The conductivity of water is a measure of the capability of water to pass electrical flow. This ability is directly dependent on the concentration of conductive ions present in the water. These conductive ions are originated due to inorganic materials such as chlorides, alkalis, carbonate and sulfides compounds and dissolved salts.
The degree to which water conducts or transmit, electricity or heat or sound in it is called conductivity of water. It is denoted by s or k.
The conductivity of water can be measured using multiple units. Some of them are:
|SI units||Siemens per meter [S/m]|
|U.S units||millimhos per centimeter [mmho/cm]|
The value of conductivity of water for various types of water is given below:
|Types of water||Conductivity Value|
|Pure distilled and Deionized water||0.05 µS/cm|
|Drinking water||200 to 800 µS/cm.|
|Rain or Snow water||2 to 100 µS/cm|
Conductivity is nothing but the measure of the capability of water to pass the flow of electric current. This ability of conductance is said to be directly proportional to the concentration of the ions present in the water.
The Compounds which dissolve into the ions are known as the electrolytes. The more the number of ions present in the electrolyte, then the higher is the conductivity of water. In a similar way, fewer the number of ions present in water, then less conductive is the conductivity of water. De-ionized or distilled water can also act as an insulator due to the very low value of conductivity. Seawater is said to possess a very high value of conductivity.
Pure water is said to be a bad conductor of electricity. Normal water is said to have impurities present in the form of ions called minerals etc. These ions are known to be responsible for the conduction of electric current in the water. Because, the electrical current in water is transported by the ions present in them, and the conductivity is said to increase with the increase in the concentration of ions in them.
The salt water is a good conductor of electricity. Its conductivity is greater than normal water. This is because salt molecules are made of sodium ions and chlorine ions (NaCl).
Till now we have learnt that conductivity is purely the result of conductive ions present in the water. But how it actually conducts is the question. It can be simply explained by the following steps:
This shows that, though the conductivity of the water increases with the addition of ions, it tends to remain electrically neutral.
Specific conductance is the measurement of conductivity that is made at a temperature of 25° C. This is called the standardized method of achieving the conductivity. As the temperature of the water affects the conductivity reading, reporting the conductivity at about 25° C allows the data to be compared easily. The Specific conductance is basically reported in uS/cm at about a temperature measuring 25° C.
If the measurement of conductivity is accomplished at a temperature of 25° C, then it can be called as the specific conductance. And, If the measurement is done at different temperatures and later corrected to the temperature of 25° C, then it is called as the temperature coefficient.
Q1) How conductivity and Salinity are related?
Ans: Conductivity is directly proportional to salinity. That is when salinity increases, the conductivity will also increase.
Q2) How temperature is related to the conductivity of water?
Ans: When the temperature is increased, the conductivity of the water will also increase.
Q3) Why is salt water conductive?
Ans: Saltwater is conductive due to the presence of Sodium and Chloride(NaCl) ions in it.
Q4) What factors affect conductivity in the water?
Ans: The factors affecting the conductivity of water are-
Q5) How does the conductivity of water is tested?
Ans:The electrical conductivity of water is measured by determining the resistance of the solution between two flat/cylindrical electrodes separated by a fixed distance. An alternating voltage is applied in order to avoid electrolysis. Thus, the resistance is measured by a conductivity meter.
Q6) What is the conductivity of distilled water?
Ans: The distilled water conductivity is 0.05 µS/cm.
Q7) What is the conductivity of drinking water?
Ans: The drinking water conductivity is 200 to 800 µS/cm.