1. Purpose of this Minilab
Learn about and determine the coefficient of thermal expansion.
Determine the lowest possible temperature (absolute zero).

2. Thermal Expansion in one Dimension (Length Change)
change in temperature
change in length
initial length
coefficient of thermal expansion (depends on the material)

3. Thermal Expansion Apparatus
length gauge
Thermistor
(resistance depends on temperature)
3 different
metal tubes

4. Inserting the Metal Tube
Gauge
pin
Angle
bracket
Attach thermistor.
Tighten screw.
Insert metal pin
as shown.
Tighten screw.

5. Cover Thermistor with Insulation, Attach DMM.

6. Thermistor Thermistor has resistance that changes with temperature.
Conversion scale is on the thermal expansion apparatus.
You need to interpolate to get temperature for values in between
those that are listed.
Interpolation procedure is shown in manual.

7. Steam Generator ( Change Temperature of Metal Rod)
Rubber hose goes to metal
rod.
Second
outlet
should be
plugged.
Remove
plug and
fill in
sufficient
amount of
water.
Dial lets you change the amount of
steam generated.

8. Steam from
steam
generator
Put small cup here
to catch condensed
water.
Lift this end up so that condensed water
runs out the other end of the metal rod.

9. Measurement
Set gauge to “zero” at room temperature.
Start steam generator.
Watch resistance (to monitor temperature) and length expansion.
Record highest temperature (lowest resistance) measured.
Record maximum expansion measured.
Calculate the coefficient of thermal expansion.
Note: Due to time delays relating to thermal conduction the
highest temperature and the largest expansion may not happen
exactly at the same time.

10. Absolute Zero Temperature
For ideal gases (gases at low pressure)
Pressure
Temperature
(in degrees Kelvin)
Volume
Universal gas constant
Amount of gas in moles

11. Absolute Zero Temperature
The ideal gas law implies:
As the gas is cooled more and more, the pressure sinks
(if the volume of gas and the amount of gas is kept constant).
 For P = 0 the lowest possible temperature is reached.

12. Estimating Absolut Zero Temperature
Keep volume of gas constant.
Keep amount of gas constant.
The P versus T graph is a straight line with slope nR/V.
Plot T in degrees Celsius.
Determine lowest possible T in Celsius.
Determine the uncertainty in lowest T. P T
Measuring at least
two points lets
you extrapolate to
P=0.

13. Determining the Pressure of the Gas Inside the Sphere
Gauge Pressure = Pressure inside the sphere – Pressure outside the sphere
Read gauge
Measure with barometer
Varying the Temperature of the Gas in the Sphere
Dip the sphere into boiling water (to get approx. 100 Celcius).
Dip the sphere into ice water (to get approximately 0 Celcius).
Use the same sphere at different temperatures.
(the amount of gas in different spheres may not be the same).

14. Estimating the Uncertainty in Lowest TP T
Possible range of lowest
temperature.