Gurney called the local structure of liquid water "ice-like." As the temperature rises, more H-bonds are loosened, or broken, allowing further collapse of the open semi-regular ice-like structure, AND more thermal motion ensues tending to open the separation between O's in more random way. When ice melts, the hydrogen bonds holding the O's in the solid diamond lattice open up and the structure partially collapses, enough to make a fluid, but considerable H-bonding remains and parts of the open, diamond like 3-D lattice remain. As these intermolecular interactions of water increase, the local arrangements become more like the space-wasting structure of ice, in which each oxygen is surrounded tetrahedrally by four hydrogens." "Water is highly hydrogen-bonded both in the lattice, ice, and in the liquid state. Here's what everyone said on a particular chemistry email list where your question was posted: "Liquids generally become more dense as the temperature drops because molecular movements are slowing down, allowing the amount of intermolecular interactions to increase. ![]() That is: the thermal properties are not enough to break all the h-bonds apart, but the h-bonds have not formed enough to widen the distance between water molecules to be as great as in ice (which is why ice is lighter than water). At 4 degrees C these two forces work out to make water the most dense. This causes a kind of hexagonal 3D lattice to form which eventually becomes the 6-sided structure of ice crystals. This occurs in water whereby an O of one molecule will form a weak bond with the H of a neighboring molecule. One is the fundamental thermal force, that as things get warmer, the molecules move around more, so they get farther apart and so become less dense. Viewed 38621 times The answer Barry Shellīasically it's because of two opposing forces: thermal kinetic expansion and H-bonding. ![]() ![]() Why does water reach its maximum density at +4C instead of 0C? Why is water's density greater than ice's density although water is a liquid? Eray, a 19 year old male from the Internet asks on October 4, 1999,
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |