How do materials' properties affect their conductivity?

Materials' properties such as their atomic structure, temperature, impurities, and physical state significantly influence their conductivity.

The atomic structure of a material is a key determinant of its conductivity. Metals, for instance, have a sea of free electrons in their atomic structure, which allows them to conduct electricity efficiently. These free electrons can move and carry an electric charge, resulting in high conductivity. In contrast, insulators like rubber and glass have tightly bound electrons that cannot move freely, leading to low conductivity.

Temperature also plays a crucial role in conductivity. For most metals, as the temperature increases, the conductivity decreases. This is because the increased thermal energy causes more vibrations in the atomic lattice, which obstruct the flow of electrons, reducing conductivity. However, for semiconductors, the opposite is true. As temperature increases, so does conductivity, because more electrons gain enough energy to jump into the conduction band and carry an electric charge.

Impurities can also affect a material's conductivity. For example, in semiconductors, adding specific impurities can increase the number of free electrons or create 'holes' (places where an electron could exist but doesn't), both of which increase conductivity. This process, known as doping, is used to control the conductivity of semiconductors in electronic devices.

Lastly, the physical state of a material can influence its conductivity. Solids generally conduct better than liquids, which in turn conduct better than gases. This is because in solids, atoms are closely packed together, allowing electrons to move and transfer energy more easily. In liquids and gases, the atoms are further apart, making it harder for electrons to move and conduct electricity.

In summary, a material's conductivity is influenced by a variety of factors, including its atomic structure, temperature, impurities, and physical state. Understanding these factors can help us manipulate and utilise materials more effectively in a range of applications, from electronics to energy transmission.