Which of the following is considered a visual sign of a potential chemical hazard?

• A. Presence of a strong odor without any visible reaction
• B. Decrease in mass of a solid after heating
• C. Formation of unexpected color changes in a chemical mixture
• D. Increase in temperature of a solution without any visible change

Answer: (C)

Verified step by step guidance

1. Understand that a visual sign of a potential chemical hazard is an observable change that indicates a chemical reaction or danger, such as a color change, formation of gas, or precipitate.
2. Review each option to identify which involves a visible change: 'Presence of a strong odor' is a sensory change but not visual; 'Decrease in mass' is a measurement change, not visual; 'Increase in temperature' is a physical change detected by instruments, not visual.
3. Recognize that 'Formation of unexpected color changes in a chemical mixture' is a direct visual indicator, as color changes often signal chemical reactions or hazards.
4. Conclude that among the options, the unexpected color change is the visual sign of a potential chemical hazard because it can be seen directly and suggests a chemical process occurring.
5. Remember that visual signs are important for safety because they provide immediate clues about chemical hazards without needing instruments.