Question

When water freezes, it expands. Using your knowledge of density, how do you explain why ice cubes float in water?

Answer 1

In the above question, it is asked why ice cubes float in water. Any substance which floats in a given body has less density than the substance in which that substance is kept. Density can be defined as mass per unit volume.

Complete step by step solution:
The reason for ice floating in water is probably due to its density less than water.
It is usually considered that most substances are dense in their solid state as compared to their liquid form. But it is not true in the case of water molecules.
When water freezes into the solid form, its molecules come closer and get compact in a small space. As the molecules are not able to move in their solid state and hence, it cannot form a ring like structure as it used to do in a liquid state. So, we can say that H bonding in solid state is not that much stronger as compared to liquid state. Because of this weaker hydrogen bond, ice cubes are less dense than water molecules. So, ice cubes float in water.

Note:
Water is actually more dense at ${{4^\circ }}$ C. It is less dense at any temperature above or below ${{4^\circ }}$ C.
Hydrogen bonding can be defined as a special type of dipole-dipole attraction between molecules. It is not a covalent bond to a hydrogen atom. It is formed from the attractive force between a hydrogen atom covalently bonded to a very electronegative atom such as a N, O, or F atom and another very electronegative atom.