LABQUEST 2 DATA LOGGER

Transcription

1 Page 29 LABQUEST 2 DATA LOGGER OBJECTIVES: 1. To introduce the fundamentals of the use of the LabQuest 2 data logger. 2. To illustrate the use of Logger Pro graphing software to graph and analyze data collected with the LabQuest 2. ASSIGNED READING: Laboratory Exercises: Graphing INTRODUCTION: The LabQuest 2 data logger provides a versatile and portable device for collecting data in the chemistry laboratory. The LabQuest 2 is actually a handheld computer to which probes capable of measuring a variety of properties, e.g., temperature, pressure, light intensity, ph, etc., can be connected. The LabQuest 2 includes software capable of analyzing the data thus collected, but more comprehensive data analysis functions are available by transferring the data to a computer running the Logger Pro software introduced in the exercise on Graphing. The LabQuest 2 data logger/logger Pro graphing software combination provides a convenient and powerful system for collecting, examining, graphing, and analyzing data associated with a variety of experiments. When a solid salt is dissolved in water, heat may be given off (termed an exothermic process) or heat may be absorbed (termed an endothermic process). These two processes form the basis for portable hot- and cold-packs used, for example, by athletic trainers. In this exercise, you will use the LabQuest 2 data logger and Logger Pro graphing software to measure and analyze the heat of solution of a salt assigned by your instructor. PROCEDURE : I. Setting up the LabQuest 2 to collect data 1. Sign out a LabQuest 2, a mini-usb cable, and a stainless-steel temperature probe from the stockroom. 2. Turn on the LabQuest 2 unit (red power button on top. Wait until the unit has booted completely; be patient, this may take seven or eight seconds.

2 Page 30 LABQUEST a. The screen displayed will be the LabQuest 2 Application Meter screen, indicated by the meter icon on the left at the top. b. Notice, at the bottom of this screen there are three icons. The third one, which looks like a small battery, indicates the level to which the battery is currently charged (this is indicated in the picture at the bottom of page 29. If it shows only a small level of charge, go to the storeroom and either exchange your LabQuest 2 device or obtain an AC adapter which can be used to charge the battery of your original LabQuest 2 device. 3. If the Meter screen is not displayed, either press the HOME button, which is the middle button found on the right side of the LabQuest 2 unit, or use the stylus to tap the HOME icon on the menu bar at the bottom of the screen. 4. Connect a stainless-steel temperature probe to Channel 1 of the LabQuest 2. Note that the probe is automatically recognized and the current temperature displayed. 5. Along the right-hand edge of the screen, the default data collection parameters are displayed. For the temperature probe, the default Mode is Time Based. For this exercise, it will need to be changed. Tap the Mode box to bring up the Data Collection screen. Tap the at the top of the screen, then tap Events with Entry. Next, tap the Name box with the stylus and using the popup keypad enter the event name: Mass of Salt. Then, specify in the Units box: g. Be sure to check the Average over 10 seconds box. Finally, tap OK. You are now ready to begin data collection.

3 LABQUEST Page 31 II. Collecting Data 1. Place 50 ml of water in a Styrofoam cup. 2. Weigh out four separate g samples of the assigned salt. Weigh the samples on separate pieces of weighing paper. Label the papers Sample 1, Sample 2, Sample 3, and Sample 4. Record the mass of each sample (to two decimal places) in the first column of the table on page Tap the Graph icon at the top of the screen to switch to the Graph screen. Place the temperature probe in the water in the Styrofoam cup. Tap the Data Collection icon (left end of the menu bar at the bottom of the screen); the green arrow will change to a red box and a new KEEP icon will appear next to the data collection icon. Stir the water with the temperature probe and monitor the temperature displayed in the right-hand panel of the screen. When the temperature has stabilized, tap the Keep icon and wait 10 seconds for the temperature to be measured (the temperature will be measured once per second and the average of these 10 values will be reported). When the temperature measurement is completed, a new screen will appear and you will be prompted to Enter value for Event. Use the stylus and the keyboard at the bottom of the screen to enter the Total Mass of Salt Added, i.e. (0.00 g), and tap OK. The data point just collected will appear on the graph (you may see an additional point on the graph which represents the current temperature). 4. Add Sample 1 of your salt, stir with the temperature probe until the salt has completely dissolved and the temperature has stopped changing. Tap KEEP and wait for the average temperature to be measured. Use the keyboard and stylus to enter the Total Mass of Salt Added, i.e. the mass of Sample Repeat step 4 three more times, once for each of the remaining salt samples (Sample 2, Sample 3, and Sample 4). Add salt, stir until the salt has dissolved and the temperature has stabilized. Tap KEEP and wait for the temperature to be measured. Make sure that when you enter Total Mass of Salt Added, that you use the sum of the masses of all salt samples added to that point). 6. When all four samples of salt have been added and the data recorded, tap the Data Collection icon again; the red box will change back to a green arrow. 7. Tap the Table icon and copy the data from this table into the table on your Data Report Sheet. 8. Disconnect the temperature probe from the LabQuest 2. Do not turn the LabQuest 2 off. III. Printing Graph With Logger Pro 1. Take your LabQuest 2 to one of the lab computers. If the Logger Pro program is not running on the computer, start it by double clicking on the appropriate icon on the desktop. If Logger Pro is running with someone else s data, click File, New. If you are using a PC, the following screen will be presented: Do you want to save the changes you made to Untitled.cmbl? Click No. You should now have a blank data table and graph screen. If you are using a Mac computer, when you click File, New the following screen will be presented: Do you want to save the current file before closing? Click Don t Save. You should now have a blank data table and graph screen. 2. In order that the graph that you will be printing occupies as much of the page as possible, you will want to print it in landscape rather than in portrait mode. On the menu bar, click File, then Page Setup. Select Landscape icon as the orientation. You should also check to be sure that the proper printer has been selected (your instructor will tell you what printer to use). When done, click OK. 3. Connect your LabQuest 2 unit to the computer with the mini-usb cable provided (the small connector attaches to the LabQuest 2 and the large connector to the computer). The Logger Pro program should automatically detect the connected LabQuest 2 and the following image should appear on the LabQuest 2 screen:

4 Page 32 LABQUEST A Remote Data Available dialog box will open on the computer. Click Yes to the question asking you whether you want to retrieve data now. This will open a Retrieve Remote Data dialog box. Make certain the default option to Import remote data into the current session is checked. Also, make certain the box labeled LabQuest 2: make data available for multiple retrievals. is checked (this will allow you to conveniently import the same data into Logger Pro again if something goes wrong). Your data will now appear in Logger Pro with the data columns and graph axes labeled as you specified in the LabQuest 2 Application. (NOTE: In Logger Pro and most other computer software designed for analyzing measurements, the units for each quantity are given once, in the heading of the column, rather than being included in each cell with the individual measured values). 4. You will now need to format the graph as described in the Graphing exercise on page 23. Click on the graph to make it active. On the menu bar, click Options, then Graph Options. Click on the Graph Options tab. Confirm that the box labeled Point Symbols is checked, and that the box labeled Connect Points is unchecked. Enter an appropriate title for your graph. Finally, click Done or OK. 5. In principle, the change in temperature should be directly proportional to the mass of salt added, i.e., there should be a linear relation between the temperature and mass of salt added. On the tool bar, click on the Linear Fit button (the button has a diagonal red line superimposed on a blue curve). The line of best fit will appear on the graph along with a box containing the equation for this line (slope and intercept) as well as the goodness of fit parameters (correlation and RMSE). Position this box so that no data points are obscured (click anywhere inside the box and drag it to wherever you want it to appear). 6. Use the Analyze function of Logger Pro to determine the temperature that would have been expected after adding 3.75 g of salt. Click Interpolate on the drop-down menu. A vertical line will appear on your graph with a small circle where it crosses the line of best fit. The coordinates of the center of the circle will be displayed in a box on the graph. The position of this line can be moved by dragging the mouse. Drag the line until the Mass in the box is 3.75g. Read the corresponding value of Temperature in C. Record this value on your Data Report Sheet. 7. Obtain a copy of your data table and graph. To print your graph, use the Ctrl P command from the keyboard. In the Printing Options dialog box that appears, be sure that Print Footer is checked. Fill in your name, and then click OK. Now click OK again. Attach the printed data table and graph to your Data Report Sheet.

5 LABQUEST Page 33 Name Section Mass of Salt Samples (g) Total Mass of Salt Added (g) Temperature ( C) No salt added 0.00 g (Sample 1) g (Sample 1) g (Sample 2) g (Samples 1+2) g (Sample 3) g (Samples 1+2+3) g (Sample 4) g (Samples ) g Equation of line of best fit: M (slope): b (intercept): Fit parameters: Correlation: RMSE: What temperature would you expect to have observed after adding 3.75 g of salt?

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