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.
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>cooler water should fall to the bottom while warmer water rises to the top, correct?
Not correct. While it’s true in general that substances expand as heated, it’s not always so straightforward near phase change boundaries. Ice is less dense than water, that’s why it floats. And liquid water is [not at it’s densest at 0 degrees, but at around 4 degrees](https://www.open.edu/openlearn/pluginfile.php/471504/mod_oucontent/oucontent/18543/ddd2c58c/6625d7f1/s206_blk1_part5_f3_01.eps.jpg).
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