Chemical substance

A chemical substance is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be chemical elements, chemical compounds, ions or alloys.

Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Other chemical substances commonly encountered in pure form are diamond (carbon), gold, table salt (sodium chloride) and refined sugar (sucrose). However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.

Chemical substances exist as solids, liquids, gases or plasma, and may change between these phases of matter with changes in temperature or pressure. Chemical reactions convert one chemical substance into another.

Chemistry

Chemistry is a branch of physical science that studies the composition, structure, properties and change of matter. Chemistry includes topics such as the properties of individual atoms, how atoms form chemical bonds to create chemical compounds, the interactions of substances through intermolecular forces that give matter its general properties, and the interactions between substances through chemical reactions to form different substances.

Chemistry is sometimes called the central science because it bridges other natural sciences, including physics, geology and biology. For the differences between chemistry and physics see Comparison of chemistry and physics.

Scholars disagree about the etymology of the word chemistry. The history of chemistry can be traced to alchemy, which had been practiced for several millennia in various parts of the world.

Etymology

The word chemistry comes from the word alchemy which was an earlier set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism and medicine. It is often seen as linked to the quest to turn lead or another common starting material into gold. Alchemy, which was practiced around 330, is the study of the composition of waters, movement, growth, embodying, disembodying, drawing the spirits from bodies and bonding the spirits within bodies (Zosimos). An alchemist was called a 'chemist' in popular speech, and later the suffix "-ry" was added to this to describe the art of the chemist as "chemistry".

Drug

A drug is any substance other than food, that when inhaled, injected, smoked, consumed, absorbed via a patch on the skin or dissolved under the tongue causes a physiological change in the body.

In pharmacology, a pharmaceutical drug or medicine, is a chemical substance used to treat, cure, prevent, diagnose a disease or promote well-being. Traditionally drugs were obtained through extraction from medicinal plants, but more recently also by organic synthesis. Pharmaceutical drugs may be used for a limited duration, or on a regular basis for chronic disorders.

Pharmaceutical drugs are often classified into drug classes—groups of related drugs that have similar chemical structures, the same mechanism of action (binding to the same biological target), a related mode of action, and that are used to treat the same disease. The Anatomical Therapeutic Chemical Classification System (ATC), the most widely used drug classification system, assigns drugs a unique ATC code, which is an alphanumeric code that assigns it to specific drug classes within the ATC system. Another major classification system is the Biopharmaceutics Classification System. This classifies drugs according to their solubility and permeability or absorption properties.

Employment

Employment is a relationship between two parties, usually based on a contract where work is paid for, where one party, which may be a corporation, not-for-profit organization, or other entity is the employer and the other is the employee. Employees work in return for payment, which may be in the form of an hourly wage, by piecework or an annual salary, depending on the type of work an employee does and/or which sector she or he is working in. Employees in some fields or sectors may receive gratuities, bonus payments or stock options. In some types of employment, employees may receive benefits in addition to payment. Benefits can include health insurance, housing, disability insurance or use of a gym. Employment is typically governed by employment laws or regulations and/or legal contracts.

Employee or employers

An employee contributes labor and expertise to an endeavor of an employer and is usually hired to perform specific duties which are packaged into a job. An employee is a person who is hired to provide services to a company on a regular basis in exchange for compensation and who does not provide these services as part of an independent business.

Employment (short story)

"Employment" is a classic science fiction story pioneering the concept of de-extinction by L. Sprague de Camp. It was first published in the magazine Astounding Science-Fiction for May, 1939. The story appeared under the pseudonym Lyman R. Lyon (the name of his maternal great-grandfather) as the magazine's policy did not allow the name of any author to be repeated on the same contents page, and de Camp had another piece in the same issue under his actual name (part one of his article "Design for Life"). It first appeared in book form in the anthology Imagination Unlimited (Farrar Strauss and Young, 1952; It later appeared in the anthologies Men of Space and Time (The Bodley Head, 1953), and Science Fiction Inventions (Lancer Books, 1967), as well as the de Camp collection The Best of L. Sprague de Camp (Doubleday, 1978). It was credited to de Camp's real name in all publications subsequent to its first appearance. The story has been translated into German.

Plot summary

Employment (album)

Employment is the debut studio album by English indie rock band Kaiser Chiefs, released in March 2005 on B-Unique Records. Employment takes its inspirations from the Britpop and new wave movements, 70's-era punk rock and Beach Boys-esque West Coast music.

The album originally charted at number three in the UK Albums Chart on 13 March 2005, but charted at number two almost a year after its release, due to the band's success at the Brit Awards. Employment went on to become the fourth best-selling album in the United Kingdom that year.

Background

It was Kaiser Chiefs themselves that chose to work with producer Stephen Street. According to Street he had been introduced to Nick Hodgson after an Ordinary Boys gig in which Kaiser Chiefs were the support act. Hodgson gave Street a demo CD and said that they would love to work with him. The band's new label B-Unique suggested they try a test session with Street. In mid-August 2004 they visited the producer at a basement studio space at Olympic Studios he was renting with engineer Cenzo Townsend and recorded "I Predict a Riot".