USING THE EA-100 DATA ANALYZER AND THE

USING THE EA-100 DATA ANALYZER AND THE FX-9850 GA PLUS CALCULATOR by Dr. James A. Roberts, Professor of Physics The University of North Texas Denton, Texas 76203

OBJECTIVE: This demonstration exercise is designed to show how heat is lost from a hot cup of water when it is placed in a room to cool. Two experiments are conducted, one with a simple cup of water and the second with a cup of water with a spoon placed in the water to act as a "radiator".

MATERIALS NEEDED 1. An EA-100 model data analyzer manufactured by Casio, Inc.
2. A graphing calculator, model CFX-9850 Ga Plus.
3. Connecting cables to connect the EA-100 into the graphing calculator.
4. A matching temperature probe for the EA-100 data analyzer.
5. About 100 cc of H2O to be heated.
6. A pyrex measuring cup.
7. A small spoon (metal). You may want to experiment with a pure silver or a stainless steel spoon to see if there is a difference in the rates of cooling. PROCEDURE: 1. Heat the water to about 95 deg C.
2. Place the thermometer probe in the water after it has been heated to near boiling, either in a microwave oven or by some other form of heating.
3. Set the rate of sampling of the EA-100 at 60 seconds and the number of samples to be taken at 200.
4. Start the data gathering with the EA-100 and relax for the next 30 minutes.
5. Transfer the data from the EA-100 to the model CFX-9850 graphing calculator. THOUGHT QUESTIONS 1. When the metallic conductor, spoon, is added does the rate of cooling appear to change?
2. Would a change of the composition of the container change the outcome of the experiment? If so how?
3. What effect do you think the surface area of the water would have on the rate of cooling?
4. What would be the effect of putting insulating materials around the container? ANALYSIS OF THE RESULTS The trend of the two curves is a measure of the rate of cooling for the system. You may expect some results to differ as you explore different surface areas, different composition containers, addition of insulating materials, etc. You may want to test some of these effects.
By conducting this experiment you should have a better understanding of how heat flows out of a reservoir. QUESTIONS 1. Do you expect the cup of water to cool at a faster rate if placed outside on a cold winter day than in a warm room?
2. Do you expect the rate to slow on a hot summer day?
3. Can you think of a general rule that would allow you to guess the nature of the cooling?
4. What factors do you think will affect the nature of the cooling?
5. Would salt water cool at a different rate than pure water? Dirty water? Impure water?

TABLE 1. A table of experimental data for a cup of water cooling without a spoon in it (TEMP 1) and with a spoon to increase the rate of cooling. (TEMP 2) Time is min and temperature is in degrees C.

TIME(MIN) T1 T2 TIME(MIN) T1 T2 TIME (MIN) T1 T2

1          90.4   93.1          13             67.8     67.3     25             54.4     53.5
2          95      95              14             66.1     65.7     26             53.5     52.8
3          90.9   90.9           15            64.7     64.3     27             52.8     51.9
4          87.9   87.5           16            63.5     63.1     28             52.1     51.2
5          84.6   84.2           17            62.2     61.6     29             51.4     50.3
6          82.1   81.4           18            61        60.4
7          79.3   78.7           19            60        59.4
8          77.1   76.5           20            59        58.2
9          75.3   74.4           21            58        57.3
10        73      72.5           22            57.1     56.3
11        71.3   70.5           23            56.1     55.3
12        69.5   68.8           24            55.3     54.4

Figure 1. Schematic set up for determining the cooling rates of a volume of heated water using the EA-100 data analyzer and the CFX-9850 Ga Plus graphing calculator by Casio, Inc.

Figure 2. A plot of raw data taken for a cup of water cooling without a spoon in it (square) and another plot of the same amount of water cooling with a spoon ("radiator") in it (triangle).

Figure 3. An expanded plot of raw data taken for a cup of water cooling without a spoon in it (square) and another plot of the same amount of water cooling with a spoon ("radiator") in it (triangle).