--- title: Air and why we need it — a lesson of Mova's school · trees and pragmatics description: «Air and why we need it», a lesson of the world course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Air is a mixture of gases: about four fifths is nitrogen, about one fifth is oxygen, and the rest is a little argon, a tiny amount of carbon dioxide --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [World](https://md.mova.elamur.ai/free/en/corpora/school/world/) / Air and why we need it # Air and why we need it Lesson 17 of the world course of Mova's primary school: 18 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: [the lesson at school](https://md.mova.elamur.ai/free/en/school-run/world/17-air-oxygen-carbon-dioxide/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/0/) — Air is a mixture of gases: about four fifths is nitrogen, about one fifth is oxygen, and the rest is a little argon, a tiny amount of carbon dioxide and some water vapour. - [1](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/1/) — People and animals breathe in air and use its oxygen to release energy from their food; they breathe out air with less oxygen and more carbon dioxide. - [2](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/2/) — Green plants take in carbon dioxide and, using the energy of sunlight, make their food and give out oxygen. - [3](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/3/) — Fire needs oxygen too: a flame goes out when its air is cut off, which is how a fire blanket smothers a fire. - [4](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/4/) — The layer of air around the Earth, the atmosphere, also keeps us warm and protects us from harmful rays from the Sun. - [5](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/5/) — For example, if you put a glass jar over a burning candle, the flame soon goes out, because it has used up much of the oxygen inside. - [6](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/6/) — Air is a mixture of gases, mostly nitrogen and oxygen. - [7](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/7/) — About one fifth of the air is oxygen. - [8](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/8/) — Air holds only a tiny amount of carbon dioxide, much less than one part in a hundred. - [9](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/9/) — We need oxygen to release energy from our food. - [10](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/10/) — The air we breathe out has less oxygen and more carbon dioxide and water vapour than the air we breathe in, but it still has some oxygen. - [11](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/11/) — Plants take in carbon dioxide and give out oxygen when they make food in sunlight. - [12](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/12/) — Burning needs oxygen; without it a fire goes out, and a car engine, which burns fuel, needs air coming in for the same reason. - [13](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/13/) — The air gets thinner the higher you go, so climbers on the highest mountains may carry oxygen. - [14](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/14/) — Air takes up space: push an upturned glass straight down into water and the air trapped inside keeps the water out of most of the glass. - [15](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/15/) — Air has weight: the air in a classroom weighs more than a hundred kilograms. - [16](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/16/) — Most fish take in oxygen dissolved in the water through their gills. - [17](https://md.mova.elamur.ai/free/en/corpora/school/world/17-air-oxygen-carbon-dioxide/17/) — Carbon dioxide in the air helps trap heat; more of it makes the Earth warmer. - ← previous: [Climate zones](https://md.mova.elamur.ai/free/en/corpora/school/world/16-climate-zones/) - next →: [Materials and their properties](https://md.mova.elamur.ai/free/en/corpora/school/world/18-materials-and-properties/) - ↑ back to [World](https://md.mova.elamur.ai/free/en/corpora/school/world/)