Chemistry is the scientific discipline involved with elements and compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances.
In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant chemistry (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties of the soil on the moon (astrophysics), how medications work (pharmacology), and how to collect DNA evidence at a crime scene (forensics).
Chemistry addresses topics such as how atoms and molecules interact via chemical bonds to form new chemical compounds. There are four types of chemical bonds: covalent bonds, in which compounds share one or more electron(s); ionic bonds, in which a compound donates one or more electrons to another compound to produce ions (cations and anions); hydrogen bonds; and Van der Waals force bonds.
Lysergic acid diethylamide
, commonly called LSD
, or LSD-25
, is a semisynthetic psychedelic drug
. The short form LSD comes from "L
iethylamid". A typical single dose of LSD during the 1960s was between 100 and 200 micrograms, a tiny amount roughly equal to one-tenth the weight of a grain of sand. Today, a typical single dose of LSD can be as low as 25–50 micrograms, although they are more commonly 50–100 micrograms. Threshold effects can be felt with as little as 20 micrograms.
The effects of LSD can vary greatly, depending on factors such as previous experiences, state of mind and environment, as well as dose strength. Generally, LSD causes expansion and altered experience of senses, emotions, memories, and awareness for 8 to 14 hours. In addition, LSD may produce visual effects such as moving geometric patterns, "trails" behind moving objects, and brilliant colors. LSD does not produce hallucinations in the strict sense but instead illusions and vivid daydream-like fantasies, in which ordinary objects and experiences can take on entirely different appearances or meanings. At higher doses it can cause synaesthesia. The drug sometimes spurs long-term or even permanent changes in a user's personality and life perspective.
LSD is synthesized from lysergic acid derived from ergot, a grain fungus that typically grows on rye. LSD is sensitive to oxygen, ultraviolet light, and chlorine, especially in solution (though its potency may last years if the substance is stored away from light and moisture at low temperature). In pure form it is colorless, odorless, and mildly bitter. LSD is typically delivered orally, usually on a substrate such as absorbent blotter paper, a sugar cube, or gelatin.
Introduced by Sandoz Laboratories as a drug with various psychiatric uses, LSD quickly became a therapeutic agent that appeared to show great promise. However, the extra-medical use of the drug in Western society in the middle years of the twentieth century led to a political firestorm and government insider panic that resulted in the banning of the substance for medical as well as recreational and spiritual uses. Despite this, it is still considered a promising drug in some intellectual circles.
History and Philosophy of Chemistry
Activation energy is the energy that must be overcome for a chemical reaction to occur. Here, the sparks generated by striking steel against a flint provide the activation energy to initiate combustion in a Bunsen burner. The blue flame will sustain itself after the sparks are extinguished because the continued combustion of the flame is now energetically favorable.
(1893-1981) was an American physical chemist
, who won the 1934 Nobel Prize in Chemistry
for his work on isotopes
, specifically the discovery of deuterium
, a hydrogen
isotope, and the production of heavy water
. He also performed pioneering research in cosmochemistry
, which studies the origin and development of elements
and their isotopes, primarily within the solar system. Urey, along with his student Stanley Miller
, may be best remembered for the renowned Miller-Urey experiment
, which shows that a mixture of ammonia
, when exposed to ultraviolet radiation
, can interact to form amino acids
, the "building blocks" of terrestrial life. This experiment followed on from Urey's work on the oxygen
, and is considered to be pioneering work in the field of paleoclimatology
, as it attempts to explain the composition of the early Earth's atmosphere.
Techniques used by chemists
Equipment used by chemists
Chemistry in society
Chemistry in industry
Background color shows subcategory in the metal–metalloid–nonmetal trend: