Question

Assertion: Density of water decreases when cooled from 4°C to 0°C. Reason: Water has negative co efficient of thermal expansion at low temperatures (i.e. below 4°C)

Water has a peculiar property, which is different from any other substance it's density decreases with temperature and density of solid state (ice) is lesser than density of liquid (water). If observed carefully the density is maximum at 4°C. it helps us in many ways and is important for sustenance of life on Earth. Especially aquatic life.