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Topic: Oil and Water (Read 928 times) |
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rmsgrey
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Oil and Water
« on: Feb 8th, 2005, 7:50pm » |
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Until I spent the last 20 minutes searching for it, I'd have sworn this one would be here somewhere already in some form...
You have two two-litre bottles, each containing a litre of pure liquid - one containing water; the other an oil of similar density.
You also have a small beaker, which starts empty.
You fill the beaker from the water bottle, empty it into the oil bottle, cap the bottle, and give it a good shake to mix it. You then (without giving it a chance to separate) fill the beaker from the oil bottle and empty it into the water bottle.
Assuming there is no spillage at any point, and no liquid is left in the beaker, is there more water in the oil bottle or oil in the water bottle?
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Here's the actual question (I was talking to rmsgrey about this question before he posted it.) 
You are given two glass jugs. Each contains the same
volume, V , of liquid. One jug contains pure alcohol, and the other
jug contains pure water. A modest quantity, Q, ofwater is poured
from the water jug into the alcohol jug, which is then thoroughly
mixed. The same modest quantity, Q, of (now diluted) alcohol is
then poured back into the water jug to equalize the volumes of
the jugs at their initial levels.
The initial concentration of alcohol in the alcohol jug equals the
initial concentration of water in the water jug (at 100%). What
is the relationship between the final concentrations of alcohol in
the alcohol jug and water in the water jug?
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Noke Lieu
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Re: Oil and Water
« Reply #2 on: Feb 8th, 2005, 9:57pm » |
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water is always about 56 molar. Pure alcohol is about 17 molar.
Next?
No- it's been here before, unless my hurried reading has misdirected me. someone gave a beautiful demonstration with marbles. ten black in one bottle, ten white in the other...
First time I came across it I did it with ratios though. will search for you.
This isn't the thred I was looking for, but it seems good enough
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| « Last Edit: Feb 8th, 2005, 10:01pm by Noke Lieu » |
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Padzok
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Re: Oil and Water
« Reply #3 on: Feb 9th, 2005, 12:16am » |
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I'm sure there is a good way to do it mathematically
... but if you start trying to do it mathematically then you miss the simple intuitive leap that if both containers have 1 litre of liquid at the end, then however much oil is in the water must be exactly matched by the volume of water in the oil.
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towr
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Re: Oil and Water
« Reply #4 on: Feb 9th, 2005, 12:31am » |
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There is a good reason why you shouldn't do it with alcohol and water.. You won't get the answer you expect.
Water and wine work better (although still the precise results won't be what you want)
Leaving chemistry behind us..
::There is an equal volume in each bottle, and whatever misses of one type of liquid resides in the other bottle, and vice versa. So they must be equally diluted/poluted::
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| « Last Edit: Feb 9th, 2005, 12:42am by towr » |
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rmsgrey
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Re: Oil and Water
« Reply #5 on: Feb 9th, 2005, 3:03pm » |
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on Feb 9th, 2005, 12:31am, towr wrote:There is a good reason why you shouldn't do it with alcohol and water.. You won't get the answer you expect.
Water and wine work better (although still the precise results won't be what you want) |
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Which is why I picked oil and water - being immiscible, the total volume should remain constant
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