Name:
Class:
Date:
HEAT TRANSFER
1. Temperature
All particles of matter have kinetic energy. The faster the particles move, the more kinetic energy they
have. Temperature is a measurement of the average kinetic energy of the particles in an object
at a particular location. Three common scales for measuring temperature are the Fahrenheit, Celsius,
and Kelvin scales.
On the other hand, thermal energy is the total energy of ALL the particles in an object. To use an
analogy, imagine a crowd of people in a room. Temperature is like counting the average amount of money
each person has in his or her pocket. Thermal energy is like counting the total money that everyone in the
room has by adding it all up.
2. Heat
Heat occurs when thermal energy moves from one place to another when a temperature difference exists.
Heat always moves from a warmer location to a cooler location. Heat can be transferred by three
processes: conduction, convection, and radiation.
3. Conduction
Conduction is the process where heat is transferred from one particle to another by direct
contact. If you have ever picked up a cup of hot chocolate and it warmed your hands, you have
experienced conduction. Conduction occurs any time that objects at different temperatures are in contact.
When the particles meet, some of the kinetic energy of the particles in the warmer object is transferred to
the particles in the cooler object. As long as the objects are touching, conduction continues until the
temperatures of the objects are equal. Conduction occurs mainly in solids, but it can also occur between a
liquid and a solid.
A conductor is a material that conducts heat easily. Metals such as silver, copper or steel are good
conductors because they have a high density. This means that their particles are closely packed together.
An insulator is a material that does not conduct heat easily. Insulators such as wood, wool, paper,
straw, and cork are good insulators because they have a low density. This means that their particles are
loosely packed together, with space between them. Air is the best insulator, so any materials that can trap
air, such as Styrofoam or aerogel, are particularly good insulators.
4. Convection
Convection is the process where heat is transferred by the movement of large number of
particles in a fluid such as a liquid or a gas. Heated fluids are less dense than cooler fluids because the
particles in the fluid have expanded. This causes the heated fluids to rise. As the warmer fluid moves away,
cooler fluid takes its place. This flow of particles creates a circular motion called a convection current.
5. Radiation
Radiation is the transfer of thermal energy in the form of electromagnetic waves. Unlike
conduction and convection, radiation does not require matter, or particles, to transfer thermal energy. For
example, all of the sun’s thermal energy must travel through 150 million kilometers of empty space to reach
Earth. While the sun is our biggest single source of thermal radiation, all warm objects radiate heat to their
surroundings in some amount.
Different materials absorb heat radiation at different rates. The color of an object affects the amount of
radiation that is absorbed. Black or dark objects absorb thermal radiation better than light colored
objects. Black or dark objects also release thermal energy better than light or silvery objects. White or
silvery objects reflect thermal radiation best.
QUESTIONS: HEAT TRANSFER
1. Define “temperature”.
2. Define “heat”.
3. A full bathtub and a cup of water have the same temperature, but the bathtub has more thermal
energy. Explain why this is.
4. In what direction does thermal energy always travel?
5. Heat is transferred directly from one particle of matter to another by a process called
________________________.
6. A material that conducts heat well is called a(n) ____________________. A material that does not
conduct heat well is called a(n) ___________________.
7. Classify each of the following materials as either a conductor or an insulator by writing the correct term
on the line.
a.
air ____________________
b.
wool ____________________
c.
wood ____________________
d.
ceramic tile _______________
e.
iron ____________________
f.
glass ____________________
8. How is heat transferred by convection?
9. The circular motion of fluid caused by the rising and sinking of heated and cooled fluid is known as a(n)
________________________________________.
10. Is the statement true or false? Radiation requires matter to transfer thermal energy. ________
11. Two twin boys are playing outside on a hot, sunny day. One of the twin boys is wearing a black shirt
and the other, a white shirt. The twin in the black shirt feels hotter. Explain why.
12. Fill in the spaces in the table below by writing either conduction, convection, or radiation.
Heat Transfer Example
Type of Heat Transfer
a. A lake is heated by warm water coming out of a hot spring at
the bottom of the lake.
b. Sunlight melts a wax crayon left outside on a warm sunny day.
c.
A burner set on a hot stove heats the bottom of a pot.
d. The inside frame of your front door feels cold during the winter.
e. A kite rises high above a hot, sandy beach.
f.
You feel the warm glow from a fireplace when sitting by it.
13. When heat transfers from one substance to another, what happens to the temperature of the substance
giving off thermal energy and what happens to the temperature of the substance taking in heat energy?
14. An ice cube is placed in a cup of warm water. Why is it wrong to say that the warm water cools down
because the ice transfers its “coldness” to the water. What is actually happening?
Name:
Class:
Date:
REVIEW – CONDUCTION, CONVECTION & RADIATION
Instruction:
For each example below, circle which type of heat transfer best relates to what is being
described: conduction (cond), convection (conv), or radiation (rad)
1. The sun makes you
feel warm on a bright,
sunny day
COND
CONV
RAD
5. The handle of a pan
gets hot when it is on
the stove.
COND
CONV
RAD
9. A tin cup gets hot
when you pour coffee
into it.
COND
CONV
RAD
13. Solar panels are
normally painted
black.
COND
CONV
RAD
17. White is the best
color to wear on a
hot sunny day.
COND
CONV
RAD
21. An ice cube melts in
your hand.
COND
CONV
RAD
2. Meat is heated while
sitting on a hot frying
pan.
3. Transfer of heat by
the movement of
particles in a fluid.
4. Smoke and hot air go
up a chimney.
COND
COND
COND
CONV
RAD
CONV
RAD
CONV
RAD
6. The safest place to be
in a fire is low to the
floor.
7. Hot air balloons are
full of warmer air and
rise up.
8. The outside of a bowl
of soup gets hot.
COND
COND
COND
CONV
RAD
CONV
RAD
CONV
RAD
10. The roof of your car
gets hot in the sun.
11. Many kitchen pans
have plastic handles
that stay cool.
12. Transfer of heat
energy by direct
contact.
COND
COND
COND
CONV
RAD
CONV
RAD
CONV
RAD
14. You can cook a
marshmallow over a
campfire.
15. Transfer of heat by
electromagnetic
waves.
16. The outside of a pipe
gets hot when it
carries hot water.
COND
COND
COND
CONV
RAD
CONV
RAD
CONV
RAD
18. Heat is transferred in
oceans by water
currents.
19. You get warm
standing in front of a
glowing fireplace.
20. The top floor of a
house is warmer
than the 1st floor.
COND
COND
COND
CONV
RAD
CONV
RAD
CONV
RAD
22. Cats and dogs grow
thicker coats before
the winter.
23. Most coffee cups are
not made of metal.
24. The bottom of
expensive pans are
coated in copper.
COND
COND
COND
CONV
RAD
CONV
RAD
CONV
RAD