The thermal expansion coefficient of water varies significantly with temperature

Question

The thermal expansion coefficient of water varies significantly with temperature. It is at but decreases as the temperature is lowered until it becomes zero at . Below it is slightly negative, reaching a value of at . (This behavior is related to the fact that ice is less dense than water.)With this behavior in mind, imagine the process of a lake freezing over and discuss in some detail how this process would be different if the thermal expansion coefficient of water were always positive. What is the biological significance of this process?

Explanation / Answer

as the 4deg C water cools below C , it become denser, and therefore sinks , but as it approaches zero degrees it turns to ice and ice is generally less dense than water , so the water will turn to ice will float once it reach a temperature of zero degrees celsuis. the temperature of the bottom of the water is cooler than the surface of the lake . Doesn't the temperature of water stay around 4 degrees celsuis at the bottom of the water, since it will float to the top if you continue to cool the water to zero degrees since ice is typically zero degree and if you warm the water the water will rise.

at zero degrees , temperature is zero and coefficient is negative. The problem asks me if the process would be any different if the coefficient were positive.I wouldn't think so because even if change in temperature is negative , and change in delta V is negative, since water is larger than ice, the coefficient is still positive.

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