Graeme+N+sf

Depressing Freezing Point

__Problem:__ What substances make the best depressant of freezing point for water?

__Hypothesis:__ If salt (solute) is added to the water (solvent), then the solution's new freezing point will be depressed the most.

__Procedure:__ 1.) Prepare ice bath, and fill beaker with 200 ml of water.  2.) Add 1/2 tsp. of solute to water, to create new solution, and mix thoroughly, until substance is completely dissolved. Place into ice bath, and place thermometer inside of solution.  3.) Wait until solution begins to freeze, and record temperature at which this occurs. Place in table. 4.) Empty solution into safe disposal spot, and repeat process with the following increments of substance- 1 tsp., 1 1/2 tsp., 2 tsp.  5.) Repeat all steps with all substances being tested.

__Materials:__ - beaker (able to hold 200 ml)  - access to ice and water  - sugar - salt  - baking soda - large glass bowl - thermometer - stirring rod - (optional) graduated cylinder to accurately measure amount of water

<span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 110%; text-align: left;">__Abstract:__ <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**Objective-** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;"> The objective of the experiment was to determine which substance lowered the freezing point of water the most. The freezing point of a liquid is the temperature at which the liquid changes states of matter, from a liquid to a solid. I hypothesized that if salt was added to the water, then the water’s freezing point would be the lowest.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**Procedure/Materials-** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;"> The substances tested in the experiment were salt, sugar, baking soda, and alcohol. The controls groups were pure water, and antifreeze. Various amounts of the substances were added to the 200 ml of water, which were then submerged in a beaker of ice cold water after being properly mixed.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**Results-** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;"> According to the data, salt proved to be the best substance to lower the freezing point of water. Salt, in all increments it was applied to in the experiment, had significantly lowered the freezing point below that which the other solutions did, proving it to be the best substance for the objective.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**Conclusion-** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;"> As stated in my hypothesis, I believed that salt would be the best substance to depress water’s freezing point. The experimental data supported my hypothesis, establishing salt as the best freezing point depressant tested. This means that out of the three substances tested, it lowered the freezing point the most, which would cause water to stay as a liquid for a longer period when dropping in temperature. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;"> The data from the experiment can be applied to one very important aspect of winter life, the removal of ice from streets and sidewalks. Ice, as most know, melts when it reaches, and warms past its melting point. If the melting point were to be lowered in a stable, arctic environment, the ice could potentially melt without the natural temperature needing to lower. Thus, various substances, i.e. the substances tested, can be spread on the ice to depress its freezing point and cause it to melt. Salt is already used across the world to do just that, which is the best decision in substance, as proven by the experiment’s data.

<span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 110%; text-align: left;">__Experimental Background:__ The topic explored in this project was freezing point depression. The project explored the problem of which substances were the best for lowering water’s freezing point. Salt is the substance of choice for doing so, but many other substances have the ability to depress freezing point. My hypothesis was that if salt was added to the water, then the lowest freezing point would be achieved, showing the most freezing point depression. The independent variable in the experiment is various substances that will be tested, sugar, salt, and baking soda. The dependent variable in the experiment is freezing point of the new solution, or the margin of freezing point depression. The control groups for the experiment are water and antifreeze. For the experiment, the various substances will be mixed with 200 ml of water in various increments, and then submerged in an ice bath, where they will sit until they freeze. The temperature at which they froze were recorded, and organized into multiple tables and graphs, after being compiled and averaged. The equipment used, a large glass container, a small beaker, a graduated cylinder, a thermometer, a stirring rod, and a 3 small containers, were very basic equipment used for science. The thermometer was borrowed from a friend who owned many pieces of chemistry equipment. <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 110%; text-align: left;"> Water is a chemical substance with the chemical formula of H20. It is a molecule consisting of one oxygen atom, and two hydrogen molecules, that have been connected by covalent bonds. It is a liquid at ambient conditions, but it is found on Earth in both a gaseous form, water vapor, and a solid form, as ice. Water is transparent in the visible electromagnetic spectrum. Water carries a slightly negative charge because it is not linear, and the oxygen atom has higher electro negativity than hydrogen atoms. Water is a good solvent, and is often referred to as the universal solvent. Some substances that dissolve in water include salts, sugars, acids, alkalis, and some gases such as oxygen, and carbon dioxide. All major components of cells are also dissolved in water. The boiling point of water is dependent on the barometric pressure. So, depending on what the air pressure is that the water is presently in, so water boils at a different temperature at the top of Mt. Everest than it does at the bottom of the ocean. The lower the air pressure, the lower the temperature it takes to boil water, as all liquids.Freezing-point depression describes the phenomenon in which the freezing point of a liquid is lowered when another substance or compound is added, so the solution that is made had a lower freezing point than the pure solvent. This can be observed in an example of salt water and pure water. Salt water, because it is a solvent that has been mixed with salt, has a lower freezing point than pure water, which is why our oceans do not freeze at 32 degrees, where pure water would freeze and become ice. Using this information, freezing-point depression has been applied to our daily lives, in order to avoid freezing. Take driving in the winter time on ice as an example. As we all I know, driving on ice can be very dangerous. In order to clear up roads and sidewalks, salt is applied to the icy roads to make the ice melt by lowering the freezing temperature. In car engines, antifreeze, a form of ethylene glycol, is added to keep the cooling water from freezing, which allows the engine to continue working without the threat of overheating. Freezing-point depression can be measured using a formula that measures a solvent’s and solute’s polar mass, and the difference between the two.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">__Log Book:__ -11/14/11- Borrowed thermometer from friend. GN <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;"> -11/15/11- Collected all materials, compiled them in stash. GN <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">-11/17/11- Ran salt experiment, recorded all data in tables, did not put into graphs. GN <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">-11/23/11- Ran sugar experiment, recorded data, no graph. GN <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">-11/24/11- Ran baking soda experiment, recorded data, no graph. GN <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">-12/27/11- Began compiling data, averaging, and creating graphs. GN <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">-12/28/11- Wrote parts of project, including abstract, experimental background, and parts of experiment. GN <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">-12/5/11- Finished nearly all writing portions of project. Had trouble attaching pictures to Wiki, looking for alternative. GN <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 110%; text-align: left;"> __Experimental Results:__ - Figure 1

- Figure 2

Figure 3

Figure 4 Figure 5 Figure 6

__Pictures__:
Figure 7- Stirring until solute is fully dissolved is crucial to the accuracy of the experiment. Properly breaking down and mixing the solute into the solvent will create the proper solution to be tested.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">__Discussion:__ The experiment tested the difference in freezing point of various solutions with ranging substances and increments of those substances, to determine the substance that best depressed the freezing point. The hypothesis of the experiment was, //if salt (solute) is added to water (solvent), then the solution's new freezing point will be the most depressed.// After compiling, averaging, and reviewing the data, I established that salt was indeed the best substance to depress freezing point, which supported my hypothesis fully. In all trials with varying increments of the substance, saltwater solution was consistently lower in freezing point temp., and when averaged, was also lower in all trials. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">In the first set of trials, with 1/2 tsp. of a substance being added to water, salt was consistently lower than the other two substances. Both baking soda, and sugar were flatlined at 32 degrees F, showing no immediate effect on the freezing point. (Figures 4&5) However, salt showed some effect on the freezing point, dropping the freezing point around 31 degrees F on three occasions during the several trials conducted. (Figure 3) In the second set of trials, with a whole tsp. of a substance being added to the water, salt was again the best depressant. The salt showed more consistency during these trials, dropping the freezing point to 31 degrees F for most tests, with very small amounts of fluctuation. (Figures 3) It is really starting to separate itself from the other two substances starting in this trial. Baking soda showed more life in this trial, especially compared to the sugar. Baking soda dropped to 31 degrees on multiple occasions, and sugar only dropped to 31 degrees three times. (Figures 4&5) Baking soda seems to be separating itself from sugar at this stage in the experiment. The third trials, which had 1 1/2 tsp. of a substance added to the water, showed more proof of my hypothesis, and proving some of my previous predictions false. Salt reigns supreme in these trials, dropping below 30 degrees, which the other two substances have barely scratched, as seen on Figures 3-5. Also, baking soda has fallen back into rhythm with sugar, and is now showing similar results. shattering my prediction that baking powder would be a better freezing point depressant than sugar. The final trials, which applied 2 tsp. of a substance to the water, further proved my hypothesis. Salt dropped to its lower freezing point temperature of 28 degrees, as seen in Figure 3. In Figures 4&5, baking soda and sugar barely scratched 30 degrees again, but baking soda showed more improvement than sugar, which brought hope and revival to my earlier prediction that baking soda would make a better depressant than sugar.The averages of all the trials only helped solidify the proof that the Figures 1-5 showed. Salt was always lower than the other substances in AL trials, and dropped about 1 degree F for every 1/2 tsp. of it that was added to the water. my prediction that baking soda was a better depressant was also proven at this stage in the experiment, when the average of it was shown to be lower in nearly all trials as well, as seen in the Figure 2&6. All substances had some effect on the freezing point of water, which was 32 degrees and one control group. (Figure 2&6) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">The experiment had a large area for improvement. First of all, the accuracy of the temperature readings were very crude, and not as accurate as they could have been. Temperature readings were hard to break down into decimals to get the most accurate reading, which could have helped further prove the hypothesis correct, or any other predictions. So, the application of a better, more accurate thermometer would be a huge improvement to the project (possible electric thermometer that records to tenth or hundredth decimal). Taking away the control group of antifreeze would also be a smart modification to the project. It did not serve much purpose to the outcome or comparison of substance in the project. Although it shows the ultimate freezing point depression, it was in a very different "ballgame" to be useful for comparing with the other substances, that only dropped a few degrees in freezing point during the experiment. Also, the addition of more substances to test would be a good modification to make to the project, because it would give more basis for the comparison of the data. Possible substance additions could include ethyl alcohol, milk, lemons juice, baking powder, flour, etc. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">There was a rather moderate margin for error during the experiment. First of all, as stated before, the thermometer did not allow for a very accurate reading, and therefore, did not fully represent the true freezing temperature of the various solutions. The lack of accurate readings could very have totally changed the outcome of the experiment in terms of averages. Another source of error was the trouble encountered with fully dissolving baking soda and sugar. Salt dissolved easily, but the other two substances did not fully dissolve, and this could have very well had an effect on the ability of those substances to drop the freezing point. If the substances were to fully dissolve like the salt, they could have very well dropped a few more degrees and kept up with the salt. The next source of error was the fluctuating temperature of the external environment when running the experiments. Because of the temperature changes day to day, as well as season to season, the external environments temp. could have had an effect on the temp. at which the solutions froze.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">__Conclusion:__ The hypothesis of the project stated that //if salt (solute) is added to water (solvent), then the solution's new freezing point will be depressed the most//. This was proven correct, and is plainly seen when observing all Figures, but especially the averages of all the trials, found in Figures 2&6. After running 9 trials of various increments of 3 substances, and compiling and averaging them, it was determined that salt was the best freezing point depressant, dropping anywhere between ..44 to 3.11 degrees below its competitors, who consistently measured in above 31 degrees, which salt surpassed in Set #2 of trials (1 tsp.). Although the source of error from the lack of truly accurate measurements could have significantly changed the data, and average, the margin of difference between teh substances and their averages proves that salt is the best freezing point depressant.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">__Application:__ The data and conclusions drawn from this experiment can prove to be very useful and beneficial in a few applicable situations. First of all, the data can be used for the prevention of water freezing. Salt can be added to water in any amount, and could control the freezing point, preventing the water from freezing. If the desired water needed to be purified after this process, simply evaporating and collecting it would separate the water and salt, and restore the water's original properties. Also, as many know, the results from this project support the real-life application of salt to icey roads and sidewalks to melt ice. The salt drops the freezing point of the ice in order to melt it, since the environmental temperature would most likely be slightly below that of the ice. So this study of various substances effects on freezing point could apply to the spreading of salt on icey roads and walkways. Also, furthering this study by exploring and comparing other substances with similar properties to slat (like the presence of sodium) could help lead to the discovery and application of better materials for melting ice, or lowering freezing point.

<span style="font-family: 'Arial Black',Gadget,sans-serif; font-size: 130%;">**** Other pictures will be an email sent to myself that I will show you. I attempted to attach multiples, and it simply kept replacing the one that was already there. i then attempted to attach them to a Word doc and attach that doc to the page, but that also failed. so I have moved onto Plan C.**