Factory is the opposite of Artist. Writer is a type of Artist. Writer is a type of Worker. Politician is a type of Worker. 
Combine is a synonym of Compound. Compound is a type of Chemical. Chemical is related to Gas. 
Factory <--Antonym--> Artist <--IsA-- Writer --IsA--> Worker <--IsA-- Politician 
Combine <--Synonym--> Compound --IsA--> Chemical <--RelatedTo--> Gas 