MHS Chemistry
Speed of Boiling Salt Water

I recently came across the following exchange in Science Teacher magazine (Oct 2003, p. 59), in an article about synchronous and asynchronous discussions using computers:

Student 1: well, i thought that since a potato is basically a root, being underground, it would absorb as much water as possible.

Student 3: from making mack and chesse i know salt makes water boil quicker

Instructor [to Student 3]: Yes salt lowers the boiling temp of water

Well, my understanding has always been that (a) salt makes water boil slower, and (b) salt makes water boil at a higher temperature. So the student was incorrect, which was fine, because s/he was in the middle of the learning process (the lesson was about osmosis), and so was the instructor, which was not fine, because even if it was in theheat of discussion, there should have been a correction soon after, or at least in the article referring to the exchange from which the above was extracted.

So then I got to wondering, is it enough to prove this statement by referring to the text and an equation or two? (No.) Is it possible that I am in error here (well, not likely J). And then I realized that I should let you, the student, find out and report your findings. So here is your assignment:

Question
How does the addition of salt affect the boiling of water?

Procedure
You investigate how the addition of salt to water affects its boiling properties. Find out if it changes the rate at which the boiling temperature is reached, and if it changes the boiling temperature. Beakers, graduated cylinders, thermometers, water, salt, and laboratory equipment will be supplied.

Write Up
After the title section, you should include a hypothesis that includes your prediction of the answer to the question listed above. Then you should provide a short procedure, which is a numbered list of steps you performed. It should include a description constants and variables used (what you changed on purpose, what you kept the same). Your data & results section should describe the temperature and time for each set of variables. Finally, your analysis should state whether or not your prediction was correct, and whether or not the student and instructor above were correct.

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