The “official” first day of Winter is still a way off, but it sure seems pretty wintery out to me! As the weather continues to get colder, and the snow keeps piling up, it’s the perfect time to hit your students in the head… with some meteorological/scientific knowledge.
Water freezes in the cold, obviously, which is why your local lakes and ponds are frozen solid on top. But what about the rest of the water, below the surface? Why doesn’t the whole lake freeze? It’s all about density, as this quick and easy Demo Science science demo will help you explain to your students. (Or whoever you do the experiment for.)
Water You Waiting For? Science It Up!
Liquid water and frozen water (or “ice” as the kids are calling it these days) have very different density levels. This is pretty easy to demonstrate—all you need for this experiment are a large jar, very cold water to put in said jar, and ice cubes (at least one; at most 7,500).
Fill the jar with water, then drop in your ice cubes. They will, of course, float to the top. That’s what ice does in water. But wait… water and ice are the same thing. Why does the ice rise to the top instead of just reaching a float stasis somewhere in the middle of the watery depths? Again: destiny. You are the chosen one! Wait, wait, wait, sorry: density, not destiny. Just ignore that “chosen one” stuff. *conspiratorial wink*
Ice See What You Did There
Ice is less dense than water because, as it freezes, the molecules in water expand and spread out. Due to what we’ll call the “Laws of Density,” water (almost always) freezes from the top down. Because of this, lakes and such don’t freeze completely—the top layer freezes and expands, essentially “blocking” the cold from reaching the water underneath.
This also extends to your plumbing. When the water freezes, your pipes will tend to get leaks because of the H20 expansion. It takes more effort for the water heater to work and extends greater pressure on the plumbing system. If this happens, don’t try to fix the leaky pipes yourself, instead, call a plumber.
The frozen layer will be thicker depending on how cold it ultimately gets—ice can’t block all the coldness—but it’s all but impossible for a true lake-sized lake to freeze all the way through. Which is good for the fishes and other critters that live underwater throughout the winter. They’d be all kinds of dead if the whole thing was iced up!