Q.Why do solids have a definite volume?

The particles in a solid are held in fixed positions by strong forces, so the distances between them stay constant. With no freedom to expand or move apart, the solid occupies a definite volume.

Step 1 – Fixed positions.

In a solid the particles occupy fixed positions in a regular arrangement, held by strong intermolecular forces.

Step 2 – Constant interparticle distances.

Since the particles only vibrate about their mean positions and cannot move apart, the inter-particle distances remain essentially constant.

Step 3 – Consequence.

With the spacing fixed and the particles unable to spread out (unlike a gas) or flow (unlike a liquid taking a container's shape), the total space occupied is fixed — the solid has a definite volume.

Use the same fixed-position argument: strong forces keep constant interparticle distances, so the occupied space (volume) is fixed and definite.

• Explaining definite volume by "close packing" only, without mentioning strong forces holding particles at fixed distances.
• Confusing definite volume with definite shape (rigidity) — the question asks specifically about volume.
• Claiming solids are incompressible "because there is no space between particles"; there are voids, but the fixed separations are the key point.