Here's why:

* Insulators resist the flow of heat. They have a structure that prevents heat energy from easily passing through them.

* Conductors allow heat to flow easily through them.

Styrofoam is made of expanded polystyrene, which contains many tiny air pockets. These air pockets act as barriers to the transfer of heat energy. The air itself is a poor conductor of heat, and the small, trapped pockets of air prevent heat from moving through the material quickly.

This is why Styrofoam is commonly used in coolers to keep things cold. It helps to slow down the transfer of heat from the warmer environment into the cooler, preserving the cold temperature inside.