Chapter U3.7, Problem 3E

Interpretation Introduction

Interpretation : The correct statement has to be selected.

Concept Introduction : Every substance has a specific density at a specific temperature. With change in temperature density of the substance also changes.

Answer to Problem 3E

1. Sample A occupies a larger volume and has a lower density.

Explanation of Solution

Reason for true statement: This is because sample A is warmer than sample B. It has large volume as the gas expands on heating. Since density is inversely proportional to volume; warm air has less density.

This is because sample A is at a higher temperature than sample B. So it is warmer than sample B. Warm air is less dense than cold air. The gas particles in warm air are farther apart so they have more spacing between molecules. Thus the volume is large. Since density is inversely proportional to volume; warm air has less density.

Conclusion

Reason for false statements: (B) This is incorrect as sample A has low density and large volume.

(C) This is incorrect as sample B has molecules moving at low average speed due to low temperature.

Explanation: Sample A is at a higher temperature than sample B. So the volume of sample A is larger than sample B. as volume is larger, density is less. Sample B has higher density than sample A.

The density of a substance changes as the temperature changes. For solids and liquids, this change is small and for gases the change is much larger.