Final answer:
It is true that flammable substances have a lower flash point compared to combustible substances. Flammable substances ignite at normal working temperatures, while combustibles need higher temperatures. This is reflected in the NFPA 704 rating system and related to the volatility of the substances.
Step-by-step explanation:
The statement that the flash point for a flammable substance is lower than the flash point of a combustible substance is True. The flash point of a substance is the lowest temperature at which it can vaporize to form an ignitable mixture in air.
Flammable substances have a lower flash point and can be set on fire at normal working temperatures, while combustible substances require a higher temperature to ignite.
As per the National Fire Protection Agency (NFPA) 704 Hazard Identification System, substances are rated on a scale from 0 to 4, with 0 indicating that the substance will not burn and 4 indicating a flash point below 73 °F (indicative of flammable substances).
Combustible substances would have a higher flash point, generally above 100 °F but not exceeding 200 °F. Volatile substances, with their low boiling points, are more likely to be flammable due to weaker intermolecular interactions, while nonvolatile substances are less likely to ignite readily.