Keeping in the heat

1. READ/play the text
2. CLICK the picture (and video)
3. TRY this:

Q1: What is a free and invisible material that holds heat?

[Answer]

We use many materials to keep us warm. Our clothes and our homes both use materials that keep things warm.

A material that keeps the heat in is called an insulator.

There is no easy way to see whether a material holds the heat. One surprising material is actually invisible, weighs nothing and is free – it is the air around us. Many clothes are made to trap air inside them.