Thread: anamolous behaviour of water

what is responsible for the anamolous behaviour of water. water increases in volume after reaching 4 degree celsius and continues to do so at lower temperatures. i want to know what happens at the moleculer level.

Originally Posted by parag

what is responsible for the anamolous behaviour of water. water increases in volume after reaching 4 degree celsius and continues to do so at lower temperatures. i want to know what happens at the moleculer level.

Its actually higher temperatures.

As a liquid heats up, the atoms/molecules gain energy proportionally(they wizz around more). The resulting excitement creates more spaces between them.

Water volume increases at temperatures both higher and lower than 4C (39F), the temperature of maximum density. The expansion above 4C is due, as Maxwell says, to increased molecular activity. Expansion below 4C is due to the molecules starting to form an open crystal pattern prior to freezing. It is caused by water's property of hydrogen bonding. Liquid ammonia shows a similar pattern.

Oh yeah, I see what you mean. OOOPS

To expand a little on what SteveF has already said:

Hydrogen bonding in water wants to form to water molecules into a crystal, but at normal warm temperatures there is too much molecular motion for the crystal to form. Once the water cools down to around 4 C, the hydrogen bonding forces are finally able to overcome the thermal motion of the water molecules and the water molecules begin to order into a crystal. The spacing between each water molecule in the crystal is more than the spacing between molecules when the molecules are just moving around randomly, so the water expands.

MMMMmmmm.

This is so relevant.

In addition to all the possible answers to the previous posts, this behavior of water can actually be understood as a phenomenon that as temperature decreases to a certain extend, molecules would retain different form and behaves differently, which at high temperature, it is the same. Although macroscopically they only seem to be gaining kinetic energy and having more entropy, microscopically they could be actually changing their state of particles. What I mean is that, given enough energy increase, eventually the spin property of Quarks would have to be unified and this as a result, would unified the Electromagnetic, Strong and Weak forces. I am, however, not saying water IS this result of changing state of particles, I'm saying that water CAN BE understood like so, but they are not the same. This is because the increase in water's temperature is simply too little! Well, I hope this is an interesting side topic or a different way to "think" of why water behaves so.

So, and this is probably entirely hair-brained and naive again, but what if matter itself is nothing more than a distortion of space? 11 dimensional space that is. Einstein already said that gravity is just that, so maybe ALL forces could be exlained that way? Then could the big bang maybe have been that a huge amount of virtual particles sprang into existance at the same time ( statisticaly improbable but not impossible?) and the combined energy of all those ripples in 11 dimensional space collapsing again could undergo 11 dimensional interference, creating matter. All matter has a half-life, so that could satisfy the law that energy can't come from nothing (stretching it to be sure, but who knows).and further, maybe the expansion of space can be explained as matter slowly uncurling. The speed of light might then be governed by the speed at which a wave propagates through the fabric of space?

What do you think of this?

The simple answer: Water crystalises. Most substances don't do that.

Or rather, most crystal formations form from a mix of substances, but somehow water ice is able to form a crystal just from that one substance.

For on opposite example: Glass isn't a crystal formation. It's just a substance that is solid at room temperature. If you cool glass down enough it will continue to shrink slightly.

Originally Posted by kojax

The simple answer: Water crystalises. Most substances don't do that.

Actually, most substances DO form crystals. Try to form a glass out of a metal. Have fun.

My understanding is that even crystalline solids show expansion/contraction upon heating/cooling. In fact I seem to remember being told that, below 0 celsius, ice too, whilst in general less dense than water, will start to contract. I presume, if this is true, that there is a theoretical temperature below which ice will be denser than water, even water at 4 celsius. (Of course, you couldn't put one into the other to see if it floats because the temperature differential between them would be so great I imagine the ice would crack up, almost explosively.)

Or am I wrong in this supposition?

You are certainly on the right track. Ice isn't merely ice. A phase diagram for water/ice shows that at various temperatures and pressures, ice can have many allotropic forms. I recall seeing as many as eleven phases for ice (labeled ice I, ice II, etc.). Of course, we are talking about pressure extremes. There is no way that ice and water could co-exist under such conditions.