How Everything Works
How Everything Works How Everything Works
 

QUESTIONS AND ANSWERS
 
Question 647

How do I graph (line or pie) the time it takes different amounts of water to freeze? — LC, TX
First, you must determine what it is that you're really measuring. If you pour a gallon of water onto a huge copper plate that's been cooled to -200° C, the water will freeze in a fraction of a second while if you put a drop of water on a hot frying pan, it will never freeze at all. You must design a sensible experiment and then repeat it with several different amounts of water. The experiment should be sure to focus on the water by avoiding situations where external effects determine the freezing time. For example, you might obtain 4 identical 1-liter containers and fill them with 1/4, 2/4, 3/4, and 1 liter of the same water respectively and then put them simultaneously in a freezer with a uniform cold temperature. Then you can record how long it takes each of them to freeze. Then use an XY graph to plot these times: the x-axis could be the amount of water in the container and the y-axis could be the time it took for the water to freeze. The four points you'll obtain probably won't form a straight line. That's because the amount of heat that must leave the water for it to freeze depends on the water's volume and the time it takes that heat to leave depends on the water's surface area. Doubling the water's volume doesn't double its surface area, so the freezing time will have an interesting and somewhat complicated dependence on the water's volume. Try it!
         

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