Tuesday, September 3, 2019
Freezing Point Of Naphthalene :: essays research papers
Freezing Point of Naphthalene I.     Purpose      To determine the freezing point of a known substance, naphthalene II.     Materials      ringstand                    gas source      test tube                    test tube clamps thermometer naphthalene Bunsen burner goggles      hose                         stopwatch III.     Procedure      1.     Assemble the Bunsen burner, attaching one end of the hose to the burner and the           other to a gas source.      2.     Assemble the ring stand so that a ring clamp is attached to the stand holding the           test tube that will be used in the experiment.      3.     Fill the test tube to approximately 1/8 capacity with naphthalene crystals.      4.      Place the thermometer in the crystals so that it is surrounded by the naphthalene           powder but not touching the sides or bottom of the test tube. Use a clamp to hold           the thermometer in place.      5.      Ignite the Bunsen burner and using direct heat melt the naphthalene powder until           it completely turns to a liquid. When the temperature reaches approximately 90o           Celsius, stop heating.      6.     Observe the change in temperature from 90o to 70o Celsius, recording the           temperature at regular intervals, preferably 15 seconds. This data will be used to           make a chart later.      7.     Once the temperature has fallen to 70o, melt the naphthalene which is now           frozen      to remove the thermometer. Properly dispose of the naphthalene liquid as           instructed by the teacher. IV.     Data      Time Elapsed          Temperature of Naphthalene          Time      Temperature      Initial (0:00)          100oC                         7:00      78.5oC      0:30               97.5oC                         7:15      78.3oC      1:00               93.0oC                         7:30      78.3oC      1:30               89.5oC                         7:45      79.0oC      2:00               86.1oC                         8:00      79.0oC      2:30               84.6oC                         8:15      79.0oC      2:45               82.3oC                         8:30      79.0oC      3:00               81.2oC                         8:45      79.0oC      3:15               81.0oC                         9:00      79.0oC      3:30               80.5oC                         9:15      78.5oC      3:45               80.2oC                         9:30      78.1oC      4:00               80.0oC                         9:45      78.0oC      4:15               79.9oC                         10:00      78.0oC      4:30               79.8oC                         10:15      77.5oC      4:45               79.4oC                         10:30      77.0oC      5:00               79.1oC                         10:45      76.5oC      5:15               79.1oC                         11:00      76.0oC      5:30               79.0oC                         11:15      75.2oC      5:45               78.9oC                         11:30      73.8oC      6:00               78.8oC                         11:45      73.0oC      6:25               78.8oC                         12:00      72.1oC      6:30               78.7oC                         12:15      71.1oC      6:45               78.6oC                         12:30      70.3oC V.     Graph      (See following pages) VI.     Calculations      Using 80.1 oC as the theoretical value for the freezing point of naphthalene, we can now      determine percent error.      Percent Error = ((Theoretical - Experimental) / Theoretical) x 100      Percent Error = ((80.1 oC - 79.0 oC) / 80.1oC) x 100      Percent Error = 1.4% VII.     Conclusions      In this lab, we heated the known substance naphthalene in a test tube to approximately 100oC and observed its temperature while it cooled to approximately 70oC. Over a time period of 12 minutes and 30 seconds, we recorded the temperature at regular 15 second intervals, and, with this data, constructed a chart showing the general curve. Upon inspection of the graph and our data chart, we found the experimental freezing point of naphthalene to be around 79oC.
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