Which term describes the measure of the degree of increase in dimensions when a material is heated?

• A. Transparency
• B. Thermal expansion
• C. Twisting
• D. Volume

Answer: (B)

When a material is heated, its dimensions tend to grow. This is called thermal expansion. The reason is that as temperature rises, atoms vibrate more and take up slightly more space, so lengths, areas, and volumes increase. The amount of linear growth per degree of temperature change is described by the coefficient of linear expansion, α, with ΔL = α L0 ΔT. For volume, the corresponding relation uses β, with ΔV = β V0 ΔT, and for most isotropic materials β is about 3α, linking how length changes relate to changes in area and volume. So the measure of how much dimensions increase is thermal expansion. Transparency is about light passing through, twisting is a deformation from torque, and volume is the amount of space an object occupies—each is a different concept, not the specific measure of dimensional growth due to heating.