Question

Why do solids have a definite shape and volume but not gases.

Answer 1

Definition of matter

Matter is made up of very small particles called atoms. Atoms are the building blocks of matter.

According to kinetic theory of matter, all matter exist in three states- solid, liquid, and gas

Solid state-

• The particles are tightly packed.
• The interparticle force of attraction is very strong.
• The interparticle space is almost negligible and so the movement of particles is very limited and they move about their fixed position only.
• Kinetic energy of the particles is very low.
• Solids have fixed shape and definite volume. Particles of solid cannot move easily from their position and so the solids are hard and difficult to compress.
• The strong inter-particle force of attraction prevent the particles from sliding over each other and so the solids cannot flow.

Gaseous state -

• In gaseous state, the particle are present far apart from each other.
• The inter-particle force of attraction is negligible as compared to solids and liquids. Hence the particle move around freely and independently.
• The interparticle space is very large and so the gases occupy the entire space available in a container and do not have a definite volume and can be compressed easily.
• Kinetic energy of the particle is very high. The particles move around freely colliding with each other and also with the walls of the container.
• Gases have no fixed shape and no fixed volume. Gases can easily flow and specially in the entire space available.