MCQ Detailed View

The dielectric constant of a substance is a measure of how effectively it can reduce the electric field within it. It is also called the relative permittivity. At room temperature (around 25°C), the dielectric constant of water is approximately 80, which is considered very high compared to many other materials.

This property arises because water molecules are polar. Each molecule has a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. When an electric field is applied, these dipole molecules align themselves in the direction of the field, opposing and weakening the external electric field. This alignment reduces the overall force between charges placed in water, making water an excellent dielectric medium.

The high dielectric constant of water has several important consequences. In physics, it explains why water can store electrical energy effectively in capacitors when used as a dielectric. In chemistry, it explains why water is a universal solvent. Since it can significantly reduce the electrostatic forces between ions, it allows salts and many polar compounds to dissolve easily. For example, sodium chloride (NaCl) dissolves readily in water because the attractive forces between Na⁺ and Cl⁻ ions are weakened by the surrounding polar water molecules.

In contrast, non-polar liquids like benzene or hexane have very low dielectric constants (typically less than 5). That is why they cannot dissolve ionic substances as effectively as water.

In summary, the dielectric constant of water at room temperature is about 80. This unique property makes water one of the most important substances in both natural processes and scientific applications, especially in fields like electrostatics, material science, and chemistry.