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

(N/A) Copper does not react with cold water,hot water,or steam.
However,iron reacts with steam.
If the hot water tanks are made of steel (an alloy of iron),the iron present in the steel would react vigorously with the steam formed from the hot water.
$3Fe(s) + 4H_2O(g) \to Fe_3O_4(s) + 4H_2(g)$
This reaction would lead to the corrosion and degradation of the tank.
That is why copper is used to make hot water tanks,and not steel.