question - particle model of matter

[Fearless™]

OK. We all know that the molecules of a solid are tightly packed usually in crystal lattice format. The molecules of a liquid are more loosely packed, and the molecules of a gas move around, etc.

Therefore, the volume of a solid < the volume of a liquid < the volume of a gas. and same with density.

But take water for example...

Ice (solid) has a greater volume than water. It's got less density and thus floats on top. Why?

[poison arrow]

Now, I Learnt The Reason 4 This In School..........but Now I Cant Remember. It'll Come Back To Me. :d

[Fearless™]

Originally Posted by poison arrow

Now, I Learnt The Reason 4 This In School..........but Now I Cant Remember. It'll Come Back To Me. :d

LOL. just make sure you remember it soon, because I need the answer by Friday.

[The Voice]

As water freezes, it expands until the temperature reaches around 4 degrees Farenheit. But I don't have my Physics book handy so I can't remember if the molecules actually expand or they just move farther apart.

[Western_Samurai]

Isn't this something you could just google?

Anyways, water is just one of the exceptions to the rule. Water's crystaline solid state arranges the molecules farther apart than in the liquid form.

[Fearless™]

I can google, but I don't want to read pages and pages, and still don't have what I need. I just thought this might be easier...and I thought water is at it's greatest volume when it is 4ºC <<

[Western_Samurai]

Originally Posted by Fearless Virgin

I can google, but I don't want to read pages and pages, and still don't have what I need. I just thought this might be easier...and I thought water is at it's greatest volume when it is 4ºC <<

I think you mean, it's at it's least volume ie most dense.
As it cools further crystals start forming and the molecules expand.

[Fearless™]

Originally Posted by Western_Samurai

I think you mean, it's at it's least volume ie most dense.
As it cools further crystals start forming and the molecules expand.

Umm...really? idk. I remember it being the greatest volume Anyhow...could you pls just elaborate on how Water's crystaline solid state arranges the molecules farther apart than in the liquid form. Like...as in...why does it do that.

[Western_Samurai]

From wikipedia:

An unusual feature of ice frozen at a pressure of one atmosphere is that the solid is some 8% less dense than liquid water. Ice has a density of 0.917 g/cm³ at 0 °C, whereas water has a density of 0.9998 g/cm³ at the same temperature. Liquid water is most dense, essentially 1.00 g/cm³, at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the temperature drops to 0 °C. (In fact, the word "crystal" derives from Greek word for frost.) This is due to hydrogen bonds forming between the water molecules, which line up molecules less efficiently (in terms of volume) when water is frozen. The result of this is that ice floats on liquid water, an important factor in Earth's climate. Density of ice increases slightly with decreasing temperature (density of ice at −180 °C (93 K) is 0.9340 g/cm³).

[Fearless™]

Originally Posted by Western_Samurai

From wikipedia:

becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the temperature drops to 0 °C.

thanks...I think that's the answer I was looking for =)