Ice is less dense than liquid water because in ice each water molecule
- A. loses one of its hydrogen atoms
- B. is hydrogen bonded to four others in an open tetrahedral arrangement
- C. moves faster than in the liquid
- D. is compressed closer to its neighbours
Explanation
Every molecule uses its two hydrogens and its two lone pairs, so a rigid open cage with large empty spaces is formed, and this occupies more volume than the same molecules jostling in the liquid. Water is therefore anomalous in expanding on freezing, which is why pipes burst in winter and why ice floats. Almost every other substance contracts as it solidifies.