Home › UCE (O-Level) › Chemistry › Intermolecular forces › Ice cubes float on the liquid water in a glass. …
Ice cubes float on the liquid water in a glass. Which unusual property of water explains this?
AA very high specific heat
BA high heat of vaporisation
CA low melting point value
DA less dense solid phase
Answer & Solution
Correct answer: D. A less dense solid phase
1. An object floats when it is less dense than the liquid around it.
2. Most materials contract when they solidify, so their solid phase is denser.
3. Water expands instead, so its solid phase is less dense than its liquid phase.
4. This behaviour also comes from the hydrogen bonds between water molecules.
5. Floating ice insulates the water below it and lets life survive under a frozen surface.
6. Specific heat and heat of vaporisation are real properties of water but neither one decides whether a solid floats.
_Source: Siyavula Physical Sciences Grade 11 (Everything Science, CC BY 4.0), Chapter 4: Intermolecular forces_