If a certain piece of metal is cooled it will conduct electricity better is it a law, theory or hypothesis

This is a hypothesis.

Explanation:

The statement is a hypothesis because it is vague and unclear about various things. It talks about the conduction of electricity through the metal, but doesn't specify the metal. It doesn't talk about a specific metal, it just says a certain metal. If the statement had certified what metal, then the study will have been narrowed. But, it has not. So, it is probably a hypothesis, not a theory or a law.