Freezing Point Depression Lab

The first part of the lab began by one lab member adding 10.0 mL of DI water to a test tube while another lab member obtained a beaker full of ice and salt. After both these steps were complete the test tube was put in the beaker full of ice. Immediately following the test tube be being placed in the beaker, a temperature probe was inserted into the test tube. The initial temperature was recorded and after the temperature was recorded in 30 second increments. Once the water exhibited supercooling and then remained consistent at .1 °C for 3 readings it was determined that the water had froze and formed crystals. Evidence that crystals formed allowed for it to be confirmed that the water actually hit freezing point at .0

The freezing point depression constant for water that was experimentally determined in this analysis was 0.0479 °C/m, which was derived from the slope of the trend line in Figure 4. This is significantly lower than the constant stated in the literature of 1.86 °C/m.1 The freezing point temperature determined via cryoscopy should have been much lower in the high sucrose concentration solutions.

pH was recorded every time 1.00 mL of NaOH was added to beaker. When the amount of NaOH added to the beaker was about 5.00 mL away from the expected end point, NaOH was added very slowly. Approximately 0.20 mL of NaOH was added until the pH made a jump. The pH was recorded until it reached ~12. This was repeated two more times. The pKa of each trial are determined using the graphs made on excel.

Through our data acquisition on day one our predicted values for the change in temperature of our NaCl solution in water was slightly off. This was most likely due to recording the freezing temperature sometime after the precise moment of the solution freezing. However, we predicted that as we doubled our concentration of NaCl in solution the freezing point depression would also double which is consistent with our results. Through our day one experiments we were able to better understand the ability of NaCl as a deicer by understanding how the freezing point depression changes based on concentration. We could further test these results by testing with different concentrations of NaCl.

After each of the solids were completely dry, each was placed into a MelTemp device. The temperature at which each solid began to melt and completed melting was recorded.

The freezing point constant (Kf) of water is 1.86 °C m-1. Each mass amount and Van’t Hoff factor was calculated then analyzed in a table.

The melting point of the final product, diphenylacetylene, was found to be 65-68 degrees Celsius which is right around the ideal 61 degrees Celsius melting point; this shows that purification during the lab worked and that the sample was almost 100% pure. Since only 0.01g of diphenylacetylene was collected and the theoretical yield was calculated to be 0.049g, this experiment had a 20.41% yield. A few sources of error that explain the low percentage could be the loss of crystals when transferred from the test tube to the suction apparatus or when they were transferred from the suction apparatus to the filter paper to be dried and then weighed. Crystals could have also been lost if more than 5 drops of methanol was added because excess methanol would dissolve the crystals. The experiment was successful when looking at the crystals collected from the addition step and the elimination step; however, to improve the percent yield and collected product the the test tubes could have been allowed to cool down in the ice bath past the 5 minutes to ensure all the crystals formed

Testable Question: Does the type of material placed on ice affect the rate in which the ice melts? Purpose: When it snows in the winter time or rains and freezes, what can we use to melt away the ice, snow, and sleet faster than salt, if there is anything that melts ice faster than salt. If there is something that can melt the frozen precipitations quickly, it will benefit us. Also, melting the ice at a faster rate will lower the rate of slips and falls even faster.

The topic is Chemistry of Making Ice-Cream: Lowering the Freezing Point of Water. In this experiment the scientist will be researching how to lower the freezing point of water using salt and/or sugar. The Independent Variable in this experiment is the solutes that the scientist uses which are, chemicals that dissolve in liquids. The Dependent Variable is the temperature/freezing points of the substances(°C). A constant is this experiment would be the use of salt and sugar and the control would be the pure water because it is important for determining the freezing point of the water in the experiment.

Purpose: The purpose of this laboratory was to gain an understanding of the differences between the freezing points of pure solvent to that of a solvent in a solution with a nonvolatile solute, and to compare the two.

In the experiment we did in science class what I observed was that when the water is added to the dry ice it automatically starts to make fog and then after a few minutes it started to boil. The water started to boil and then the dry ice dissolves completely into the water. Then the only thing that you can see is the bubbles in the water.

The purpose of this experiment is to identify an unknown substance by measuring the density and boiling point. I will be able to conclude which substance is my own from a list of known options stating what its real boiling point and density is.

The objectives of this lab are, as follows; to understand what occurs at the molecular level when a substance melts; to understand the primary purpose of melting point data; to demonstrate the technique for obtaining the melting point of an organic substance; and to explain the effect of impurities on the melting point of a substance. Through the experimentation of three substances, tetracosane, 1-tetradecanol and a mixture of the two, observations can be made in reference to melting point concerning polarity, molecular weight and purity of the substance. When comparing the two substances, it is evident that heavy molecule weight of tetracosane allowed

The specific property observed in this lab was the freezing point depression caused by the additives. This is the change in the freezing point between a standard solvent and said solvent with added solutes. This changes the entropy of the system, making the properties change somewhat, lowering the freezing point itself with the addition of more solute. Hence, the term ‘freezing point depression’.

temperature remains fairly constant will minimize uctuations in the rest of the data and optimize its accuracy. However, the longer the equilibration time the longer the simulation will take. Therefore an equilibration time of 700fs has been assigned. The coldest system has been used for this experiment. The colder the system the slower the atoms will move and thus the longer it will take for the polymer to reach its equilibrium state. Therefore the coldest system will give the largest equilibration time, meaning at any higher target temperature the system will take less long to equilibrate. This will ensure the data is accurate at all temperatures.