This wonder we call water

Early this week my wife and I took the springer spaniel, Freckles, for a walk from our Birch Lake cabin. We hiked down our private road, along a short section of snowmobile trail, and then onto the lake. Here Noelle hesitated; she had never skated or walked on a frozen lake before. Freckles had no such trepidation and tugged hard at the leash. We followed, taking an arcing path across the ice to where our pier would be in summer.

Isn’t it wondrous that we can walk on the lakes in winter, and that the water below teems with life forms, active and dormant? We owe it all to a singular property of water. Most liquids contract as they cool and keep on contracting until they solidify. Water, on the other hand, contracts until it reaches 4 degrees Celsius (39 degrees Fahrenheit), at which point it begins to expand, and continues to expand until it becomes ice. So as a lake cools down toward the freezing point (zero Celsius, 32 Fahrenheit), the densest water at 4 degrees Celsius is at the bottom. Ice forms at the surface and, because it is less dense than the water, it floats. Soon a skin of ice covers the lake, and it gets thicker with cold days and nights as winter deepens. This ice then insulates against the subzero temperatures and keeps the water below in the liquid state, in which life thrives.

Why water behaves this way is a matter of chemistry and physics – of molecular vibration, positive and negative charges, molecular shapes, hydrogen bonds and such. I don’t claim to understand it all. I do marvel at how earth’s most abundant substance – the one life depends on, the one life is made of – shows this benevolent anomaly of expanding, not shrinking, as it cools toward freezing. What if this were not so? Ice crystals forming on the surface would sink. As more and more water froze, would it begin collecting on the bottom? And would our lakes continue to freeze all winter, until they froze solid?

When walking on a frozen lake, or drilling through the ice and lowering golden shiner minnows from tip-ups to catch winter walleyes, it is wondrous to contemplate the special properties of water.