What Is Conductivity In Chemistry?

Kate Onissiphorou

by Kate Onissiphorou

9th February 2022

Conductivity is the transfer of energy through contact with a material or materials. It can refer to electric conductivity, acoustic conductivity or thermal conductivity. A material can be a good conductor or a good insulator.

Different types of materials have varying degrees of conductivity. The unit of conductivity can also vary depending on the type of energy that’s being transferred. For example, electrical conductivity is measured in siemens per metre, while heat conductivity is measured in watts per metre-kelvin.

A material’s conductivity is influenced by several factors, including temperature, the composition of the material, its state of matter, and its structure. The conductivity of a material has huge implications for its practical uses and applications. 

What Are Different Types of Conductivity?

The energy being conducted can be in any form that can propagate through a material. It could be electricity, thermal energy, sound energy or ionic energy, for instance.

Here are some examples of the different types of conductivity:

  • Thermal conductivity – thermal conductivity is a material’s ability to conduct heat or thermal energy. Thermal conductivity is normally measured in watts per metre-kelvin or W/mK. Although materials that have good thermal conductivity (e.g. metals) are efficient in transferring heat, they also dissipate heat easily. As a result, they’re often used as heat sinks, such as in the case of aluminium heat sinks in electronic circuits. Conversely, materials like gases that have low thermal conductivity (i.e. high thermal resistivity) are good insulators.A graphic showing the conduction process
  • Electrical conductivity metallic and polarised materials are good electrical conductors. Conductivity is measured in the SI unit siemens per metre or S/m. Materials that are good conductors play a vital role in generating and transmitting electricity. Cities and industries are dependent on these electrical conductors for power. Although metals such as gold are excellent conductors, copper is mainly used because it’s cheaper and relatively abundant.
  • Ionic conductivity this type of conductivity is similar to electrical conductivity but at a molecular level. It’s a measure of how ions (charged particles) move through the molecular structure of matter. Chemicals that are capable of allowing ions through their molecular or crystalline structure are known as electrolytes. They’re typically in a solid or liquid state. Ionic conductivity is crucial to how batteries work.
  • Acoustic conductivity refers to the capacity of a material to allow the propagation of sound waves through its structure. Unlike electromagnetic waves, which include heat, sound waves cannot travel through a vacuum. Instead, they require a medium like air through which to travel.
    Close up of a person playing the guitar

    Sound waves require air to travel

  • Hydraulic conductivity this is a measure of how well water can penetrate a porous substance such as a rock surface. Hydraulic conductivity is crucial in the study of agriculture and hydrology.

All of these types of conductivity are important in chemistry as they enable us to analyse the physical behaviours of various substances under different conditions. For example, measuring the ionic conductivity of a substance can help researchers develop better batteries with increased capacity and longevity.

What is Electrical Conductivity in Chemistry?

Electrical conductivity is vital for generating, transmitting, distributing, storing and using electrical energy. From high-voltage electricity generated by power plants to low-powered electricity stored in small batteries, the electrical conductivity of metals, semiconductors, and other materials is central to the technological marvels we enjoy today. Whether it’s a digital wristwatch or a Maglev bullet train, metal conductivity plays a crucial role in everything around us.

Electrical conductivity in chemistry is defined as the ability of valence electrons in a substance to freely move, especially when induced in the presence of moving magnetic fields. 

In simple terms, an electrically conductive substance easily allows the flow of an electrical current with minimal resistance. Electrical conductivity is measured in the unit siemens per metre (S/m). It is a ratio of the current density to the strength of the electric field.

Various electrically conductive materials have specific conductivity levels at certain temperatures. As a general rule, colder temperatures tend to make a metal more conductive. The table below shows the comparative conductivity of 10 key metals.

A table showing the conductivity of metals

How to Determine Electrical Conductivity in Chemistry

Aside from studying the conductivity of metals, chemistry is also concerned with determining the conductivity of solutions. A solution’s conductivity is directly proportional to the number of ions it contains.

An electrical current is passed through a solution to determine its conductivity, which is then measured in siemens litre per mole per centimetre.

What is Thermal Conductivity in Chemistry?

Conduction requires a solid medium. Hence, thermal conductivity can be defined as the speed or rate at which thermal energy is transferred through a substance. It can be measured according to the unit cross-sectional area of a substance. There must be a temperature gradient to allow the movement of the thermal energy.

Thermal conduction is different from convection and radiation. In convection, the heat is carried by a fluid (liquid, gas or molten substance). Radiation doesn’t require a medium, but instead propagates as electromagnetic waves.

Measuring Conductivity in Chemistry

Typically, a conductivity electrode and pH meter are used to measure the conductivity of a solution. You can use conductivity measurements to indirectly measure the concentration of ions in a solution. You can also deduce the relative dissociation constants of specific ions. Below is the comparative conductivity of some common ions.

A table showing the molar conductivity of selected ions

Measuring conductivity can help us to analyse the composition of substances. It can also be useful in industrial processes such as electroplating.

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