What does the coefficient of thermal expansion tell us?

The coefficient of thermal expansion is a measure that indicates how much a material expands or contracts in response to changes in temperature. Specifically, it focuses on the change in length per unit length per degree change in temperature, which is why the correct answer relates to the change in length.

Materials generally experience expansion when heated and contraction when cooled. This property is crucial in various applications, especially in pipefitting and construction, as it impacts the fitting and installation of piping systems to prevent issues such as buckling or fracturing due to temperature changes. Understanding the coefficient of thermal expansion helps pipefitters to calculate and accommodate these changes in their designs and installations, ensuring structural integrity and proper functioning of systems under varying thermal conditions.

The other choices refer to different physical properties; density, volume, and mass have their own coefficients of expansion but are not specialized to the linear dimensions the coefficient of thermal expansion addresses. Thus, the key takeaway is that the coefficient of thermal expansion specifically quantifies how the length of an object changes with temperature variations.