Freezing Point Depression Lab

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Introduction The objectives in this laboratory were to be able to calculate the freezing point depression among three trials of unknowns, be able to correctly measure the freezing points of p-xylene, and to be able to calculate the molar masses of the unknowns by found freezing point depression values. This was done to be able to understand and apply a concept names supercooling. Supercooling is when a liquid is put far under its original freezing point and remains a liquid or gas. This happens when a substance is cooled so quickly that it’s easier for it to stay a liquid than to crystalize, until it reached its nucleation point and begins to heat up returning to its freezing point (image 4). The supercooling of p-xylene was observed in three …show more content…

With time (t) on the x-axis and temperature (Celsius) on the y-axis, the exponential change could be easily observed. At the beginning of the laboratory the masses of the combined polypropylene test tube and 100 mL beaker were recorded by a digital electronic scale. A dry polypropylene test tube was obtained and approximately 2 mL of p-xylene was squirted into it with the use of a pipette. This was added to the beaker and weighed. 10 drops of toluene was then added and weighed again. The polypropylene test tube, which now contained 10 mL of p-xylene and 10 drops toluene was removed from the beaker and placed into a replica 100 mL beaker which was halfway filled with an ice water mixture. The temperature sensor, which was connected to the microlab application was placed inside of the polypropylene test tube and stirred rapidly around the outskirts of the bottom of the polypropylene test tube. The mixture began freezing, giving off an icy slush complex. Once the temperature appeared to have reached the nucleation point and leveled out at its freezing point, the application was stopped. This value was recorded in the laboratory manual. The temperature sensor was rinsed off then wiped, the beaker was re-filled with ice, and the test tube was put into the test tube rack to be thawed. Once thawed, this was discarded into the waste bin

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