ï temperature sensor

ï base and support rod

ï beaker, 250 mL

ï beaker, 400 mL

ï Beral-type pipets, thin stem (6)

ï Bunsen burner

ï forceps

ï iron ring and wire gauze

ï apron and safety goggles

2. Follow all safety directives given by your teacher.

2. Connect the temperature sensor to Analog Channel A on the interface.

3. Open the Science Workshop document titled as shown;

ï Note: For quick reference, see the Experiment Notes window. To bring a display to the top, click on its window or select the name of the display from the list at the end of the Display menu. Change the Experiment Setup window by clicking on the "Zoom" box or the Restore button in the upper right hand corner of that window.

4. The "Sampling OptionsÖ" for this experiment are: Periodic Samples = Slow at 1 measurement per second and "Keyboard" sampling with Parameter = Volume Increase and Units = Drops.

1. Fill a 400 mL beaker three fourths full of water. Begin gently heating it to about 20 degrees above room temperature. Then stop heating. You can use the temperature sensor to periodically check its temperature. With the reduced Experiment Setup window selected, click the "MON" button and watch the Digits temperature display.

3. Take a clean, dry thin stem beral pipet and completely fill it with water.

4. To remove the last bit of air you can bend it in the shape of an upside down "U" with its tip under water. Gently squeeze the pipet until all the air is gone. Then with the tip still under water straighten out the beral pipet and let it completely fill with water.

5. Wipe off the outside, but do not blot any water out of the end of the pipet.

6. To determine the exact volume of a thin stem beral pipet, you will carefully count out the number of drops of water in your beral pipet.

ï It is a good idea to practice making uniformly sized drops before actually determining the volume of the pipet. You might also want to do this twice to be certain that you are getting fairly consistently sized drops and that you are counting accurately.

ï Throughout the experiment the same person should measure out all of the drops so that they remain uniform in size.

7. Record the volume of your empty beral pipet. This is the volume of air in an empty beral pipet at room temperature and pressure

1. When you are ready to begin recording data, click the "REC" button to begin data recording. The Keyboard Sampling window will open. Adjust its position on your screen.

2. Place the temperature sensor in the beaker of cold water. When the temperature has stabilized, type in "0" and click on the "Enter" button. The increase is zero since at room temperature there would be no increase in volume.

3. Place the temperature sensor in the hot water. (You should not be heating it at the present.) The temperature water should be about 20 degrees above that of the room temperature water.

4. Take a clean dry beral pipet. Hold it near its tip with a forceps. Be careful not to pinch the opening closed.

5. Submerge the bulb and most of the of the stem of the pipet in the warm water.

ï The stem can bend, but its tip must remain above the surface of the water and the stem cannot have any sharp folds that close off the air movement in and out of the bulb.

ï As the air in the beral pipet is heated it will expand and some will go out the tip of the pipet.

6. Wait a minute or two for the temperature and pressure of the air in the beral pipet to equilibrate. Then place your finger tip securely over the open end of the pipet.

7. Record the temperature of the hot water in your Data Table. Remove the covered beral pipet from the hot water bend it into the shape of an inverted "U" and place it in the beaker of room temperature water as shown in the diagram below.

8. Once it is submerged then you can release your finger from the tip of the beral pipet, but continue to hold it under water in the inverted position using your forceps. As the air inside cools, it will contract and the pressure inside the pipet will drop. Some of the room temperature water will be forced into the stem of the pipet.

9. Once the water level in the stem has stabilized, place your finger over the end of the pipet and remove it from the water. Quickly wipe off any water on your hands and the outside of the beral pipet. Take care not to blot any water out of the pipet itself.

10. Carefully count the number of drops that were forced up into the pipet when it was cooled. This equals the amount by which the volume of the air expanded at the higher temperature. If necessary heat your hot water slightly to maintain the recorded temperature.

11. Type in the number of drops by which the volume increased in the Keyboard Sampling dialog box. When the digital display reaches the recorded temperature, click on the "Enter" button.

13. Repeat the data recording procedure until you have at least 5 data points. Do not go above 80 C. when you are done, click on the "Stop Sampling" button to stop your data collection.

ï A calculator appears. To type in the formula for the total volume, click the "INPUT" menu button and select "Keyboard Input".

ï This selects the values you entered in Keyboard Sampling for the Volume Increase in drops.

2. Use the cursor to click on the "plus" button in the calculator. Then type in your total volume for the empty beral pipet.

3. Fill in the Calculation Name, Short Name, and Units as indicated. Finally click on the "=" button on the calculator.

ï You now have a formula for determining the total volume of air in the beral pipet. Your formula will have your volume of the empty pipet and not "124" as in the example.

4. Close the calculator window.

5. Click the Table display to bring it to the front. Click the "Add Column" menu button and choose Calculations, Total Volume from the menu.

ï Your table will display the Volume increase, the Temp (DegC), and the total Volume (Drops).

6. With the Table selected, click on the File menu from the menu bar and choose "Print Active Display" to print the Table.

7. Click the Graph to make it active. Click the "Plot Input" menu button and select the Calculator Input for the vertical axis.

8. Click on the "Input" menu button for the horizontal axis and select "Analog Sensor A, Temperature" from the Input menu.

9. Click on the axis labels to adjust the maximum and minimum values.

10. For the vertical axis set the minimum volume to 0 and the maximum to a value slightly bigger than your largest volume.

11. For the horizontal axis start with -400 and 100.

(Later you can fine tune it when you know where your V vs. T line intersects the temperature axis. Click on the Resize button in the upper right corner of the Graph window to enlarge your graph.)

12. To determine your estimate of Absolute Zero, click on the "Statistics" button in the lower left corner of the Graph window. Then click on the "Statistics" menu button which appears on the right. Select Curve Fit, Linear Fit from the Statistics menu. If you cannot see the point at which the line intersects the horizontal Temperature axis you can either change the minimum value for that axis or click on the Zoom out button in the lower right corner ( a circle with a minus sign in it.

ï The smaller the chi^2 value is, the better your linear fit.

13. Click on the "Smart Cursor" button then move the Smart Cursor to the point at which the V vs. T line intersects the Temperature axis. This temperature that corresponds to a volume of zero is your experimental value for Absolute Zero. Note the values at each point are displayed on the respective axes when you are using the Smart Cursor.

14. Record your experimental value for Absolute Zero.

Ý

2. What are some possible sources of error in this experiment and how could they have affected your results?