Friday, May 19, 2006

Ice by Mariana Gosnell

Ice by Mariana Gosnell

Oh, how I tried to read this book, but it was as cold as - well you know what. In any case, here are few nuggets I chipped off of the block that were worth keeping.

Water is densest at 39F. Below 39F, water expands because the clustering effect from increased hydrogen bonding between slowed molecules overrides the more-efficient packing effect of slowed down molecules. Above 39F, water expands because molecules are moving faster and taking up more room. p14

It takes the loss of 1 calorie (1/1000 of kilo-calorie which is the Calorie you eat) for the temperature of 1 gram of water to be lowered 1 degree Celsius, but a gram of water to change into ice once it has been lowered to the freezing point, it must give up another 80 calories more! The forfeiture of those 80 calories doesn't lower the temperature one whit, since the loss doesn't go towards lowering the speed of the molecule's movement [temperature is measure of energy and movement is kinetic energy]. It goes into increasing the number of hydrogen bonds between molecules. In water at 32F, about 15% of the molecules will be H bonded, while ice at the same temp will be 100% bonded. In order for ice to melt then, it must gain 80 calories, the heat going to breaking hydrogen bonds in the lattice. p16

Capacious as the crystal lattice [of ice] is, there's not enough room for most particles to fit inside it. Therefore, no matter how filthy the water from which ice crystals are formed, they will be pure H20. p18

Like all liquids, water needs something to get the freezing [crystallization] process started, and that something is usually a foreign particle: dust, saltgrain, speck of bacteria, etc. [Without a nucleation promoter] water can reach -40F, a temperature at which bonding is so enhanced that some icelike clusters reach a critical size of 50 to 100 molecules capable of being nucleators themselves. [So 100% pure water won't freeze at 32F w/o a nucleator present!] p19

The ice surface is not dormant… We think that every atom or molecule within a solid can move just a little in its stable position, but its not the same with ice. Every molecule in ice rotates with high speed like a propeller… In ice the speed can reach 1M cycles per second. The vibration of the spinning molecule is often so great that the molecule breaks free of the H bond holding it in the lattice and departs. [That's how ice can sublimated without melting.] The ice surface is constantly being eroded and redeposited, like topsoil. p27

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