Which has larger thermal conductivity, pure silver or sterling silver (92.5% Ag, 7.5% Cu)?

• A. Sterling silver has larger conductivity
• B. They are equal
• C. Pure silver has larger conductivity
• D. Silver has no conductivity

Answer: (C)

In metals, heat is carried mainly by free electrons. The easier these electrons can move without being scattered, the higher the thermal conductivity. Pure silver provides a nearly perfect lattice for electrons, so they travel with long mean free paths and transfer heat very efficiently.

Forming sterling silver introduces copper atoms into the lattice. These impurities disrupt the regular atomic spacing and create more scattering centers for electrons. That scattering reduces how far electrons can travel before colliding, which lowers the metal’s ability to conduct heat.

So pure silver conducts heat better than sterling silver, making it the larger thermal conductor.