Plasma, the fourth state of matter

Arrangement of molecules in solids:

The molecules in solids are packed close to each other. The only movements they make are small vibrations about their fixed positions. The spaces between molecules are known as inter-molecular spaces. These are almost negligible in solids. Due to this, the molecules attract each other very strongly. This force of attraction, known as the intermolecular force of attraction, holds the molecules together.

Arrangement of molecules in liquids:

The molecules in a liquid can move about within the container. They are less tightly packed than in solids, that is, they have bigger intermolecular spaces. The molecules of liquids do not have fixed positions. The intermolecular forces of attraction between the molecules of a liquid are weaker than those in solids.

Arrangement of molecules in gases:

The molecules in gases are far apart from one another. They have huge intermolecular spaces between their molecules. There are almost no intermolecular forces of attraction holding them together. The molecules collide with each other and move in all directions. The molecules of gases have more kinetic energy than liquids and solids.

In the solid state the molecules are compactly arranged at ordinary temperature. 

Solids will have a closely built grid of atoms. When the temperature increases above 

the critical value, solids melt and become liquids. The grid of atom is broken but the 

bond between the molecules is not broken. When the liquid is heated, it turns into a 

gas. If we increase the temperature further, the electrons and the nucleus no longer 

stay together. The electrons are removed or pulled from the atoms and Plasma State 

is formed.

Example: When ice is heated above 0 degrees centigrade it melts and becomes liquid water. When water is heated above 100 degrees centigrade it is transformed into gas or steam. If the temperature of steam is increased further, the electrons and the nucleus of the atom will not stay together. That is the electrons will detach from the atoms forming ions and the plasma state is formed.

Plasma state does not have definite shape or volume like gaseous state of matter. This state of matter can exist only in the very high temperature. Atoms lose electrons in this state. Electrons are free to move. In Plasma state the bare nuclei are swimming in the sea of electrons.

Plasma state is the fourth state of matter. Plasma state is not ordinarily found in natural state on earth. But, plasma state is the most common state of matter found outside the earth. Plasma is neutral. Plasma state is found in the environment of planets, stars, and space. Particles in space exist in the form of plasma. Space is not an empty vacuum.  But, it is made of ions and charged particles. These charged particles can conduct electricity and sound. 

Solids, liquids and gases are considered as low energy particles which are present in

the earth's crust whereas plasma is considered to be a higher energy particle. Plasma state exists outside the earth. Plasma state consists of gases sufficiently heated to a high temperature so that the atoms ionise themselves.  Most of the matter in the universe is in the plasma state. The plasma state exists in our sun, solar wind, interstellar and inters planetary spaces, northern lights or aurorae, solar wind, Earth’s ionosphere, tail of comets  and when the lightning strikes the earth.

Plasma is a state of matter in which all matter is ionized and it occurs in the form of ions and electrons. An ion is formed when an atom or a molecule gains or loses electrons. The electrons move freely with positively charged ions, called cations. Plasma state is a collection of both positively charged cations and negatively charged electrons. If we have to ionise an element we need to pull electrons. For that high energy is required to pull electrons from its nuclear attraction. Therefore, on earth, the plasma state can be produced under controlled conditions at high temperatures. Plasma state is used in making neon sign lamps, Plasma TVs, fluorescent lights and in welding flames.

Solids and liquids can be ionized to become plasmas. This requires extreme temperatures to create plasma. When gas is heated, it is called thermal plasma and it gives off more heat, light, radiation and noise or vibration. Many devices have been designed to make to use of these energies efficiently. Plasmas are not always hot they can be cold too, as long as matter is ionized. A tube light, a CFL, and a plasma TV screen are comparatively cool to touch.

Uses of Plasma:

Micro-plasma welding is a method used to join paper thin sheets of metals. The joint becomes invisible after polishing. Stainless steel water storage tanks and other kitchen implements are made this way.

Plasma spray process is a use of thermal plasmas. It is the only coating process that can apply any material on to any material.

1.    Metal on to metal: Titanium on to mild steel, to prevent corrosion of steel.

2.   Non-metal on to metal: alumina on to stainless steel. Alumina reduces the wear and tear on the stainless steel vessel due to industrial processes.

3.   Metal on to non-metal: copper on to porcelain used in capacitors. Plasma-spraying copper onto the porcelain makes it 'solderable', so that electric wires can be attached to it.

4.    Non-metal on to non-metal: Teflon on to magnesia (ceramic). Some chemicals like hydrofluoric acid can corrode the ceramic vessels they are kept in; coating them with Teflon prevents corrosion.

5.    Cold plasmas are used in sterilizers for bio medical tools and as a hand washer.

6.    Neon in its plasma form is used for lighting.