Chemical Reactions and Temperature Investigation

My group's hypothesis was that due to greater energy in the heated water, the alka-seltzer would dissolve at a quicker rate, followed by the room temperature water and finally the chilled water.

For our test of the hot water, the initial room temperature was 24.5 degrees C. We set up the beaker and plugged in the hot plate. The tempe rature in the water immediately started to climb. After a few minutes, the water temperature had gotten to 55 degrees C, but we had forgotten to grab our tongs, so we took the water off the burner and let it return to 50 C. As soon as we dropped the alka-seltzer tablet into the hot water it began to fizz and dissolve. The tab floated on the surface, probably suspended by vapor releasing from the water. The tablet had completely disappeared 22.46 seconds into the experiment. After the alka-seltzer dissolved, the temperature in the water was 48.9 degrees C.



For the room temperature test, we didn't need to do anything more than measure the initial temperature of the water prior to the reaction. It measured 25.3 degrees C. Once the alka-seltzer was added, the temperature actually started to decrease, dropping to 24.9 degrees by the end of the experiment. The tablet visibly took longer to dissolve than in the heated reaction. In addition, the tablet sank directly to the bottom of the beaker in this experiment. In the end, it took 36.4 seconds for the alka-seltzer to dissipate.



In the final test, we added ice cubes to half the mount of water we had used in our previous two tests. We stirred well, until the ice had melted slightly into the water. Our thermometer measured the water temperature at 1 degree C before we added the tablet. Once the alka-seltzer had been introduced, a pattern became clear among the experiments. This reaction was by far the slowest of all. Like the room temperature test, the tablet sank to the bottom of the beaker. The alka-seltzer didn't fully dissolve until 2 minutes and 8 seconds after the start of the test. The tablet raised the water's temperature to 1.3 degrees C. The pattern shown by the three experiments was that the warmer the solvent, the faster the reaction. This is because there is more energy in hot materials, and more energy makes things happen more quickly.



Our hypothesis was supported. The hottest water dissolved the water the fastest, because it had more energy than any of the other test samples. Only the heated water made the tablet float, because it as creating more vapor that rose to the surface and carried the alka-seltzer with it. Two errors that may have occurred would have been in our heated test. Fist, we overheated our beaker at first, so we had to wait for he temperature to come back down to 50 degrees C. Also, we didn't follow the directions correctly and took out our thermometer before the experiment occurred. This may have lead to an inaccurate measurement for the ending temperature of that test. We corrected this mistake through the rest of the testing session.