Your question states: Why is ice less dense than liquid water? There reason why Ice is less dense than liquid is because ice has compact molecules that are tight together and they stay still. But as for water, those molecules are lose and they are more free than ice.
The answer is: Ice expands (volume is increasing) when it freezes, because of hydrogen bonds.
When molecule frezes, it lose energy. When molecules are far apart, it means the volume is greater and it expands.
For example, ice expands when water is freezing.
Hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen atom (H), covalently bound to a highly electronegative atom such as flourine (F), oxygen (O) and nitrogen (N) atoms.
The correct answers are B. Constellations can be used for navigational purposes, D. Constellations are used by astronomers to locate objects in the night sky., and E. Constellations are used by astronomers to locate objects in the night sky.
