He is helium.
1. Brief introduction
Helium, chemically known as He, is a colorless, odorless, non-flammable gas with an air content of about 5.2 parts per million. it is chemically inactive, and does not combine with other elements or compounds in its usual state. On July 10, 1908, the Dutch physicist Onnes liquefied helium for the first time.
2. Chemical properties
Helium is a monatomic gas, chemically inactive. Helium generally does not produce compounds, in the low-pressure discharge tube by the excitation can form He +2, HeH plasma and molecules.
3. Physical Properties
At room temperature and atmospheric pressure, helium is a colorless, odorless gas. Its volume content in dry air is 5.24 × 10-6.
The substance with the lowest critical temperature discovered by man. It appears dark yellow when a low-pressure discharge is performed. Helium cannot be solidified simply by cooling a saturated liquid to absolute zero.
For helium to solidify, a corresponding pressure must be applied. At 2.173 K, helium will be converted, more or less, from a normal liquid to a fluid with unique properties.
Fluids with temperatures above 2.173 K are called helium I. Liquids below this temperature are called Helium II. Helium II is a superfluid. It has zero entropy, very high thermal conductivity and almost zero viscosity.
Because of the low temperature of liquid helium, when certain metals or metal compounds are cooled with liquid helium, the electrical resistance of the metal or metal compound disappears completely, a phenomenon known as superconductivity, and this temperature is called the critical temperature.
Because helium transmits sound almost three times as fast as air, a person who inhales helium speaks at a higher frequency. This interesting phenomenon makes people who inhale helium speak in a shrill voice, as if they were old-time cartoon characters.
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Applications of helium
1. Inflatable helium balloons:
Helium is widely used to inflate helium balloons because it is lighter than air, and the balloons float in the air, creating colorful visual effects for celebrations and entertainment occasions.
2.? Cooling applications:
Because of its cryogenic properties, liquid helium is used to cool superconductors, magnetic **** vibration imaging (MRI) equipment and other high-tech devices to maintain cryogenic conditions.
3.? Gas mixtures:
Helium is often mixed with other gases for gas welding and cutting, as it provides a high-temperature flame for metalworking and welding operations.
4.? Helium Detectors:
Helium is used in helium detectors to detect helium leaks, which are critical for industrial safety and laboratory environments.
5.? Aerospace applications:
Helium is used to fill weather detection instruments, satellite altimeters, balloons, etc. in order to measure atmospheric and meteorological data.