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
Water is densest as 4C, so the ice at 0C rises to the top.
This is a neat phenomenon with water (and very few other liquids), but becasue of it life exists. If water was like all other liquids and froze bottom up, nothing would have lived through ice ages. Since there was a coating of ice on top, life survived in the water under the ice. No floating ice, no water underneath, no life survives
Water is densest as 4C, so the ice at 0C rises to the top.
This is a neat phenomenon with water (and very few other liquids), but becasue of it life exists. If water was like all other liquids and froze bottom up, nothing would have lived through ice ages. Since there was a coating of ice on top, life survived in the water under the ice. No floating ice, no water underneath, no life survives
Most of the answers focus on how ice floats. However the other very important factor is that air above the lake is far colder than the sand or sludge at the bottom of the lake. So as the colder water sinks, it gets warmed up by the bottom of the lake. So ice crystals first form at the surface, and since ice floats, they stay there.
Most of the answers focus on how ice floats. However the other very important factor is that air above the lake is far colder than the sand or sludge at the bottom of the lake. So as the colder water sinks, it gets warmed up by the bottom of the lake. So ice crystals first form at the surface, and since ice floats, they stay there.
Two other points to add. First, the freezing temperature of water changes with pressure. Water lower in a pind is under pressure from the water above it so it freezes at lower temperatures than the surface water.
Second water at the surface is exposed to the air. Wind cooling makes it freeze first.
Two other points to add. First, the freezing temperature of water changes with pressure. Water lower in a pind is under pressure from the water above it so it freezes at lower temperatures than the surface water.
Second water at the surface is exposed to the air. Wind cooling makes it freeze first.
Latest Answers