S4.14.1 For the adult
The air and its layers
Mei climbs a high mountain and finds it hard to breathe. What is the air made of, and why is there less of it up there?
What this chapter teaches
Dry air is about 78 % nitrogen, 21 % oxygen, 0.9 % argon and 0.04 % carbon dioxide. The air thins with height. The atmosphere has four layers, and the ozone layer in the stratosphere takes in most of the harmful ultraviolet.
Three questions to ask
There is no one right wording. Listen for the idea.
- What are the two biggest gases in dry air, and about how much of the air is each?
- Why is it hard to breathe at the top of a high mountain, if the share of oxygen is the same?
- What does the ozone layer do, and which layer is it in?
After the chapter, the learner can
- Give the rough share of each gas in dry air
- Name the layers of the atmosphere in order
- Explain how the ozone layer protects life from ultraviolet
What they copy into their notebook
Dry air: 78 % nitrogen, 21 % oxygen, 0.9 % argon, 0.04 % carbon dioxide. Layers: troposphere (weather), stratosphere (ozone), mesosphere, thermosphere. Ozone takes in UV.