Acid rainAcid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid rain has a pH level lower than this and ranges from 4–5 on average. The more acidic the acid rain is, the lower its pH is. Acid rain can have harmful effects on plants, aquatic animals, and infrastructure.
History of chemistryThe history of chemistry represents a time span from ancient history to the present. By 1000 BC, civilizations used technologies that would eventually form the basis of the various branches of chemistry. Examples include the discovery of fire, extracting metals from ores, making pottery and glazes, fermenting beer and wine, extracting chemicals from plants for medicine and perfume, rendering fat into soap, making glass, and making alloys like bronze.
1944Below, the events of World War II have the "WWII" prefix. January 1944 January 2 – WWII: Free French General Jean de Lattre de Tassigny is appointed to command French Army B, part of the Sixth United States Army Group in North Africa. Landing at Saidor: 13,000 US and Australian troops land on Papua New Guinea, in an attempt to cut off a Japanese retreat. January 8 – WWII: Philippine Commonwealth troops enter the province of Ilocos Sur in northern Luzon and attack Japanese forces. January 11 President of the United States Franklin D.
Pericyclic reactionIn organic chemistry, a pericyclic reaction is the type of organic reaction wherein the transition state of the molecule has a cyclic geometry, the reaction progresses in a concerted fashion, and the bond orbitals involved in the reaction overlap in a continuous cycle at the transition state. Pericyclic reactions stand in contrast to linear reactions, encompassing most organic transformations and proceeding through an acyclic transition state, on the one hand and coarctate reactions, which proceed through a doubly cyclic, concerted transition state on the other hand.
Green chemistryGreen chemistry, similar to sustainable chemistry or circular chemistry, is an area of chemistry and chemical engineering focused on the design of products and processes that minimize or eliminate the use and generation of hazardous substances. While environmental chemistry focuses on the effects of polluting chemicals on nature, green chemistry focuses on the environmental impact of chemistry, including lowering consumption of nonrenewable resources and technological approaches for preventing pollution.
Trịnh lordsThe Trịnh lords (Chúa Trịnh; Chữ Nôm: 主鄭; 1545–1787), formally titled as Viceroy of Trịnh (Trịnh vương; 鄭王), also known as the House of Trịnh or the Trịnh clan (Trịnh thị; 鄭氏), were a noble feudal clan that ruled Northern Vietnam (referred to then as Tonkin), during the Later Lê dynasty, Đại Việt. The Trịnh clan and their rivals, the Nguyễn clan, were both referred to by their subjects as "Chúa" (Lord) and controlled Đại Việt while the Later Lê emperors were reduced to only a titular position.
Lê dynastyThe Lê dynasty, also known in historiography as the Later Lê dynasty (Hậu Lê triều, chữ Hán: 後黎朝 or nhà Hậu Lê, chữ Nôm: 茹後黎), officially Great Việt (Đại Việt; Chữ Hán: 大越), was the longest-ruling Vietnamese dynasty, having ruled from 1428 to 1789, with an interregnum between 1527 and 1533.
