Conductors and Non-conductors
Class : 12
The substances which allow the passage of electric current through them are called conductors. It may, however, be pointed out that all conductors do not conduct electricity to the same extent. Depending upon the ease with which they allow the passage of electricity, they are termed as good conductors or poor conductors. Although it is not possible to sharply distinguish between the good and poor conductors, but a rough division is possible on the basis of relative ease with which the conductor allows the passage of electricity. The substances which do not conduct electricity are called non-conductors or insulators.
Classification of Conductors
Conductors, in general, can be classified in three categories, viz., gaseous, metallic and electrolytic. The gases conduct electricity under high potential difference at low pressure, or when exposed to certain radiation. Here, our concern is mainly on metallic and electrolytic conductors.
Metallic Conductors
In metallic conductors, the charge carriers are the electrons, the atomic nuclei remaining stationary, and the passage of electric current is not accompanied by any movement of matter. Such a mode of conduction, generally called metallic conduction, is not only exhibited by the pure metals, but also by alloys, carbon, and certain solid salts and oxides. Metallic conductors are the best conductors of electricity. The metallic conduction decreases with rise in temperature.
Electrolytic Conductors
Substances like salts in molten state and in solution conduct electricity through them. However, unlike metallic conductors this class of conductors undergo chemical change during the passage current through them. Substances which in the form of solution in a suitable solvent or in molten state allow the passage of current and simultaneously undergo chemical transformation are called electrolytic conductors or electrolytes and the conduction as electrolytic conduction. Generally, electrolytes are either ionic compounds such as Nacl, CaCl2, etc. or polar covalent compounds such as HCL, CH3COOH, etc. On the other hand, the substances that do not conduct electricity either in molten state or in solution phase are called non electrolytes, e.g., sugar, glucose urea, etc. The electrolytic conductors transport current through the movement of charged particles called ions. Since ions are heavy, the electrolytic conductors are less conducting as compared to the metallic conductors. The electrolytic conduction increases with the rise in temperature.
Thus, electrolytic conduction mainly occurs through movement of charge carrying ions and it is always accompanied by electrochemical changes.
Classification of Electrolytes
Electrolytes in the form of solution in a suitable solvent (usually water) or in molten state split into ions and hence, conduct electric current. However, all the electrolytes do not ionize to the same extent. Depending upon the extent of ionization, the electrolytes are divided into two classes: strong electrolytes and weak electrolytes.
1) Strong electrolytes: The electrolytes which ionize or dissociate almost completely into ions in aqueous solution are called strong electrolytes. The solution of strong electrolytes is a good conductor of electricity and has a high value of equivalent conductance even at low concentrations. The examples of such electrolytes are given below.
Acids: HCL, H2SO4, HNO3, HCLO4, HBR, HI, etc.
Bases: NaOH, KOH, Ca(OH)2, Mg(OH)2, etc.
Salts: Practically all salts are strong electrolytes like NaCL, CaCL2, KCL, etc.
Classification of Conductors
Conductors, in general, can be classified in three categories, viz., gaseous, metallic and electrolytic. The gases conduct electricity under high potential difference at low pressure, or when exposed to certain radiation. Here, our concern is mainly on metallic and electrolytic conductors.
Metallic Conductors
In metallic conductors, the charge carriers are the electrons, the atomic nuclei remaining stationary, and the passage of electric current is not accompanied by any movement of matter. Such a mode of conduction, generally called metallic conduction, is not only exhibited by the pure metals, but also by alloys, carbon, and certain solid salts and oxides. Metallic conductors are the best conductors of electricity. The metallic conduction decreases with rise in temperature.
Electrolytic Conductors
Substances like salts in molten state and in solution conduct electricity through them. However, unlike metallic conductors this class of conductors undergo chemical change during the passage current through them. Substances which in the form of solution in a suitable solvent or in molten state allow the passage of current and simultaneously undergo chemical transformation are called electrolytic conductors or electrolytes and the conduction as electrolytic conduction. Generally, electrolytes are either ionic compounds such as Nacl, CaCl2, etc. or polar covalent compounds such as HCL, CH3COOH, etc. On the other hand, the substances that do not conduct electricity either in molten state or in solution phase are called non electrolytes, e.g., sugar, glucose urea, etc. The electrolytic conductors transport current through the movement of charged particles called ions. Since ions are heavy, the electrolytic conductors are less conducting as compared to the metallic conductors. The electrolytic conduction increases with the rise in temperature.
Thus, electrolytic conduction mainly occurs through movement of charge carrying ions and it is always accompanied by electrochemical changes.
Classification of Electrolytes
Electrolytes in the form of solution in a suitable solvent (usually water) or in molten state split into ions and hence, conduct electric current. However, all the electrolytes do not ionize to the same extent. Depending upon the extent of ionization, the electrolytes are divided into two classes: strong electrolytes and weak electrolytes.
1) Strong electrolytes: The electrolytes which ionize or dissociate almost completely into ions in aqueous solution are called strong electrolytes. The solution of strong electrolytes is a good conductor of electricity and has a high value of equivalent conductance even at low concentrations. The examples of such electrolytes are given below.
Acids: HCL, H2SO4, HNO3, HCLO4, HBR, HI, etc.
Bases: NaOH, KOH, Ca(OH)2, Mg(OH)2, etc.
Salts: Practically all salts are strong electrolytes like NaCL, CaCL2, KCL, etc.
The equations for the ionization or dissociation reactions of reactions of strong electrolytes are written with only single headed arrow (----> ) directed to the right. For example,
HCL + Water ---------> H+(aq) + Cl-(aq)
Na+Cl- + Water ---------> Na+(aq) + Cl-(aq)
Weak electrolytes: The electrolytes which ionize to a small extent in aqueous solution are called weak electrolytes. Aqueous solution of a weak electrolyte is a poor conductor of electricity and has a low value of equivalent conductance. The example s of such electrolytes are given below.
Acids: H2SO3, H2CO3, all organic acids such as phenol, oxalic acid, acetic acid, etc.
Weak electrolytes: The electrolytes which ionize to a small extent in aqueous solution are called weak electrolytes. Aqueous solution of a weak electrolyte is a poor conductor of electricity and has a low value of equivalent conductance. The example s of such electrolytes are given below.
Acids: H2SO3, H2CO3, all organic acids such as phenol, oxalic acid, acetic acid, etc.
Bases: NH4OH, organic bases such as alkyl amines etc.
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