State the reason for the following:
$(a)$ Potato chips manufacturers usually flush bags of chips with nitrogen gas.
$(b)$ Iron articles lose their shine gradually.
$(c)$ Foods should be kept in airtight containers.

(N/A) Potato chips manufacturers flush bags with nitrogen gas to create an unreactive environment,which prevents the oxidation of fats and oils,thereby stopping the chips from becoming rancid.
$(b)$ Iron articles lose their shine because they react with moisture and oxygen present in the atmosphere to form a layer of hydrated iron oxide,a process known as corrosion or rusting.
$(c)$ Foods should be kept in airtight containers to minimize their exposure to oxygen and moisture,which helps in preventing oxidation and slowing down the growth of microorganisms,thus keeping the food fresh for a longer period.