p-nitrophenol melts at a higher temperature than o-nitrophenol because it:

1. Melting requires energy to pull separate molecules apart from one another. 2. p-nitrophenol forms many intermolecular hydrogen bonds, linking molecule to molecule. 3. Breaking that network needs a large amount of energy, so the melting point is high. 4. o-nitrophenol's single hydrogen bond is intramolecular, holding one molecule's own groups together. 5. That bond does nothing to hold neighbouring molecules together, so less energy separates them. The two compounds are isomers, so mass is identical. _Source: NECTA ACSEE 2023 Chemistry 132/1, Question 3: Chemical Bonding_