Which category of hazardous material is NOT based on its physical state?

The category of hazardous material that is not based on its physical state is toxicity. Toxicity refers to the harmful effects a substance can have on health, which is independent of whether the substance is a gas, solid, or mixture. Toxicity is determined by the chemical composition and biological effects of the substance, rather than its physical state. This classification focuses on the potential harm posed by the material upon exposure, which can occur regardless of whether the material exists as a solid, liquid, or gas.

The other categories—gas, solid, and mixture—are all defined by their physical states. A gas is characterized by its ability to expand and fill any container, a solid has a definite shape and volume, and a mixture consists of two or more substances combined. These classifications are directly based on the physical properties of the materials rather than their potential health effects.