Physics
Explain the following:
Fishes survive in ponds even when the atmospheric temperature is below 0°C.
Answer
In winter, when the atmospheric temperature drops below 0°C, the surface water of a pond cools and contracts. It continues to sink until the entire water mass reaches a temperature of 4°C. Further cooling causes the top layers to expand and become less dense, preventing them from sinking. When the air temperature falls below 0°C, the surface water loses heat and gradually freezes into ice. However, the water beneath the ice layer remains at 4°C. The layer of water in contact with the ice is at 0°C, while the layers below gradually increase in temperature up to 4°C. Fish can survive in the pond because the ice acts as an insulator, preventing heat transfer from the water to the atmosphere.
Related Questions
Explain the following:
In winter, water tank (or ocean) starts freezing from the surface and not from the bottom.
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A glass bottle completely filled with water and tightly closed at room temperature, is likely to burst when kept in the freezer of a refrigerator.
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A hollow glass sphere which floats with it's entire volume submerged in water at 4°C, sinks when water is heated above 4°C.