Final answer:
A flammable liquid is one with a low flash point, the temperature at which it can ignite. The NFPA 704 system classifies fire hazards based on flash points, with ratings from 4 for highly flammable substances to 0 for non-flammable. Isopropyl alcohol is a typical example of a flammable liquid.
Step-by-step explanation:
A flammable liquid is defined as a liquid that can easily catch fire, generally characterized by having a flash point below a certain temperature. The flash point of a substance is the lowest temperature at which its vapors will ignite when given an ignition source. Waste liquids such as used solvents and waste oils typically have flash points below 60 °C, and they are considered flammable. The NFPA 704 Hazard Identification System includes a red diamond that indicates the level of fire hazard associated with a substance based on its flash point. Under this system, a rating of '4' means the flash point is below 73 °F, making it highly flammable, whereas a rating of '0' indicates that the substance will not burn.
According to the NFPA 704, ignitable compressed gases and oxidizers present hazards as they may catch fire under specific conditions or allow substances to burn in the absence of air/oxygen, respectively. The NFPA 704 ratings help in quickly identifying the hazards of a material, which is essential for ensuring safety in handling and emergency situations.
Isopropyl alcohol is an example of a flammable liquid with a boiling point (82.5 °C) that is above room temperature (25 °C), but a flash point that is well below room temperature, making it highly flammable at normal ambient temperatures.