They have different properties than the metals from which they are made. Melting two or more metals and mixing them together makes an alloy. The mixture is then allowed to cool and harden to a solid. In its final form and alloy consists of a solution in which the metal components are thoroughly mixed with each other. For example, stainless steel is an alloy of iron, chromium, carbon, and nickel.
Stainless steel is stronger than iron, lighter than iron, and resists rusting.
Also, a pure aluminum cooking pot would be soft and weak, and would wear away quickly. The water should be warm, not hot. Talk with the students about what alloys are a solution of two or more metals with properties of its own. Place students into groups of 4-6. Each group should place their data results on the spreadsheet and the class will compare the results.