Now, explain why ice floats. Why is 4o C the critical temperature in this story?

Ice is less dense than water.

Water freezes at 4°C as a result of a lower number of hydrogen bond preventing the molecules from interacting. This yields ice of about 10% lower density when compared to water

Explanation:

Ice floats on water because it is less dense than water.

Water form more fixed stable hydrogen bond when it freezes preventing it from forming further hydrogen bonds or closeness with neighbouring water molecules. This explains why ice has a lesser density than liquid water when compared with most substances that has higher density in its solid form than in its liquid form.

Note:

Only At 4°C

Water is more dense

At a temperature greater than 4°C

Water is less dense

At a temperature lower than 4°C

Water is less dense