Which statement about the compressibility of a solid is correct?

• A. It is highly compressible
• B. It can be compressed moderately
• C. It can be compressed slightly
• D. It lacks compressibility

Answer: (D)

Solids resist compression because their particles are held in a fixed, tightly packed arrangement by strong interatomic or intermolecular forces. When pressure is applied, the spacing between particles can decrease only a little, so the volume changes very little. This is reflected in a high bulk modulus, meaning the material is very incompressible. Since a solid changes its volume very little under typical pressures, describing it as lacking compressibility captures the practical idea: solids are effectively incompressible compared with gases or liquids. Of course, no material is perfectly incompressible, but for most purposes solids are treated as having negligible compressibility, which is why that statement is the best description.