Known Substance Naphthalene In A Test Tube example essay topic
454 words
Freezing Point of Naphthalene. Purpose To determine the freezing point of a known substance, naphthalene II. Materials ring stand gas source test tube test tube clamps thermometer naphthalene Bunsen burner goggles hose stopwatch. 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 90 o Celsius, stop heating.
6. Observe the change in temperature from 90 o to 70 o 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 70 o, melt the naphthalene which is now frozen to remove the thermometer. Properly dispose of the naphthalene liquid as instructed by the teacher.
IV. 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) / 80.1 oC) x 100 Percent Error = 1.4%VII. Conclusions In this lab, we heated the known substance naphthalene in a test tube to approximately 100 oC and observed its temperature while it cooled to approximately 70 oC. 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 79 oC. This results in 1.4% error when compared to the actual value for the freezing point of naphthalene, 80.1 oC. Considering the impurities in the consumer grade naphthalene, the interference of outside air on the temperature of the test tube and its contents, and the inaccuracy of 1/10 measurements on a thermometer graduated by whole numbers, the error we acquired in this lab was minimal and easily explained.
