Why is ice less dense than liquid water?

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.

answer: cellular respiration takes in food and uses it to create atp, a chemical which the cell uses for energy. usually, this process uses oxygen, and is called aerobic respiration. it has four stages known as glycolysis, link reaction, the krebs cycle, and the electron transport chain.