69.gas气体

Gas

气体

There are three kinds of matter(物质): solids, liquids and gases.

Gas is intangible, so you can't touch(触摸) it.

Gas moves(运动) very freely.

Gas will become solid or liquid when the temperature gets low(低的).

On the other hand, a solid can change(改变) into gas when the temperature gets high.

Are there any good examples of these changes?

Of course, dry ice will be the case.