In winter , water tank (or ocean) starts freezing from the surface and not from the bottom?

Explain the following……

1-In winter , water tank (or ocean) starts freezing from the surface and not from the bottom, why?

Ans-In cold weather ( or winter) , when the atmospheric temperature starts falling below 0⁰ C , water at the surface of a pond (or lake) initially at temperature above 4⁰ C , begins to radiate  heat to the atmosphere, so the temperature of water near the surface starts falling . When temperature  of  water at the surface falls below 4⁰ C, water contracts and its density increase and therefore, it sinks to the bottom.

ANOMALOUS EXPANSION OF WATER:

If we take some water at 0⁰ C and start heating it, we find that it contracts in the temperature range from 0^o C to 4^o C. On heating it further above 4^o C, it expand . Similarly, it water initially at a temperature above 4^o C is cooled , it contracts till the temperature of water reaches 4^o  C. On further cooling it below 4^o C to 0^o C, its expands. This unusual expansion of water on cooling it in the temperature range 4^o C to 0⁰ C is called anomalous expansion of water.

Related Question:

1- Do pipes burst in cold weather?

2-How cold does it have to be for pipes to freeze and burst?

3-What causes water pipes to burst?

4-In winter , water tank (or ocean) starts freezing from the surface and not from the bottom.?

7- 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?

Here the link you can see the Answer:

https://knowledgecraker.blogspot.com/2020/06/explain-following-water-pipes-in-cooler.html