Romance is related to Date. Date is the opposite of Birthday. Birthday is related to Holiday. 
Chemical is related to Salt. Salt is related to Rock. Rock is related to Popular. Popular is related to Demand. 
Romance <--RelatedTo--> Date <--Antonym--> Birthday <--RelatedTo--> Holiday 
Chemical <--RelatedTo--> Salt <--RelatedTo--> Rock <--RelatedTo--> Popular <--RelatedTo--> Demand 