It is my understanding that within a given medium warmer substances tend to rise and cooler substances fall, i.e. warmer air above cooler.
Assuming the same is true with water then in a lake the cooler water should fall to the bottom while warmer water rises to the top, correct? If so, I would expect that lakes would freeze from the bottom up. Can you please explain why this isn’t the case?
Thanks for your explanation.
In: 23
It’s not that warmer things rise, it’s that warmer things tend to “spread out” as the molecules get more giggly, and that makes them less dense. Denser objects fall. Less dense rise. That’s why a helium balloon rises without being cooler. Helium is less dense than nitrogen and oxygen, which push the helium upward as they fall below it.
Ok so what about ice? Water has a particularly weird, rare property that it actually is less dense when it’s frozen. This because it’s crystalline structure is less more widely packed than when it’s liquid. This is why ice cubes float. Also why, when it freezes on top (the area exposed to cold air) the ice doesn’t sink to the bottom. Luckily.
Because if it did sink, then more would freeze and sink. And more. And eventually it would all be frozen and never melt. And earth would be a giant ice ball. With no life.
Read a book called Cat’s Cradle. It’s about people who invent something called Ice 9 that basically works this way.
Latest Answers