Written by: Laurens Allaart and Romy Willemsen
Summary:
In our study we investigated whether sodium chloride is actually the best substance to melt ice. Therefore we started looking for alternative materials which could be used to clear the streets of ice. These substances needed be able to lower the melting-point of the ice.
Therefore we came out on sugar and urea. We wanted to test whether these compounds might even work better to melt ice. We did this by scattering a bit of each compound over ice cubes and measuring the molten water per unit of time.
Introduction:
Our research had to do with the melting point of ice. We were given a few examples of inquiries, one of which was to find variants for salt. Given that there has been a salt shortage for two years in the Netherlands, measured every minute the quantity molten ice. After five minutes we saw how little molten water was created per minute, and we decided to measure every five minutes.
Results: this seemed an interesting topic. The only question was what alternatives we would be testing in our study. Because this would not be a large-scale study, we soon decided not to test more than two alternatives. The first compound that we would be investigating was obvious, because like salt, we use it often in daily life: sugar. As a second compound, we chose urea, since we knew that urea also lowers the melting point of ice a lot. Our research question was: "Is salt truly the best de-icing substance?" We expected that salt would lower the melting point the most, as it is used to melt the ice on the roads.
Experimental design:
We took four 10 ml graduated cylinders containing four equally sized funnels. In these funnels we placed filter paper to ensure that no unsolved matter would be falling down.
We placed four ice cubes of the same size in the funnels, and then we added the same 3.0 grams of salt, sugar and urea. Next, we
1
2
3
4
5
10
15
20
25
30
35
40
Urea
0
0
0,1
0,6
0,9
1,6
2,2
3,5
5,2
6
6,7
7,3
Salt
0
0
0,1
0,1
0,2
1
1,8
3
4,1
5,4
6,1
7,8
Sugar
0
0
0,1
0,1
0,3
1,4
2,3
3,4
4,3
5,2
6,2
7,2
Blanco
0
0
0,1
0,1
0,1
0,6
1
1,4
1,9
2,4
2,9
3,6

9
8
7
6
5
4
3
2
1
0
0 10 20 30
Discussion and Conclusion:
As you can see in the chart above all substances help to lower the melting point of ice and all these substances would help if sprinkled on the street. All these substances make ice melt faster than almost two times if you wouldn’t sprinkle, but we wanted to investigate whether salt could be replaced with another substance.
At the start of the experiment you can see that urea and sugar make ice melt faster. After about
25 minutes you can see that urea is a lot better than the rest of the substances, but after 40 minutes the best substance to melt ice is proven to be salt. This would mean that sugar and urea dissolved completely before the salt does, and thus finished reacting earlier. This can be explained by looking at the molar mass of the substances.
Urea, (NH
2
)
2
CO, has a molar mass of 48.025 grams. Sugar, C
12
H
22
O
11
, has a molar mass of
342.30 grams. Salt has a molar mass of 58.44 grams. This means that we have 0.062 mol urea, 0.088 mol 0.51 mol sugar and salt are used.
It is known that for each particle that is dissolved, the solutions freezing point lowers. It is therefore not surprising that urea is more effective than sugar, given that we have used many more molecules. The reason that salt is eventually worked better is that the salt dissolves itself into
Ureum
Zout
Suiker
Blanco
40 50 two ions, sodium and chloride. Because of this, there are two times more particles are formed. This makes it plausible that our results are correct and that salt is really the best compound to be used for melting ice.
Something else that has not been considered yet, the price of the substance. Prices always vary a bit, and it will all be cheaper when buying large quantities, but when looking at the prices in the supermarket, salt is the cheapest. The price per kg of salt is € 0.35, sugar costs € 0.89 per kg an and urea € 0.46.
This makes salt not only the best compound to melt ice, it is also the cheapest product.
This makes salt in all aspects the best choice.
Our hypothesis is confirmed.

Evaluation:
In the results you can clearly see that there was no constant melting process, especially in the urea-trend. This is striking, particularly because at the sugar experiment and the blank test as well there is in a constant upward trend. This makes it more likely that a factor other than just the ability of lowering the melting point has played a part in our study. When we think of points to improve, these are the easy problems: First, we obviously should have used crushed ice instead of ice cubes. This has everything to do with the distribution of the salt. If you use ice cubes, a thick layer of half dissolved salt arises on top of the ice cube. This ensures no further contact with ice, rendering the test useless. By gently stirring in the funnel, we tried to make sure that the half dissolved salt is able to get back into contact with fresh ice, but this is not the same as a test with crushed ice. When using crushed ice, there would probably not have appeared a layer of half dissolved salt on the ice, and there would be no need to stir. The agitation can never be exactly the same for all tests, and this ensures a small deviation in the results.
Another problem is that we have conducted the tests in an area of about 20 ºC. This is not an appropriate environment, because as the outside temperature is far above the freezing point, you do not need to sprinkle salt. We would have to repeat the tests in a environment where the temperature is below zero. Furthermore, it is notable that all three substances in different fineness occurred.
The salt was almost powder, sugar was in coarse grains and urea was even coarser, almost in small pills. For improved reliability, the substances need to be used in the same fineness.
Other problems are not as easy to improve.
Of course there will always be some measurement errors, especially if you use a graduated cylinder 10mL, because the sensitivity of the measuring equipment is not precise enough to measure the small amounts of water that melt per time unit. The last problem we have found that water got stuck in the filter that we used, and that was a different amount for all tests.
Further studies would have to take the problems above in consideration. Also you could try to determine the quantity in a fairer way, for instance by using the same amount of moles, or the same amount of money spent on buying the compounds.
Bibliography: www.albert.nl
http://nl.wikipedia.org/wiki/Ureum http://nl.wikipedia.org/wiki/Keukenzout http://www.newton.dep.anl.gov/askasci/chem
99/chem99504.htm
ICY-road salt
Chemie in onderzoek