Conductivity of Water

PhysicsElectricity

Introduction

We know that liquids like water carry electric currents due to the presence of salt in them. We get water from natural sources like rivers, lakes, and streams. Minerals are present in this water. They are nothing but salts that carry electric current.

Let's understand the concept of conductivity before studying the conductivity of water.

Conductivity of Water

Conductivity is the ability of a material to pass the electric current through it.

The conductivity of water is the measurement of the capacity of ions present in water to pass electric flow. The conductivity of water depends on the concentration of ions. If the concentration of ions is more, the conductivity of water is high.

If the concentration of ions is less, the conductivity of water is less. The conductivity of water is denoted by k or s. A conductivity meter is an instrument used to measure the conductivity of water.

Units of Conductivity of Water

• SI unit- Siemens per meter (S/m)
• US unit- millimhos per centimetre (mMho/cm)

Conductivity of Saltwater

Saltwater is a good conductor of electricity. Salts break their bond and dissolve in water. They have both cations and anions. Cations are positively charged ions while anions are negatively charged ions. When the electric current is passed through water, cations and anions carry electric current.

Example 1

We will take the example of sodium chloride in water. Sodium is a cation and chloride is an anion. Both carry electric current. There are some other minerals present in water other than sodium ions and chloride ions. Water also contains cations like calcium and magnesium. Anions like carbonates and sulphates are present in water.

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Use of Conductivity of Water

• The conductivity of water is used to determine the total dissolved solids (TDS) of water. Total dissolved solids are the number of ions in water. The test of total dissolved solids is carried out to determine the purity of lakes, rivers, and streams. If the salinity of the water is more in rivers or lakes, then some processes are carried out to reduce salts. These processes make water drinkable for us. The conductivity of water is done regularly. Conductivity in rivers or lakes can be harmful to aquatic plants and animals so necessary precautions are taken.

• The measurement of the conductivity of water helps in the agricultural field. The quality of crops depends on the quality of water. The conductivity of water is also used in irrigation and manufacturing unit.

• The conductivity of water is also used in the industry of packaged drinking water.

Factors Affecting the Conductivity of Water

• Temperature.
• The concentration of ions in solution.

Values of Conductivity in Various Types of Water

• Pure water or distilled water - 0.05 $\mathrm{\mu S/cm}$
• Rainwater- 2 to 100 $\mathrm{\mu S/cm}$
• Drinking water- 200 to 800 $\mathrm{\mu S/cm}$
• Seawater- 50 $\mathrm{m S/cm}$

Specific Conductance

Specific conductance is the measurement of conductivity of a substance at 25°C. It is the standard method to determine the conductivity of water. The readings obtained from specific conductance of water are considered standard. The rise and fall in temperature may cause a change in the conductivity of water.

The unit of specific conductance is uS/cm at a temperature of 25°C

Facts About the Conductivity of Water

• The amount of salt varies in various types of saltwater. Therefore, conductivity also varies from water to water.

  The Atlantic Ocean has more salt content than the Pacific Ocean.

• The human body is a good conductor of electricity. In the human body, the cells have ions like sodium, potassium, chlorine, carbonates, etc. They conduct electricity in our bodies.

Conclusion

Water conducts electricity in presence of salts. The conductivity of water is studied because water is the basic need of human beings. We have to perform a test of the conductivity of water to get good quality water for drinking. The good quality of water is always important for domestic and industrial use.

FAQs

Q1. Is pure water a good conductor of electricity?

Ans: Pure water is not a good conductor of electricity. But the presence of salts or electrolytes can make water a good conductor of electricity.

Q2. What is specific conductance?

Ans: It is the measure of the conductivity of a substance at the temperature of 25°C

Q3. How is temperature related to the conductivity of water?

Ans: When the temperature of the water is increased, the conductivity of the water is also increased.

Q4. What is the conductivity of drinking water?

Ans: The conductivity of drinking water is 200 to 800 μS/cm.

Q5. What is the conductivity of distilled water?

Ans: The conductivity of distilled water is 0.05 μS/cm.