# Coefficient of thermal expansion

The coefficient of thermal expansion is a physical property that indicates how a material expands or contracts when subjected to a temperature change. It describes the relative change in length, volume, or other dimension-related properties of a material per degree of temperature change.

The coefficient of thermal expansion is typically expressed in units of "per degree Celsius" or "per Kelvin." There are three types of expansion coefficients that are differentiated based on the type of measurement:

1. Linear expansion coefficient: It denotes the relative change in length of a material per degree of temperature change. This coefficient is often expressed in units of "per degree Celsius."
2. Area expansion coefficient (bilinear expansion coefficient): It represents the relative change in area of a material per degree of temperature change. This coefficient is twice the value of the linear expansion coefficient and is commonly given in units of "per degree Celsius" or "per Kelvin."
3. Volume expansion coefficient (cubic expansion coefficient): It indicates the relative change in volume of a material per degree of temperature change. This coefficient is three times the value of the linear expansion coefficient and is also expressed in units of "per degree Celsius" or "per Kelvin."

The coefficient of thermal expansion depends on the atomic or molecular properties of a material. As materials are heated, the atoms or molecules absorb thermal energy and begin to vibrate or move, resulting in an increase in volume and expansion of the material.

Knowledge of the coefficient of thermal expansion is important in various fields. In engineering, it is considered when designing components and structures to understand their thermal behavior and minimize deformations. In materials science, the coefficient of thermal expansion aids in the selection of materials for specific applications where temperature changes play a role.

It is important to note that different materials have different expansion coefficients, and this can lead to issues when materials with different expansion coefficients come into contact. Temperature changes can induce stress or deformations that may result in damage or malfunction. These effects need to be considered in the design and material selection process, especially in environments with extreme temperature conditions.

Overall, the coefficient of thermal expansion is an important property of materials that characterizes their behavior during temperature changes and holds significant relevance for various technological applications.