# How can you tell if boiling water from a cooking pot has reached 100° C?

I don't have a kettle, so I use a cooking pot at home to boil water. I boil water on high in the cooking pot and as soon as I see the big bubbles/steam forming, I assume the water has reached 100° C. Is that correct?

If the water has reached 100° C and I let it settle off the stove for 1 min, what's the average temperature of the water after that period of time?

EDIT

I'm trying to make some coffee from my french press and from what I've read, people recommend to wait 1 min before pouring the hot water in the press. I'm not getting a lot of coffee flavour from the french press after letting it infuse for 5 min. I was curious to know if the temperature of the hot water can drop a lot in 1 min.

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You are correct with the assumption that the water reaches 100°C when it starts to boil. As for the average temperature, I think it would be really hard to calculate since you would have to take into account what temperature the room is in and what not. –  duchessofstokesay Feb 12 '11 at 14:25
Pick up the book Thermodynamics for Dummmies. It will help you calculate heat loss based on ambient room temperature and the size of the vessel. –  Brian Feb 12 '11 at 16:59
I'm gonna be a bit pedantic and say, "Use a thermometer". It's really the only way to tell with 100% certainty (limited by the acccuracy of your thermometer, of course). –  Marti Feb 12 '11 at 22:54

As long as you are talking about a normal pot with or without a normal lid (i.e. not a pressure cooker) and you are reasonably close to sea level, you're right, boiling water is at 100°C. However, if you start to climb in altitude, that is no longer the case, at 300m, water boils at 99°C, at 600m, 98°C and so on. Wikipedia has a page with information about High altitude cooking that contains a reference table.

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... and that it's mostly pure water -- if it's a solution (ie, there's salt or sugar disolved in it), the boiling point is slightly higher. (not much though, you can only raise it about °4C, and that's for a saturated solution, which would be very salty) –  Joe Feb 12 '11 at 21:11
This would go for water in a kettle also though. –  vwiggins Feb 14 '11 at 10:13