Converting the same amount of very hot water into steam requires 540. The high amounts of energy required to change water from its liquid state make water tend to stay a fluid. The process of freezing water involves slowing down the activity of the water molecules until they contract and enter into a solid state. Once the ice is cooled down to 4 degrees or less, the hydrogen bonds no longer contract, but they become rigid and open, and the ice becomes less dense. Because the ice has become less dense, it floats on liquid water.
Water freezes from the top down.
Once the top freezes, it acts as an insulator, so that the water beneath it takes a very long time to cool off enough that it freezes. This also traps just enough warmth to keep marine animals alive during the winter. The process of turning water into steam is a different story. Because it requires the breaking of water s hydrogen bonds, this process takes far more energy than it does to turn water into ice. The extra energy that is used in converting water into steam helps keep the overall temperature from getting too hot.