The state of matter is largely dependent on the ___________ of a substance.

• A. Pressure
• B. Temperature
• C. Volume
• D. Density

Answer: (B)

Temperature is the main factor that determines the state of matter because it reflects the average kinetic energy of the molecules. When temperature is high at a given pressure, molecules have more energy to overcome intermolecular attractions, so a solid becomes a liquid and a liquid becomes a gas. Lowering temperature reduces energy, leading to solidification or condensation. Pressure can shift the exact temperatures at which these transitions occur, but temperature largely drives which state a substance will be in. In hazmat work, this matters because changes in temperature can cause phase changes that alter how a material behaves—its flow, containment, and vapor production—so predicting the state helps with storage, spill response, and ventilation decisions. For example, water at ordinary atmospheric pressure is solid below 0°C, liquid between 0°C and 100°C, and gas above 100°C.