Ice skating

Sprinkled throughout the text are a number of short notes in the margin. Many of these are of the now, hear this variety, others are mnemonics, and still others make points that we forgot to put in the text. (These were contributed by your fellow students.) Some—probably fewer than we think—are supposed to be humorous. See, for example, the reference to ice skating on page 239 through five editions WLM thought it was uproariously funny. 

I haven t given up hope of participating in activities I used to enjoy. I never would throw away my ice skates, even though my kids always said, Nobody s gonna have an ice skating rink in Pensacola I said, One day, somebody s gonna build me one, and they did I don t know if I can physically put on the skates and skate now, but one day I m gonna ask somebody to sharpen my skates, and somebody to hold my hand, and do it ... 

FIGURE 15.3 Indoor concentrations of N02 measured in ice skating rinks using different types of power for the ice resurfacers. The median and the 25th and 75th percentiles are shown in each case (adapted from Brauer et al1997). 

Friends on a crowded ice-skating rink tend to stay together. Strangers, however, tend to disperse. 

Le Chatelier s principle states that a system will shift in the direction that nullifies the effect of a pressure change. Increased pressure favors the denser phase. Figure 7.4 shows the effects of temperature and pressure on water. Note that because liquid water is denser than ice, increased pressure lowers the melting point. It is said that forces required for ice skating are very low because the pressure of the skates on the ice creates a liquid film. At constant temperature,... 

Anyone who has eaten an ice cream cone on a hot summer afternoon is familiar with melting. Ice cream drips, popsicles liquefy, and ice cubes slowly melt in a glass of water. Likewise, anyone who has filled an ice cube tray with water and placed it in a freezer knows something about freezing. We take advantage of frozen water to cool our drinks and food, and even to glide on with ice skates. 

An Olympic gold medal winner laces up her ice skates. 

You have only to think about water to appreciate how different the three states of matter are. Flying, swimming, and ice skating are all done in contact with water in its various forms. Clearly, the arrangements of the water molecules must be significantly different in its gas, liquid, and solid forms. 

If that were all there were to the story, this would be a short chapter and chemistry would be considerably less rich. But as we mentioned above, pressure plays an integral role in the wide-ranging behaviors of various materials, which adds another dimension to the discussion. In a mixture, composition also has to be considered, which adds one more factor. Pressure accounts for why ice skating is fun but dry-ice skating is not, and the composition consideration addresses why good pizza goes bad. WeTl start with ice skating and have pizza later. 

S.C. Colbeck, Pressure melting and ice skating, American Journal of Physics, 1995, 63, 888. 

J. Furzer and T. Weber, Heating arrangement for ice skate blades, U.S. Patent 6988735, Published January 24, 2006. 

The fact that ice is iess dense than iiquid water is the reason that ice coiiects at the top of the iiquid rather than at the bottom. If it were not for this fact, ice-skating and ice fishing wouid not be possibie. 

Hard-Boiling an Egg on a Mountaintop, Pressure Cookers, and Ice Skating... 

The blades of ice skates are quite thin, so that the pressure exerted on ice by a skater can be substantial. Explain how this fact enables a person to skate on ice. 

He married the former Diane McKee of Berlin, New Hampshire, in 1968. Weather permitting. Friary sails on ice skates a trade book he wrote on this winter sport was published recently. His other hobbies include listening to traditional jazz, splitting firewood, reading a newspaper while walking a dog, and writing about himself in the third person. 

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