Earth’s atmosphere
The shell of air around Earth is called the atmosphere. Air is a mixture of gases. Most of it is nitrogen (N₂) and oxygen (O₂). There are also small amounts of carbon dioxide (CO₂) and water vapour. Oxygen is needed for breathing. When we breathe out we release carbon dioxide; plants take it in and, in light, make sugar and oxygen. The higher we go, the thinner the air and the harder it is to breathe. The atmosphere also protects us from the Sun’s harsh rays and space rocks, and weather forms in it.
Observation “Our breathing”: sitting calmly, count how many breaths you take in a minute (hand on chest). Then jump on the spot 20 times and count again. When are there more? Why? Record in a table. Then a role game “person and plant”: one child gives oxygen (leaf), another gives carbon dioxide (person), swapping “air” cards. Safety: stop if you feel out of breath.