Question

which best explains why a crystal is incompressible?

• its molecules switch positions when they are compressed.
• there is little, if any, space left between its adjacent molecules.
• its molecules remain in position without vibrating.
• the molecules of a crystal behave like those of a gas.

Explanation:

Analyze the definition of incompressibility

Incompressibility refers to the inability of a substance to be squeezed into a smaller volume. For a material to be highly incompressible, its constituent particles (atoms, ions, or molecules) must already be packed extremely close together, leaving virtually no empty space between them to be reduced under pressure.

Evaluate the options based on crystalline structure

• Option 1: "Its molecules switch positions when they are compressed." This describes fluid flow or plastic deformation, not the fundamental reason for incompressibility.
• Option 2: "There is little, if any, space left between its adjacent molecules." This directly explains incompressibility because particles in a crystal lattice are tightly packed in a highly ordered, close-contact arrangement.
• Option 3: "Its molecules remain in position without vibrating." This is incorrect because particles in a solid always vibrate about their fixed positions at temperatures above absolute zero.
• Option 4: "The molecules of a crystal behave like those of a gas." This is incorrect because gas molecules are widely separated and highly compressible.

Select the best explanation

The tight packing and lack of empty space between adjacent molecules in a crystal lattice prevent them from being pushed closer together, which best explains why a crystal is incompressible.

Answer:

• Its molecules switch positions when they are compressed.
• There is little, if any, space left between its adjacent molecules. (Correct answer)
• Its molecules remain in position without vibrating.
• The molecules of a crystal behave like those of a gas.