11.1 - Do Liquids Conduct Electricity?

In this section, we will explore whether liquids can conduct electricity. Electricity is the flow of electric charge, and conductors are materials that allow this flow of charge to pass through them easily. While metals are known to be good conductors of electricity, the ability of liquids to conduct electricity depends on the presence of certain substances dissolved in them.

Liquids in their pure form (like pure water) do not conduct electricity well. However, when certain substances like salts, acids, or bases are dissolved in water, they dissociate into ions, making the liquid capable of conducting electricity. These ions, which are charged particles, help in the movement of electric charge through the liquid.

When an electric current is passed through a liquid, the ions present in the liquid move towards the electrodes, creating a flow of charge. The process is similar to how current flows through a metal wire, but in the case of liquids, it's the ions that carry the current rather than electrons.

Key Concepts:

• Pure Water and Electricity: Pure water is a very poor conductor of electricity because it has very few ions.
• Electrolytes: Substances that dissociate into ions when dissolved in water are called electrolytes. Examples include common salt (NaCl), acids like HCl, and bases like NaOH.
• Ionization: The process of dissolving substances like salts, acids, or bases in water to form ions is called ionization. For example, when NaCl (sodium chloride) dissolves in water, it dissociates into sodium ions ($\text{Na}^+$) and chloride ions ($\text{Cl}^-$).

Examples of Conducting Liquids:

• Salt Water: When table salt (NaCl) is dissolved in water, it forms sodium ($\text{Na}^+$) and chloride ($\text{Cl}^-$) ions, which can carry electric charge.
• Acidic Solutions: Acids like hydrochloric acid (HCl) dissociate into hydrogen ions ($\text{H}^+$) and chloride ions ($\text{Cl}^-$), making the solution conductive.
• Base Solutions: Alkalis like sodium hydroxide (NaOH) dissociate into sodium ions ($\text{Na}^+$) and hydroxide ions ($\text{OH}^-$), which also conduct electricity.

Experiment: Conductivity of Liquids

An experiment can be conducted to test the conductivity of different liquids. The basic setup consists of a battery, two electrodes, and a liquid sample. When the electrodes are placed in the liquid and a current is passed, a bulb connected to the circuit will glow if the liquid conducts electricity. The brightness of the bulb indicates the conductivity of the liquid.

Steps:

1. Set up a simple circuit with a battery, bulb, and two electrodes.
2. Place the electrodes in different liquids, such as distilled water, salt solution, vinegar, and sugar solution.
3. Observe the bulb for any glowing. A glowing bulb indicates that the liquid is conducting electricity, while a non-glowing bulb shows that the liquid does not conduct electricity.

Why Do Some Liquids Conduct Electricity?

The ability of a liquid to conduct electricity depends on the presence of free-moving charged particles (ions) in the liquid. In a non-conducting liquid, there are no free ions, so no current can flow. However, when electrolytes dissolve, they break apart into ions that can move freely and carry electrical charge. The more ions present, the better the liquid will conduct electricity.

Formula for Conductivity:

The electrical conductivity ($\sigma$) of a solution can be expressed as:

$ \sigma = \dfrac{1}{\rho} $

Where $ \rho $ is the resistivity of the solution, and $ \sigma $ is the conductivity. The resistivity depends on the nature and concentration of ions in the liquid.