o The Frog Blog: Science Fact of the Week 56 - Helium

Monday, 14 June 2010

Science Fact of the Week 56 - Helium

This is the last ever Science Fact of the Week! We will introduce a new feature at the start of the next academic year. To see all 56 SFOTW click here.

Helium (He) is an unreactive, colourless, and odourless gas. It is the second most abundant element in the universe after hydrogen. Helium has the lowest melting point of any element. It is the only liquid that cannot be solidified by lowering the temperature. It remains liquid down to absolute zero at ordinary pressures, but can be solidified by increasing the pressure.

Helium has many uses including cryogenic research because its boiling point is near absolute zero. It is also used in the study of superconductivity, as an inert gas shield for arc welding, as a protective gas in growing silicon and germanium crystals and producing titanium and zirconium, for pressuring liquid fuel rockets, for use in magnetic resonance imaging (MRI), as a cooling medium for nuclear reactors, and as a gas for supersonic wind tunnels. A mixture of helium and oxygen is used as an artificial atmosphere for divers and others working under pressure. Helium is most widely used for filling balloons and blimps.

Most of the Earth's helium is extracted from natural gas although there is a small amount found in the atmosphere (0.00052%). Helium is produced continually by the radioactive decay of uranium and other elements, gradually working its way into the atmosphere.

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