adding salt to water to make it boil faster?

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adding salt to water to make it boil faster?

Postby luckydog » Sat Jun 06, 2009 5:52 am

Hi;

I am an "older" student and as part of a class I am to design an experiment (this is a methods class for K-5). I picked a topic that I always wondered about based on my question: Does adding salt to water really make it boil faster? (To be able to cook pasta is my reason for asking.) My instructor is not telling me I should not be doing this experiment, but I am gathering this is truly a difficult experiement...I am gathering perhaps not suitable for elementary students. Is there anyone who has thoughts on this experiement or experience with it. I have (I think) identified my controlled variable, dependent variables, and independent variables...being the different amounts of salt added. I had picked 1 tsp, and 2 tsp, but this is not enough varied amounts.... If anyone has thoughts, again, I would appreciate it.

Thanks!
luckydog
 
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Project Question: Does adding salt to water help it boil faster? (As a busy mom this question was relevant to me)
Project Due Date: topic due by 6/7 project due by 6/14
Project Status: I am just starting

Re: adding salt to water to make it boil faster?

Postby MelissaB » Sat Jun 06, 2009 10:46 pm

Hi,

Can you tell us where you got the instructions for this experiment (I don't see it on the Science Buddies site)? From the sounds of it, I don't think that this is too advanced for k-5 students. What is it exactly that you're having trouble with?

The different amounts of salt is only one type of variable, not three. Take a look at Science Buddies' variable guide, here: http://www.sciencebuddies.org/science-f ... bles.shtml and then post back if you still have questions about types of variables.
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Re: adding salt to water to make it boil faster?

Postby Craig_Bridge » Wed Jun 10, 2009 9:21 am

The concept is too advanced for the K-2 end of the spectrum but it should be able to be understood by the 4-5 end.

You really need to do some research on this. Completely disolving most anything in water will raise the boiling point. All other things being equal, distilled water will boil at a lower temperature than salt water. Note: If you don't use distilled water, the amount of salt you add to "hard" water might not change the boiling point significantly because it might be small compared to all of the minerals already disolved in the water.

If the scientific question being asked involves how fast you can cook pasta, then having a higher temperature pot of boiling water means pasta in that pot will be cooking at a higher temperature. This would make it a compound problem and beyond the average 5th grader.

The real problem with doing these kinds of experiments in a typical K-5 building is not having appropriate space to safely do them with a sufficient margin of safety.
-Craig
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