Don’t Drink the Water

waterRecent events in Flint Michigan reaffirm the tenuous but critical relationship we have with water.  Recent events in my life have made me wonder increasingly what the nature of water truly is.

For example, why does water tend to roll down your upper arm in the shower, and then drip off your elbow?  And why do ice cubes in the lower of stacked trays seem to develop strange irregular undulations on their tops, like the freezing water had some how sloshed around while freezing?

Even a modest inquiry into the nature of water reveals how mysterious it really is.  To this day, there is still debate about what force or forces are responsible for water sticking together!

Nevertheless, here are some interesting items that I learned today in my quest to make water a bit less mysterious to me:

  • Since buoyant forces arise out of gravity, when water boils in a zero gravity environment, it does so by creating not a zillion little water vapor bubbles that rise, a la Archimedes, but one giant water vapor bubble in the middle of the boiling water.
  • The hexagonal structure of ice crystals accounts for water increasing in volume from 4 degrees Celsius down to zero degrees Celsius.
  • The deeper we walk into a swimming pool, while still maintaining contact with the pool’s floor, the harder it is to walk (this one’s pretty simple).
  • Ducks float (at least in part) because they trap air under their wings.
  • The low relative humidity of dry air inside the house during winter is responsible for increased susceptibility to colds, because dry respiratory tracks are better breeding grounds for the viruses that cause colds.
  • You can get sunburned on a cloudy day, because clouds block infrared radiation well, but ultraviolet radiation poorly.
  • There is a linear relationship between salinity and salt water density (this one’s pretty simple too).
  • The specific gravity of the Great Salt Lake varies with the salinity of portions of the lake, but at its highest salinity, the specific gravity of the lake is about 1.17.
  • Moist air retains more heat, and your body senses that, so moist air feels warmer than dry air of the same temperature.
  • The most abundant (neutron-less) isotope of hydrogen is called protium.

As to why the ice cubes in the lower trays in my freezer have such irregularly shaped surfaces, the phenomenon might be caused by ice spikes that get tamped down by the tray or trays above.

You can learn more about water here and here.

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Author: Bob Mahoney

Physics teacher

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