Flowing Heat
4th grade science experiment
Matt Weisenberger, matt@caer.uky.edu
University of Kentucky,
Center for Applied Energy Research
2540 Research Park Dr., Lexington, KY 40511
859-257-0322
Overview
• What is Heat?
• Three Experiments
– (1) Thermal Diffusivity
– (2) Thermal Expansion
– (3) Heat Capacity
• Procedure
•  Questions  Materials & Observations
•  Results & Conclusions
What are Heat &
Temperature?
• Heat is ENERGY
• The more heat-energy within a material,
the hotter it will feel.
• Heat always flows… from hotter areas to
cooler areas… not the reverse.
• Temperature is a measurement of the
amount of heat within a material.
• Materials that feel hot have a lot of heat
in them. You feel that heat flowing into
your cool hand.
Experiment 1:
Thermal Diffusivity
– What is thermal diffusivity?
– Through which materials does heat flow
faster?
Answer
Thermal diffusivity tells us how fast heat
is conducted through a material.
Materials such as copper and steel
conduct heat faster than materials such
as wood and plastic.
Experiment 1: Materials
1. Hot plate
2. Rods of copper, glass, and
graphite (about 2 in. long X 3/8
in. diameter)
3. Paraffin wax
Procedure
1. Stand three rods, made of different
materials, with the exact same length
(approx. 2 in. long) on a hot plate.
2. Turn the hot plate on “high.”
3. Place a small sliver of wax on the top
surface of the rods and watch to see
which rod melts the wax the fastest
and which one the slowest.
– The material upon which the wax melts
first has the highest thermal
diffusivity.
– The material upon which the wax melts
second has the second highest thermal
diffusivity, etc.
Observations
Copper
wax melts 2nd
Graphite
wax melts 1st
Glass
wax melts 3rd
Results & Conclusions
• Graphite had the highest
thermal diffusivity.
• Copper had the 2nd highest
thermal diffusivity.
• Glass had the lowest thermal
diffusivity.
Experiment 2.
Thermal Expansion
– What is thermal expansion?
– Which materials expand more?
• Answers
Heat-energy causes the atoms of a
material to vibrate. As they
vibrate, they push each other
apart. This causes the material to
expand.
Experiment 2: Materials
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Metal Tubing:
- copper: 8 ft long, about ¼ inch diameter, bendable
- aluminum: 8 ft long, about ¼ inch diameter
Toothpicks (2)
Colored tape
Funnel
Rubber hose with hose clamps (6 in. long with a
diameter that will fit snugly around tubing)
Laboratory ring stand with clamp
Wood blocks (about 2 in X 2 in X 2 in)
Source of hot water
Pitcher full of ice water
Hot water vessel such as a teapot, coffee pot,
etc.
Bucket
Experiment 2: Procedure
1.
2.
3.
4.
5.
6.
Approximately 18 inches from one end, bend
each tube 90º (see photo on slide 12).
Rest the other end on a wooden block (see
photo).
Vertically support the bent end using the
laboratory ring stand (see photo).
Attach a funnel to the supported end using
the rubber hose and clamp (see photo on slide
13).
Make several “toothpick flags” by wrapping a
piece of colored tape around a toothpick so
that it resembles a small flag (see photo on
slide 14).
Place the toothpick end of the flag between
the metal tube and wooden block (see slide 14
photo).
Experiment 2: Procedure
7. Place the hot water vessel onto the hot
plate and bring to a boil.
8. Place a bucket beneath the straight end
of the copper tube.
9. While the students are looking at the
toothpick flag, pour some boiling water
into the funnel and observe the amount
and direction that the flag spins.
10. Next, pour the ice water into the funnel
and observe the flag spinning in the
opposite direction.
11. Repeat steps 8 – 10 with the aluminum
tube.
Metal Tube Assembly
Funnel Assembly
Close-Up of “Toothpick Flag”
Conclusions
●The more the flag spins, the
greater the thermal expansion
of the metal tube, thus:
1. Aluminum has the highest
thermal expansion
2. Copper has the least thermal
expansion
Helpful Hints &
Observations
• Keep students away from the
funnel and bucket when pouring
the boiling water!
• It is helpful to put the tube
assembly on a long table.
• When watching the flag spin,
make a note of how many
revolutions it spins.
Experiment 3.
Heat Capacity
• Questions
– What is heat capacity?
• Answer
The amount of heat-energy
necessary to raise the
temperature of 1g of a material
1ºC.
Experiment 3: Materials
1.
2.
3.
4.
5.
6.
7.
Hot Plate
Beaker or pan that can be used to boil
water
Metal tongs
Rods or cylinders of copper, plastic,
and graphite (approx. 1 in. diameter X 1
in. long)
Glass beakers (150 ml capacity)
Thermometer or thermocouple
Stopwatch (or ordinary watch that can
measure seconds)
Procedure
1. Weigh three rods, of exactly the same
size, made of plastic, graphite, and copper
and heat to 100ºC in boiling water.
2. Using tongs or tweezers drop one of the
materials into 100ml of water that is at
room temperature.
3. Measure the temperature increase of the
water for 1 minute.
– The material which most heats the
water has the highest heat capacity.
4. Repeat for the other two materials.
Conclusions
• The Plastic has the highest heat
capacity.
• The graphite has the 2nd
highest heat capacity.
• The copper has the lowest heat
capacity.
Helpful Hints &
Observations
• Thermocouples work best, but if
using a thermometer get one that
can accurately measure small
temperature changes.
Heat Flow in Action
Questions
– How do thermal diffusivity, thermal expansion,
and heat capacity work together? -- Thermal
conductivity
– What is thermal conductivity?
Answers
– The three heat experiments show how heat flow
affects materials.
– The thermal conductivity is related to all three
of the above and is a number that characterizes
the speed at which, heat-energy flows through a
material of constant area when one end is at a
high temperature and the other is at a lower
temperature.
Resources
Materials for most of these
experiments can be purchased
from hardware stores and
scientific equipment suppliers
such as Fisher Scientific and
Ward’s. Another excellent
source is McMaster Carr
(www.macmaster.com)