# The Naked Scientists Forum

### Author Topic: What causes the density of water to change in the way that it does?  (Read 1721 times)

#### erickejah

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##### What causes the density of water to change in the way that it does?
« on: 23/06/2009 00:40:37 »
Why does the density of water is graph as a parabola function. And why is the peak at 4°C?
« Last Edit: 26/06/2009 23:30:05 by chris »

#### lightarrow

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##### Re: What causes the density of water to change in the way that it does?
« Reply #1 on: 23/06/2009 19:57:16 »
Why does the density of water is graph as a parabola function. And why is the peak at 4°C?
Don't know if it could be reasonably approximated with a parabola (near the vertex, every function with a minimum and which graph is bent can be appr. with a parabola) but the general behaviour can be understood: for T slightly > 0, density increases because water molecule are more packed in the liquid; at the same time, increasing T, molecular agitation increases and so intermolecular distances so there will be a value of T were the increased packagin goes to an end, and the increased agitation begins to win; at this point density starts decreasing.

#### erickejah

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##### Re: What causes the density of water to change in the way that it does?
« Reply #2 on: 25/06/2009 04:11:41 »
are any other elements or substances with this behavior?

#### lightarrow

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##### Re: What causes the density of water to change in the way that it does?
« Reply #3 on: 25/06/2009 15:18:28 »
are any other elements or substances with this behavior?
Ga, Sn, Si, Ge, Bi

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##### Re: What causes the density of water to change in the way that it does?
« Reply #3 on: 25/06/2009 15:18:28 »