Which term describes materials that sense environmental changes and react?

• A. Smart materials
• B. Polymorph
• C. Quantum-tunnelling composite (QTC)
• D. Thermochromic ink

Answer: (A)

These materials are smart materials. They’re designed to sense changes in their environment—like temperature, light, stress, or magnetic fields—and then respond by changing their properties or behavior, such as altering shape, stiffness, color, or electrical resistance. That built-in sensing and reacting makes them useful for adaptive, automatic responses in products and systems.

Polymorph is a heat-softening polymer used mainly for hand-molding and modeling, so it doesn’t embody the sensing-and-reacting capability. Quantum-tunneling composite is a specific pressure-sensitive material that changes resistance, which is a sensing feature, but it’s just one example rather than the broad category. Thermochromic ink changes color with temperature, showing a stimulus-response, but again it’s a particular type of material rather than the general class that covers a variety of sensing and reacting behaviors.