Physics Java Labs Physics Java Labs Before you start your lab report, it might be useful to look at a sample report. Lab: Phase Transitions Purpose of experiment: Here you can explore the phase diagram of water. We start the experiment with an unknown quantity of ice at at temperature of -50°C. By heating the sample and measuring the temperature repeatedly, you can see the response of water in all of its phases to heating. This experiment has two purposes: To explore, measure, and plot the phase disgram of water To determine the mass of the unknown quantity of water by comparing to the known values of the latent heats of melting and boiling, or to the specific heat capacity of water. Instructions for performing the experiment: Run the java applet by clicking this button: (It will open in a separate window). Please note: Each time you reload the applet, it will use a different quantity of water. So please be sure to complete all of your measurements before closing the applet window. However, you can use the START and STOP buttons in the applet as often as you want and thus reset the initial temperature and heat conditions without changing the mass of the water. In order to conduct your experiment, you need to first select a heating rate by clicking on one of the radio buttons on the heater below the bottle. Please note that the faster the heating rate you select, the larger the measurement errors will become. However, the smaller the heating rate is, the longer the experiment lasts. So you need to find a compromise that is acceptable to you. As you add heat, the total heat inserted into the calorimeter containing the unknown mass of water is displayed on the heater. In addition, the temperature of the H20 rises, as indicated by the green bar on the thermometer. You can measure the temperature by clicking on the thermometer at the upper end of that green bar. The result of your temperature measurement and heat measurement is then displayed in the text area on the right. (The displayed values include the measurement errors.) We recommend that you measure the temperature very frequently, every few seconds. Once the enclosed quantity of H20 has reached a temperature of approximatly 170°C, the heater shuts off automatically, and your run has ended. We suggest that you first perform a quick scan of the entire phase diagram with the maximum heating rate. You should not measure the temperature at this point, but just make rough notes on the pointswhere the temperature changes rapidly, and where it stays roughly constant. Then you can make another run for your measurements. (It is possible to adjust the heating rate during a given measurement, too!) Now it is time to plot your results. You can either export the data with copy and paste from the text area, or you can simply use the plot button provided by the applet. Generate a plot by using your favorite graphing program or by screen capture of the applet, and include it into your lab report. From the known values of the latent heats and specific heat capacities of the different phases of H20 you can now figure out the total mass of H20 contained in our calorimeter. Write this number down and explain how you came up with your answer. Also, try to give an estimate for the error in your answer. Finally, write the report with your favorite word processor or text editor and email it (as email attachment) back to the instructor. Help: If you are somewhat confused and don't really know how to extract the mass, here is an idealized sample plot and further explanations. © W. Bauer, 1999
