Noble Gases Solutions - Helium: The inert gas
Balloons
Helium is used to fill party balloons and weather balloons.
Helium is about seven times less dense than air, so a balloon filled with helium will rise if the balloon itself is light enough. Hydrogen can do the same job but unlike helium it is flammable.
Diving
Helium is used in breathing gas mixtures to prevent deep sea divers suffering from 'the bends'.
The pressure increases as a diver descends, so breathing gases have to be supplied under pressure. Nitrogen in air causes 'nitrogen narcosis' below 30 m, a dangerous condition similar to being drunk. The high partial pressure of nitrogen underwater allows excess nitrogen to dissolve in the blood. If the diver returns to the surface too quickly, nitrogen bubbles form and block blood vessels. Helium is much less soluble than nitrogen: 'heliox', a mixture of 80% helium and 20% oxygen, reduces the chance of these potentially fatal problems happening.
Medicine
Magnetic resonance imaging (MRI) scanners help diagnose conditions such as tumours and cysts.
MRI and nuclear magnetic resonance (NMR) spectroscopy need very powerful magnetic fields, provided by superconducting magnets. Metals only become superconductors with zero resistance at very low temperatures. Liquid helium is the coldest liquid on Earth and boils at just -268.9 °C, so it is used to cool the coils of the magnets. Proton NMR is widely used in chemistry to analyse the structure of organic compounds.