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Liquid hydrogen is a common rocket propellant, and it can also be used as the fuel for an internal combustion engine or fuel cell. [citation needed] Solid hydrogen can be made at standard pressure, by decreasing the temperature below hydrogen's melting point of 14.01 K (−259.14 °C; −434.45 °F).
Parts-per-million cube of relative abundance by mass of elements in an average adult human body down to 1 ppm. About 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium ...
1937 – The first hydrogen-cooled turbogenerator goes into service at Dayton, Ohio. 1938 – The first 240 km hydrogen pipeline Rhine-Ruhr. [13] 1938 – Igor Sikorsky from Sikorsky Aircraft proposes liquid hydrogen as a fuel. 1939 – Rudolf Erren – Erren engine – US patent 2,183,674 – Internal combustion engine using hydrogen as fuel.
Cavendish discovered hydrogen as a colorless, odourless gas that burns and can form an explosive mixture with air, and published a paper on the production of water by burning inflammable air (that is, hydrogen) in dephlogisticated air (now known to be oxygen), the latter a constituent of atmospheric air (phlogiston theory).
Because of its flammability, liquid hydrogen should be kept away from heat or flame unless ignition is intended. Unlike ambient-temperature gaseous hydrogen, which is lighter than air, hydrogen recently vaporized from liquid is so cold that it is heavier than air and can form flammable heavier-than-air air–hydrogen mixtures.
Hydrogen compounds are compounds containing the element hydrogen. In these compounds, hydrogen can form in the +1 and -1 oxidation states. Hydrogen can form compounds both ionically and in covalent substances. It is a part of many organic compounds such as hydrocarbons as well as water and other organic substances.
Heavier elements were formed during supernovae at the end of a stars lifecycle. Carbon , currently the fourth most abundant chemical element in the universe (after hydrogen, helium, and oxygen ), was formed mainly in white dwarf stars , particularly those bigger than twice the mass of the sun. [ 52 ]
A liquid is made up of tiny vibrating particles of matter, such as atoms, held together by intermolecular bonds. Like a gas, a liquid is able to flow and take the shape of a container. Unlike a gas, a liquid maintains a fairly constant density and does not disperse to fill every space of a container.