In the electrolytic refining of metals, the insoluble impurities present in the impure metal settle down at the bottom of the container below the anode. What is this called?

Which method is used to collect $H_2$ gas in a gas jar in the laboratory?

$(i)$ Given below are the steps for the extraction of copper from its ore. Write the reactions involved:
$(a)$ Roasting of copper $(I)$ sulphide
$(b)$ Reduction of copper $(I)$ oxide with copper $(I)$ sulphide
$(c)$ Electrolytic refining
$(ii)$ Draw a neat and well-labelled diagram for the electrolytic refining of copper.

Name two metals which react with dilute $HNO_{3}$ to evolve $H_{2}$ gas.

An alloy has a low melting point and is,therefore,used for electrical fuses. Name the alloy and write its constituents.

Name any one metal which reacts neither with cold water nor with hot water but reacts with heated steam to produce hydrogen gas.