How does the kinetic molecular theory explain state changes at molecular level?

The kinetic molecular theory explains state changes as a result of changes in energy and movement of molecules.

The kinetic molecular theory is a fundamental concept in chemistry that describes the behaviour of matter in different states - solid, liquid, and gas. It postulates that all matter is composed of tiny particles (molecules or atoms) that are in constant motion. The energy of these particles, their movement, and the forces of attraction between them determine the state of the matter.

In a solid state, the particles are closely packed together and vibrate about fixed positions. They have low kinetic energy, which is the energy of motion. The forces of attraction between the particles are strong enough to keep them in fixed positions, hence the definite shape and volume of solids.

When a solid is heated, the particles gain energy and vibrate more vigorously. This increased kinetic energy overcomes the forces of attraction between the particles, causing them to move out of their fixed positions and slide over each other. This is the process of melting, resulting in a change of state from solid to liquid.

In a liquid state, the particles have more kinetic energy than in a solid state. They are not in fixed positions but can move around each other, although they are still closely packed. The forces of attraction are weaker than in solids, allowing liquids to flow and take the shape of their container.

If a liquid is heated further, the particles gain even more kinetic energy. Eventually, the kinetic energy becomes so great that it breaks the forces of attraction completely. The particles move freely and far apart from each other, resulting in a change of state from liquid to gas. This is the process of boiling or evaporation.

In a gas state, the particles have the highest kinetic energy. They move rapidly and randomly in all directions, and the forces of attraction between them are negligible. This explains the ability of gases to expand and fill their container.

In summary, the kinetic molecular theory explains state changes at the molecular level as a result of changes in the kinetic energy of the particles and the forces of attraction between them.