Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

Answer

We know that Iron is a reactive metal . Its alloy, steel , is also relatively reactive . Copper, on the other hand, lies low on the reactivity series .

Hence, 

• Steel would react with hot water to form iron oxide and hydrogen gas.
• Iron is more prone to rusting than Copper. 
• Copper is a better conductor of heat than steel , hence it’s more suitable for making hot water tanks.