liquidssolidsphasechanges - Chris Stanton November 30, 2006...

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Unformatted text preview: Chris Stanton November 30, 2006 Lab Report: Liquids, Solids, Phase Changes I. Introduction This experiment uses information about vapor pressures and phase diagrams to manipulate the temperatures and pressures of certain substances to examine them at different points. The first part of the experiment involves the boiling of water. Once the water is boiling, you can manipulate the temperature of the water to make it continue to boil even after it is removed from heat. The experiment also involves seeing the triple point of CO 2 by using solid carbon dioxide and watching as it simultaneously appears in all three phases. Eventually, since the CO 2 is held in a closed pipette, the pipette will burst because of the increasing pressure. This experiment also allows you to view the triple point of t-butanol by using a water aspirator. Here, just like in the CO 2 portion, the triple point is observed, but, in this case, there is simultaneous freezing and boiling of a liquid. Other experiments will allow you to calculate the boiling and freezing points for t- butanol. The last part of the experiment involves the molar enthalpy of vaporization of nitrogen. Using water and liquid nitrogen, a series of trials can be run to determine the enthalpy of vaporization of nitrogen. II. Experimental Procedure: Boiling Point of Water 1. Place 20 mL of distilled water in a 125 mL Florence flask, add three boiling chips, and begin to heat the water to boiling. 2. Once boiling has occurred for at least a minute, use crucible tongs to place a rubber stopper in the flask. Then remove the flask from heat and make sure the rubber stopper is secure. 3. By then holding the glass upside down and running cold water over it for 5 to 10 seconds, you can witness the water boil again. This occurs because as the pressure is coming down due to less evaporation, the cold water lowers the temperature so the boiling will actually occur again. III. Experimental Procedure: Triple Point of CO 2 1. This part was demonstrated by an instructor. 2. A Beral pipette is obtained and the tip is cut off. Pour 20 mL of cold tap water into a 100 mL beaker and then place this beaker inside of a 600 mL beaker. 3. Transfer 4 or 5 small chunks of pulverized dry ice into the pipette (approximately filling of the pipette bulb). 4. Fold the plastic tube of the pipette over a couple of times and seal it with a screw clamp. If there is not a good seal, gas will escape and the experiment will not operate correctly. 5. Pick up the pipette with crucible tongs and submerge it somewhat in the cold water. As the CO 2 warms, it should begin to liquefy, and the triple point will be seen (when the solid and liquid are in equilibrium with the vapor)....
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liquidssolidsphasechanges - Chris Stanton November 30, 2006...

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