Four States of Matter

Matter is anything that possesses mass and occupies space. In other words, one which you can weigh and measure volume is matter. Matter includes everything which satisfies the above two conditions: mass and volume. As we know, all substances around us compose of atoms. Atoms have mass and occupy space; hence they are matter. So, we can say that anything which is composed of atoms is matter. Some of the examples of matter are pen, banana, phone, car, rocket, milk, water, air etc. We ourselves are made up of atoms; so, we also are matter.

States of matter

In the cold winter season, water starts to freeze and a layer of ice forms on the surface of the water. This phenomenon is observed in rivers and lakes in colder countries. When a vessel filled with water is kept on a kitchen stove, it boils. We can see the water vapour leaving the vessel. Therefore, water exists in forms: solid as ice, liquid as water, gas as vapour. These different forms of water are called states of matter. A state of matter is a distinct form of matter. There are four classical or fundamental states of matter, viz. solid, liquid, gas, and plasma. The latter among the four is not common in comparison to the rest three.

Solid

In solids, constituent particles are very close to each other. The freedom of movement in solids is less. This is because of strong attractive forces among the particles. Thus, solids have a definite volume and a definite shape. Solids deform only when subjected to an external force.

The constituent particles of solids do possess internal energy because of which the particles vibrate about their mean position. The vibration increases with the rise in temperature. Various properties associated with solids are elasticity, plasticity, rigidity, malleability, ductility, conductivity etc. Solids can further classify as amorphous (or non-crystalline) and crystalline solids. In amorphous solids, the particles are randomly arranged; there is no orderly repeating pattern. Examples of amorphous solids include rubber, chalk, plastic etc. While in crystalline solids, the particles are regularly arranged in a symmetrical manner to form a unit cell. This cell is repeated over the entire crystal. The examples are this form of solids are sodium chloride, ice, sugar, diamonds, rubies, metals etc.

Solids on heating convert into liquids. This is called melting of solids. When ice is left open in air, it slowly melts to form liquid water. The Solid can directly transform into gas through a process of sublimation.

Liquid

Liquids come between solids and gases. The constituent particles in liquids are close to each other. Though, they are not as close as in solids. Intermolecular forces among particles are relatively stronger in comparison to gases but weaker to solids. The particles in liquids can easily move around each other. Liquids have a definite volume but not a definite shape. They assume the shape of a container in which they are placed. Most liquids are incompressible. Some of the properties associated with liquids are density, flowability, conductivity, viscosity, refractive index, surface tension. Liquids on heating transform into gases by process of vaporisation. But on freezing they solidify.

Gas

Gases have neither a definite volume nor a definite shape. They take the volume and shape of a container in which they are stored. The constituent particles of gases are far apart from each other. The intermolecular force of attraction is very weak. The particles can move freely in any direction. The velocity of particles in gases is much higher relative to liquids and gases. Since the particles in gases are far apart, there is a lot of empty space between the particles. So, they can easily compress. Gas has the lowest density compare to solid and liquid. Some of the properties pertaining to gases are density, pressure, temperature, viscosity. Gases can liquefy under compression or cooling. This process is called condensation of liquids. They can also to directly transform into solid through a process deposition (or desublimation).

Plasma

Plasma is the last fundamental state of matter. Unlike the above three, it does not exist in normal condition. It is generated when gas is heated to extreme temperature or there is a high voltage difference between two points. In such extreme conditions, electrons in atoms get energize and depart from the parent atoms. These dissociated electrons move freely in space. It is also known as ionisation of the gas.

It is like positively charged nuclei swimming in the ocean of free electrons. This is like conductive metals.

Like gas, plasma does not have a definite shape and volume. Like metal, plasma conducts electricity; it produces a magnetic field. Examples of plasma are electric sparks, lighting during a thunderstorm, neon signs, the corona of Sun.

Comparison among states of matter

The below table is the summary of all the above points.

Associated Articles

• Classification of matter
• Properties of matter