6.15 - How properties explain noble-gas uses
A useful gas must suit the job it does. This lesson links helium's lift and non-flammability, argon's protection of hot metals, and neon's use in signs to the properties that make each application work.
Helium for lift without burning
Helium has a much lower density than air: the same volume has less mass. A helium-filled balloon can rise when the total mass of the filled balloon, including its helium and load is less than the mass of the air it displaces. A balloon carrying too heavy a load will not rise simply because it contains helium.
Helium is also non-flammable: it does not burn in air. Hydrogen provides even more lift, but it is flammable. Helium is therefore used in balloons and airships where avoiding a fire risk matters. Its low density explains the lift; its non-flammability explains the fire advantage over hydrogen.
Argon protects hot metals
Inert means very unreactive. An inert atmosphere surrounds a material with a gas that does not readily react with it. This is useful when oxygen in air would cause an unwanted reaction.
During welding, a flow of argon shields the hot metal from air. Oxygen could react with the metal to form an oxide. Argon keeps oxygen away and does not itself readily react with the metal, reducing oxidation at the weld.
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