# The Naked Scientists Forum

### Author Topic: Water Water Everywhere.....  (Read 3602 times)

#### neilep

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##### Water Water Everywhere.....
« on: 19/02/2008 22:56:51 »
"Water Water Everywhere But Not A Drop To Drink" wrote Samuel Taylor Coleridge about a billion years ago !

Should he be alive today, not only would he benefit from a free bus pass but I wonder if he would be able to answer my question that follows after this rather nice picture :

You have fresh water...and sea water.....they're the main two eh ?

Say I placed a litre of each in identical pots and heated them up using the exact same strength of heat source......which one would boil first ?..OK !!....which one would reach 100c first ?....and then..which one would return to room temperature first when left to cool !

Such is the excitement that is the rock star style of my life that I find myself asking this at nearly 11pm on a Tuesday night !

Take pity and answer this for me will ya ?......and can ewe also explain why the differences...if any  ?

Sea Ya !!...Water silly question !!

#### DoctorBeaver

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##### Water Water Everywhere.....
« Reply #1 on: 19/02/2008 23:25:49 »
Adding salt will raise the boiling point of the water. Therefore, if both containers are at the same initial temperature & you use identical heat sources, the fresh water will boil first.

P.S. Such is the excitement that is my life I'm answering questions about water at 11:25 on a Tuesday night

#### another_someone

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##### Water Water Everywhere.....
« Reply #2 on: 19/02/2008 23:40:14 »
Say I placed a litre of each in identical pots and heated them up using the exact same strength of heat source......which one would boil first ?..OK !!....which one would reach 100c first ?....and then..which one would return to room temperature first when left to cool !

Boiling and coming to 100°C is not the same thing.

As for the question pertaining to the issue of boiling, I thought you rather liked cooking - do you not put salt in the water to delay the boiling of the water as you cook?

#### neilep

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##### Water Water Everywhere.....
« Reply #3 on: 20/02/2008 13:18:24 »
Adding salt will raise the boiling point of the water. Therefore, if both containers are at the same initial temperature & you use identical heat sources, the fresh water will boil first.

P.S. Such is the excitement that is my life I'm answering questions about water at 11:25 on a Tuesday night

Thank YOU Dr Beav......so the salt adds a few degrees needed to reach boiling !.....ta very much .

We both lead exciting lives !.........but something tells me that yours is particularly more so....

#### neilep

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##### Water Water Everywhere.....
« Reply #4 on: 20/02/2008 13:21:34 »
Say I placed a litre of each in identical pots and heated them up using the exact same strength of heat source......which one would boil first ?..OK !!....which one would reach 100c first ?....and then..which one would return to room temperature first when left to cool !

Boiling and coming to 100°C is not the same thing.

As for the question pertaining to the issue of boiling, I thought you rather liked cooking - do you not put salt in the water to delay the boiling of the water as you cook?

Thanks You George........why yes..yes, I do enjoy cooking......I have tried to reduce my salt intake....... so recently I have not been able to empirically study this.

I am assuming the salt has little if no effect on the cooling down ?

#### another_someone

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##### Water Water Everywhere.....
« Reply #5 on: 20/02/2008 14:28:18 »
Say I placed a litre of each in identical pots and heated them up using the exact same strength of heat source......which one would boil first ?..OK !!....which one would reach 100c first ?....and then..which one would return to room temperature first when left to cool !

Boiling and coming to 100°C is not the same thing.

As for the question pertaining to the issue of boiling, I thought you rather liked cooking - do you not put salt in the water to delay the boiling of the water as you cook?

Thanks You George........why yes..yes, I do enjoy cooking......I have tried to reduce my salt intake....... so recently I have not been able to empirically study this.

I am assuming the salt has little if no effect on the cooling down ?

It will have a slight, but very slight, effect on the ability of water to absorb heat; but the main difference it makes is to raise the boiling point (which is why I suggested that boiling and temperature are different things), and so allows the water temperature to rise above 100°C without losing heat by boiling.

#### DoctorBeaver

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##### Water Water Everywhere.....
« Reply #6 on: 20/02/2008 19:39:41 »
Adding salt will raise the boiling point of the water. Therefore, if both containers are at the same initial temperature & you use identical heat sources, the fresh water will boil first.

P.S. Such is the excitement that is my life I'm answering questions about water at 11:25 on a Tuesday night

Thank YOU Dr Beav......so the salt adds a few degrees needed to reach boiling !.....ta very much .

We both lead exciting lives !.........but something tells me that yours is particularly more so....

Yeah, I also clear poo out of a horse's living quarters

#### Bored chemist

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##### Water Water Everywhere.....
« Reply #7 on: 20/02/2008 20:36:32 »
A quick search indicates that the heat capacity of saltwater is a bit less than fresh water so the brine will heat and cool faster (all other tings being equal). Which one would boil first is a more complicated question and I'm a bit tired.

#### The Naked Scientists Forum

##### Water Water Everywhere.....
« Reply #7 on: 20/02/2008 20:36:32 »