Skip to content
Material World
Element · O

Oxygen

The most abundant element in the Earth's crust, and the reason most metals must be smelted rather than found.

Oxygen makes up nearly half the crust by mass, almost all of it locked into silicates and oxides. That is precisely why metallurgy exists: aluminium, iron, silicon and titanium are all abundant, and all of them are found bonded to oxygen rather than as metal. Smelting is the business of persuading oxygen to let go.

How tightly it holds determines how hard a metal is to win. Iron oxide gives up its oxygen to carbon at furnace temperatures; aluminium oxide does not, which is why aluminium waited for electricity.

Uses

Industrial oxygen is overwhelmingly a steelmaking reagent. Blowing pure oxygen through molten iron burns out excess carbon far faster than air can, and the basic oxygen furnace is built around that fact.

Medical oxygen is the use most people encounter, and welding and cutting the one most visible — an oxy-fuel flame is hot enough to cut steel plate. Oxygen also drives wastewater treatment, where it feeds the bacteria that do the actual work.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is used as

  • Corrosion protection — application · as the element that both causes corrosion and forms the protective oxide films that prevent it

is an input to

  • Smelting — process · as the element removed, not added
  • Basic oxygen steelmaking — process · blown through the melt at supersonic velocity; the carbon burning out supplies all the heat needed

is found in

  • Sodium hydroxide — compound
  • Beta quartz — mineral
  • Air — material · 20–21% · about twenty-one per cent, and all of it a biological product — photosynthesis put it there over roughly two billion years
  • Indium tin oxide — material · the other half of both oxides, and the reason the material is transparent at all: it is a wide-band-gap oxide, doped until it conducts Wikidata
  • Polyethylene terephthalate — material · in the ester links that join the units — and the reason hot water can break the chain, which is what chemical recycling exploits
  • Nylon — material · in the amide link
  • Polycarbonate — material · in the carbonate links the polymer is named for
  • Obsidian — rock · the other half of the silica, and of the alumina and alkalis with it
  • Cotton — material · which is why cotton takes up a quarter of its weight in water without feeling wet
  • Seawater — material · as water, and dissolved as gas — the dissolved fraction is what everything in the sea breathes
  • Yttrium aluminium garnet — compound · the framework the two cations sit in
  • Optical fibre — material · the other half of the silica
  • PMMA — material · in the ester group, which is what makes the polymer transparent and what makes it depolymerise cleanly when heated
  • POM — material · every other atom of the chain; the same bond that makes it stiff makes it unzip to formaldehyde when overheated
  • PEEK — material · in the ether links between rings, which give the chain just enough flexibility to be processable at all
  • PLA — material · in the ester links — and the reason it hydrolyses, which is both the resorbable suture and the compostability claim
  • Aramid fibre — material · in the amide carbonyl
  • Silicone rubber — material · the other half of the backbone; the Si–O bond is stronger than C–C and is not attacked by ultraviolet light
  • Epoxy resin — material · in the epoxide rings that give the resin its name, and that the hardener opens to build the network
  • Polyurethane — material · in the urethane link and throughout the polyol
  • Phenolic resin — material · the phenolic hydroxyl and the methylene bridges' origin in formaldehyde
  • Borosilicate glass — material · the other half of every oxide in it
  • Fused silica — material · two per silicon, in a continuous random network
  • Zirconia — compound · two per zirconium, and mobile enough at temperature that hot zirconia conducts oxygen ions — which is what an exhaust sensor measures with
  • Gypsum plaster — material · in the sulfate and in the water of crystallisation that gives the material its fire resistance
  • Resin — material · in the carboxylic acid groups of the rosin acids, which is what makes rosin a flux rather than merely a glue
  • Amber — material · around 10 per cent, and in the Baltic material partly as the succinic acid the trade calls succinite after
  • Nacre — material · in the carbonate
  • Water — compound · one atom, and eighty-nine per cent of the mass — which is why water is heavy for a molecule so small
  • Beeswax — material · in the ester and acid groups, which is the small polar fraction that lets wax bind to a surface rather than merely sit on it
  • Lithium iron phosphate — compound · and the point is how tightly: it is not released on abuse the way a layered oxide releases it
  • NMC cathode — compound · and it is released from the lattice when the cell overheats, which is what makes thermal runaway self-sustaining
  • Lithium cobalt oxide — compound · in layers, and released on overheating — LCO is the least thermally stable of the common cathodes
  • Ferrite — material · and it being an oxide is the point: an insulator that is nevertheless magnetic
  • Aluminium oxide — compound PubChem
  • Quicklime — compound PubChem
  • Sulfuric acid — compound PubChem
  • Albite — mineral Wikidata
  • Anorthite — mineral Wikidata
  • Apatite — mineral
  • Aragonite — mineral Wikidata
  • Azurite — mineral Wikidata
  • Baryte — mineral Wikidata
  • Bastnäsite — mineral
  • Beryl — mineral Wikidata
  • Borax — mineral Wikidata
  • Calcite — mineral Wikidata
  • Cassiterite — mineral Wikidata
  • Chromite — mineral Wikidata
  • Columbite — mineral
  • Corundum — mineral Wikidata
  • Fayalite — mineral Wikidata
  • Forsterite — mineral Wikidata
  • Gypsum — mineral Wikidata
  • Hematite — mineral Wikidata
  • Ilmenite — mineral Wikidata
  • Lepidolite — mineral
  • Magnetite — mineral Wikidata
  • Malachite — mineral Wikidata
  • Microcline — mineral Wikidata
  • Monazite — mineral
  • Muscovite — mineral Wikidata
  • Olivine — mineral
  • Orthoclase — mineral Wikidata
  • Plagioclase — mineral
  • Pollucite — mineral Wikidata
  • Pyrolusite — mineral Wikidata
  • Quartz — mineral Wikidata
  • Rutile — mineral Wikidata
  • Scheelite — mineral Wikidata
  • Spodumene — mineral Wikidata
  • Strontianite — mineral Wikidata
  • Talc — mineral PubChem
  • Topaz — mineral Wikidata
  • Uraninite — mineral Wikidata
  • Vanadinite — mineral Wikidata
  • Wulfenite — mineral Wikidata
  • Xenotime — mineral Wikidata
  • Zircon — mineral Wikidata
  • Amethyst — mineral variety Wikidata
  • Ruby — mineral variety Wikidata
  • Sapphire — mineral variety

is produced by

  • Air separation — process · the largest output by tonnage, and the reason air separation units sit beside steelworks

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • PubChem
    US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors
  • NIST — National Institute of Standards and Technology
    United States Department of Commerce · US Government work — public information, credit requested

Questions this page answers

Where it comes from, and what it becomes

Follow Oxygen back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Oxygen → is produced by (the largest output by tonnage, and the reason air separation units sit beside steelworks) → Air separation → takes as input (the feedstock, and an unusual one in being free, unlimited and available anywhere — the cost is entirely the energy to liquefy it) → Air

Downstream — what it becomes

  • Oxygen → is an input to (as the element removed, not added) → Smelting → produces (as blister copper, refined electrolytically afterwards) → Copper → is a component of → Bronze → is used to make (cast in a two-piece mould with a core, which is what bronze does better than the copper it replaced) → Bronze socketed axe → is associated with → Bronze Age complete chain
  • Oxygen → is an input to (blown through the melt at supersonic velocity; the carbon burning out supplies all the heat needed) → Basic oxygen steelmaking → produces (most of the world's primary steel) → Steel → is associated with (produced in small quantities long before it could be made reliably) → Iron Age complete chain
  • Oxygen → is used as (as the element that both causes corrosion and forms the protective oxide films that prevent it) → Corrosion protection
  • Oxygen → is an input to (as the element removed, not added) → Smelting → produces (as blister copper, refined electrolytically afterwards) → Copper → is a source for (much of world supply arrives as a by-product of copper mining rather than from cobalt-first operations) → Cobalt → is a component of (the balance, and both the reason it works hot and the reason it is expensive) → Samarium–cobalt magnet → is used as (weaker and untroubled by heat, which keeps it where temperature rather than strength is the constraint) → Permanent magnets
  • Oxygen → is an input to (blown through the melt at supersonic velocity; the carbon burning out supplies all the heat needed) → Basic oxygen steelmaking → produces (most of the world's primary steel) → Steel → is an input to (and the same steel becomes a spring, a cutting edge or a machinable bar depending only on the schedule) → Heat treatment → produces (laid up as fibre and resin and cured under heat and pressure, usually in an autoclave — and the cure schedule is as much of the specification as the fibre is) → Carbon fibre composite → is used as (aircraft primary structure since the 1990s, where stiffness per unit mass is what is being bought) → Structural engineering
  • Oxygen → is an input to (as the element removed, not added) → Smelting → produces (as blister copper, refined electrolytically afterwards) → Copper → is used as → Electrical conduction

These are the most distinct paths onward. Oxygen ends up in others besides.