats up
because it touches the metal pot.
Convection
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Warm water is less dense than cool water. You
learned about density in Lesson 16.
This difference in density makes warmer water
rise in the pot.
Cool water is denser than warm water. This
makes cool water sink in the pot.
As cooler water reaches the bottom, it heats up
and rises.
Convection
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Water up at the top is now cooler than the water below,
so it begins to fall.
This constant rising and falling of warm and cool water
makes convection currents.
Convection currents transfer heat throughout the
water.
Convection currents also warm your room. As air near
a radiator or a vent is heated, the air rises toward the
ceiling. Then the air cools and sinks. This happens over
and over, spreading heat throughout your room.
Convection
Convection
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Convection currents also move heat through
Earth’s atmosphere.
Cold air sinks because it is denser, and warm air
rises because it is less dense.
This ongoing cycle produces currents of moving
air, which we call winds.
Convection is responsible for much of Earth’s
weather.
Convection
Radiation
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In both conduction and convection, particles of matter
transfer heat energy.
The particles can be in a solid, such as the bottom of a
pot.
They can be in a liquid, such as the water in the pot.
Or they can be in gases, such as the air in your room
or in Earth’s atmosphere.
However, heat can also be transferred through empty
space.
Radiation
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The transfer of heat through space is called
radiation.
That is how heat from the sun, which is millions of
kilometers from Earth, reaches your skin.
The sun’s energy travels as waves through space.
When the energy in sunlight reaches your skin, the
energy makes particles in your skin move faster.
This movement increases the temperature of your
skin, and you feel the sun’s warmth.
Radiation
1. Which kind of heat transfer takes place
when you put a spoon in a cup of soup
and the spoon gets hot to the touch?
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A. convection
B. conduction
C. temperature
D. radiation
1. Which kind of heat transfer takes place
when you put a spoon in a cup of soup
and the spoon gets hot to the touch?
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B. conduction
2. Which kind of heat transfer can
take place through space?
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A. radiation
B. conduction
C. convection
D. temperature
2. Which kind of heat transfer can
take place through space?
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A. radiation
3. Which kind of heat transfer causes
wind?
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A. radiation
B. conduction
C. temperature
D. convection
3. Which kind of heat transfer causes
wind?
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D. convection
4. When sand is heated by the sun,
which kind of heat transfer is this?
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A. conduction
B. temperature
C. radiation
D. convection
4. When sand is heated by the sun,
which kind of heat transfer is this?
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C. radiation