20 Fun Oxygen Facts for Kids

Oxygen (atomic number 8 and symbol O) is one of those elements you simply can't live without. You find it in the air your breathe, the water you drink, and the food you eat. Here are some quick facts about this important element. You can find more detailed information about oxygen on the oxygen facts page.

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Get 10 Interesting Facts About Oxygen

By Anne Marie Helmenstine, Ph.D.

1. Animals and plants require oxygen for respiration.
2. Oxygen gas is colorless, odorless, and tasteless.
3. Liquid and solid oxygen are pale blue.
4. Oxygen also occurs in other colors, including red, pink, orange, and black. There is even a form of oxygen that looks like a metal!
5. Oxygen is a non-metal.
6. Oxygen gas normally is the divalent molecule O₂. Ozone, O₃, is another form of pure oxygen.
7. Oxygen supports combustion. However, pure oxygen itself does not burn!
8. Oxygen is paramagnetic. In other words, oxygen is weakly attracted to a magnetic field, but it doesn't retain permanent magnetism.
9. Approximately 2/3 of the mass of the human body is oxygen because oxygen and hydrogen make up water. This makes oxygen the most abundant element in the human body, by mass. There are more hydrogen atoms in your body than oxygen atoms, but they account for very little mass.
10. Excited oxygen is responsible for the bright red and yellow-green colors of the aurora.
11. Oxygen was the atomic weight standard for the other elements until 1961 when it was replaced by carbon 12. The atomic weight of oxygen is 15.999, which is usually rounded up to 16.00 in chemistry calculations.
12. While you need oxygen to live, too much of it can kill you. This is because oxygen is an oxidant. When too much is available, the body breaks excess oxygen into a reactive negatively charged ion (anion) that can bind to iron. The hydroxyl radical can be produced, which damages lipids in cell membranes. Fortunately, the body maintains a supply of antioxidants to combat day-to-day oxidative stress.
13. Dry air is about 21% oxygen, 78% nitrogen, and 1% other gases. While oxygen is relatively abundant in the atmosphere, it is so reactive it is unstable and must be constantly replenished by photosynthesis from plants. Although you might guess trees are the main producers of oxygen, it is believed about 70% of free oxygen comes from photosynthesis by green algae and cyanobacteria. Without life acting to recycle oxygen, the atmosphere would contain very little of the gas! Scientists believe detecting oxygen in a planet's atmosphere may be a good indication it supports life, since it is released by living organisms.
14. It is believed much of the reason organisms were so much larger in prehistoric time is because oxygen was present at a higher concentration. For example, 300 million years ago, dragonflies were as large as birds!
15. Oxygen is the 3rd most abundant element in the universe. The element is made in stars that are around 5 times more massive than our Sun. These stars burn carbon or helium together with carbon. The fusion reactions form oxygen and heavier elements.
16. Natural oxygen consists of three isotopes, which are atoms with the same number of protons, but different numbers of neutrons. These isotopes are O-16, O-17, and O-18. Oxygen-16 is the most abundant, responsible for 99.762% of the element.
17. One way to purify oxygen is to distill it from liquefied air. An easy way to make oxygen at home is to put a fresh leaf in a cup of water in a sunny spot. See the bubbles forming on the edges of the leaf? Those contain oxygen. Oxygen may also be obtained through the electrolysis of water (H₂O). Running a strong enough electric current through water gives the molecules enough energy to break the bonds between hydrogen and oxygen, releasing pure gas of each element.
18. Joseph Priestly usually gets credit for discovering oxygen in 1774. Carl Wilhelm Scheele likely discovered the element back in 1773, but he didn't publish the discovery until after Priestly made his announcement.
19. The only two elements oxygen doesn't form compounds with are the noble gases helium and neon. Usually, oxygen atoms have an oxidation state (electric charge) of -2. However, the +2, +1, and -1 oxidation states are also common.
20. Fresh water contains about 6.04 ml of dissolved oxygen per liter, while seawater only contains about 4.95 ml of oxygen.

Sources

• Dole, Malcolm (1965). "The Natural History of Oxygen". The Journal of General Physiology. 49 (1): 5–27. doi:10.1085/jgp.49.1.5
• Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
• Priestley, Joseph (1775). "An Account of Further Discoveries in Air". Philosophical Transactions. 65: 384–94. 
• Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. ISBN 0-8493-0464-4.