Answer:
Their molecules are more spread out which makes it a good insulator.
Explanation:
There is no material that insulates perfectly and completely prevents heat exchange, but there are materials that, in practice, delay this exchange a lot. These materials are good thermal insulators. Among them we can mention the plastic foam, feathers and furs.
Any material that satisfactorily and conveniently minimizes heat transmission (thermal exchange) between two physical systems can be considered a thermal insulator. These materials have highly dispersed molecules and this makes it difficult for heat to be transmitted.
