Acetic Acid

a chemical compound, more correctly called ethanoic acid, which is the acid found in vinegar. It is present as a solution in water of strength 3 to 6%, in other words there are 3 to 6 parts of acetic acid in 100 parts of water. The chemical formula for acetic acid is CH₃COOH which contains two carbon atoms bonded together; to one are bonded three hydrogen atoms and to the other one one oxygen and one hydroxyl group (OH). Acetic acid is made from ethanol or acetylene.

Taken from Dictionary of Science

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Acetic acid, CH₃COOH, also known as ethanoic acid, is an organic acid, which gives vinegar its sour taste and pungent smell. It is a weak acid, in that it is only a partially dissociated acid in an aqueous solution. Pure, water-free acetic acid (glacial acetic acid) is a colourless liquid that absorbs water from the environment (hygroscopy), and freezes at 16.5 °C (62 °F) to a colourless crystalline solid. The pure acid, and concentrated solutions, are dangerously corrosive.

Acetic acid is one of the simplest carboxylic acids. It is an important chemical reagent and industrial chemical, used in the production of polyethylene terephthalate mainly used in soft drink bottles; cellulose acetate, mainly for photographic film; and polyvinyl acetate for wood glue, as well as synthetic fibres and fabrics. In households, diluted acetic acid is often used in descaling agents. In the food industry acetic acid is used under the food additive code E260 as an acidity regulator and as a condiment on chips.

The global demand of acetic acid is around 6.5 million tonnes per year (Mt/a), of which approximately 1.5 Mt/a is met by recycling; the remainder is manufactured from petrochemical feedstocks or from biological sources. Dilute acetic acid produced by natural fermentation is called vinegar.

Taken from Wikipedia

Dark Reaction

a stage in PHOTOSYNTHESIS which is not directly dependent on light. It takes place within the CHLOROPLASTS of the cells of green plants.

Taken from Dictionary of Science

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Photosynthesis, or the light-independent reactions, are chemical reactions that convert carbon dioxide and other compounds into glucose. The reactions occur in the stroma, the fluid-filled area of a chloroplast outside of the thylakoid membranes. These reactions take the products of the light-dependent reactions and perform further chemical processes on them. There are three phases to the light-independent reactions, collectively called the Calvin Cycle: carbon fixation, reduction reactions, and ribulose 1,5-diphosphate (RuDP) regeneration.

The light-independent reactions are sometimes referred to as the dark reactions, though that term may be misleading as they do not actually require darkness to proceed. The term "light-independent" is used to emphasize that the reactions continue even in the absence of light as long as the proper substrate compounds are available. However, because the availability of substrates in plants depends on photosynthesis, the reactions cannot be said to be entirely "light-independent." The term "dark reactions" may be more accurate in CAM (Crassulacean acid metabolism) plants, which only take up CO₂, which is necessary for the reactions to proceed, at night.

Taken from Wikipedia

Radical

a group of atoms within a compound, which are not able to exist on their own and are not changed when the substance is involved in chemical reactions.

Taken from Dictionary of Science
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In chemistry, radicals (often referred to as free radicals) are atoms, molecules, or ions with unpaired electrons on an open shell configuration. The unpaired electrons cause them to be highly chemically reactive. Radicals play an important role in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes, including human physiology. For example, superoxide and nitric oxide regulate many biological processes, such as controlling vascular tone. "Radical" and "free radical" are frequently used interchangeably, although a radical may be trapped within a solvent cage or be otherwise bound. The first organic free radical identified was triphenylmethyl radical, by Moses Gomberg in 1900 at the University of Michigan.

Historically, the term radical has also been used for bound parts of the molecule, especially when they remain unchanged in reactions. These are now called functional groups. For example, methyl alcohol was described as consisting of a methyl "radical" and a hydroxyl "radical". Neither are radicals in the modern chemical sense, as they are permanently bound to each other, and have no unpaired, reactive electrons. They can, however, be observed as radicals in mass spectrometry when broken apart by irradiation with energetic electrons.

Taken from Wikipedia

Calcium Carbonate

a common chemical compound in nature with the formula CaCo3. In the form of calcite, it is an abundant MINERAL in rocks especially LIMESTONE, CHALK and MARBLE. It is used by man in the manufacture of cement and fertilizer.

Taken from Dictionary of Science

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Calcium carbonate is a chemical compound with the chemical formula CaCO₃. It is a common substance found in rock in all parts of the world, and is the main component of shells of marine organisms, snails, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime, and is usually the principal cause of hard water. It is commonly used medicinally as a calcium supplement or as an antacid, but excessive consumption can be hazardous.

Taken from Wikipedia

Qualitative Analysis

the chemical examination of a sample to discover what substances are present.

Taken from Dictionary of Science

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In the qualitative analysis procedure, the chemical properties of an unknown substance are determined by systematically reacting the unknown with a number of different reagents. By predetermining what the particular reaction will produce if a specific ion is present, the ions that actually are in the solution can be identified. For example, if a reaction is known to produce a precipitate if ion A is present and a precipitate is formed when the reaction is run, then ion A may be present in solution (there may be, and usually are, other ions that will also precipitate with a particular reagent). If no precipitate is formed when the reaction is run, then ion A is clearly not present in the unknown solution and a different reaction will have to be run to determine what ions are present.

There are two general situations in which qualitative analysis is used - in the identification of a simple salt, or the identification of multiple cations in a solution.

Taken from Wired Chemist

Labile

a term used in chemistry which means not stable, likely to change.

Taken from Dictionary of Science

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The term is used to describe a relatively unstable and transient chemical species. As a general example, if molecule exists in a particular conformation for a short life-time, before adopting a lower energy conformation, the former molecular structure is said to have 'high lability' (such as C₂₅, a 25-carbon fullerene spheroid). The term is sometimes also used in reference to reactivity - for example, a complex which quickly reaches equilibrium in solution is said to be labile (with respect to that solution).

Taken from Wikipedia

Caffeine

a naturally-occurring chemical substance that is found in tea leaves, coffee beans and other plants. It acts as a weak stimulant on the central nervous system so after drinking a cup of coffee or tea, a person may feel more alert.

Taken from Dictionary of Science

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Caffeine is a bitter, white crystalline xanthine alkaloid that is a psychoactive stimulant drug. Caffeine was discovered by a German chemist, Friedrich Ferdinand Runge, in 1819. He coined the term kaffein, a chemical compound in coffee, which in English became caffeine.

Taken from Wikipedia