Final answer:
Copper and gold are good thermal conductors and poor insulators due to their high density of free electrons. Air, however, is a good insulator because it is a poor thermal conductor, incorporating many small pockets that impede the transfer of heat.Option II is the correct answer.
Step-by-step explanation:
To answer which materials listed below are good insulators, we need to look at their thermal conductivity properties. Among the materials you listed:
- Copper
- Air
- Gold
Copper and gold are both excellent thermal conductors due to their high density of free electrons which allow them to transport thermal energy efficiently. Thus, they are not good insulators. On the other hand, air is a very poor conductor of thermal energy, making it a good insulator.
This is because it incorporates many small pockets of air, taking advantage of its poor thermal conductivity. Materials like Styrofoam, fiberglass, wool, and goose-down feathers are also good insulators, as they too incorporate air into their structure.
So, in conclusion, out of the materials listed: air is a good insulator, while copper and gold are not.