Chemistry is related to Subject. Subject is a type of Message. Narrative is a type of Message. Narrative is a synonym of Tale. 
Necessity is related to Slope. Fall is a type of Slope. Fall is related to Airplane. Airplane can be used for Flying. 
Chemistry <--RelatedTo--> Subject --IsA--> Message <--IsA-- Narrative <--Synonym--> Tale 
Necessity <--RelatedTo--> Slope <--IsA-- Fall <--RelatedTo--> Airplane --UsedFor--> Flying 