Chapter 12, Problem 73A

Interpretation Introduction

Interpretation:

The reason for ice to floats in water but solid benzene sinks in liquid benzene needs to be explained.

Concept introduction:

A solid object can float in liquid, if its density is less than liquid and solid can sink in liquid if the density is more than liquid.

The density is related to mass and volume as follows:

$d=\frac{m}{V}$

Thus, density is inversely proportional to volume.

Explanation of Solution

When water is converted to solid ice, the volume of water gets increases. Since, density is inversely proportional to volume thus, density of solid ice will be less than water and it can float in liquid water.

When liquid benzene is converted into solid benzene, its volume decreases thus, density increases.

Due to higher density of solid benzene than liquid benzene, solid benzene will sink in liquid benzene.

Also, if surface tension of a liquid is less, the solid will sink in liquid. Due to weak intermolecular forces in benzene, benzene liquid has less surface tension thus, solid benzene can sink in liquid benzene. The intermolecular forces in water are strong due to H-bonding thus, solid water will float on the surface of liquid water.