TEACHER NOTES
CHILDREN HAVE FELT THE HEAT OF THE SUN, HAVE FELT THE HEAT
INSIDE A CAR AND KNOW THAT THEIR BODY IS WARM.
Topic: HEAT
WHAT IS HEAT? Heat Is energy.
Heat moves in three different ways:
CONDUCTION, CONVECTION, AND RADIATION.
Conduction is heat transfer from molecule to molecule. If someone touches an ice
cube or hot plate they know because the heat is transferred from the warmer object to the
cooler object from molecule to molecule. Remember heat always travels from high
concentration to low concentration. If something feels cold, it is because the heat is going
from you to it.
Convection is heat transfer by a circulation of rising warm air(less dense) and
sinking cooler air (denser). In reality, the more dense air sinks forcing the less dense air
upward. We have all heard that warm air rises because it is less dense, but we sometimes
forget that moist air is less dense than dry air. This, simply put, is because the atomic
mass of a water molecule is 18amu and the mass of dry air is around 29amu, so warm
moist air forms convection currents better than warm dry air. This is also why the more
convective a cell or cloud becomes, the greater the chance it will produce hail and severe
weather. Convection is extremely important in the summer time along the eastern
Rockies and Plains states just east of the Rockies, as convection currents will build
thunderstorms that rise to above 50,000 ft in elevation. (Emphasize that the more dense
air forces the lighter air to rise. Don't just say "hot air goes up.")
Radiation is heat transferred by infrared waves. We have all felt the warmth of the
sun or heat from a camp fire without touching them. We also know that light colored
clothing reflects the heat and dark absorbs the heat. This is all due to infrared radiation or
radiant heat. We also know that on a summer day, the infrared gets in our car and heats it
up, but is absorbed inside the car and when you open the door, wow! It is hot!
Background
Heat moves in fluids through several processes, including convection. Convection is the
transfer of heat by the actual movement of the heated material.
Any substance that flows is considered a fluid. This includes such things as water,
shampoo, sunscreen, and even honey. Although not necessarily obvious, even gases, such
as air, can be classified as fluids.
Consider what happens to the water in a pot as it is heated over an open camp stove.
The water at the bottom of the pot heats up first. This causes it to expand. Since the
warmed water has a lower density than the water around it, it rises up through the cooler,
dense water. At the top of the pot, the water cools, increasing its density, which causes it
to sink back down to the bottom. This up and down movement eventually heats all of the
water. The continual cycling of the fluid is called a convection current.
Convection currents are found in many places and on many scales, from huge convection
currents in the atmosphere, oceans, and even in the earth's interior to smaller convection
currents found in a cup of hot cocoa or a fish tank. Meteorologists usually use
"convection" to refer to up and down motions of air. Heat gained by the lowest layer of
the atmosphere from radiation or conduction is most often transferred by convection
Learning Goals
Part 1
1. Students will understand that temperature changes can cause density changes in
water.
2. Students will be able to express that the same phenomenon happens in air.
3. Students will understand that temperature-driven density changes will produce
currents in a fluid medium.
What is heat? Heat is energy
Heat moves in three different ways: RADIATION, CONDUCTION, AND
CONVECTION.
Heat travels in waves like other forms of energy, and can change the matter it touches.
Heat can be released through a chemical reaction( such as the nuclear reaction that make
the sun burn.
Eg. A burning candle release light and heat waves
The sun releases all kinds of energy waves.

Grade level: 5 to 9

Time:
o
o
Part 1

Teacher introduction/instructions: 15 minutes

Student activity: 30 minutes
Part 2

Teacher instructions: 10 minutes

Student activity: 20 minutes
Part 1: Currents in Water
Materials

For the class:are okay

Pitchers or jugs for hot and cold water

Food coloring

Small container for food coloring (a small cup would work fine)

Medicine dropper or pipette

Four Styrofoam cups

Data sheet
Procedure
1. Tell the class that they will conduct several experiments to trace the currents
when water is not evenly heated.
o
In the first experiment, they will observe the movement of a drop of food
coloring in still water.
o
Then they will add a heat source and drop the food coloring in different
places in the saucer.
2. Place three styrofoam cups upside down on a piece of paper.
3. Place the plastic plant saucer on top of the cups as shown. The cups should be
near the outer edges of the saucer and evenly spaced.
4. Fill the plastic saucers three-quarters full with cool water. To make certain the
water is still, let it sit before the experiment. Be careful not to bump the desk or
table at any time during the experiment.
5. Using a dropper, slowly release a small amount of food coloring at the bottom of
the saucer of water. Slowly remove the dropper, taking care not to stir the water.
6. Observe and record on the data sheet what the drop does as it sits in the tray. Ask
students to draw what happens.
Variations
Repeat the experiment with the following variations. Ask students to record their
observations after each variation. Make certain they start each trial with a clean saucer of
water. Having several dump buckets placed around the classroom will be helpful.
For the following three trials, place a cup of hot water under the center of the saucer as
shown. Fill the cup almost to the top.
Trial A:
Place a
drop of
food
coloring
on the
bottom
of the
saucer in
the
center,
over the
cup of
hot
water.
Take
care not
to stir
the
water.
Trial B:
Place a
drop of
food
coloring
on the
bottom
of the
saucer
about
halfway
between
the
center
and the
side.
Take
care not
to stir
the
water.
Trial C:
Place
two
drops of
food
coloring
on the
bottom
of the
saucer,
one
halfway
between
the
center
and side
of the
saucer,
the other
in the
center.
Take
care not
to stir
the
water.
Observations and Questions
1. For each trial, ask students to draw their observations from an overhead view,
including an explanatory caption for each drawing. The drawings should show the
movement of the colored water (currents) and its relationship to the hot water or
heat source for convection.
2. Have students repeat the exercise, showing their observations from a side view.
3. What effect does the hot water in the center under the saucepan have upon the
currents?
4. What type of heat transfer is taking place? How do you know? (Convection is
occurring because we can observe the movement of the colored water within the
liquid. Convection transmits heat through the movement of molecules.)
Middle division activity.
Passing the ball- conduction
Student one is hot passes the ball to student two who then passes it to student 3 and so
on along the line to student 10.
This way of heat transfer from one student to another is called conduction.
Throwing the ball- Radiation
Student one could just throw the ball (heat) to student 10.
Radiation can occur across empty space.
Passing the ball- Convection
Student 1 could hold the ball (heat ) and walk with it along the line to student 10. At
each position a cold student change places with him.
This is like the rising of hot liquid and is called convection.