49 Fun Facts About Oxygen

What does oxygen's atomic number, 8, actually count?

Protons in its nucleus: eight of them make an atom oxygen, whatever else it carries. Add or remove a single one and it becomes a different element entirely.

Roughly what fraction of Earth's atmosphere is oxygen gas, by volume?

About 21% goes in with every breath, and most of it comes straight back out: exhaled air still holds around 16% oxygen, which is why mouth-to-mouth rescue breaths can keep someone alive.

Oxygen is best known as a gas, but where is it the most abundant element of all?

Earth's crust is nearly half oxygen by weight, locked up with silicon in rock and sand. The air and oceans together hold only a tiny share of the planet's oxygen.

Oxygen is the universe's third most abundant element; which is second?

Helium and hydrogen were made in the Big Bang itself. Oxygen came later, forged inside stars by fusing helium and scattered when those stars died.

What is the chemical formula of ozone?

O3 is ozone: three oxygen atoms in one molecule. Its name comes from the Greek for 'to smell', after the sharp odour it gives the air near electrical sparks and lightning.

High in the atmosphere, what splits oxygen molecules into the lone atoms that build the ozone layer?

Ultraviolet light from the Sun makes the very shield that blocks it: the atoms it frees build ozone, and that ozone then absorbs more ultraviolet before it can reach the ground.

Why is Joseph Priestley usually credited with discovering oxygen, though Carl Scheele made it first?

His work was published first. Scheele's book on the gas sat with its printer for two years and came out only in 1777, well after Priestley's account was in print.

What did Joseph Priestley, a believer in phlogiston theory, name the oxygen he made in 1774?

Dephlogisticated air was his name because he thought the gas was ordinary air stripped of phlogiston, the supposed essence of fire, and so able to soak up more from a flame and keep it burning longer.

Who, with Peter Habeler, made the first ascent of Mount Everest without bottled oxygen in 1978?

Reinhold Messner and Habeler did what many doctors and climbers had thought impossible. Two years later Messner went back and climbed Everest without oxygen again, this time entirely alone.

Octopus and horseshoe crab blood carries oxygen with hemocyanin, which turns blue because it contains which metal?

Copper turns blue when it binds oxygen. Horseshoe crabs are caught and bled for that blue blood, which is used to test vaccines and injections for bacterial toxins.

Who first recognised oxygen as an element and correctly explained its role in combustion, in 1777?

Antoine Lavoisier heated tin in a sealed vessel and found the metal gained just the weight the trapped air lost. Burning, he argued, takes something from the air rather than giving off 'phlogiston'.

Oxygen's name means 'acid-former', yet which common acid contains none?

Hydrochloric acid is only hydrogen and chlorine, as Humphry Davy proved, which sank the idea that oxygen is what makes an acid. By then the name was too well established to change.

NASA's MOXIE experiment, carried by the Perseverance rover, made oxygen from which gas in the air of Mars?

Carbon dioxide makes up about 95% of Mars's thin air, and MOXIE pulled one oxygen atom off each molecule. Over two years it made 122 grams, about what a small dog breathes in ten hours.

Which gas do the French still call 'azote', from the Greek for 'lifeless'?

Nitrogen makes up most of every breath, yet on its own it puts out flames and suffocates animals. English later switched to 'nitrogen', but French and several other languages kept the older name.

Which chemist assumed water was HO, and so put oxygen's atomic weight at half its true value?

John Dalton could not count atoms, so he assumed the simplest recipe: when two elements form only one known compound, it has one atom of each. For water that guess was wrong.

To keep liquid oxygen and other liquefied gases cold, James Dewar invented which everyday item in 1892?

The vacuum flask began as lab glassware for storing ultra-cold liquids. In 1904 two German glassblowers saw it could keep drinks hot or cold, and sold it as the Thermos.

Who flew the first liquid-fuelled rocket in 1926, burning gasoline with liquid oxygen?

Robert H. Goddard's rocket climbed just 12.5 metres and was back on the ground of his Aunt Effie's farm in 2.5 seconds. NASA still ranks that hop alongside the Wright brothers' first flight.

Oxygen gas is colourless, but what colour is liquid oxygen?

Pale blue, because liquid oxygen absorbs red light. That is a different effect from the blue of the sky, which comes from air molecules scattering sunlight.

Liquid oxygen clings to a strong magnet because each oxygen molecule has two unpaired what?

Electrons normally pair off and cancel each other's magnetism. Oxygen's two loners do not, so the liquid is pulled toward a magnet strongly enough to hang between its poles.

Which Apollo mission had to abandon its Moon landing after an oxygen tank exploded on the way there?

Apollo 13 lost the oxygen it needed for both breathing and electrical power, so the three astronauts moved into the lunar module and used it as a lifeboat to loop around the Moon and get home.

Mars owes its red colour to dust rich in which compound of oxygen?

Iron oxide is the stuff of rust: iron minerals in the Martian soil have combined with oxygen, coating the whole planet in red-brown dust.

Which part of a cell uses the oxygen you breathe to release energy from food?

Mitochondria, the cell's 'powerhouses', carry their own DNA, because they descend from free-living bacteria that took up residence inside our distant ancestors' cells.

Scientists read ancient temperatures from the ratio of oxygen-18 to oxygen-16 preserved in what?

Seashells and ice cores both preserve the water of their day. Water with light oxygen-16 evaporates more readily and ends up locked in ice sheets, so in cold spells the sea and its shells grow richer in oxygen-18.

Which crashed spacecraft returned solar-wind samples showing the Sun has more oxygen-16 than Earth?

Genesis hit the Utah desert at about 300 km/h when its parachutes failed to open, shattering its collectors. Scientists still recovered enough solar wind from the wreckage to make the measurement.

What process produces the free oxygen in Earth's atmosphere?

Photosynthesis frees its oxygen from water, not from carbon dioxide: plants and algae use sunlight to pull H2O apart, keep the hydrogen and release the oxygen as waste.

Which microbes first filled Earth's air with oxygen in the Great Oxidation Event, over two billion years ago?

Cyanobacteria gave off the gas as waste, and it was poison to much of the life of the day. The upheaval may have caused one of Earth's first mass die-offs.

Which protein in red blood cells binds oxygen and turns bright red as it does?

Hemoglobin has a dangerous weakness: it grips carbon monoxide more than 200 times as tightly as oxygen, which is how fumes from a faulty boiler can starve the body of oxygen.

In which tiny air sacs of the lungs does oxygen pass into the blood?

Alveoli number in the hundreds of millions, and their thin walls add up to some 70 to 80 square metres. Oxygen dissolves poorly, so the lungs need all of that area to absorb enough of it.

Hospitals rely on oxygen, but which industry is the biggest single user of the commercially produced gas?

Steelmaking blows pure oxygen into molten iron to burn out carbon and other impurities. That turns a batch into steel in under an hour, where older furnaces needed ten hours or more.

Ethylene glycol, made in bulk by reacting ethylene with oxygen, is the main ingredient of which car fluid?

Antifreeze is mostly ethylene glycol, and the same chemical is a raw material for polyester. Oxygen's handiwork ends up in car radiators and polyester clothes alike.

What is the most common industrial method for extracting oxygen from air?

Distilling liquid air works because its gases boil at different temperatures. As the chilled liquid warms, nitrogen boils away first, at -196 °C, leaving behind oxygen, which stays liquid until -183 °C.

Mountaineers give what name to altitudes above about 8,000 metres?

The death zone has only about a third of the air pressure found at sea level, so every breath brings in too little oxygen. Climbers on Everest can last no more than two or three days up there.

Why do space suits hold oxygen at only a third of normal pressure?

For flexibility: every movement has to fight the pressure inside, so a fully inflated suit would be too stiff to work in. Pure oxygen at a third of the pressure still gives the blood a normal supply.

Why did the 1967 Apollo 1 launch-pad fire spread so quickly?

The cabin was filled with pure oxygen at more than sea-level pressure for the test. In that atmosphere a spark from the wiring made the nylon netting and Velcro around the crew burn like kindling.

Why do deep divers avoid breathing pure oxygen?

It turns toxic under pressure: only a few metres down, pure oxygen can bring on sudden convulsions, which underwater usually means drowning. Deep divers thin it out with nitrogen or helium instead.

Premature babies were once kept in oxygen-rich incubators until it was found the practice caused what?

Blindness from too much incubator oxygen became an epidemic among premature babies in the 1940s and 50s. Stevie Wonder, born six weeks early in 1950, lost his sight this way.

Hyperbaric oxygen chambers are used to treat which diving injury?

Decompression sickness, 'the bends', strikes when a diver surfaces too fast and gas dissolved in the body fizzes out as bubbles. Oxygen under pressure squeezes the bubbles back into solution so they can be breathed out.

Which icy moon has a wisp of an oxygen atmosphere, made as radiation splits water on its surface?

Europa's frozen surface is battered by radiation that breaks water apart; the light hydrogen drifts off into space and the oxygen stays. It is a reminder that oxygen alone does not prove a world has life.

The oxygen-starved waters off the mouth of the Mississippi are caused mainly by run-off of what?

Fertiliser washed downriver feeds vast blooms of algae. When the algae die and sink, the bacteria that rot them use up the water's oxygen, and fish must flee or suffocate.

Oxygen's oxidation state is -2 in nearly all its compounds, but -1 in which family?

Peroxides contain two oxygen atoms bonded to each other and give up the extra oxygen readily. That is why hydrogen peroxide bleaches hair and, in concentrated form, has been used as rocket propellant.

Oxygen atoms high in the atmosphere give the aurora its most common colour, which is what?

Green is the glow of oxygen atoms struck by particles streaming in from the Sun. Higher up, where the air is thinner, the same atoms shine a rarer deep red instead.

Oxygen-15, which has a half-life of about two minutes, is used as a tracer in which medical scan?

PET scans pick up the gamma rays released when oxygen-15's positrons meet electrons. It decays so quickly that it has to be made in a cyclotron beside the scanner and used at once.

Joseph Priestley, a discoverer of oxygen, is also credited with inventing which fizzy drink?

Soda water came first: in 1767 Priestley hung a bowl of water over a fermenting vat at a Leeds brewery and found it soaked up the gas. Johann Schweppe later built a business on the idea.

Which chemicals, once common in fridges and spray cans, were phased out for destroying the ozone layer?

CFCs drift up to the stratosphere, where sunlight knocks loose chlorine atoms that destroy ozone again and again. Since a 1987 treaty phased them out, the ozone hole has been slowly recovering.

The 'fire triangle' says a fire needs fuel, oxygen and which third ingredient?

Heat completes the triangle, and removing any one side puts a fire out. That is why 'stop, drop and roll' works: rolling on the ground starves the flames of oxygen.

The Space Shuttle's main engines burned liquid oxygen with which fuel, carried in its giant orange tank?

Liquid hydrogen and liquid oxygen combine to make water, so the exhaust of the Shuttle's main engines was mostly steam. The tank was orange because NASA stopped painting it white after two flights, saving about 270 kg.

French chemist Joseph Gay-Lussac worked out the recipe for water in 1805 alongside which famous explorer-naturalist?

Alexander von Humboldt, just back from five years exploring the Americas, joined his friend in Paris. Their measurements showed that water always takes two volumes of hydrogen for every one of oxygen.

Which word describes exercise, such as an all-out sprint, that is fuelled without using oxygen?

Anaerobic effort breaks down glucose without waiting for oxygen, which is fast but cannot last. The heavy breathing after a sprint is the body taking in extra oxygen to recover.

Which gas do welders burn with oxygen for the hottest flame?

Acetylene burns with oxygen at well over 3,000 °C, hot enough to melt steel. Add an extra jet of pure oxygen and the same torch will slice straight through a thick steel plate.