化学英语证书考试(PEC)常用词汇定义

化学英语证书考试（PEC）常用词汇定义

Absorbents - Absorbents are material that take up or absorb any liquids or vapors that come in contact with it.

Acetyl - Any chemical compound with an acetate group.

Acid- It is a water soluble sour tasting chemical compound. An acid has pH less than 7. The molecule contains hydrogen and are sour tasting compounds and their generic formula is AH.

Acidosis - Acid poisoning in the blood

Additives - In the manufacturing process of plastics, polymer is just one constituent. There are other chemicals like impact modifiers, colorants, reinforcements, plasticisers and stabilizers etc that give specific properties to the plastics. These are called additives.

Agrochemical - Chemicals, like hormone, fungicide, or insecticide, that improve or protects the crop production.

Alcohols - Alcohol in chemistry means any organic compound in which a hydroxyl group (OH) is bound to a carbon atom, further bound to other hydrogen and/or carbon atoms.

Aldehyde - An important starting material and intermediate in organic synthesis. Many aldehydes of industrial significance are used as solvents, perfumes, and flavouring agents or as intermediates in the manufacture of plastics, dyes, and pharmaceuticals.

Aliphatic - Any organic compound in which the main structure is a chain of carbon atoms joined to each other.

Alkali - A compound that has the ability to neutralize an acid to form a salt. A substance which is somewhat irritating or corrosive to the skin, eyes and mucous membranes. Turns red litmus paper to blue. Common strong alkalis are sodium and potassium hydroxide.

Alkenes - Unsaturated hydrocarbons that contain one or more carbon-carbon double bonds.

AllChemE - Alliance for Chemical Sciences and Technologies in Europe. The representative body for chemistry and chemical engineering in Europe.

Amines - Amines are organic compounds containing nitrogen. Here one or more hydrogen atoms are replaced by alkyl groups or other groups where the nitrogen is bonded to a carbon atom in the group. Amine are used in rubber, dyes, pharmaceuticals, and synthetic resins and fibres and in a host of other applications.

Amorphous solid - A noncrystalline solid with no well-defined ordered structure.

Anhydride- Any chemical compound obtained, either in practice or in principle, by the elimination of water from another compound.

Aromatics- Aromatics, so called because of their distinctive perfumed smell, are a group of hydrocarbons including, mainly, benzene, toluene and the xylenes. These are basic chemicals used as starting materials for a wide range of consumer products. Almost all aromatics come from crude oil, although small quantities are made from coal.

Atom - Atom is the basic building block of chemistry. Atoms, also called chemical elements, can combine with one another to form compound. It is the smallest unit of matter that cannot be decomposed into simpler substances by ordinary chemical processes.

Biocide- Biocides are formulations of one or more active substances which can kill or control viruses, bacteria, algae, moulds or yeasts.

Burden of the Past - The 30,000 Existing Chemicals estimated to be on the EU market, for which little or no information is available, in particular about their long-term effects on human health or the environment.

CAS number - Chemical Abstracts System number; CAS? is the producer of the world's largest and most comprehensive databases of chemical information. It is a division of the American Chemical Society.

Catalyst - A substance which aids or promotes a chemical reaction without forming part of the final product.

Catalytic cracking- The process of breaking up heavier hydrocarbon molecules into lighter hydrocarbon fractions by use of heat and catalysts.

Category- A group of closely related chemicals whose physico-chemical, ecotoxicological or toxicological properties follow a regular pattern because of structural similarity.

Chemical Reaction- A chemical process in which substances are changed into different substances with different properties.

Colloid - Colloidal systems are stable dispersions of microscopic solid particles.

Composite - A solid material made of two or more different substances, combined to produce a new substance whose properties are superior to the original components in a specific application.

Compound- A compound (or molecule) is a combination of two or more different chemical

elements (atoms) held together by chemical bonds.

Contaminant- An impurity not intended to be present in the product that may be introduced through such things as poor cleaning, processing, lack of appropriate environmental and personnel controls during the manufacturing process, handling and distribution.

Centrifugal Compressor- A centrifugal compressor compresses air or gas by means of mechanical rotating rotating vanes or impellers.

Chemical Recycling - Chemical recycling is the process of recycling waste products by partially altering their chemical structure.

Chromatography - Chromatography is a process for separating mixtures such as gases into their component parts for analytical purposes.

Dioxins (PCDDs)- General name given to 210 organic compounds containing carbon, oxygen and hydrogen with one to eight chlorine atoms.

Distillate - The liquid obtained through distillation.

Distillation - The process of boiling a liquid and collecting its condensed vapour. This process is used to purify liquids and to separate liquid mixtures.

Emulsifier - An emulsifier (or emulsifying agent) is a substance which can be used to produce an emulsion out of two liquids that normally cannot be mixed together (such as oil and water). Emulsifiers are common in foods to maintain consistency within puddings, powders, etc.

Ester - Any of a class of organic compounds made from the chemical reaction between an alcohol and an organic acid.

European chemicals legislation - Mainly based on four legal instruments on chemicals currently in force in the Community : ·

Excipient - Any substances other than the active drug or product which have been appropriately evaluated for safety and are included in a drug delivery system.

Extinguishing Agents - Media suitable for controlling or putting out a fire, when properly applied.

Fertiliser - Substance that adds inorganic or organic plant nutrients to soil and improves its ability to grow crops, trees, or other vegetation.

Flame retardants - Any chemical compound used to raise the ignition point of such materials as cloth or plastic, and thereby increase their resistance to combustion

Flammable - A material which is easily ignited.

Flocculant - Flocculants are products used in waste treatment to separate unwanted components from water and sludge.

Hygroscopic - Capacity to absorb water.

Impurity - A substance unintentionally contained in a product other than the desired substance.

Inhibitor- A substance which is added to another substance to prevent an unwanted chemical reaction from occurring.

Inorganic Chemicals - A category of chemicals that do not include carbon and its derivatives as principal elements.

Isomerisation- The chemical process by which a compound is transformed into any of its isomers i.e., forms with the same chemical composition but with different structure or configuration and, generally different physical and chemical properties

Latex - A water emulsion of a synthetic rubber or plastic obtained by polymerization and used especially in coatings, paints and adhesives.

Melting Point - The temperature at which a solid substance changes to liquid state

Non-Combustible - A material which will not ignite, burn or support combustion when subjected to heat or fire.

Organic Chemicals - Organic chemicals are based on carbon compounds.

Ozone Depletion - Chemical destruction of the stratospheric ozone layer over and above natural processes.

Petrochemical - An organic compound that has been derived from petroleum or natural gas.

Phthalate- Phthalates, or phthalate esters are manufactured from methanol and are used as plasticisers to soften the plastic. They are also used in other non-PVC applications like paints, rubber products, adhesives and some cosmetics.

Polymer - When individual molecules (monomers) link up in a chain-like fashion, they form a polymer. The chemical reaction that forms a polymer is called polymerization.

Solution - Uniformly dispersed mixtureof the solvent and the solute. The solvent can be water or any other fluid and solute is the dissolved substance.

Solvent - A solvent is a liquid that has the ability to dissolve, suspend or extract other materials, without chemical change to the material or solvent. Solvents make it possible to process, apply, clean or separate materials. Water is an inorganic solvent. Organic solvents include hydrocarbon solvents, oxygenated solvents and chlorinated solvents.

Stabilizer - A stabilizer is a substance added to another substance to prevent an alteration of its physical state.

Surfactant - Surfactants are products used as detergents, dispersing agents, emulsifiers, wetting agents, foaming or anti-foam agents, and solubilisers. They also constitute the raw material for the formulation of household products such as fabric detergents, shampoos, housecleaning products, as well as industrial auxiliary products for facilitating work in the manufacture of textile, flotation agents for ore, metal working, etc. They are used in other sectors of industry such as food processing, metallurgy, pharmaceuticals and public works.

Viscous - Having resistance to flow.

Volatility- The tendency or ability of a liquid to pass into the vapour phase; liquids such as alcohol or gasoline, because of their tendency to evaporate rapidly, are called volatile liquids.