A liter of water weighs 2.2 pounds at 39.2 degrees Fahrenheit. However, as the temperature changes, either higher or lower, the density decreases and so does the weight. This is due to the anomalous expansion of water.
With most substances, as they cool, their density increases because the activity of the atoms and molecules reduces and the substances contract. This changes the material from a gas to a liquid to a solid, which increases the weight of the substance. Water, however, actually decreases in density as it changes from a liquid to a solid. This is why ice floats on water.
