For point 1 put the probe in an ice water bath and

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Unformatted text preview: repeat the procedure for point 2 using a warmed or cooled beaker. To use melting and boiling points, we take advantage of the fact that water freezes at 0o C, and boils at 100o C. For point 1, put the probe in an ice-water bath, and after it has a minute or so to equilibrate, type “0” in for the point and click “set.” Do the same for point 2 in the boiling water, only type in “100” before clicking “set.” This method is not as accurate as the former, because for these values to be true, the water must be absolutely pure, and the pressure must be exactly 760 torr; any deviation will result in slightly lower melting and slightly higher boiling points. Once calibration is complete, be sure to press “OK” rather than “cancel.” Automatic Data Collection If you have not opened it yet (or you have closed it), open the “Setup” dialog box. For most probes, you will see “Sample Rate” followed by a number and a pull-down menu. This is for automated data collection. If “Hz” is in the pull-down menu, this means “per second.” For example, the temperature probe defaults to 2 Hz; this means that Pasco will collect 2 data points every second, or one data point Dakota State University Page 19 of 232 Using the Pasco System General Chemistry I and II Lab Manual every 0.5 seconds. If it were at 10 Hz (which you can change by pressing the “+” and “- ” icons after the pull-down menu), then there would be 10 data points per second, or one data point every 1/10th of a second. Sometimes you want this kind of rapid data collection, but usually it serves to do nothing but sop up valuable hard drive space and slow down your computer. Think about what it is you are measuring, and decide on how rapidly you wo uld like the data points to be taken. For example, if I wanted to measure the temperature under my armpit, I don’t need a temperature update every 0.5 seconds; instead, maybe I’ll choose 10 seconds instead, that is, one new date point every 10 seconds. So, I will go to the pull-down menu, and choose “seconds” rather than “Hz.” Then I will click “+” until I get to 10. Once I close the window, Pasco will remember my choices. Choosing displays Now, there are a variety of ways we can view the data as we are collecting it. The default is usually to bring up a graph, which I usually like to keep. Other options include Digits (my other usual choice), FFT (for “Fast Fourier Transform”; we usually will not use this), Histogram, Meter, Scope, Sound Analyzer, Sound Creator, Table (another common favorite) and Workbook. You will see these to the left of the screen near the bottom (if not, click on the “Displays” tab on the left near the bottom). For our armpit experiment, I want to see the digits, and keep a table of the data, so I will click and drag the digits icon and the table icon onto the view screen. For each of these displays, I recommend playing with the options so you can see what they can do. At this point, if you press “Start” you will see that Pasco begins taking data at the rate of 1 point...
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This note was uploaded on 09/18/2012 for the course CHEMISTRY 1010 taught by Professor Kumar during the Fall '11 term at WPI.

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