Lesson 5 Choosing Suitable Materials
We use heat insulators to keep things hot or cold. These heat insulators trap air. The trapped air cuts down heat from going through the material.
Polystyrene materials contain trapped air. They are good insulators of heat. They are used to make food containers.
Other examples of insulators are sawdust, towels, cotton wool, coconut husks and tissue papers. These materials can be used to wrap hot things to keep them warm. They can also be used to wrap frozen things to keep them cold.