* Vacuum: A vacuum is a space with no matter, so it cannot conduct heat at all. This is why thermoses use a vacuum between their walls to prevent heat loss.
* Styrofoam: Styrofoam is a good insulator, meaning it's very poor at conducting heat. The air trapped within the styrofoam's structure slows down heat transfer. This is why it's used in coffee cups and coolers.
* Air: Air itself is a relatively poor conductor of heat. This is why warm air can be trapped within a building, preventing heat loss.
* Wool: Wool fibers trap air, making it a good insulator. This is why wool clothing keeps us warm in cold weather.
In contrast, good examples of thermal conductivity include:
* Metals: Metals are excellent conductors of heat, which is why they are used in pots and pans.
* Water: Water is a good conductor of heat, which is why it's used for cooling systems.
* Diamond: Diamond is the best thermal conductor of all known materials.
Key takeaway: Non-examples of thermal conductivity demonstrate materials or situations that resist the flow of heat.
