Solid State

Solids are the chemical substances which are characterised by define shape and volume, rigidity, high density, low compressibility. The constituent particles (atoms, molecules or ions) are closely packed and held together by strong interparticle forces

Characteristic properties of the solid state:

Ø They have definite mass, volume and shape.

Ø Intermolecular distances are short.

Ø Intermolecular forces are strong.

Ø Their constituent particles (atoms, molecules or ions) have fixed positions and can only oscillate about their mean positions.

Ø They are incompressible and rigid.

Cause of Existence of Solid State

The solid state exists because of following reasons. They are:

· Intermolecular Forces

· Thermal Energy

Intermolecular Forces

The forces between constituent particles of matter inside solid are known as intermolecular forces. The forces are attractive in nature and are responsible for holding all the particles together and making the existence of solid state possible. The constituent particles are held such that they can’t move from their position and adhere to only oscillate about their mean position. There are four types of intermolecular forces, namely:

· Dipole-Dipole forces

· London Dispersion forces

· Hydrogen bonding

· Induced-dipole forces

All the first three intermolecular forces are collectively called Van der Waals Forces and are responsible for the existence of solid.

Thermal Energy

The energy acting between constituent particles of matter in a solid is known as Thermal Energy. Thermal energy is also called Kinetic Energyand is responsible for motion of molecules inside solid lattice. Thermal energy increases with increase in temperature. And hence more the thermal energy faster will be the movement of molecules. At low temperature the value of thermal energy is low and intermolecular forces are stronger. This resists the flow of molecules and adhere them to oscillate about their mean position.