By: Jordan Vlaminck
1. Obtain and wear goggles.
2. Prepare an ice-water bath.
4. Prepare a room water bath.
5. Prepare a hot water bath.
6. Prepare the Temperature Probe and Gas Pressure Sensor for data collection.
a.Plug the Gas Pressure Sensor into CH1 and the Temperature Probe into CH2 of the computer interface.
b.Obtain a rubber-stopper assembly with a piece of heavy-wall plastic tubing connected to one of its two valves. Attach the connector at the free end of the plastic tubing to the open stem of the Gas Pressure Sensor with a clockwise turn. Leave its two-way valve on the rubber stopper open (lined up with the valve stem as shown in Figure 2) until Step 9.
c.Insert the rubber-stopper assembly into a 125 mL Erlenmeyer flask. Important: Twist the stopper into the neck of the flask to ensure a tight fit.
d.Close the 2-way valve above the rubber stopper—do this by turning the valve handle so it is perpendicular with the valve stem itself (as shown in Figure 3). The air sample to be studied is now confined in the flask
7. Prepare the computer for data collection by opening the file “07 Pressure-Temperature” from the Chemistry with Computers folder of LoggerPro.
8. Click collect to begin data collection.
9. Collect pressure vs. temperature data for your gas sample:
a.Place the flask into the ice-water bath. Make sure the entire flask is covered (see
Figure 4). Stir.
b.Place the temperature probe into the ice-water bath.
c.When the pressure and temperature readings displayed in the meter stabilize, click keep. You have now saved the first pressure-temperature data pair.
10. Repeat the Step-9 procedure using the room-temperature bath.
11. Repeat the Step-9 procedure using the hot-water bath.
12. Click stop when you have finished collecting data. Turn off the hot plate. Record the pressure and temperature values in your data table, or, if directed by your instructor, print a copy of the table.
13. Examine your graph of pressure vs. temperature (°C). In order to determine if the relationship between pressure and temperature is direct or inverse, you must use an absolute temperature scale; that is, a temperature scale whose 0° point corresponds to absolute zero. We will use the Kelvin absolute temperature scale. Instead of manually adding 273 to each of the Celsius temperatures to obtain Kelvin values, you can create a new data column for Kelvin temperature.
a.Choose New Calculated Column from the Data menu.
b.Enter “Temp Kelvin” as the Name, “T Kelvin” as the Short Name, and “K” as the Unit. Enter the correct formula for the column into the Equation edit box. Type in “273+”. Then select “Temperature” from the Variables list. In the Equation edit box, you should now see displayed: 273+“Temperature”. Click done.
c. Click on the horizontal axis label and select “Temp Kelvin” to be displayed on the horizontal axis.
14. Decide if your graph of pressure vs. temperature (K) represents a direct or inverse relationship:
a.Click the Curve Fit button.
b.Choose your mathematical relationship from the list at the lower left. If you think the relationship is linear (or direct), use Linear. If you think the relationship represents a power, use Power. Click try fit.
c.A best-fit curve will be displayed on the graph. If you made the correct choice, the curve should match up well with the points. If the curve does not match up well, try a different mathematical function and click try fit again. When the curve has a good fit with the data points, then click ok.
d.Autoscale both axes from zero by double-clicking in the center of the graph to view Graph Options. Click the Axis Options tab, and select Autoscale from 0 for both axes.
15. Print a copy of the graph of pressure vs. temperature (K). The regression line should still be displayed on the graph. Enter your name(s) and the number of copies you want to print.
temp(C): 11---- 20.4 -------- 45.5
temp(K): 284.048-- 293.376------- 318.546
constant K: 0.322------- 0.32---------- 0.314