Oxygen is a key component of the atmosphere and is critical for the support of life. Its reactivity makes it essential for respiration and combustion reactions - both of which release energy.
Oxides are formed when oxygen combines with other elements. Much of Earth's crust (48.5% by mass) is composed of oxygen in the form of oxides
2.9 Activity 1. The compositon of Air
Students should:
- 2.9 know the approximate percentages by volume of the four most abundant gases in dry air
Students should:
- 2.10 understand how to determine the percentage by volume of oxygen in air using experiments involving the reactions of metals (e.g. iron) and non-metals (e.g. phosphorus) with air
Initial volume = 115. Final volume = 91.
| Initial volume/ml | Final volume/ml | Volume change/ml |
| 115 | 91 | 24 |
Volume change = 24.
percentage change = (24 / 115) * 100 = 21%
Conclusion: 21% of the atmosphere is oxygen
Students should:
- 2.11 describe the combustion of elements in oxygen, including magnesium, hydrogen and sulfur
Students should:
- 2.12 describe the formation of carbon dioxide from the thermal decomposition of metal carbonates, including copper(II) carbonate
- 2.13 know that carbon dioxide is a greenhouse gas and that increasing amounts in the atmosphere may contribute to climate change