Fact 1: When metal conducts heat , that metal expands.

Fact 2: Conduction is the passing of heat through a medium.

Given the two facts above, answer the question "What is the result of imperfect passing of heat through a metal, on that metal?" with the following options: 
- contamination
 - expansion
 - sweating
 - Energy.
 - forces
 - burning
 - Evaporation
 - electricity


 

  expansion       