Concise Dictionary Of Chemistry E-Book

• Herausgeber: V&S Publishers
• Kategorie: Bildung
• Sprache: Englisch
• Veröffentlichungsjahr: 2018

Seitenzahl: 453

Beschreibung

Important terms used in Chemistry and their accurate explanation

Leseprobe

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© Copyright: ISBN 978-935-05733-0-3

DISCLAIMER

While every attempt has been made to provide accurate and timely information in this book, neither the author nor the publisher assumes any responsibility for errors, unintended omissions or commissions detected therein. The author and publisher make no representation or warranty with respect to the comprehensiveness or completeness of the contents provided.

All matters included have been simplified under professional guidance for general information only without any warranty for applicability on an individual. Any mention of an organization or a website in the book by way of citation or as a source of additional information doesn't imply the endorsement of the content either by the author or the publisher. It is possible that websites cited may have changed or removed between the time of editing and publishing the book.

Results from using the expert opinion in this book will be totally dependent on individual circumstances and factors beyond the control of the author and the publisher.

It makes sense to elicit advice from well informed sources before implementing the ideas given in the book. The reader assumes full responsibility for the consequences arising out from reading this book. For proper guidance, it is advisable to read the book under the watchful eyes of parents/guardian. The purchaser of this book assumes all responsibility for the use of given materials and information. The copyright of the entire content of this book rests with the author/publisher. Any infringement/ transmission of the cover design, text or illustrations, in any form, by any means, by any entity will invite legal action and be responsible for consequences thereon.

Contents

Publisher's Note

Introduction

        A

        B

        C

        D

        E

        F

        G

        H

        I

        J

        K

        L

        M

        N

        O

        P

        Q

        R

        S

        T

        U

        V

        W

        X

        Y

        Z

AppendicesAppendix – I

Appendix – II

Appendix – III

Appendix – IV

Appendix – V

Publisher's Note

Innumerable books are available in the market on science and its allied branches, like, physics, chemistry, and biology et al, both as textbook and reference manual. Written for different age-groups and class, quite a number of these books come replete with jargon-filled terms; and just fail to connect with readers’ inclination and curiosity level. On top of that, new words keep finding their way into the books every other day. Every new addition contributes to difficulty in comprehending the matter.

An average reader is interested only in knowing what a specific word means without getting lost with heavy sounding inputs.

Following an open-ended discussion with a cross-section of students and other stakeholders we realised that many books on science (physics, chemistry and biology) take readers’ understanding of scientific terms for granted and make short passing references while alluding to the term in the text. Presentations of this nature in no way assist readers in understanding the subject properly.

You need to suffer no longer.

V&S Publishers has come out with four dictionaries of terms; in science, physics, chemistry and biology. These have been compiled to help readers grasp the meaning of popular scientific terms. For easy reference terms have been arranged alphabetically. Terms that have come into the reckoning even in the early 2012 have been incorporated and suitably explained in such a way that an average secondary and senior secondary student can grasp them easily. High resolution images, illustrations and examples, where appropriate, have been added for reader's convenience. For all readers, who have not made a special study of any science subject, explanations of terms will be found to be easily comprehensible.

An attempt has been made to include important scientific charts, tables, constants, conversion tables as appendices to make this dictionary more useful. A glossary of Nobel Prize winners and their contributions is an added attraction.

We would be happy to have your views and comments about the book.

Introduction

What is Chemistry?

Chemistry is the branch of science that deals with the identification of the substances of which matter is composed; the investigation of their properties and the ways in which they interact, combine, and change; and the use of these processes to form new substances.

Why is the study of Chemistry Important?

Chemistry has a reputation for being a complicated and boring science, but for the most part, that reputation is undeserved. Fireworks and explosions are based on chemistry, so it's definitely not a boring science. If we take classes in chemistry, we'll apply math and logic, which can make studying chemistry a challenge if we are weak in those areas. However, anyone can understand the basics of how things work, and that's the study of chemistry. In a nutshell, the importance of chemistry is that it explains the world around us.

Everyone can and should understand basic chemistry, but it may be important to take a course in chemistry or even make a career out of it. It's important to understand chemistry if we are studying any of the sciences because all of the sciences involve matter and the interactions between types of matter. Students wishing to become doctors, nurses, physicists, nutritionists, geologists, pharmacists, and (of course) chemists all study chemistry. We might want to make a career of chemistry because chemistry-related jobs are plentiful and high-paying. The importance of chemistry won't be diminished over time, so it will remain a promising career path.

How is Chemistry Classified?

Chemistry deals with the structure and composition of matter and the chemical reactions that are responsible for changing the state and properties of matter. Chemistry is the science of atoms, molecules, crystals and other aggregates of matter and the chemical processes that change their energy and entropy levels as also their structure and composition. Chemistry has been sub-divided into distinct disciplines that deal with specific branches of chemistry. The different branches deal with different aspects of the study of matter. Take a look at them:

Organic Chemistry: This branch of chemistry deals with the study of the organic matter. The substances that primarily consist of carbon (C) and hydrogen (H) are termed as organic. The discipline that deals with the study of the structure, composition and the chemical properties of organic compounds is known as organic chemistry. This branch also deals with the chemical reactions that are used in the preparation of organic chemical compounds.

Inorganic Chemistry: It is the branch of chemistry that relates to the structure, composition and behaviour of inorganic compounds. All the substances other than the carbon-hydrogen compounds are classified under the group of inorganic substances. Oxides, sulphides and carbonates form the important classes of inorganic compounds. Industrial inorganic chemistry deals with the branch of applied science such as the manufacture of fertilizers, while the descriptive inorganic chemistry deals with the classification of compounds based on their properties.

Analytical Chemistry: This is a very important branch of chemistry that deals with the analysis of the chemical properties of natural and man-made materials. The study does not restrict itself to any particular type of chemical compounds. Instrumental analysis is a prominent part of modern analytical chemistry. Analytical chemistry primarily deals with the study of the chemicals present in a substance, in what quantity they are, and how they define the chemical properties of the substance.

Physical Chemistry: This branch of chemistry applies the theories of physics to atoms and subatomic particles. When physical chemistry is applied to the chemical interaction between atoms and subatomic particles, the study is known by the name, quantum mechanics. It is a relatively vast field that deals with intermolecular forces, rates of chemical reactions as well the conductivity of different materials.

Biochemistry: This discipline of chemistry represents a peep of biology into chemistry. It deals with the structure and behaviour of the components of cells and the chemical processes in living beings. The complex and large bio-molecules are usually composed of similar units that repeat. The complex molecules are known as polymers and the basic units they are composed of are known as monomers. Biochemistry deals with the study of cellular constituents like proteins, carbohydrates, lipids, and nucleic acids as also the chemical processes that occur in cells.

Nuclear Chemistry: It is a popular and one of the very important branches of chemistry that studies radioactivity. It revolves around the study of the nuclear properties of and the chemical processes in radioactive substances. This branch also covers the study of the equipment used for the performance of nuclear processes. The effects of the absorption of radiation, the production and use of radioactive materials and radiotherapy come under this branch of chemistry. Nuclear chemistry also deals with the non-radioactive areas of life.

Chemistry is a very vast subject as it delves into the enormity of the universe. While dealing with the study of the structure and behaviour of matter, it makes an attempt to encompass the study of the fundamental units that make up the universe.

Chemistry in Everyday Life

Chemistry is important in our day-to-day life. See how:

Cooking – Chemistry explains how food changes as we cook it, how to preserve food, how it rots, how our body uses the food we eat, and how ingredients interact to make food.

Cleaning – A very significant Part of the importance of chemistry is it explains how cleaning works. We use chemistry to help decide what cleaner is best for dishes, laundry, ourselves, and our home. We use chemistry when we use bleaches and disinfectants and even ordinary soap and water. How do they work? That's chemistry!

Medicine – We need to understand basic chemistry so that we understand how vitamins, supplements, and drugs can help or harm us. A substantial part of the importance of chemistry lies in developing and testing new medical treatments and medicines.

Environment – Chemistry is at the heart of environmental issues. What makes one chemical a nutrient and another chemical a pollutant? How can we clean up the environment? What processes can produce things we need without harming the environment?

We're all self-proclaimed chemists. We use chemicals every day and perform chemical reactions without thinking much about them. Chemistry is important because everything we do is chemistry! Even our body is made of chemicals. Chemical reactions occur when we breathe, eat, or just sit there reading. All matter is made of chemicals, so the importance of chemistry is that it's the study of everything.

Great Chemists of All-time

Dmitri Mendeleyev (Russian) – Mendeleyev devised the Periodic table of elements. He predicted that several more elements would be discovered.

Antoine Lavoisier (French) – Lavoisier showed that air is a mixture of oxygen (O) and nitrogen (H). He disproved the old Theory of phlogiston and determined the nature of combustion. Lavoisier wrote the first modern book on chemistry and explained the law of conservation of matter.

Henry Cavendish (British) – Cavendish showed that water could be produced from two gases and discovered hydrogen.

Amedeo Avogadro (Italian) – Avogadro is the first to distinguish molecules from atoms. He developed Avogadro's Constant (The number of particles of a substance in a mole). He also studied the effect of combining volumes.

Jons Jakob Berzelius (Swedish) – Berzelius developed symbols for many of the chemicals. He calculated the atomic weights accurately of many of them and discovered Selenium, Silicon and Thorium.

John Dalton (British) – Dalton developed an atomic theory of matter and explained the laws of partial pressure.

Robert Boyle (Irish) – Boyle studied gases and showed how pressure and volume at constant mass were indirectly proportional to one another.

Joseph-Louis Gay-Lussac and Jacques Charles (Both French) – Studied gases and showed that gas volume at constant pressure increases with temperature.

Friederich Wöhler (German) – Friederich Wöhler is considered as the father of Organic Chemistry. He was the first chemist to synthesise an organic compound, Urea.

Carl Scheele (Swedish) – Carl Scheele was co-discover of oxygen (O) with Joseph Priestley. He also discovered chlorine, manganese and molybdenum.

Marie Curie (Polish) – He isolated radioactive elements radium and polonium.

Josiah Gibbs (American) – Founder of Chemical Thermodynamics.

Jacobus van't Hoff (Dutch) – He was one of the earlier chemists to speak about the 3-D nature of molecules.

Frederick Sanger (British) – Sanger revealed the Amino sequence for insulin. He worked out methods for determining the molecular structure of nucleic acids. He was two time Nobel Prize winner.

Humphry Davy (British) – He showed the connection between electrochemistry and the elements. He discovered the elements Potassium, Sodium, Barium, Calcium and Magnesium amongst others.

Joseph Priestley (English) – Oxygen co-discoverer.

Henri Le Chatelier (French) – Chatelier developed the principle that every change in a stable chemical equilibrium will result in a shift in the direction of the equilibrium to reduce the effects of the change.

Frederick Soddy (British) – Introduced the isotope theory of elements.

Svante Arrhenius (Sweden) – Established modern electrochemistry.

Germain Hess (Swiss/Russian) – Introduced Hess's Law for determining the heat of reactions.

Wilhelm Ostwald (Latvian) – Discovered Dilution law. He also invented process to make nitric acid by oxidising ammonia. He also developed a theory of colour.

Daniel Rutherford (Scottish) – Discoverer of Nitrogen.

Friederich Kekulé (German) – Kekulé was an organic chemist. He described the ring structure of benzene.

Stanislao Cannizzaro (Italian) – Cannizzaro established the use of Atomic weights in Chemical formulas and calculations.

Linus Pauling (American) – Pauling applied Quantum Theory to determine Chemical Structure (especially of proteins). He also showed how electrons effect the formation of molecules.

Johannes Brønsted Danish and Thomas Lowry (British) – Independently introduced the Brønsted-Lowry definition of an acid as something that donates a proton and a base as something that accepts a proton.

Leo Baekland (Belgian/American) – Father of the Plastics Industry.

William Ramsay (Scottish) – Co-discovered Argon with Lord Rayleigh. Ramsay was the first to identify Helium, Neon, Krypton and Xenon.

Henri Moissan (French) – Moissan isolated fluorine. He invented the electric furnace and also discovered Carborundum and produced artificial diamonds in a laboratory.

Theodore Richards (American) – Richards performed extensive work on atomic weights to reveal the existence of isotopes.

Dorothy Hodgkin (British) – Crystallographer. He used x-ray crystallography to reveal the structure of such molecules as penicillin and insulin.

Thomas Graham (Scottish) – He developed Graham's Law of Diffusion. He was the founder of Colloidal Chemistry.

Fritz Haber (German) – He invented the process to make ammonia from nitrogen in the air known as the Haber process. His invention allowed Germany to continue making explosives after the World War I ban in spite of the blockade on the importation of nitrates.

Irving Langmuir (American) – Langmuir was a High Temperature chemist. His works led to the development of the tungsten lamp. He also studied gases. Research in this field would have practical implications with respect to the use of atomic hydrogen in welding torches.

Peter Debye (Dutch) – Worked on molecular structure. He pioneered x-ray powder photography.

Harold Urey (American) – Harold isolated Heavy water and discovered deuterium.

Paul Flory (American) – Paul Flory was a leading figure in the field of Polymerisation. He also studied properties of plastics, rubbers and fibres.

William Perkin (British) – Perkin was noted for his work on dyes. He also invented mauve.

George Washington Carver (American) – Agricultural chemist. His research involved the synthesis of products from peanuts, sweet potatoes and soybeans.

François Raoult (French) – Raoult developed the law which relates vapour pressure of a solution to the number of molecules of solute dissolved in it.

Future of Chemistry

As chemists, biologists and other scientists continue to unveil nature's secrets, a flood of facts accumulates with stunning momentum. Each answer is a new beginning – material for new experiments. After much effort was spent in the last century finding individual puzzle pieces, scientists can now revel in the process of fitting the pieces together.

Not that everything has been figured out – not by a long shot. Perhaps ironically, as science grows larger in scope and broader in focus, some of the most promising tools to synthesise the hows, whats, and wheres of human biology are exceedingly tiny.

Unravelling – and making sense of – different components of chemistry that aid the genetic instructions that spell life for organisms as diverse as flies, plants, worms, and people have sparked the most exciting revolution. Every minute of every day, scientists all over the world work feverishly, weaving a compelling tale of the chemistry that underlies our health.

It's all very exciting, but the progress mandates still more work. Much more work!

Among the questions still awaiting answers are these:

How to synthesise foods that feed the growing number of people?

How to manufacture clothes that clean themselves automatically?

How to prevent ageing?

How to produce medicines that prevent sickness?

How to keep our brain alert for all-time?

How to convert bacteria to our benefit?

How do the 6-foot long stretches of DNA in every cell in our bodies know how to keep our biochemical factories running smoothly?

When will someone figure out how to fight disease by manipulating the intricate sugar coatings on our cells?

Who will invent the tools that will revolutionise chemistry labs of the future?

What unexpected places hold treasure troves for new medicines?

A

Abatement

Action taken to reduce air pollution which involves the use of control equipment or some new process. This refers to a reduction or lessening as opposed to elimination of a type of discharge or pollutant.

Ablation

The weathering of a glacier by surface melting, or rock weathering by hydraulic erosion.

Abrasion

The susceptibility of the surface of a paper sample to being abraded during a standard test.

The tendency of papermaking materials to abrade slitter knives, dies, etc.

Absolute density

The absolute density is a measure of the mass of one millilitre of gas at standard temperature and pressure.

Absolute zero

Absolute zero is the theoretical temperature of -273.16°C or -459.67°F or 0 k at which entropy reaches its minimum value. The laws of thermodynamics state that absolute zero cannot be reached using only thermodynamic means. A system at absolute zero still possesses quantum mechanical zero-point energy, the energy of its ground state. The kinetic energy of the ground state cannot be removed. However, in the classical interpretation it is zero and the thermal energy of matter vanishes. The zero point of any thermodynamic temperature scale, such as Kelvin or Rankine, is set at absolute zero.

Absolute ZeroThermometers compare FahrenheitCelsius and Kelvin scales

Absorbance

The logarithm (must be specified as to base 10, lg, or base e, ln) of the reciprocal of transmittance [ln (Io/It) or lg (Io/It)], where Io and It are the monochromatic radiances (intensities) of light incident on and transmitted through, respectively, a sample which is usually contained in a sample cell.

Absorber

A device used commonly for sampling by absorption in which a gaseous or liquid material is removed from another gas or liquid by selective absorption; these include: scrubber, impinger, packed column, spray chamber, etc. A substance used to absorb energy form any type of radiation.

Absorption

The process of one material (absorbent) being retained by another (absorbate); this may be the physical solution of a gas, liquid, or solid in a liquid, attachment of molecules of a gas, vapour, liquid, or dissolved substance to a solid surface by physical forces, etc. In spectrophotometry, absorption of light at characteristic wavelengths or bands of wavelengths is used to identify the chemical nature of molecules, atoms or ions and to measure the concentrations of these species. The transfer of a component from one phase to another.

Absorption cross section

A measurement of an atom or molecule's ability to absorb light at a specified wavelength, measured in square cm/particle.

Absorption line

A narrow range of wavelengths in which a substance absorbs light; a series of discrete absorption lines can be used as an unambiguous identification for many relatively simple chemical species.

Abstraction reaction

A reaction that takes any atom away from another chemical species. Classical examples in atmospheric chemistry are the gas phase removal of hydrogen from methane by hydroxyl radical or the following solution phase reaction:

HSO3 + H2O2 → HSO4− + H2O

Acceleration

Measure of how fast velocity is changing, so we can think of it as the change in velocity over change in time. The most common use of acceleration is acceleration due to gravity, which can also appear as the gravitational constant (9.8 m/s2).

Accommodation coefficient

Also sticking coefficient. A measure of the efficiency of capture of molecules or atoms which collide with aerosol particles, cloud droplets, etc. The accommodation coefficient is the fraction of the collisions which result in the capture of the molecules (atoms, radicals, etc.) by the particle, cloud droplet, etc., fraction of colliding molecules which are not reflected but which enter the surface of an aqueous aerosol.

Accretion

The process by which aerosols grow in size by external addition of various chemical species; a form of agglomeration.

Accumulation mode particles

(Also known as secondary particles) These are particles that are formed in the atmosphere due to both the chemical and physical processes that take place with the interactions of primary gaseous emissions. The primary gaseous emissions are injected into the atmosphere by combustion processes such as from a car or from a coal burning plant.

Accuracy

An indication of how close a measurement is to its accepted value.

Acetal

Acetal is an organic compound, pleasant smelling, formed by addition of ethyl alcohol to ethanal (acetaldehyde). It is used as a solvent and in synthetic organic chemistry. Acetals are used as protecting groups for carbonyl groups in organic synthesis as they are stable with respect to hydrolysis by bases and with respect to many oxidizing and reducing agents.

Acetaldehyde

CH3CHO, a fairly simple aldehyde (second in the analogous series after formaldehyde) that is found in the atmosphere as a result of emissions from the manufacture of acetic acid, plastics, raw materials, and as a product in some polluted air oxidation reactions, for instance, acetaldehyde is found in urban air all over the world. Also called Ethanal.

Acetic acid

CH3COOH, a carbonyl compound that is emitted into the troposphere by both natural and anthropogenic processes. In the troposphere, acetic acid is present in the gas phase and is highly water soluble. Since acetic acid is highly water soluble, it is found in high concentration as acidic precipitation, such as in fog water and cloud droplets in urban areas. Also known as Ethanoic Acid.

Acetone

CH3COCH3, a carbonyl compound that is found in the atmosphere as a reactive gas. Acetone is considered to be a volatile organic compound (VOC), which is emitted into the atmosphere by industrial processes. Acetone has been linked to the formation of ozone in the troposphere due to the fact that it is a source of free radicals. Also known as Propanone.

Acetyl

A functional group with chemical formula -COCH3.

Achiral

A group containing atleast two identical substituents.

Acicular

Another word for “needle-shaped,” as in the case of aragonite calcium carbonate particles.

Acicular habit

An acicular habit describes the shape of a large crystal that looks like spikes coming out from one point. Think about those koosh balls for this example.

Acid

A species which reacts in liquid water to generate hydrogen ions (conventionally represented as cations H+ or hydronium, H3O+); anions (e.g., sulphate, SO42−; nitrate, NO3−) which were associated with the H+ in the acid are also released. Important acids in the atmosphere include sulphuric acid (H2SO4), nitric acid (HNO3), and organic acids (e.g., formic acid, HCO2H; acetic acid, CH3CO2H, etc.).

Brønsted acid—A molecular entity capable of donating a proton to a base, (i.e. a “proton donor”) or the corresponding chemical species. For example: H2O, H3O+, CH3CO2H, H2SO4, HSO4−.

Lewis acid—A molecular entity (and the corresponding chemical species) that is an electron-pair acceptor and therefore able to react with a Lewis base to form a Lewis adduct, by sharing the electron pair furnished by the Lewis base.

Acid alum

A mixture of aluminium sulphate (papermaker's alum) and sulphuric acid.

Acid anhydride

Hydrocarbon containing two carbonyl groups.Acyl group attached with carboxylate group.eg- RCOOCOR’

Acid deposition

A broad term that includes any forms of acids that accumulate in the atmosphere, for instance, acid rain, fog, haze. The term can be used to explain the long term effects of these events on the environment as well as the main causes of acid rain, fog or haze. The term functions as a category that any aspect of anthropogenic acid in the environment can be placed.

Acid halide

Acyl group with any halogen attached with carbon of carbonyl group.eg.- RCO-X (X= F,Cl,Br,I).

Acid rain

Acidified particulate matter in the atmosphere that is deposited by precipitation onto a surface, often eroding the surface away. This precipitation generally has a pH less than 5 and sometimes much lower depending on the concentration of acidic components.

Acid-base indicator

A dye that changes colours under different conditions of pH Values.

Acid-base titration

The procedure used to determine the concentration of an acid or base involving the gradual addition of either an acid or base.

Acidic

Describes a solution with a high concentration of H+ ions.

Acidic paper making

Forming paper from stock that has a pH value usually in the range of 3.5 to 6.5, and usually in the presence of aluminium species, e.g. alum.

Acidification

In the gas phase this process happens when compounds like nitrogen oxides and sulphur oxides are converted in a chemical reaction in the gas phase or in clouds into acidic substances. These acids are rained-out or dry deposited. Significant amounts of the compounds containing nitrogen and sulphur are a direct result of anthropogenic activity. An example reaction that takes place in soil occurs from the oxidation of reduced sulphur (for instance, pyrite) exposed during, for instance, strip mining of lignite. This can be represented as:

4SO42−+ 8H+ + 2Fe(OH)2

Acidity

Ability of an aqueous sample to contribute hydrogen ions during a titration with base.

Acid-pulse (dry deposition)

Deposit of powder-like substance over the ground surface; especially effecting plant leaves; that when contacted by water has a very low pH.

Acrolein (CH2CHCHO)

The simplest double-bonded aldehyde, produced in urban smog, contributing greatly to eye and lung irritation. It is a constituent of internal combustion engine exhaust, cigarette smoke, and biomass burning, and from the incomplete combustion of plastics and fuels. Also called Propenal.

Acrylic acid

Acrylic acid (propenoic acid) is a colourless liquid, smelling like acetic acid. It can be formed by acrolein oxidation. It readily polymerizes and is used in the manufacture of acrylic resins, transparent plastic materials (organic glass).

Actinide series

The actinide series is one of two series of inner transition elements. Elements 89 through 103 are a part of this series. The elements include uranium, berkelium, and nobelium.

Actinium

Symbol: Ac Atomic Number: 89 Atomic Mass: 227.03amu. It is one of the elements in the actinide series of inner transition elements. It may also be classified as a rare earth element. Actinium is the first element of the actinide series. It is used as a source of neutrons in experiments that involve radioactivity. You will not find the element in regular use anywhere in the natural world.

Activated charcoal

Activated charcoal or activated carbon is charcoal that has been activated for adsorption by steaming or by heating in a vacuum. Charcoal is obtained by burning wood, nutshells, coconut husks or other materials. Charcoal becomes activated by heating it with steam to approximately 1000 °C in the absence of oxygen. The chemical nature of amorphous carbon, combined with a high surface area makes it an ideal medium for the adsorption of organic chemicals. A single gram of such material can have 400 m2 to 1 200 m2 square meters of surface area. Activated charcoal is widely used to decolourize liquids, recover solvents, and remove toxins from water and air.

Activated complex

An unstable, short-lived particle formed as the result of a collision of particles in a chemical reaction. The activated complex is located at the top of a potential energy diagram. Bonds are in the process of both being formed and being broken.

Activating group

Any group which activate any molecule by increasing positive or negative charge on carbon atom.Mainly towards neucleophilic or electrophilic substitution reactions.

Activation energy

When reactions proceed, a certain amount of energy is needed for the whole process to begin. The energy needed to get the reaction started (get it over the hump) is called the activation energy. The energy required to start a chemical reaction. If a reaction is not spontaneous, it requires a specific amount of energy to proceed. That required energy is the activation energy. Enzymes and catalysts can decrease the activation energy of a reaction.

Active chlorine

Active chlorine can be a single chlorine atom that is a radical (“Cl dot”) and therefore highly reactive. It can also be a molecule containing chlorine that is reactive (ClO). Active chlorine's most notable role in atmospheric chemistry is in catalytic destruction of ozone in the stratosphere and the accumulation of active chlorine at the earth's polar stratosphere during the polar night that leads to major ozone hole formation during the spring.

Active transport

Active transport is the carriage of a solute across a biological membrane from low to high concentration that requires the expenditure of (metabolic) energy.

Activity series

a list of metals and hydrogen arranged in order of their chemical reactivity, such that any element in the series will displace ions of the elements below it from aqueous solutions of their salts.

Activity series of metals

A list of metals arranged in decreasing order of chemical reactivity. Very active metals react with water. Active metals react with acids. Least reactive metals do not react with acids.

Acyl group

A group having alkyl or aryl group with a carbonyl group RCO-

Adam's catalyst

A catalyst for hydrogenation and hydrogenolysis in organic synthesis. Also known as platinum dioxide

Addition reaction

A reaction where a product is created from the coming together of 2 reactants.

Additivity principle

The hypothesis that each of several structural features of a molecular entity makes a separate and additive contribution to a property of the substance concerned. More specifically, it is the hypothesis that each of the several substituent groups in a parent molecule makes a separate and additive contribution to the standard Gibbs energy change (or Gibbs energy of activation) corresponding to a particular equilibrium (or rate of reaction).

Address-message concept

Address-message concept refers to compounds in which part of the molecule is required for binding (address) and part for the biological action (message).

Adduct

A new chemical species AB, each molecular entity of which is formed by direct combination of two separate molecular entities A and B in such a way that there is change in connectivity, but no loss, of atoms within the moieties A and B. Stoichiometries other than 1:1 are also possible, e.g. a bis-adduct (2:1). An “intramolecular adduct” can be formed when A and B are groups contained within the same molecular entity. This is a general term which, whenever appropriate, should be used in preference to the less explicit term complex. It is also used specifically for products of an addition reaction.

Adhesion

Adhesion is one type of attraction force between the molecules of a substance and the container or another object. You stay wet when you get out of the bathtub because of adhesive forces. Some of the water molecules want to stick to you.

Adiabatic lapse rate

The rate of decrease of temperature with increasing altitude in the atmosphere. If heat is neither gained nor lost from the air parcel under consideration, then the lapse rate is said to be adiabatic and the energy to expand the volume of the parcel or rising air comes from the kinetic energy of the gas molecules in that parcel. The expansion of the parcel causes these molecules net kinetic velocity to decrease and this is equivalent to cooling the air. In dry air the dry adiabatic lapse rate is about 9.8 C/km (the sign is traditionally positive although the temperature is decreasing with altitude).

Adsorbed

Solid material used to capture either a gas or liquid; often activated carbon is employed as the solid because of its high surface area per unit mass.

Adsorbent

An adsorbent is the solid material to which another species is adsorbed in a surface layer. A condensed phase at the surface of which adsorption may occur.

Adsorption

The process by which molecules of gas, dissolved substances, or liquids adhere to the surface of solids through either weak physical forces (physical adsorption) or stronger chemical forces (chemical adsorption). The enrichment (positive adsorption, or briefly, adsorption) of one or more components in an interfacial layer.

Advection

The transport of air, its properties (such as heat), trace materials, fog, cold air, etc., solely by mass motion of the atmosphere, generally in a horizontal direction.

Aeration

The process by which a volume filled with a liquid becomes permeated with air or another gas; aeration is often accomplished by spraying the liquid into the air, bubbling air through a liquid, or agitating the liquid to promote surface absorption of air.

Aerobic

Oxygen-dependent or requiring oxygen.

Aerobic respiration

Organisms utilize oxygen to break down components, derive energy, and generate needed biomolecules. Carbohydrates are cycled into water and carbon dioxide.

Aerometer

Instrument used to measure the density of gases.

Aerometric measurements

Measurements of the temperature, pressure, air motion (velocity vectors), or other physical measurements to characterize an air mass.

Aerosol particles

One of the components of an atmospheric air parcel, comprised of minute solids particles part of which is almost certainly water.

Aerosol scavengers

Cloud droplets which attract an aerosol into snow, rain or some other water precipitate by coagulation and accretion.

Affinity

Affinity is the tendency of a molecule to associate with another. The affinity of a drug is its ability to bind to its biological target (receptor, enzyme, transport system, etc.) For pharmacological receptors it can be thought of as the frequency with which the drug, when brought into the proximity of a receptor by diffusion, will reside at a position of minimum free energy within the force field of that receptor.

Afforestation

The process or act of changing land into forest by planting trees, seeding, etc. on land formerly used for something other than forestry. This can obviously be contrasted with deforestation.

Agglomerate

The most general term indicating that small particles come together and stick.

Agglomeration

A process by which atmospheric particles collide and stick to each other forming a new particle. Many of the particles emitted from automobile tailpipes are agglomerations of smaller particles formed in the combustion process.

Agonist

An agonist is an endogenous substance or a drug that can interact with a receptor and initiate a physiological or a pharmacological response characteristic of that receptor (contraction, relaxation, secretion, enzyme activation, etc.).

Agostic

The term designates structures in which a hydrogen atom is bonded to both a carbon atom and a metal atom. The term is also used to characterize the interaction between a CH bond and an unsaturated metal centre, and to describe similar bonding of a transition metal with Si-H compounds. The expression “μ-hydrido-bridged” is also used to describe the bridging hydrogen.

Air mass

A qualitative term to describe a widespread body of air with approximately uniform characteristics which had been identified at a given time over a particular region of the earth's surface. Sometimes an air mass is marked by inert tracers such as SF6 which may be added to it. The composition of a given air mass undergoes alteration as it migrates, chemical changes occur, compounds are removed by dry and wet deposition, and new impurities are added to the mass.

Air parcel

A volume of air, the component makeup and concentrations of which remain relatively static, that tends to travel around the earth changing geographic location and position above earth as an intact unit. Air parcels can be tracked.

Air pollutant

A substance, gaseous material or aerosol which has been introduced into the air (either by human activity or by natural processes) in sufficient concentration to produce a measurable effect on humans, animals, vegetation, or materials (monuments, etc.): SO2, NO2, H2S, CO, hydrocarbons, etc.

Air pollution

Usually the presence of substances in the atmosphere, resulting either from human activity or natural processes, present in sufficient concentration, for a sufficient time and under circumstances such as to interfere with comfort, health or welfare of persons or the environment.

Air pollution control

Measures taken to control the purity of the air to some degree specified by law.

Air pollution control district

A geographical region designated by law in which the emissions of some specified air pollutants are controlled to a degree specified by law.

Air pollution index or air quality index

A mathematical combination of the concentrations of air pollutants (weighted in some fashion to reflect the estimated health impact of the specific pollutant) which gives an approximate numerical measure of the quality of the air at a given time. These indices have little scientific basis but have been used to inform the public (in a qualitative fashion) of the degree of pollution present at a given time.

Air pollution survey

A study of the concentrations and geographical distribution of specified air pollutants in a given area and an assessment of the damage, if any, which the pollutants have caused.

Air quality act of 1967

The first national act in the United States to regulate emissions into the atmosphere; the act was closely related to a previous act created in 1963. The bill was created in response to growing urban areas that were having obvious pollution problems.

Air quality assessment

A prescribed level of atmospheric pollution allowed for a certain compound during a specific time in a specific geographical area. Standards are set by some regulating body, office or agency.

Air quality characteristic

One of the quantifiable properties relating to an air sample: concentration of a constituent, wind speed, temperature, etc. The quantity of air quality characteristic is the true value of the characteristic being investigated; it is recognized that in practice, this value can only be approximated by existing methods.

Air quality index (aqi)

An accounting or measurement of specified toxic levels of pollutants in the air. Based on the EPA air quality act, it gives the indicator (number) of different gas phase concentration levels to determine if it is hazardous to be outside or not, that is to breathe the air is a specific region.

Air resource management

The detailed planning and the implementation of air pollution control programmes designed to preserve the health and welfare of the people in the region, the plant and animal life, physical property, good visibility, and other factors which determine the air quality and the maintenance of an aesthetically acceptable environment.

Air sampling network

A number of air sampling stations which are established in a given geographical region at which measurements of both pollutant concentrations and meteorological quantities (wind speed, direction, rain fall, humidity, etc.) are made to determine the extent and the nature of the air pollution and to establish trends in the concentrations of the air pollutants with time.

Air stripping

Air stripping is a process for the removal of volatile organic contaminants from groundwater. The groundwater flows downward inside a tower filled with materials (the packing) over a large surface area. Air is introduced at the bottom of the tower and is forced upward past the falling water. The volatiles evaporate from the water and are collected in air filters or released to the atmosphere.

Air, composition of pure

The composition of air is variable with respect to several of its components (e.g., CH4, CO2, H2O) so “pure” air has no precise meaning; it is commonly considered to be air which is free of dust, aerosols, and reactive gaseous contaminants of anthropogenic origin. The composition of the major components in dry air is relatively constant (percent by volume given): nitrogen, 78.084; oxygen, 20.946; argon, 0.934; carbon dioxide, 0.033; neon, 0.0018; helium, 0.000524; methane, 0.00016, krypton 0.000114; hydrogen 0.00005; nitrous oxide, 0.00003; xenon, 0.0000087. The concentration of carbon dioxide, methane, nitrous oxide, the chlorofluorocarbons and some other species of anthropogenic origin are increasing measurably with time. Relative clean air which is free of most reactive anthropogenic pollution (NO, NO2, SO2, non-methane hydrocarbons, etc.), often used as a reference sample in the calibration and operation of instruments, is purchased under the designation of zero air.

Air-float clay

A type of kaolin clay products that are prepared for use by an air-sorting process to obtain particles a good size range for the application.

Aitken particles

Aerosol particles below 0.1m in diameter. These generally are the most numerous among all particles in the air. Their concentrations can be determined with the Aitken counter which measures total particle number density. Owing to their small size, Aitken particles contribute little to the total mass concentration of all aerosol particles; this is determined primarily by particles of diameter > 0.1m.

Akd

Alkylketene dimer, a synthetic sizing agent in the form of an aqueous dispersion of waxy particles, useful for wet-end addition.

Albedo

The fraction of the energy of electromagnetic radiation reflected from a body (or surface) relative to the energy incident upon it. The reflection of light from a surface is, of course, dependent on the wavelength of the light, the nature of the surface, and its angle of incidence with the surface. The term albedo usually connotes a broad wavelength band (visible, ultraviolet, or infrared), whereas the terms reflectivity and spectral albedo are used to describe the reflection of monochromatic (single wavelength or small band of wavelengths) radiation.

Alchemy

Alchemy is an ancient, non-scientific form of chemistry. In the middle ages, alchemists were people who tried to turn one element into another (usually lead (Pb) into gold (Au)).

Alcohols

When the elements making up an organic compound are Carbon, Hydrogen and Oxygen and the Hydrogen and Oxygen combine in such a way as to form a -C-OH group, the Organic Compounds formed are referred to as Alcohols and the Functional Group (-OH) is referred to as the “O H” Group. The most common Alcohol is Ethyl Alcohol or Ethanol (C2H5OH) which is present in all beers, wines and liquors.

Aldehyde

A class of organic compound of general formula: R(C=O)H, where R is an hydrogen atom or hydrocarbyl group (e.g., CH3, C2H5, etc.). These are products of hydrocarbon oxidation. The simplest aldehydes are formaldehyde (methanal, HCHO), acetaldehyde (ethanal, CH3CHO), and propionaldehyde (propanal, CH3CH2CHO). They also react rapidly with HO-radicals in the atmosphere to produce acyl (RCO) and acylperoxyl (RCOO2) radicals. Formaldehyde is the most abundant aldehyde in the atmosphere (formed from the natural hydrocarbon, CH4, as well as other hydrocarbons) where its mixing ratios are often > 0.2 ppbv even in relatively clean air. Acetaldehyde is a major precursor to peroxyacetyl nitrate (PAN) in the troposphere.

Aldol reaction

When two similar aldehydes are reacted with each other, a product having both aldehyde(>C=O) and alcohol(OH) group is formed. This reaction is called aldol reaction.

Alert levels

Also referred to as air quality index (AQI). This is a measure of different levels of concentration of air pollutants in the air. This index by another name was originally established in 1976. With each pollutant level, there is a warning depending on the concentration and its effects to the public. Alert levels can be found for any of five pollutants and the levels have colour and number indicators that warn the public. The pollutants upon which the air quality index is based are ground-level ozone, particulate matter, carbon monoxide, sulphur dioxide, and nitrogen dioxide.

Aliphatic

A non-cyclic, non-aromatic, hydrocarbon chain (e.g. alkanes, alkenes, and alkynes)

Aliphatic compounds

Hydrocarbons that contain only single covalent bonds, double covalent bonds separated by more than two carbon atoms, or a triple covalent bond are referred to as Aliphatic Compounds. The Aliphatic Compounds make up the majority of Hydrocarbons.

Aliquot

A representative portion of the whole.

Alkaline papermaking

Forming paper from stock that has a pH value in the range from about 7 to 9.5.

Alkalinity

Ability of an aqueous sample to contribute hydroxyl ions during a titration with acid.

Alkaloid

Alkaloids are basic nitrogen organic compounds (mostly heterocyclic) derived from plants and having diverse pharmacological properties. Alkaloids include morphine, cocaine, atropine, quinine, and caffeine, most of which are used in medicine as analgesics or anaesthetics. Some alkaloids are poisonous, e.g. strychnine and coniine, and colchicine inhibit cell division.

Alkanes

Alkanes are hydrocarbons containing only Single Covalent C-C Bonds are called Alkanes.

Alkenes

Alkenes are hydrocarbons containing at least one Double Covalent C=C Bond.

Alkoxide ion

The conjugate base of an alcohol without the terminal H atom. For any alcohol R-OH, the corresponding alkoxide form is R-O−.

Alkyl

A hydrocarbon having formula CnH2n+1

Alkyl group

Part of an organic chemical compound that is made up mainly of carbon and hydrogen atoms in the approximate ratio of two hydrogen atoms per carbon atom (-CH2-).

Alkylation

Addition of alkyl group in a compound.

Alkyne

An unsaturated hydrocarbon containog triple bond.and having general formula CnH2n−2

Allosteric binding sites

Allosteric binding sites are contained in many enzymes and receptors. As a consequence of the binding to Allosteric binding sites, the interaction with the normal ligand may be either enhanced or reduced.

Allosteric enzyme

An allosteric enzyme is an enzyme that contains a region to which small, regulatory molecules (“effectors”) may bind in addition to and separate from the substrate binding site and thereby affect the catalytic activity.

Allosteric regulation

Allosteric regulation is the regulation of the activity of allosteric enzymes.

Alloy

A mixture of a metal with one or more other elements. eg. steel (iron & carbon), solder (lead & tin), bronze (copper & tin) and brass (copper & zinc).

Allyl

An alkene hydrocarbon group with the formula:

H2C=CH-CH2-.

Allylic substitution reaction

A substitution reaction occurring at position 1/ of an allylic system, the double bond being between positions 2/ and 3/. The incoming group may be attached to the same atom 1/ as the leaving group, or the incoming group becomes attached at the relative position 3/, with movement of the double bond from 2/3 to 1/2.

Alternant

A conjugated system of pi electrons is termed alternant if its atoms can be divided into two sets so that no atom of one set is directly linked to any other atom of the same set.

Example of alternate π system

Example of non-alternate π system

(two atoms of unstarred set are dircetly linked)

Alternative energy source

Any energy source that can be harnessed without the use of burning fossil fuels. Such alternative sources are almost always a renewable energy source such as hydroelectric power, wind power, and solar power.

Alum

Its formula K2SO4.Al2(SO4)3.24H2O. A white or Colourless Crystalline compound. It is used as mordant for dyeing and in tanning of leather goods.

Aluminium

Symbol: “Al” Atomic Number: “13” Atomic Mass: 26.98amu. Aluminium is a light element and classified as a basic metal. There is more aluminium than any other metal in the Earth's crust. You will also find aluminium in utensils, foil wrap, power lines, soda cans, and airplane structures.

Aluminium trihydrate

A very bright mineral having the same chemical composition as alum floc.

Ambient air

The outdoor air in the particular location.

Ambient air quality

A general term used to describe the quality of the outside air. Usually adjectives such as good, fair, bad, etc. are used by the media to describe this; often some form of air pollution or air quality index is employed to determine the specific descriptive term to be used. These are very qualitative terms of little or no scientific value.

Americium

Symbol: “Am” Atomic Number: “95” Atomic Mass: (243)amu. Americium is one of the elements in the actinide series of inner transition elements. It may also be classified as a rare earth element. This element is radioactive and can be safely used in small amounts. You might find it in nuclear reactors and some smoke detectors.

Ames/salmonella test

A screening test employed in predicting the mutagenic and the potential carcinogenic activities of chemicals in the environment. It employs Ames test strains of salmonella bacteria (his−) which lack the ability to produce histidine. The compound to be tested, the bacteria and a small amount of histidine (insufficient to permit colony growth but enough to allow sufficient growth for expression of mutations) are added to agar. The bacteria are allowed to incubate for about 63 hours at 37 °C. If a significant increase in colonies above background is observed in the sample containing the test compound, then it is concluded that the chemical tested is a direct mutagen for the particular Ames strain of bacteria.

Amide

Amide is an organic compound that contains a carbonyl group bound to nitrogen. The simplest amides are formamide (HCONH2) and acetamide (CH3CONH2).

Amides

When Organic Acids have the Oxygen in the terminal -OH group of O=C-OH replaced by an Nitrogen, then the resulting compound has the terminal group O=C-NH2 and is called an Amide.

Amines

When the Oxygen of the -OH functional group of Alcohols is replaced by Nitrogen the functional group becomes -NH2 and the compounds are called Amines. The simplest Amine is Methyl Amine (CH3NH2).

Amino acids

A group of 20 different kinds of small molecules that link together in long chains to form proteins. Often referred to as the “building blocks” of proteins. The sequence of amino acids in a protein determines the structure and function of the protein.

Amino group

The amino group is a functional group with one nitrogen and two hydrogen atoms. You will find them on all of the amino acids. It can be synthesized from ammonia.

Ammonia

The molecular formula for ammonia is NH3. Ammonia is one of the most important inorganic nitrogen compounds in atmospheric water droplets. It reacts with strong acids and is one of the only known basic, gas phase atmospheric components. Atmospheric ammonia can also enhance the nucleation rate and the production of new particles in the atmosphere. These new particles can be activated to become condensation nuclei and then, through various processes, grow to a particle size of 0.05 micrometer or larger which can then be effective as cloud condensation nuclei. This process can, therefore, affect the global radiation budget. The major sources of ammonia are decaying natural organic matter, livestock wastes, fertilizers, and industrial activity.

Amorphous

A solid that has no definite shape or form because the particles are arranged randomly. eg. glass, flour, soot.

Amorphous solid

An amorphous solid has no specific organization of molecules. The other end of the spectrum would be a crystal with a highly organized set of molecules. Plastic is an example of a vitreous solid. Because of their combination of atoms, amorphous solids do not have a specific melting point. They become a liquid over a wide temperature range.

Amphipathic

Amphipathic molecules have one hydrophobic end and one hydrophilic end. You can find these molecules in the cell membrane.

Amphiphilic

A compound containing a large organic cation or anion which possesses a long unbranched hydrocarbon chain, e.g. H3C(CH2)nCO2−M+ H3C(CH2)nSO3−M+ H3C(CH2)nN(CH3)3+X− (n > 7). The existence of distinct polar (hydrophilic) and non polar (hydrophobic) regions in the molecule promotes the formation of micelles in dilute aqueous solution.

Amphiprotic

a substance that can function as an acid in some reactions and a base in others.

Amphiprotic (solvent)

Self-ionizing solvent possessing both characteristics of Brønsted acids and bases, for example H2O and CH3OH, in contrast to aprotic solvent.

Amphoteric

A chemical species that behaves both as an acid and as a base is called amphoteric. This property depends upon the medium in which the species is investigated: H2SO4 is an acid when studied in water, but becomes amphoteric in superacids.

Amylopectin

The branched-chain form of natural starch molecules, making up almost 100% of starch from waxy maize, a hybrid corn.

Amylose

The linear-chain form of natural starch molecules present in the most widely used form of corn, and also in potato and tapioca starch.

Anaerobic respiration

Living or acting in the absence of oxygen. Cellular respiration in the absence of oxygen.

Analog

An analog is a drug whose structure is related to that of another drug but whose chemical and biological properties may be quite different.

Analyser selectivity of analyses with

Ability of a device to exhibit a low or zero sensitivity to analytes (see interferant) other than the one it is intended to measure. The selectivity is described by a coefficient of interaction; it is the ratio of the device response to the substance to be measured to that of the interferant, both being at the same concentration.

Analyser sequential indication of

Indication obtained following sequential sampling or received from a sequential cell or from data processing comprising a succession of predetermined repetitive operations (or a combination of the three).

Analyser, accuracy of an analysis with

The ability of a measuring instrument to give indications approaching the true value of the quantity measured.

Analyser, continuous

An analyser in which subassemblies operate continuously.

Analyser, continuous indication

An analysis with a permanent indication related to the sample concentration. To obtain a continuous indication, the sampling and measuring cell need to be continuous. A time lag may exist between sampling and indication of measured concentration.

Analyser, dead time of

Time which elapses between the moment at which a sudden change in concentration (or a new sample) is introduced and the moment at which the detector response indication reaches the measurement threshold of the analyser, a value conventionally fixed at 10% of the final change in indication.

Analyser, discontinuous

An analyser with at least one discontinuous subassembly.

Analyser, discontinuous indication of

Indication related to the concentration during intervals of time which are not continuous.

Analyser, fall time of

When following a change in concentrations from a definite value c to 0, the time which elapses between the moment when this change is produced and the moment when the indication reaches a value conventionally fixed at 10% of the final change or indication.

Analyser, measurement threshold of

The minimum concentration of a substance which produces a quantifiable signal with a given uncertainty.

Analyser, precision of measurements with

The quality which characterizes the ability of a device to give for the same value of the quantity measured, indications which agree among themselves, not taking into consideration the systematic errors associated with variations of the indications. Repeatability characterizes the ability of a device to give indications which are unaffected by random errors.

Analyser, range of measurement of

Range of concentration between the measurement threshold and the maximum usable indication.

Analyser, resolution of

A general term which defines the ability of a device to differentiate between adjacent signals.

Analyser, response time of

Time which elapses, when there is a stepwise change in the quantity to be measured, between the moment when this change is produced and the moment when the indication reaches a value conventionally fixed at 90% of the final change in indication.