If a person compares the same amount of ice and water, ice does not have more mass than liquid water. However, the volume of the ice is greater than that of liquid water. A reason for this occurring involves the molecular structure of these two different states of water.
The bonding of liquid water involves hydrogen bonds attaching each water molecule to about 3.4 other water molecules. However, in the freezing of water into ice, the bonding exhibited between molecules is one hydrogen molecule to four molecules. In the formation of ice, the space between molecules increases due to the crystal lattice structure.
Another thing that is evident in these two substances is that ice is less dense than liquid water, which accounts for ice floating in a glass of water. The density of a substance is given by the equation mass per volume. If mass of a substance stays the same and volume increases, than the density decreases.