Question

Is heated water is more or less dense than melted snow and rainwater?

Answer 1

In general, heated water is less dense than cooler water or water that has just melted (as that water is quite cold). Note, however, that water undergoes a density change as it nears freezing. As water cools, it becomes more dense, but at a bit above freezing, it actually expands slightly and is, therefore, less dense. As water that is just above freezing cools and changes state to a solid, it becomes slightly less dense than liquid water. This explains why ice floats. The ice is less dense than the water in which it floats (or else it would not float).