A sample of carbon dioxide that undergoes a transformation from solid to liquid and then to gas would undergo

A phase change, such as carbon dioxide transforming from solid to liquid and then to gas, is a physical change [3]. During this process, the molecular structure and chemical composition of the substance remain identical [1]. Therefore, there is no change in mass or chemical composition [3]. However, physical properties like state, shape, and density do change. Density is defined as mass per unit volume; while mass remains constant, the volume occupied by a substance significantly increases as it transitions from a solid to a liquid and then to a gas. In the gaseous state, molecules are much further apart than in the solid or liquid states, leading to a drastic decrease in density. Thus, the sample undergoes a change in density while its chemical identity remains CO2 throughout the transformation [1].

Sources

1. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 5: Changes Around Us: Physical and Chemical > C. Crushing a piece of chalk > p. 59
2. [1] https://education.nationalgeographic.org/resource/changes-matter-physical-vs-chemical-changes/