How does the top of a lake freeze

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In summary, the surface of a lake can freeze because of the peculiar property of water where it expands when it freezes, making ice less dense than liquid water. This allows it to float on top of the water and act as an insulator, preventing further heat loss from the water below. This phenomenon is known as the "anomalous expansion of water" and is not related to convection. However, when ice is cooled below 0 degrees Celsius, it does contract, which raises the question of why it does not sink when cooled enough.
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zhengwei
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can somebody tell me how is the surface of a lake been frozen yet the water underneath the ice layer remains unfrozen? can someone give me detailed explanation of this. including the convection theory and density as well. i mean include whatever that is connected. thanks
 
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Water has a very peculiar property- most materials contract as the cool; in particular, have a sudden sharp contraction as they change from liquid to solid- water, however, because it forms crystals, expands when it freezes.

Water ice is less dense than liquid water- it floats on top of the water.
Also ice is a good insulator. Once the ice has formed, it prevents much further heat loss from the water below it. "Convection" doesn't really have anything to do with it.
 
  • #3
i think the property is referred to as 'anamolous expansion of water'
water tends to expand when cooled from 4degCelcius to 0degCelcius
hence water at 0celcius is less dense than water at 4+celcius..

but this brings another question to my mind..
ice when cooled below 0celcius must contract(?).. therefore when cooled enough.. should it not sink..?
 

1. What causes the top of a lake to freeze?

The top of a lake freezes due to the decrease in temperature. When the air temperature drops below freezing, the surface of the lake loses heat to the colder air, causing the water molecules to slow down and eventually form ice crystals.

2. How long does it take for the top of a lake to freeze?

The time it takes for the top of a lake to freeze depends on various factors such as the size and depth of the lake, air temperature, and wind speed. On average, it can take anywhere from a few hours to several days for the top of a lake to freeze completely.

3. Why does the top of a lake freeze first?

The top of a lake freezes first because of the phenomenon known as the Mpemba effect. This effect states that hot water freezes faster than cold water due to the evaporation of warmer water molecules, which causes it to cool down faster.

4. Can the top of a lake freeze if the air temperature is above freezing?

Yes, the top of a lake can still freeze even if the air temperature is above freezing. This can happen when the water temperature is significantly colder than the air temperature, causing the water molecules to lose heat and freeze.

5. Can the top of a lake freeze solid?

Yes, the top of a lake can freeze solid under certain conditions. This typically occurs during extremely cold temperatures, where the entire body of water is below freezing, and there is no wind or water movement to prevent the formation of ice crystals on the surface.

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