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radon

(Encyclopedia)radon rāˈdŏn [key], gaseous radioactive chemical element; symbol Rn; at. no. 86; mass no. of most stable isotope 222; m.p. about −71℃; b.p. −61.8℃; density 9.73 grams per liter at STP; vale...

molecular weight

(Encyclopedia)molecular weight, weight of a molecule of a substance expressed in atomic mass units (amu). The molecular weight may be calculated from the molecular formula of the substance; it is the sum of the ato...

low-temperature physics

(Encyclopedia)low-temperature physics, science concerned with the production and maintenance of temperatures much below normal, down to almost absolute zero, and with various phenomena that occur only at such tempe...

chemical equation

(Encyclopedia)chemical equation, group of symbols representing a chemical reaction. There are a number of other symbols used in chemical equations. A symbol written above or below the reaction arrow indicates spe...

jet propulsion

(Encyclopedia)CE5 Types of jet engines: In the propeller-driven turbine a stream of high-velocity gases provides the power to drive the turbine and turn the propeller. In the jet-driven turbine the stream of gas...

Milky Way

(Encyclopedia)CE5 Position of the sun in the Milky Way Milky Way, the galaxy of which the sun and solar system are a part, seen as a broad band of light arching across the night sky from horizon to horizon; if ...

pressure

(Encyclopedia)pressure, in mechanics, ratio of the force acting on a surface to the area of the surface; it is thus distinct from the total force acting on a surface. A force can be applied to and sustained by a si...

Qatar

(Encyclopedia)CE5 Qatar or Katar both: kŭˈtər, gŭ–, kətärˈ [key], officially State of Qatar, independent emirate (2015 est. pop. 2,482,000), c.4,400 sq mi (11,400 sq km), E Arabia, coextensive with the ...

Davy, Sir Humphry

(Encyclopedia)Davy, Sir Humphry, 1778–1829, English chemist and physicist. The son of a woodcarver, he received his early education at Truro and was apprenticed (1795) to a surgeon-apothecary at Penzance. While d...

chloroform

(Encyclopedia)chloroform trīˌklôrōmĕthˈān [key], CHCl3, volatile, colorless, nonflammable liquid that has a sweetish taste and a somewhat pungent odor; it boils at 61.7℃. It dissolves freely in ethanol and...