- #1
Outrageous
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During winter why not all the water molecules on the water surface that have 4°C go deep under the water?
Water at 4 degree Celcius has maximum density
In summary: At high altitudes the air pressure is lower than at sea level, and this causes the air to balloon out of the iceberg. When the iceberg reaches the lower pressure of the ocean, the air is forced back into the ice and it causes it to float.The reason icebergs float is tha they contain a large quantity of entrained air. At high altitudes the air pressure is lower than at sea level, and this causes the air to balloon out of the iceberg. When the iceberg reaches the lower pressure of the ocean, the air is forced back into the ice and it causes it to float.
- #2
K^2
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They basically do. Water at the bottom of the frozen-over pond will be at about 4°C. That's also why lakes freeze starting from the top.
- #3
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K^2 said:
Can I say in a frozen-over pond, the highest temperature of the water will be 4 °C which is at the bottom?
- #4
K^2
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In practice, almost always, but it isn't necessarily true under all conditions. Certainly, there cannot be any water warmer than that. If there is, it will rise to the top, until it either meets colder water and cools, or until it gets to the very top and meets ice, in which case it will melt some ice and cool down. So in equilibrium, the warmest water you can have is 4°C.
However, all water in the pond could be colder than 4°C. That really should only happen right before the entire thickness of water freezes through, because while there is still a lot of water, the heat is lost only from the surface, and whatever little heat there is coming from the ground will keep the bottom at these 4°C. But if for whatever reason there is no heat from bellow, it could, in principle, be colder.
But certainly, you could say that there is no water warmer than 4°C, and whatever temperature the warmest water is, it is at the bottom.
However, all water in the pond could be colder than 4°C. That really should only happen right before the entire thickness of water freezes through, because while there is still a lot of water, the heat is lost only from the surface, and whatever little heat there is coming from the ground will keep the bottom at these 4°C. But if for whatever reason there is no heat from bellow, it could, in principle, be colder.
But certainly, you could say that there is no water warmer than 4°C, and whatever temperature the warmest water is, it is at the bottom.
- #5
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Thank you very much
- #6
Borek
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Note in the ocean things get slightly different - deep ocean water is colder, usually between 0 and 3°C.
- #7
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Borek said:
Is that because there is high concentration of salt? Since 3°C is lower than 4°C , why not lower than 0 ?
- #8
Borek
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I believe it is a combination of salinity and high pressure that changes water properties. Perhaps there is more to it, I don't know details. Sorry.
- #9
K^2
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At high pressure, the maximum density will certainly be at a lower temperature, so it's probably a factor. But I don't know how significant that would be or how the salt will play into it.
- #10
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Thank you guys
- #11
Studiot
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Do not try to apply the 'anomalous' density curve for pure (fresh) water to sea water.
For sea water the density continues to increase as temperature decreases all the way below zero (C) to the freezing point. There is no anomalous maximum.
Of course the actual value of freezing point depends on the salinity, as Borek said.
The reason icebergs float is tha they contain a large quantity of entrained air.
For sea water the density continues to increase as temperature decreases all the way below zero (C) to the freezing point. There is no anomalous maximum.
Of course the actual value of freezing point depends on the salinity, as Borek said.
The reason icebergs float is tha they contain a large quantity of entrained air.
1. Why does water have maximum density at 4 degrees Celsius?
Water molecules have a unique arrangement due to hydrogen bonding, which causes them to form a lattice structure as they freeze. When water is at 4 degrees Celsius, the molecules are close enough together to maximize their interactions but not close enough to form the lattice structure. This results in a higher density compared to water at other temperatures.
2. What happens to the density of water as it cools below 4 degrees Celsius?
As water continues to cool below 4 degrees Celsius, the water molecules start to form a lattice structure and spread out, causing the density to decrease. This is why ice, which is water in its solid form, is less dense than liquid water.
3. Does the density of water change at different pressures?
Yes, the density of water can change with pressure. At higher pressures, the molecules are pushed closer together, increasing the density. However, this effect is minimal compared to the impact of temperature on water's density.
4. How does the maximum density of water at 4 degrees Celsius affect aquatic life?
The unique property of water having maximum density at 4 degrees Celsius allows for bodies of water to freeze from the top down. This allows aquatic life to survive in the unfrozen water below the surface during the winter months. If water froze from the bottom up, it would trap and potentially kill the organisms living in the water.
5. Can other substances have maximum density at a specific temperature?
Yes, other substances can also have a maximum density at a specific temperature. This property is known as anomalous expansion and is exhibited by other substances with hydrogen bonding, such as silicon, germanium, and antimony. However, water is the only known substance to have a maximum density at 4 degrees Celsius.