Which of the following terms is used to describe the ability of a material to expand when exposed to heat?

The term that describes the ability of a material to expand when exposed to heat is "intumescent." Intumescent materials react to heat by swelling or expanding, which can create a barrier to fire and prevent the spread of flames and heat. This property is particularly useful in fire protection applications, where intumescent coatings are applied to structures to enhance their fire resistance by increasing their volume and reducing thermal conductivity when they are exposed to high temperatures.

In contrast, conductive materials transfer heat effectively and absorb it without expanding, insulative materials are designed to resist heat flow, and absorbent materials soak up liquids or gases. None of these properties directly relate to the characteristic of expanding in response to heat as seen in intumescent materials.