Which alloy is used for making aircraft parts?

Give reasons for the following:
$(i)$ Metals conduct electricity.
$(ii)$ Non-metals in general do not displace hydrogen from dilute acids.
$(iii)$ Aluminium easily combines with oxygen but still it can be used for making kitchen utensils.

Who discovered hydrogen gas?

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

Which of the following metals exist in their native state in nature?
$(i)$ $Au$
$(ii)$ $Cu$
$(iii)$ $Ag$
$(iv)$ $Fe$

Four groups are given linking a metal, its ore, and the chemical formula of the main component of the ore. How many of these are correct?
$(1)$ Iron - Magnetite - $Fe_{3}O_{4}$
$(2)$ Iron - Siderite - $FeS_{2}$
$(3)$ Copper - Copper glance - $Cu_{2}S$
$(4)$ Copper - Dolomite - $Al_{2}O_{3}$