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Q & A: boiling point, solutes, and superheating

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Most recent answer: 05/24/2013
Q:
a sample of water under study was found to boil at 102 degree celsius at normal temperature and pressure. Is the water pure. Will this freeze at 0 degree celsius. comment
- deepak solanki (age 19)
delhi
A:

It's hard to say. For pure water near sea level, the boiling point is 100°C. Higher up, it boils at lower T. However, if there are no bubbles, little pieces of dirt, teflon surfaces, etc. in the water it can heat up a little past the ideal boiling point before actual boiling begins. The reason for this "superheating" (see  ) is very similar to the reason that water can be "supercooled", which we discuss on many other answers. Superheated water can be a bit dangerous, because if you have a cup of it and then trigger the boiling (see this movie ), the boiling is sudden, like an explosion.

So without further information, I can't say if you had pure water that superheated a bit or if you had water with some solutes, such as salt or sugar, in it.

Mike W. (posted without checking until Lee returns)


(published on 05/24/2013)

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