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The wonderfully weird ways of water

By Dr. Jon

Maintaining Equilibrium

Sick of all those sleepless nights lying awake contemplating the mysteries of life? Fear not: Experts are standing by to field all of your nagging science questions. Professional ponderers here at MUN, as well as at McGill University, the University of Arkansas, and the Institute of Molecular Pathology in Vienna, await your inquiries.

If these experts don’t suffice, then we’ll track someone down with the know-how to get your question answered. I realize that in the Google age, answers are a little easier to come by than they were when I was a tyke. However, there’s still something to be said for the thoughts of a legitimate expert versus a large anonymous consensus, or a random website that surprisingly contains the information you sought.

To kick things off, I thought I’d ask myself some questions and answer them the best I could.

SUB: Dr. Jon, how come bugs can walk on water but I can’t?

Well, thanks for taking the time to write us with such a great question. In short, it’s all about the surface tension, baby. The bugs you refer to are commonly known as water striders, and there are over 500 species of the little critters.

Water striders can walk on water because of the relatively high surface tension that water possesses, which is over three times larger than that of ethanol. Water binds to itself through intermolecular forces called hydrogen bonds. In the middle of the water, or bulk, these forces are balanced.

However, this is not the case for molecules at the surface that interact more strongly with each other than the air molecules above. This leads to a surface skin that must be penetrated to enter the water. As we know from swimming, it’s usually not that hard to penetrate the surface of water, but the weight of those balancing bugs is distributed evenly enough that the force they exert is insufficient to break through the pond’s surface.

SUB: How come my tongue got stuck to the stop-sign pole last winter?

The easy answer is because someone triple-dog dared you to do it, and you’re not very good at resisting peer pressure. Physically speaking though, your tongue is a very moist object, and a metal pole is a good conductor of heat. This results in the sub-zero pole turning your tongue moisture into ice in no time flat. The ice glues you to the pole making it extremely difficult to remove without losing a layer of tongue in the process. Your best bet is to pour some hot water all over the unfortunate incident, and ease yourself off the pole as quickly as possible. A similar effect is observed with ice cubes fresh from the deep freeze, but fortunately, it’s easier to melt a bonded ice cube than a metal pole.

SUB: What’s the difference between freezing rain and sleet?

The simplest answer is that sleet is rain that freezes as it falls through a cold patch of air on its way to the ground. This results in our bombardment with small ice pellets. Freezing rain, as the name implies, is rain that remains in the liquid state until striking the ground.

Freezing rain is a little more interesting than it appears at first glance though. Water droplets falling through a sub-zero patch of air can become supercooled, meaning these droplets remain in a liquid state even though their temperature is below the freezing point. Contact with the ground, power lines, or other surfaces, initiates the crystallization process forming a thin layer of dangerous ice.

This effect can sometimes be seen with the careful, undisturbed freezing of a freezee, which will remain liquid until you touch the side, thus providing a nucleation site for ice formation.

Now it’s up to you. Send your questions to the Muse (science@themuse.ca) for a chance to put our experts to the test. No matter how obscure or irrelevant your science question may seem, it isn’t; please don’t hesitate to drop us a line.

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