Upload
phoebe-pursley
View
218
Download
2
Tags:
Embed Size (px)
Citation preview
HEAT
What do you think thisphotograph shows?
ENERGY of HEATIt takes heat to shape glass or to
make a cup of tea.
Temperature measures how hot or
cold something is.
Energy moves between objects that
have different temperatures.
HEAT is energy that moves between
objects of different temperatures.
The difference in temperatures makes
the energy move back and forth.
Temperature is
measured in
different scales.
The two scales on
this thermometer are
CELSIUS
and
FAHRENHEIT.
Clothing traps heat near our body.
Water coming from a shower head is hotter than the air
around it.
Ice cubes melt as heat transfers to them from the
warm air.
Heat moves from the burner to the pan, to the water, and
then to vapor, to the air.
This is dry ice – frozen carbon dioxide.
It is about -80 degrees Celsius /
-112 degrees Fahrenheit
HEAT
on the
MOVE
Heat moves from your hand to the
snow and the snow melts.
Your hand feels cold.
Heat is CONDUCTED from the soup
to the spoon.
Soon the spoon feels hot.
CONDUCTIONConduction is the transfer or
movement of heat between two objects
that are touching.
Conduction can also occur within an
object. Heat moves from inside your body
to warm your skin.
Your feet and hands stay warm because
heat is moving all around your body.
CONVECTIONConvection is the transfer of heat
within a liquid or a gas.
Particles in liquids and gases move
more easily because they are farther
apart.
The particles take heat with them.
Heat from a campfire warms the air
around it by convection.
Hot air rises above the cooler air in the balloon.
That’s what keeps a hot-air balloon in flight.
Heat is conducted from the burner to
the pot and then to the water.Heated water travels up, warming
the cool water above.Cooler water sinks to the bottom,
where it gets heated.The cycle repeats – this is called
CONVECTION CURRENT.
FEELING RADIANT
Heat moves by conduction
between solids that are
touching.
Heat moves by convection
through gases and liquids.
Heat can also move as
RADIATION.
Radiation is the transfer of heat without matter to carry it.
Heat leaves one object and goes instantly to another.
Standing near a campfire
you feel the warm air, you
also feel the heat through
radiation.
Heat from the sun radiates through
space and through the atmosphere
before it warms your face.
Heat radiating from this light
keeps these chick eggs warm.
RADIATION is the transfer of heat
without matter to carry it.
Heat leaves one object and is
transferred on to the other.
Radiation is the most important way
heat can move.
Life on Earth needs heat from the sun.
But space is a vacuum.
How does heat travel through the
emptiness of space?
by RADIATION!
Heat moves through some
materials very easily.
Heat from an oven moves easily into
a pan. But heat from the pan did
not pass through the oven mitt.
A material that allows heat to
move through it easily is called a
conductor. Many heat conductors
also conduct electricity well.
Glass does not conduct heat well.
If you pour boiling water into a
metal bowl the outside of the bowl
quickly gets hot. A glass bowl
gets warm more slowly.
Boiling water
in glass cup.
Boiling water in
metal pot.
Marble or stone does not conduct
heat as well as metals do. But it
can still conduct heat away from
your body. That’s why marble
feels cool when you touch it.
Metals are great heat conductors.
Some metals conduct heat better
than others do.
For the most part, solids are better
conductors of heat than liquids or
gases are. That’s because the
particles that make up a solid are
packed closely together. They vibrate,
but they don’t move apart very
much. Heat can move quickly form
one particle to another.
Look carefully at this experiment.
What happened? Why?
Particles in the hot coffee have higher kinetic energy which transmits heat to the cup and ultimately to the air
surrounding the cup.
But not all materials are conductors.
Heat does not move easily through
some materials.
And it does not move at all through
other materials.
Materials that do not conduct
heat well are called
INSULATORS.
Oven mitts are insulators.
They are made of materials that are
poor conductors of heat. When you
remove a pan of cookies from the
oven, your hands don’t get burned.
Gases can be good insulators. A thin
layer of trapped air is an excellent
insulator. In cold weather, layers of
clothing trap your body heat near
you. There is air between the layers
of clothing. Along with the clothing,
the air insulates your body.
Insulators can be used to slow
down the movement of heat. Metal
wires conduct electricity and heat.
Most wires are covered in rubber
to insulate them and keep people
safe from the electricity and heat.
Hair is an Insulator
Most furry animals stay warm in
cold weather. Fur is made of thick
hairs. Around each hair is air. The
air and the fur act as insulators,
keeping the animals warm.
How does a thermos work?
A thermos has a glass lining.
This glass lining holds the cocoa or soup.
Glass is not a good conductor of heat.
Energy can even move in a vacuum. Using
a reflective silver surface act like a mirror.
It reflects some heat back.
There is a vacuum between the inner and outer
glass layers of the thermos bottle. The vacuum
keeps conduction or convection from taking
place. Using this system reduces conduction,
convection, and radiation.
The cocoa stays hot.
How can knowledge of insulation
help us conserve energy?
When the weather is hot,
you want to keep heat
from coming into your
home. When the
weather is cold,
you want to keep heat
from leaving your home.
It costs money to cool
and heat a home. Heat leavingthe home
There are different ways to slow the
flow of heat into or out of a house.
Some things need to be done while
the house is being built.
Others things can be done to an
existing home.
Insulating a home saves money.
It also helps conserve energy.
The number 1 thing that can be done
to conserve energy is insulation.
Insulation is blown inside the walls
of a house. Insulation keeps heat
from traveling through to the attic.
Insulation keeps heat from escaping
through the walls.
The next thing that you can use
to conserve energy is windows.
New windows have two
panes of glass to limit conduction.
They also have a special coating
that limits heat radiation.
Insulating pipes is another way to
conserve energy. Hot pipes radiate
heat from water into the air.
Wrapping the pipes keeps the
heat from escaping.
Soil is a great insulator.
Basements are usually cool, even
in the summer because soil covers
the sides of basement walls.
REVIEWWORD BANK – WORDS MAY BE USED MORE THAN ONCE
insulator conductor conduction convection radiation
Heat moves easily through it: _______________________________
Heat does not move easily through it: ________________________
Solids often do this to heat: ________________________________
A thin layer of trapped air can do this to heat: _________________
Which forms of heat transfer do insulated bottles prevent: ______
______________________________________________________
Wrapping hot water pipes prevent which form of heat transfer: ___
______________________________________________________
REVIEWWORD BANK - CONDUCTION CONVECTION RADIATION
Add hot water to bath ____________________________________
Space heater ____________________________________________
Iron-on decals ___________________________________________
Clothes dryer ____________________________________________
Sunlight through window _________________________________
Sandwich press __________________________________________