Why As water is cooled from 4 and deg to 0 and deg its density?

As water is cooled from 4°C to 0°C, its density decreases due to the unique molecular structure of water. At 4°C, water reaches its maximum density because the molecules are closely packed. As it cools further to 0°C, the formation of hydrogen bonds causes the molecules to arrange themselves in a more open structure, leading to a decrease in density. This is why ice floats on liquid water.