Question

Why do solids have a definite shape?

Answer 1

Hint: Consider how inter-particle forces in solids prevent solids from changing shape because these forces are very important in determining the shape of the molecule.

Complete answer:
There are three states of matter, solid, liquid and gas. These states differ in the strength of inter-particle forces. Particles can be an atom/ion/molecule. The decreasing order of the strength of interparticle forces is solid > liquid > gas. Thus inter-particle forces are strongest for solids. They give special properties to solids. Thus solids are in-compressible and rigid, and they have definite shape and volumes. All these properties of solids can be explained on the basis of inter-particle forces.

The particles in solid state are tightly bound to each other,through very strong interparticle forces. Crystalline solids have regular geometric lattice, whereas amorphous solids have irregular structure. Constituent particles in solids have fixed position. These particles cannot move from their respective positions. They can only vibrate around their mean positions. Due to this, solids have structural rigidity. Solids are resistant to change in shape and volume.
It is possible to change the physical state from solid to liquid by supplying heat. It is also possible to change the state from liquid to gas by supplying heat. When heat is removed, a gas can be condensed into a liquid. Similarly, by removing heat, a liquid can be condensed into a solid.

Note: Solids have definite shape and definite volume. Liquids have definite volume but they do not have definite shape. Liquid takes the shape of the container. Gases neither have definite shape nor have definite volume.