HAZMAT Technician Practice Exam

What happens at the melting point of a substance?

1. A solid becomes a gas

2. A gas becomes a liquid

3. A solid becomes a liquid

4. A liquid becomes a solid

The correct answer is: A solid becomes a liquid

At the melting point of a substance, the temperature at which it transitions from a solid state to a liquid state is reached. This occurs because, at the melting point, the thermal energy of the solid material increases to the point where its molecular structure can no longer maintain the rigid, organized arrangement typical of solids. The molecules gain sufficient energy to overcome the intermolecular forces holding them together, leading to a phase change where the solid becomes a liquid. Milestones such as this are critical in understanding material properties in fields like chemistry, materials science, and environmental science, especially in the context of hazardous materials. Recognizing the state changes of substances is essential for handling and responding to hazmat incidents safely and effectively.