English for chemical engineering

The bonding of atoms in compounds involves the distribution of electrons, and is the central concern of chemistry.. geomet-7 Compounds result from chemical reactions of atoms or molecule

2 Modern chemistry grew out of the alchemy of the Middle Ages, and the attempts to transmute base metals into gold Seminal observations were made in the early eighteenth century on the changes in volume of air dur-ing combustion in a closed vessel, and the French chemist Antoine Lavoi-sier in the 1770s interpreted these phenomena in essentially modern terms

3 Atoms and elements Underlying all of chemistry is the concept of

ele-mentary units of matter which cannot be subdivided This idea was brated in classical Greek writings, and was clearly expressed by the Eng-lishman John Dalton in 1803, who called these units atoms Different kinds

adum-of atoms were recognized, each corresponding to one adum-of the chemical ments such as oxygen, sulfur, tin, iron, and a few other metals By the mid-nineteenth century, about 80 elements had been characterized, and these were organized on the basis of regularities in behavior and properties, into

ele-a periodic tele-able

4 In the early twentieth century, observations of radiation from various sources and its impact on solid targets led to the recognition of three fun-damental particles that are common to all elements; the electron, with neg-ative charge; the proton, with positive charge; and the neutron, with zero

TASKS: Defining

Classifying

LANGUAGE: Connectors

charge An atom consists of a nucleus containing protons and neutrons, and a diffuse cloud of electrons, equal in number to the number of protons and arranged in orbitals of progressively higher energy levels as the dis-tance from the nucleus increases The atomic number of an element (Z) is defined as the number of protons in the nucleus; this is the sequence of or-dering in the periodic table The mass number corresponds to the total number of protons and neutrons

5 Isotopes Most elements exist as isotopes, which have differing numbers

of neutrons All isotopes of an element exhibit the same chemical ior, although isotopes can be separated on the basis of differences in atom-

behav-ic mass The known elements total 106; of these, 88 have been detected in one or more isotopic forms in the Earth's crust The other elements, includ-ing all but one of those with atomic number above 92, are synthetic iso-topes produced in nuclear reactions that take place in nuclear piles or parti-cle accelerators Most of the isotopes of these heavier elements and also some lighter ones are radioactive; that is, the nuclei are unstable and de-cay, resulting in the emission of radiation

6 Molecules and chemical reactions Molecules are combinations of two or

more atoms, bonded together in definite proportions and specific ric arrangements These entities are called chemical compounds; a mole-cule is the smallest unit The bonding of atoms in compounds involves the distribution of electrons, and is the central concern of chemistry

geomet-7 Compounds result from chemical reactions of atoms or molecules The process involves formation and breaking of bonds, and may be either exo-thermic, in which the net bond charges lead to a more stable (lower-energy) system and heat is evolved, or endothermic, in which energy must

be added to overcome a net loss of bonding energy

8 A simple case is the reaction of hydrogen and oxygen to give water, which can be expressed as reaction (1)

2H2 + O2 2H2O (1)

H = -572 kilojoules

9 The equation is balanced; no atoms are gained or lost in a chemical tion The symbols represent the nature of the initial and final materials and

reac-also the final amounts Thus H2O represents a molecule of water or a mole, which is the quantity in grams (or other mass units) equivalent to the mo-lecular weight The symbol H indicates the energy (enthalpy) change for the process The reaction of hydrogen and oxygen is highly exothermic, and the sign of the energy change is therefore negative since the system has lost heat to the surroundings

10 Bonds Bonds can be broadly classified as ionic or covalent An ion is an

atom or molecule which has an electric charge Ionic compounds can be lustrated by salts such as sodium chloride, NaCl, in which a positive sodi-

il-um ion, Na+, and negative chloride ion, Cl-, are associated by electrostatic attraction in regular locations of a crystal lattice In solution the ions are solvated by water molecules and can conduct an electric current

11 In covalent molecules, bonds are formed by the presence of pairs of trons in overlapping orbitals between two atoms Thus when two hydrogen atoms (H.) come within bonding distance, a molecule of hydrogen is formed in an exothermic reaction, by formation of a covalent bond In this case the heat of reaction represents the energy of the HH bond [reaction (2)]

elec-2H  HH (2)

H = -435 kilojoules

12 Chemical compounds A compound is specified by the elements it

con-tains, the number of atoms of each element, the bonding arrangement, and the characteristic properties The number of unique compounds that have been isolated from natural sources or prepared by chemical synthesis is enormous; as of 1990, over 10 million substances were registered in the file maintained by Chemical Abstracts (American Chemical Society) Most

of these are organic compounds, containing from a few to many hundred carbon atoms The element carbon, unlike any others, can form long chains

of covalently bonded atoms Moreover, there can be many compounds, called isomers, with the same chemical composition Thus a molecular formula such as C8H16O can represent many thousand different com-pounds

13 Branches Traditionally, five main subdivisions are designated for the

activities, professional organizations, and literature of chemistry and chemists

14 Analytical chemistry This subdivision is an overarching discipline

deal-ing with determination of the composition of matter and the amount of each component in mixtures of any kind Analytical measurements are an integral and indispensable part of all chemical endeavor Originally, ana-lytical chemistry involved detection, separation, and weighing of the sub-stances present in a mixture Determination of the atomic ratio and thence the molecular formula of a compound is a prerequisite for any other inves-tigation; the development of balances and techniques for doing this on mil-ligram quantities of material had an enormous impact on organic chemis-try Advances since the 1950s have involved increasingly sophisticated in-strumentation; mass spectrometers are a notable example Other important methods include high-resolution chromatography and various applications

of electrochemistry A constant goal in analytical chemistry is the opment of methods and instruments of greater sensitivity It is now possi-ble to detect trace compounds such as environmental pollutants at the pic-togram level

devel-15 Biochemistry Biochemistry is the study of living systems from a

chemi-cal viewpoint; thus it is concerned with the compounds and reactions that occur in plant and animal cells Most of the substances in living tissues, in-cluding carbohydrates, lipids, proteins, nucleic acids, and hormones, are well-defined organic substances However, the metabolic and regulatory processes of these compounds and their biological function are the special province of biochemistry One of the major areas is the characterization of enzymes and their cofactors, and the mechanism of enzyme catalysis Oth-

er topics of interest include the transport of ions and molecules across cell membranes, and the target sites of neurotransmitters and other regulatory molecules Biochemical methods and thinking have contributed extensive-

ly to the fields of endocrinology, genetics, immunology, and virology

16 Inorganic chemistry This discipline is concerned with any material in

which metals and metalloid elements are of primary interest Inorganic chemistry is therefore concerned with the structure, synthesis, and bonding

of a very diverse range of compounds One of the early interests was the composition of minerals and the discovery of new elements; from this has

grown the specialized area of geochemistry Early synthetic work sized compounds of the main group elements, and particularly in this cen-tury, complex compounds of the transition metals These studies have led

empha-to soluble transition-metal catalysts, and a greatly increased understanding

of catalytic processes and the pivotal role of metal atoms in major chemical processes, such as oxygen transport in blood, photosynthesis, and biological nitrogen fixation Other contributions of inorganic chemistry are seen in advanced ceramics, high-performance composite materials, and the growing number of high-temperature superconductors

bio-17 Organic chemistry This subdivision is centered on compounds of carbon

Originally these were the compounds isolated from plant and animal sources, but the term was very early broadened to include all compounds

in which a linear or cyclic carbon chain is the main feature Two of the jor thrusts have been the elucidation of new structures and their prepara-tion by synthesis; another long-standing interest has been study of the reac-tion mechanisms and rearrangements of organic compounds Structure work on naturally occurring compounds progressed over a 150-year period from simple straight-chain compounds with 2-10 carbon atoms, hydrogen, and 1 or 2 oxygen atoms to antibiotics and toxins with many rings and as many as 100 carbon atoms In modern work, nuclear magnetic resonance spectroscopy and x-ray diffraction have become indispensable tools Paral-leling structural studies has been the synthesis of increasingly complex target molecules Synthetic work is directed also to the preparation of large numbers of compounds for screening as potential drugs and agricultural chemicals Plastics, synthetic fibers, and other high polymers are other products of organic chemistry

ma-18 Physical chemistry This discipline deals with the interpretation of

chemi-cal phenomena and the underlying physichemi-cal processes One of the classichemi-cal topics of physical chemistry involves the thermodynamic and kinetic prin-ciples that govern chemical reactions Another is a description of the phys-ical states of matter in molecular terms Experimentation and theoretical analysis have been directed to the understanding of equilibria, solution be-havior, electrolysis, and surface phenomena One of the major contribu-tions has been quantum chemistry, and the applications and insights that it has provided The methods and instruments of physical chemistry, includ-ing such hardware as spectrometers and magnetic resonance and diffrac-tion instruments, are an integral part of every other area

19 Others Each broad area of chemistry embraces many specialized topics

There are also a number of hybrid areas, such as bioorganic and ganic chemistry, analytical biochemistry, and physical organic chemistry Each of these areas has borrowed extensively from and contributed to eve-

bioinor-ry other one It is better to view chemistbioinor-ry as a seamless web, rather than a series of compartments

(from: McGraw-Hill Encyclopedia of Science and Technology, 540-542)

2 LANGUAGE INFORMATION

2.1 VOCABULARY LIST

The English expression is given on the left, and the German equivalent on the right In brackets you are given the paragraph number and line Where a word may have more than one meaning, the meaning in the context of the passage

is underlined The stress is given by means of ' before the stressed syllable

re'sult from, to result from

re'sulting in, to result in

to evolve (heat, gas )

cyclic carbon chain

 to undergo changes in structure (1,2)

 conversion from one form/state to another (1,4)

 a chemical reacts with another chemical to form a new substance (1,6)

 to transmute base metals into gold (2,2)

 to make observations on (2,2)

 to interpret phenomena in xxx terms (2,4)

 to organise sth on the basis of regularities etc into (3,7)

 to be common to (4,3)

 sth is defined as (4,7)

 to exhibit behavior (5,2)

 reactions take place in (5,6)

 reaction of H and O to give water (8,1)

 to gain or lose atoms (9,1)

 to lose heat to the surroundings (9,7)

 to form a bond (11,1)

 to isolate a compound from a source (12,3)

 to form chains of atoms (12,7)

 determination of the composition of (14,2)

 to be an integral part of sth (14,3)

 to have an enormous impact on (14,7)

 to detect compounds at a certain level (14,13)

 to be the special province of sth (15,6)

by cooling (1,5) by + -ing expresses means, underlying

(3,1) present participle (-ing) to express

what underlies

each corresponding to (3,4) present participle

a nucleus containing (4,4) containing here post modifies a nucleus; it

acts like a relative clause

resulting in (5,8) present participle = which results in

from this has grown (16,5) inversion of normal sentence order

eamless web (19,5) web has the basic meaning of

“spi-der’s web” and is used here

metaphori-cally to refer to a system of

interconnec-tions; seamless is also used metaphorically

- seam originally means the line along

which pieces of fabric are joined, so that seamless means “continuous”

2.5 VERBS, NOUNS, ADJECTIVES WITH PREPOSITIONS 2.5.1 Verbs with prepositions

 equivalent to

EXERCISE I: C OMPLETE THE FOLLOWING SENTENCES CORRECTLY

1 Inorganic chemistry is concerned _ any material in which metals are of interest

2 Organic chemistry is centered _ compounds of carbon

3 Analytical chemistry deals _ determination of the composition of matter

4 Iron reacts _ air _ iron oxide

5 An example of chemical change is the conversion _ liquid water _ solid _ cooling

6 The nuclei decay, (to result) _ the emission of radiation

7 Compounds result _ chemical reactions of atoms or molecules

This text is taken from the entry in McGraw-Hill Encyclopedia of Science and Technology on chemistry and is concerned with the definition and classifica-

tion of chemistry

This type of text is expository – it explains something – and can be

consid-ered as an answer to a particular question, or as having the structure:

DEFINITION:

[chemistry is] the science that embraces the proper-

ties

4 DEFINING AND CLASSIFYING I

4.1 CLASSICAL DEFINITIONS

The most important language act or function in this text is defining, in other words trying to say or explain what something actually is Definitions are ex-tremely important in scientific and technical language, in this case the defini-tion of subject areas or fields

The author gives a definition of chemistry in the first paragraph, which we paraphrase here slightly:

1) Chemistry is a science that embraces the properties, composition, and structure

of matter, the changes in structure and composition that matter undergoes

This type of definition is called a classical analytical definition Here is a

further example of a definition of a subject from our text, paraphrased ly:

slight-2) Analytical chemistry (S) is a discipline (G) dealing with determination of the composition of matter and the amount of each component in mixtures of any kind (D1)

The next example is also taken from the text, and shows a standard definition:

3) An ion (S) is an atom or molecule (G) which has an electric charge (D1)

These examples show that a definition must include the following three ments:

ele- S = the word, concept or species to be defined

 G = the general class or genus on the next level that includes S

 D1 Dn = the differentiating feature(s) that allow(s) us to distinguish S from other members of G

The differentiating features, D1 Dn, provide essential information about S, usually by answering questions of the following kind:

1 What is S’s purpose/objective?

2 What is its shape/appearance/structure?

3 Where does it come from?

4 What does/can it do?

5 How does it work?

6 What is it composed of?

7 Where is it used/found?

8 When is it used?