A container can protect its contents partly because of the empty space inside it. Small poc trap surro air wh solid wa reduce move between th pockets a nearby spa where war material co otherwise circulate more freely. This structure can slow the transfer of heat. Its performance depends on the materials, the size of the spaces, and whether air can move through them. Describing a material as mostly empty therefore says little by itself about how well it will work. The arrangement of that space is part of the design.

Type only the missing letters. Each box is one letter, and the number of boxes matches the letters that are missing.