Conclusion
In the same period of time, the substance ‘salt’ melted the ice the fastest of the 6 substances. It melted 46% of the ice over a period of one hour and sped up the process of melting ice by around 29% on average. Sand was the second fastest substance to melt ice and sped up the process by 15%, closely followed by sugar with a 12% speed up. The substance ‘coffee’ was not far behind and sped up the process of melting ice by nearly 6%. The soil kept the ice slightly cooler and slowed down the melting process by approximately 1%. Cotton took the longest to melt the ice and kept the ice much cooler. It only melted around 6% of the block of ice over the one hour period and slowed down the melting process by approximately 11%.
From this experiment, we may conclude that freezing point depression properties are present in salt so salt is therefore great at lowering the melting/freezing point of ice. We may also conclude that cotton has great insulating properties and can keep ice in its solid state for longer. |
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ReflectionIn the experiments, one major problem I faced was that the blocks of ice I froze were a little different. Although I had measured the same amount of water to freeze for each block of ice, the blocks of ice still had different weights. In order to resolve this problem, I decided to change my method of recording data to percentage form. That way, the original weight of the block of ice would be taken into account and therefore the results would be a fair test.
Another problem I faced was the amount of time it took to prepare and conduct the experiment. In order for the blocks of ice to freeze completely, it took over 12 hours and the I had waited 1 hour per block (although some blocks of ice were conducted simultaneously. I can minimise the amount it takes next time by freezing smaller blocks of ice and therefore it would not take as long to freeze or as long to melt, saving me a lot of time. |
DiscussionThe knowledge of how different substances may speed up or melt down the process of melting ice can be applied in numerous real life situations.
Firstly, an example of a real life situation where the freezing point depression property of salt is used is when there is a lot of ice/snow on the street and footpaths. In order to clear the ice/snow quickly to make way for cars and pedestrians, salt is spread all over it to melt it. Another real life situation where salt is used for its freezing point depression property is in home-made ice cream. Salt is added to ice to lower the melting/freezing point of ice in order to freeze the ingredients to make ice cream. Without the effect of freezing point depression, the ice-cream would not have frozen. Watch the video on the right for more detail. An example of a real life situation where you may use the insulating properties of cotton is whenever you want to keep something cool. E.g. when you have a cold drink and you want to keep it cooler for longer, you can wrap some cotton wool around it and that way, your hands won't get extremely col holding it either. The cotton will trap the heat out and trap the cold in. |
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