Water is not heavier than ice at room temperature. In fact, the density of water decreases when it freezes and turns into ice, causing ice to be less dense than liquid water.
The reason behind this phenomenon can be attributed to the unique behavior of water molecules. In the liquid state, water molecules are constantly moving, and the intermolecular forces between them allow for relatively close packing. This results in the higher density of liquid water compared to ice.
When water freezes, its molecules arrange themselves in a crystal lattice structure with more open spaces between them. This arrangement causes ice to have a lower density than liquid water. As a result, when water freezes, it expands and occupies a greater volume than the same amount of liquid water, but with less mass. This expansion during freezing is why ice cubes float in liquid water.
So, in summary, ice is less dense than liquid water due to the structural arrangement of water molecules in its solid form, resulting in ice being lighter than an equivalent volume of water.