Expert: Expert - 6/20/2005

Question
Hello, Expert, and thank you for answering me!
I'll explain my questions. I'd like to understand what happens to the water molecules when water is boiled. How do they behave? Do they release gas of some sort? Do some of them change their properties? etc.

Second, is there a difference in the above when the water is reheated after it cooled down? Do the molecules behave differently then before? Is there anything in the first heating and cooling that causes the water to be different then what they were before they were heated at all, and thus the behavior of the molecules when they're reheated differs?

You wanted an example of what I think might happen: Maybe when water is heated, it releases gas, and when it is reheated it releases less gas. If it is so, then maybe you could ,please, emphasize on that.

Thank you,
Sam.


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Followup To
Question -
Hello!
Don't worry, this is NOT a homework question.

I'd like to know, what exactly happens, physically speaking, when water is being boiled.
Second, is there a diffrernce if the water is boiled for the first time or if it's reboiled (after it cooled down)?

Thank you!

Answer -
I'm afraid I'm having trouble understanding either of your questions.

> what exactly happens, physically speaking, when water is being boiled

If you could be more specific on what exactly you think is happening, and then what it is you don't understand about the process; I can probably fill in the gap more precisely.

> is there a diffrernce if the water is boiled
> for the first time or if it's reboiled

What kind difference do you think might occur? For instance, I can assure you the color won't change; but I don't think that's what you're asking. The problem is, I can't know WHAT you're looking for. If you can tell what difference it MIGHT make, then I can more precisely answer your question.

Boiling water, letting it cool down, and then letting it boil again is something you can do in a matter of hours. If there is some difference you expect, you can very likely do an experiment and get an exact answer very quickly.

Answer
> what happens to the water molecules when water is boiled?
> Do they release gas of some sort?

It's actually a lot simpler than that. When liquid water boils, some of the water molecules in a liquid state become so energetic that they go into a gaseous state.  They remain water molecules, completely unchanged in their internal composition. They just change how they relate to other molecules.  The only "gas" that's released during boiling is water vapor.

As such, you can reheat the same water a thousand times and you won't get any change in the boiling process (other than loss of the liquid as the water vapor wisps away). The water molecules in a liquid state will become water molecules in a gaseous state, and the process will be the same on the first, second, and thousandth time.