Question

The low density of ice compared to water is due to :

• A. hydrogen bonding interactions
• B. dipole-dipole interactions
• C. dipole induced dipole interactions
• D. induced dipole induced dipole interactions

Hint:

Ice floats on water because hydrogen bonding creates an open structure with more volume.

Answer 1

The Correct Option is A

Concept: Hydrogen bonding in water Water molecules form strong intermolecular hydrogen bonds: \[ \text{H–O}\cdots\text{H–O} \]

Step 1: Structure of ice In ice, each water molecule forms 4 hydrogen bonds, creating a rigid open hexagonal structure. This structure has:
• Large empty spaces (cavities)
• Molecules held farther apart

Step 2: Structure of liquid water In liquid water:
• Hydrogen bonds are partially broken
• Molecules come closer together
• Structure becomes more compact

Step 3: Effect on density \[ \text{Density} = \frac{\text{Mass}}{\text{Volume}} \] Ice has:
• Same mass
• Larger volume \[ \Rightarrow \text{Lower density} \] Final Answer: \[ {\text{Hydrogen bonding interactions}} \]