Conductors and Non Conductors


 Conductors and Non Conductors

Substances around us can be divided into two classes based on their ability of conduct electricity:

·         Non-Conductors: Those substances which do not allow electric current to pass through them are called non-conductors or insulators. Example: - wood, plastic glass, rubber etc.

·         Conductors: Those substances which allow electric current to flow through tem are called conductors. Examples: Copper, Iron, Gold, Silver, Graphite, salt solution etc.

Conductors can further be divided into two groups:

·         Metallic ConductorsThese conductors conduct electricity or electric current by movement of electrons without undergoing any chemical change during the process. These conduct electricity in both solid as well as molten state. Example: All the metals and Graphite
·    Electrolytes: Those substances which conduct electricity only when they are present in aqueous solution or in molten state and not in solid form are called electrolytes. These conduct electricity by movement of ions in solutions.  

Why?
For a substance to conduct electricity; it must either have free electrons or ions which carry electricity with them. Electrolytes neither have free electrons nor free ion in solid state although they are ionic compound. This is because the oppositely charged ions are held together by strong electrostatic attraction and are not free to move. But when they are dissolved in water, the two ions split up and become free to move in solution and now they are free to conduct electricity. Examples of electrolytes are: NaCl, KCl,etc

Electrolytes can further be divided into strong and weak electrolytes:
Strong Electrolytes are those electrolytes which dissociate completely in aqueous solution to give constituent ions. For example: Inorganic salts like NaCl, KCl, Strong Acid like HCl, H2SO4, Strong bases like NaOH, KOH etc.
Weak Electrolytes are those electrolytes which partially dissociate in aqueous solution to give constituent ions. For example:  weak acid like CH3COOH and Weak bases like NH4 OH.
 

Electrochemical Cells

Electrochemical cells are of two types-

·      Galvanic cells (also known as voltaic cell): It is a device, in which a redox reaction is used to convert chemical energy into electrical energy, i.e., electricity can be obtained with the help of oxidation and reduction reaction. The chemical reaction responsible for production of electricity takes place in two separate compartments. Each compartment consists of a suitable electrolyte solution and a metallic conductor. The metallic conductor acts as an electrode. The compartments containing the electrode and the solution of the electrolyte are called half-cells. When the two compartments are connected by a salt bridge and electrodes are joined by a wire through galvanometer the electricity begins to flow. This is the simple form of voltaic cell.
·         Electrolytic cells: In this type of cells electrical energy is used to carry out a non-spontaneous reaction.
In simple words, one can say that in galvanic cells, chemical energy is converted into electrical energy, while in electrolytic cell electrical energy is converted into chemical energy