Assumptions
- All states of matter are made up of tiny particles. However the state of aggregation of particles is different in the three states.
- The particles are separated by empty spaces called voids.
- The particles exert attractive forces on one another. However, the magnitude of these inter-particle forces differ in three states of matter.
- The particles are not stationary, but have a tendency to acquire motion.
Particle model and three states
The basic differences between the three states of matter explained on the basis of particle model are as follows:In solids the particles are closely packed and the voids between them are very small. The average distance between the particles is of the order 10-8cm. Due to small voids, the particle motion is limited to vibratory motion and the intermolecular/particle force of attraction is very high. Thus they have a definite shape, high density, incompressibility and a high melting and boiling point.
Liquid state is intermediate of solids and gases. When compared to solids, the particles are relatively loosely packed. The average distance between particles is of the order 10-7 to 10-5cm. The inter-particle forces are relatively weaker than those in solids but stronger than those in gases. As such, the liquid particles can move about but cannot separate. Thus, liquids have a definite volume with their boiling points above room temperature.In a gas the particles are very loosely packed at random. The voids between particles are very large. The attractive forces between the particles are negligible. The motion is rapid and they move in all directions. Due to the random motion and weak inter-particle forces, they do not have any bonding surface. As a result they do not have a definite volume.
Distinction between three states of matter
| Solids | Liquids | Gases |
|---|---|---|
| Particles are very closely packed thus rigid | Particles are loosely packed thus can flow | Particles are very loosely packed and can flow |
| Voids are extremely small thus incompressible | Voids are relatively larger thus slightly compressible | Voids are very large thus highly compressible |
| Particle motion is restricted to vibratory motion | Particle motion is very slow | Particle motion is very rapid and also random |
| Inter-particle force is very large thus very dense | Inter-particle forces are intermediate resulting in low density | Inter-particle forces are negligible. Thus imparting very low density |
