What property allows heat or electricity to travel through a substance?

The correct answer, conductivity, refers to the ability of a substance to allow heat or electricity to pass through it. This property is crucial in various applications, including electrical wiring, thermal management in materials, and the design of electronic components. Conductive materials, such as metals, have free electrons that facilitate the easy flow of electrical current, while also allowing heat to transfer efficiently through them.

Density measures the mass of a substance relative to its volume and does not directly relate to heat or electrical flow. Viscosity is concerned with the thickness or resistance to flow of a fluid, thereby playing a role in fluid dynamics rather than in the conduction of heat or electricity. Elasticity refers to a material's ability to deform under stress and return to its original shape, which is not related to conductivity. Understanding these distinctions reveals why conductivity is the property directly associated with the travel of heat and electricity through substances.