Which metal ore can be concentrated by the magnetic separation method?

Give reasons for the following:
$(i)$ Most metals conduct electricity well.
$(ii)$ The reaction of iron $(III)$ oxide,$Fe_{2}O_{3}$,with heated aluminium is used to join cracked machine parts.
$(iii)$ Sodium,potassium,and lithium are stored under oil.

State whether the following statement is true or false:
Iron does not burn on heating,but iron filings burn vigorously when sprinkled in the flame of a burner.

In the $Bayer$ process,what is obtained when concentrated $NaOH$ is added to bauxite?

What is the process of extracting a metal from its ore and obtaining it in a pure form called?

Which of the following metals are obtained by electrolysis of their molten chlorides?
$(i) Na, (ii) Ca, (iii) Fe, (iv) Cu$