Chapter 2, Problem 25A

Interpretation Introduction

Interpretation: Whether the given process of sublimation, is a physical change or a chemical change needs to be explained.

Concept introduction: The nature of any substance is explained by their chemical properties and physical properties. A physical property describes the physical changes of a substance. Physical change is a temporary change; it is a reversible change. For example, color, mass, volume, etc. A chemical property describes how a substance reacts with other substances. In a chemical change, a new substance is formed and absorption of energy or loss of energy occurs; it is an irreversible change. For example, rusting, dissolving, etc.

Answer to Problem 25A

The given process is a physical change.

Explanation of Solution

In a chemical change, important point is the formation of a new substance; in the given process, called sublimation no new substance is formed. So, it is not a chemical change.

In any changes, if the composition remains the same then it is considered as an example of physical change. In the process of sublimation, a solid change to a gas, but it is still the same substance; only the state of matter has changes. So, it is a physical change.

Conclusion

The sublimation is a physical change.