Book-Advanced English for Chemistry

HO CHI MINH UNIVERSITY OF INDUSTRY FACULTY OF CHEMICAL ENGINEERING

CHEMICAL ENGLISH COURSE FOR FULLY UNDERGRADUATE PROGRAM

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Table of Contents

Unit 1 Physical Chemistry ………………………………………………..…………..…..3 Unit 2 Inorganic and Organic Chemistry……………………………………..……...16 Unit 3 Natural Rubber and Vulcanization………………………….…….……….….32 Unit 4: SOAP …………………………………………………………..…….……………52

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Table of Contents

Unit 1 Physical Chemistry ………………………………………………..…………..…..3 Unit 2 Inorganic and Organic Chemistry……………………………………..……...16 Unit 3 Natural Rubber and Vulcanization………………………….…….……….….32 Unit 4: SOAP …………………………………………………………..…….……………52

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Unit 1 Physical Chemistry Pre-reading What do you know about physical chemistry?

Reading 1

Physical chemistry is the study of the physical basis of chemical systems

and processes. It is concerned with the measurement, description, and   prediction of the characteristics of chemical systems and their interactions with each other with respect to the transfer of mass and energy. There are some important areas of its study. 1. Chemical thermodynamics deals with the transfer of energy in chemical changes and seeks to characterize the equilibrium state of chemical systems. 2. Chemical kinetics deals with the rate and mechanism of chemical changes. 3. Structure

of

matter

(molecular

structure)

is

a

broad

area

of 

experimental and theoretical description of the properties of matter at the atomic and molecular level. 4. Quantum theory explains the nature of chemical bonding while the spectra of atoms and molecules are ex plained by quantum mechanics. 5. The discipline that allows us to bring our knowledge of molecular 

structure to bear on the proble ms of equilibrium and kinetics is found in the mechanics. study of  statistical mechanics.

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Grammar Review: The passive We often choose to use passive structures when we want to talk about an action, but are not interested in who or what does / did it. Passives without `agents' are common in academic and scientific writing for this reason. Form Be + Past Participle

Reading 2 The Kinetic-Molecular Theory Applies to Liquids The Liquid State Headline 1: Unlike gases, liquids do not have the property of infinite expansibility; as a result, a given sample of a liquid has clearly defined bounding surfaces. Compared with gases, liquids are only slightly compressible and expansible, their volumes changing relatively little with changes in temperature and  pressure. In terms of the kinetic-molecular theory, the average distances Tran Huu Hai

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  between molecules are much less in liquids than in gases. Furthermore, in liquids the kinetic energy of the molecules is apparently largely overcome by the cohesive forces between them. We may consider the liquid state, then, simply as an extension of the gaseous state into the region of short intermolecular distances and high intermolecular attractions.

Headline 2: Despite the strong forces of attraction, the molecules in a liquid cannot he consider as rigidly fixed. All liquids flow, a fact which is best explained   by the assumption that there is a continuous movement or diffusion of the molecules throughout the body of a liquid. As a result of the attractive forces   between molecules, however, all liquids are characterized by a certain internal friction which tends to resist the movement of one portion of the liquid in relation to another. This internal resistance to flow is called viscosity. Viscosity is an important property from a practical as well as from a theoretical standpoint. For example, the value of an oil for lubricating   purposes is determined to a large extent by its viscosity and by the exact manner in which its viscosity varies with temperature. "heavy" oil is one that is highly viscous, whereas a "light" oil has a lower viscosity. Various devices for determining the relative viscosities of liquids are in common use; most of them depend either upon the rates of flow of liquids through capillary tubes or standard orifices, or upon the resistance which the liquids offer to the rotation of disc or paddles, or the dropping of balls through the liquids.

Headline 3: The intermolecular forces of attraction account not only for the viscosities but also for the surface behavior of liquids. Any molecule in the center of a liquid is attracted equally in all directions by the surrounding Tran Huu Hai

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molecules. At the surface, however, a molecule is surrounded by other  molecules of the liquid only in those directions which lie within the 180

0

are

  below the plane of the surface. As a consequence, a surface molecule experiences intermolecular attractions only in those directions which lie within that imaginary arc. The resultant of these attractions is an unbalanced force down ward tending to draw the surface molecules into the body of the liquid and therefore to reduce the surface to a minimum. The liquid, therefore, behaves as if it were under a strain or tension. It is this contracting force, called surface tension, which accounts for the tendency of a small mass of liquid to assume a spherical shape, since in a sphere the ratio of  surface to volume is at a minimum. It is surface tension, likewise, which accounts for the rise of certain liquids in capillary tubes, as well as for the movement of water in blotting paper or in the soil.

Headline 4: The fact that the kinetic energies of the molecules in a liquid are acting continually in oppositions to the intermolecular forces is even more strikingly demonstrated by the familiar phenomenon of evaporation. As in gases, not all of the molecules of a liquid have the same kinetic energy. At a given instant, some possess kinetic energies much greater, and others much less, than the average. Those with the highest kinetic energy (the greatest velocity) can. Actually escape into the free space above before being pulled hack  down by the attractive forces of the material left behind. If the space is sufficiently great, this process of evaporation may continue gradually until all of the liquid changes to a vapor, or evaporates. Evaporation of a given body of liquid proceeds more readily the larger  the surface area and any factor which tends to facilitate the escape of  molecules from the surface of a liquid likewise increases the rate of  evaporation. Thus, the process is accelerated by rise in temperature, which Tran Huu Hai

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increases the average kinetic energy of the molecules, as well as by decrease of the gaseous pressure above the liquid, which reduces the concentration of  molecules that tend to block the escape of other molecules from the liquid.

Headline 5: Evaporation of a liquid in a closed vessel does not appear to proceed indefinitely, for after a time the volume of the liquid remains constant. This fact is readily explainable in terms of the kinetic-molecular theory. As the concentration of free molecules above the liquid increases, more and more molecules of the vapor, in the course of their motion, collide with the surface and are recaptured by the liquid. Eventually a condition in which the rate of condensation of the vapor id equal to the rate of evaporation of the liquid is attained. Such a condition, in which two opposite changes are   proceeding at equal rates, is called dynamic equilibrium. The pressure of the vapor in equilibrium with a liquid at a given temperature is called the vapor   pressure of the liquid at that temperature. Thus the vapor pre ssure of water a t 0

0 C is 4.6 mm of mercury.

Headline 6: Ordinary evaporation is a surface phenomenon only. As a liquid is heated, however, a temperature is reached at which bubbles of vapor form rapidly throughout the whole volume of liquid. These bubbles rise to the surface and burst as the vapor escapes. The liquid is then said to boil, and the phenomenon is called boiling or ebullition. The pressure within the   bubbles is equal to the vapor pressure of the liquid at that temperature, and the bubbles obviously cannot form and increase in size until that value equals the external pressure upon the liquid. In other words. The boiling  point of a liquid is that temperature at which the vapor pressure of the liquid is equal to the external pressure acting upon the surfac e of the liquid.

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Bunsen burner

All the heat energy absorbed by a liquid at its boiling point is used to vaporize the liquid; i.e. to free the molecules from the attractive forces of  surrounding molecules and to do work in pushing back the atmosphere. For  this reason, no matter how rapidly heat is supplied, the temperature of a pure  boiling liquid remains constant, as long as the pressure is uncha nged.

Find the word in the text which is closest in meaning to: 1. cohesive forces 2. diffusion 3. internal resistance 4. heavy oil 5. surface behavior  6. surface molecules 7. the escape of liquid molecules 8. from the surface 9.  boiling

Main Ideas Which is NOT the main idea of the first two passages? 1. Liquids do not have the property of infinite expansibility. 2. A given sample of a liquid has clearly defined bounding surface. 3. The distances between molecules are much less in liquids than in gases. Tran Huu Hai

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4. All liquids flow, however, they are characterized by a certain internal friction called viscosity. 5. A `heavy' oil is one that is highly viscous.

Exercise 1 Physical chemistry is the application of physics to macroscopic, microscopic, atomic,

subatomic, and particulate phenomena in chemical systems within the field of  chemistry traditionally using the principles, practices and concepts of thermodynamics, quantum chemistry, statistical mechanics and kinetics. It is mostly defined as a large field of chemistry, in which, several sub-concepts are applied; the inclusion of quantum mechanics is used to illustrate the application of physical chemistry to atomic and  particulate chemical interaction or experimentation. Physical chemistry is mostly referred to as a macromolecular doctrine, as the majority of the principles on which physical chemistry was founded composed entirely of  macromolecular concepts, such as colloids. The relationships that physical chemistry tries to resolve include the effects of: 1. Intermolecular forces on the physical properties of materials (plasticity, tensile strength, surface tension in liquids). 2. Reaction kinetics on the rate of a reaction. 3. The identity of ions on the electrical conductivity of materials.

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Josiah Willard Gibbs (February 11, 1839 – April 28, 1903 ) was a preeminent

American mathematical-engineer, theoretical physicist, and chemist noted for his famed 1876 publication of  On the Equilibrium of Heterogeneous Substances , a graphical analysis of multi-phase chemical systems, which laid the basis for a large   part of modern-day science. Being one of the greatest American scientists of the nineteenth century, he devised much of the theoretical foundation for chemical thermodynamics as well as physical chemistry. As a mathematician, he was an inventor  of vector analysis. He spent his entire career at Yale, which awarded him the first American Ph.D. in engineering in 1863. In 1901, Gibbs was awarded the Copley medal of the Royal Society of London for    being “the first to apply the second law of thermodynamics to the exhaustive discussion of the relation between chemical, electrical, and thermal energy and capacity for external work.” This summarizes Gibbs's most fruitful contribution to science. On February 28, 2003, Yale held a 100th anniversary symposium in his honor. According to the American Mathematical Society, which established the Josiah Willard Gibbs Lectureship in 1923 to increase public awareness of the aspects of mathematics and its applications, Gibbs is one of the greatest scientists America has ever produced.  Nobelist Paul Samuelson describes Gibbs as "Yale's great physicist".

Exercise 2 Writing about this link between subjects together 

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Exercise 3  Match a word or phrase in A with its definition in B.

A

B

1. chemical changes

a. modern theory of matter /

2. equilibrium

quantum theory

3. rate of chemical

 b. arrangement and interaction of 

changes 4. mechanism of chemical changes

the particles of a substance c. explanation and prediction of the macroscopic

properties

of

a

5. Structure of matter 

system on the basis of its known

6. chemical bonding

characteristics

7. quantum mechanics 8. statistical mechanics

d.  process in which one set of  reactants is transformed into a new set of products e. condition in which no change occurs f. detailed description of the

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course of chemical reactions / reaction path g. strong attractive force that holds together atoms in molecules h. description of how fast reactants are consumed and products are formed

Exercise 4: Main Topics Complete

the

passages

with

the

appropriate

phrases describing the major branches of physical chemistry. 1………...which revolutionized physics in the early part of this century, is required for an understanding of chemistry. The spectra of atoms and molecules are explained by quantum mechanics, and their theoretical treatment yields quantities of importance in various areas of physical chemistry. The nature of chemical bonding is explained by quantum theory. 2.…………has been developed to  provide an interpretation of the properties of matter in terms of the properties of molecules, atoms, ions, and electrons. Both thermodynamic properties and kinetic properties of matter  may he calculated using statistical mechanics, provided that certain information

about

molecules

is

known

from

spectroscopic

or

other 

measurements. 3.……….involves the time factor and is concerned with molecules and mechanisms. In many reactions in organic chemistry, inorganic chemistry, and many industrial processes, the products are not in the state of  equilibrium, and the yields are controlled more by the relative rates of  Tran Huu Hai

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reaction than by thermodynamics. Chemical kinetics is based on almost all of    physical chemistry. Kinetic theory is based upon certain assumptions about molecules. The results of kinetic theory based upon classical physics have  been very useful but come into direct contradiction with certain experimental results such as the dependence of heat capacity upon temperature. However, classical kinetic theory is very helpful in understanding the results of both thermodynamics and chemical kinetics. It is necessary to obtain a completely satisfactory theory. 4………..can be determined from X-ray diffraction, electron diffraction, and molecular spectra. Information on molecule structure is of importance for  understanding chemical reactions and for calculating thermodynamic and kinetic behavior. Certain types of chemical behavior can be predicted when the molecule structure is known. 5………..is one of the most powerful tools of physical chemistry. It provides exact relations between energy and properties of systems without any information about molecules or mechanisms of processes. Thermodynamics applies to systems at equilibrium and is concerned only with initial and final states.. It has nothing to do with tulle. Thermodynamics provides an answer  to the question, `How far will this particular reaction go before equilibrium is reached?".

Exercise 6: Comprehension Questions Answ er the ques tions be low. 1. List the main differences between gases and liquids. 2. Why do various kinds of liquids not f low at the same rate? 3. What is surface tension? 4. What factor affects evaporation? 5. Explain the stab ility of the temperature of a pure liquid when it boils.

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Exercise 7: Common connectors in written English 1. Connectors which show addition also, and, as well, as well as, besides, ,furthermore, moreover, in addition to

2. Connectors which illustrate  for example, for instance, for one thing ...,for another thing 

3. Connectors which show results accordingly, as a result, consequently, so, therefore, thus

4. Connectors which show reasons because, since, for 

5. Connectors which show contrast however, in spite of, instead, nevertheless, on the one hand ... on the other  hand 

6. Connectors which show sequence  first, (at first, firstly ...), next, then, after that, finally

7. Connectors which show emphasis actually, in, fact, indeed 

Complete

the

following

statements

with

the

appropriate connectors. 1. As a liquid is heated, the average kinetic energy of the molecules is increased:…………., the viscosity of the liquid is decreased. 2. As the temperature of a liquid is increased, the kinetic energy of its molecules tends more and more to overcome forces of attraction. The surface tension of a liquid,………..decreases as the temperature rises. 3. A liquid can be made to boil at any temperature between its melting point and critical temperature if the external pressure is properly controlled. On top of Mount Everest,………. .where the atmospheric pressure is about 235 mm. of mercury, water boils at approximately 71°C. 4. …………evaporation involves the escape of molecules with ener gy greater  Tran Huu Hai

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than the average; the average kinetic energy of the molecules which remain within the liquid must decrease. 5. Some liquids…………ether and chloroform in which these forces are relatively small, flow easily, and are said to have low viscosities, or to be highly mobile.

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Unit 2 Inorganic and Organic Chemistry

Reading 1 Inorganic chemistry is the branch of chemistry concerned with the   properties and reactions of inorganic compounds. This includes all chemical compounds except the many which are b ased upon chains or rings of ca rbon atoms, which are termed organic compounds. Inorganic chemistry is often divided into the subfields of solid-state chemistry, organometallic chemistry, and Bioinorganic chemistry. Research in

inorganic

chemistry

is

leading

to

progress

in

areas

such

as

superconductivity, microchip development, and cancer research.

Solid-state chemistry Solid-state chemists study the structure and properties of inorganic compounds to fabricate new, more useful materials. Current research has   produced inorganic polymers known as poly phosphazenes, which consist of long chains of alternating nitrogen and phosphorous atoms. Poly   phosphazenes may eventually be used in the medical field to provide materials for artificial blood vessels, lim bs, and joints.

Organometallic chemistry An extremely active area of research in recent years is the study of  organometallic chemicals-compounds and of transition metals bonded to Tran Huu Hai

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organic chemical groups. Organometallic compounds are used to produce semiconductor wafers to form highly protective coatings on steel tools (such as high speed drills) and as extremely selective catalysts in certain organic compound syntheses.

Bioinorganic chemistry Bioinorganic chemists research the role of metals in living systems. One area of investigation is the roles of metals in the human body, such as how oxygen binds reversibly to the iron in red blood cells.

 Vocabulary Review Reading 2 Organic chemistry is the study of those carbon-containing molecules known as organic compounds, which are based upon long chains or rings of carbon atoms. Over 6 million organic compounds are known today and the possibility exists for countless more to be discovered and synthesized. Organic chemists determine the structure of organic molecules, study their various reactions and develop procedures for the synthesis of organic compounds. Organic chemists has had a profound effect on modern life: It has improved natural materials and it has synthesized natural and artificial materials that have, in turn, improved heath, increased comfort, and added to the convenience of nearly every product manufactured today.

All organic compounds are primarily divided into two large groups: acyclic compounds-with an open chain and cyclic compounds-with a closed chain.

Acyclic compounds are also called fatty or aliphatic (from a Greek  word meaning fat) since fats and fatty acids belong to this class. These Tran Huu Hai

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compounds may have a "normal" structure, i.e., have an unbranched skeleton similar to the skeleton of normal pentane ora branched skeleton (with various degree of branching), such as isopentane. Cyclic compounds are classified into isocyclic, in which there is a cyclic grouping consisting or several carbon atoms closed into a ring and heterocyclic, in which the ring includes one or more atoms other than carbon (heteroatoms). A special position among such cyclic compounds is occupied by so-called aromatic compounds, six-membered rings containing alternating three single and three double carbon-carbon bonds or bonds between a carbon atom and a heteroatom.

Benzene

The Formation of Nouns and Verbs from Adjectives  Additional Reading Polyvinyl Chloride (PVC): A Remarkable Polymer Polyethylene is a very useful material. However, an even more versatile material is polyvinyl chloride or PVC, for short. PVC is synthesized from the monomer vinyl chloride. Notice the similarity between this molecule and ethylene (Fig. 1).

H

H C

H

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The only difference is that a chlorine atom has been substituted for a hydrogen atom. Vinyl chloride is a water-insoluble gas at room temperature, which is readily polymerized under pressure and heat

Cl

Cl

Cl

Cl

Cl

Fig. 2 A section of the molecular chain of polyvinyl chloride. The vinv'l chloride monomer is repeated over and over in the molecule in order for the vinyl chloride units to hunt/ to each other, the carbon-carbon double bond in the monomer is utilized.

The polymer produced is a tough synthetic material which can be used for floor coverings, unbreakable bottles, clear plastic wraps, and synthetic leather. PVC can be easily molded into various shapes, and it can be colored and textured to simulate leather.

There are a number of other polymers which are derivatives of, or are similar to, polyethylene. These polymers have thousands of uses in our  technological society, from indoor-outdoor carpeting to transparent plastic glass such as Lucite and Plexiglas. A number of these substances and their  uses are listed in the following table.

Polymers that are derivatives of, or are similar to, polyethylene

Name of Uses of Pol mer  As an indoor-outdoor carpet Polypropylene fabric; also for clear plastic  bottles, plastic lab ware and

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Poly styrene

As a packaging material; in its foam form (known as Styrofoam) it is used to make

Poly

As a nonstick coating material for 

tetrafluoroethyl  pot Poly methyl

As a transparent unbreakable

methacrylate

glass

(Lucite or  Plexiglas) As a self-adhering wrap, known Poly vinylidene

commercially as Saran Wrap

Reading Diagrams and talking together How Ethanol is Produced There are the two production processes of how to make ethanol: dry milling and wet milling. Read them carefully and find the main difference between the two.

Ethanol CH3CH2OH, whose common name is ethyl alcohol, is the a lcohol we all consume in our favorite wine, liqueur, or beer. The ethanol found in these  beverages is produced through the process of fermentation, which involves the  breakdown of the sugar glucose.

The anhydrous ethanol is then blended with about 5% denaturant (such as natural gasoline) to render it undrinkable and thus not subject to beverage alcohol tax. It is then ready for shipment to gasoline terminals or retailers.

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The stillage is sent through a centrifuge that separates the coarse grain from the solubles. The solubles are then concentrated to about 30% solids by evaporation, resulting in Condensed Distillers Solubles (CDS) or "syrup." The coarse grain and the syrup are then dried together to produce dried distillers grains with solubles (DDGS), a high quality, nutritious livestock feed. The CO2 released during fermentation is captured and sold for use in carbonating soft drinks and beverages and the manufacture of dry ice.

In wet milling, the grain is soaked or "steeped" in water and dilute sulfurous acid for 24 to 48 hours. This steeping facilitates the separation of the grain into its many component parts.

After steeping, the corn slurry is processed through a series of grinders to separate the corn germ. The corn oil from the germ is either extracted on-site or sold to crushers who extract the corn oil. The remaining fiber, gluten and starch components are further segregated using centrifugal, screen and hydroclonic separators.

The anhydrous ethanol is then blended with about 5% denaturant (such as natural gasoline) to render it undrinkable and thus not subject to beverage alcohol tax. It is then ready for shipment to gasoline terminals or retailers.

The stillage is sent through a centrifuge that separates the coarse grain from the solubles. The solubles are then concentrated to about 30% solids by evaporation, resulting in Condensed Distillers Solubles (CDS) or "syrup." The coarse grain and the syrup are then dried together to produce dried distillers grains with solubles (DDGS), a high quality, nutritious livestock feed. The CO2 released during fermentation is captured and sold for use in carbonating soft drinks and beverages and the manufacture of dry ice.

In wet milling, the grain is soaked or "steeped" in water and dilute sulfurous Tran Huu Hai

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acid for 24 to 48 hours. This steeping facilitates the separation of the grain into its many component parts.

After steeping, the corn slurry is processed through a series of grinders to separate the corn germ. The corn oil from the germ is either extracted on-site or sold to crushers who extract the corn oil. The remaining fiber, gluten and starch components are further segregated using centrifugal, screen and hydroclonic separators.

The steeping liquor is concentrated in an evaporator. This concentrated   product, heavy steep water, is co-dried with the fiber component and is then sold as corn gluten feed to the livestock industry. Heavy steep water is also sold by itself as a feed ingredient and is used as a component in Ice Ban, an environmentally friendly alternative to salt for removing ice from roads.

The gluten component (protein) is filtered and dried to produce the corn gluten meal co-product. This product is highly sought after as a feed ingredient in poultry broiler operations.

The starch and any remaining water from the mash can then be processed in one of three ways: fermented into ethanol, dried and sold as dried or modified corn starch, or processed into corn syrup. The fermentation process for  ethanol is very similar to the dry mill process described above.

This process flow diagram shows the basic steps in production of ethanol from cellulosic biomass. Note that there are a variety of options for    pretreatment and other steps in the process and that several technologies combine two or all three of the hydrolysis and fermentation steps within the shaded box. Chart courtesy of the National Renewable Energy Lab.

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 Vocabulary Review Match a word in column A with its definition in column B. A 1. element 2. compound

B a. the smallest particle of a substance possessing the specific properties of that

3. mixture 4. atom 5. molecule 6. chemical bond 7. chemical

substance b. substance that increases reaction rate without being chemically changed c. building block of all the compounds and substances

reaction. d. process of breaking 8. reactants

substances apart and putting chemical components

9. products 10. catalyst

together to form new substances e. sample of elements and compounds that are mixed together but not chemically combined

Gap-filling

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Complete the passage with appropriate words below.

 

elements

solid

state

mixture

reaction

molecules

bioinorganic

organometallic

atoms

1. Inorganic chemists have made significant advances in understanding the minute particles that compose our world. These particles, called……… (1), make up the………… (2), which are the building blocks of all the compounds and substances in the world around us.

2. All chemical substances are made from combinations of the 112 chemical (3)……….found on the periodic table. Ninety elements are known to occur in nature and 22 more have been made artificially. 3.………(4)

chemists

are

working

to

develop

high-temperature

pliable

0

ceramics capable of withstanding temperature up to 1370 C (2500°F). 4. These high-temperature ceramics may someday be used to make automobile engines that produce little pollution and are highly fuel-efficient. Examples of  (5)……comple xes include iron penta carbonyl [Fe(CO)5],

ferrocen e [Fe

(C5H5)2] and phenyl magnesium bromide (C6H5MgBr). 5.………..(6) chemists study how specific transition metals might be used in drugs to fight certain diseases. For example, scientists are experimenting with  platinum complexes as anticancer drugs. 6. The air around us is (7)……….. a of gases, mainly nitrogen and oxygen, 78.03% and 20.95% by volume respectively, but containing much smaller  amounts of water vapor, argon and carbon dioxide. 7. The (8)……..of oxygen with another gas can lead to an explosion. There are two reasons of the explosion: temperature effects on the rate of a reaction and the behavior of the reacting (9)……..

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Decide whether the following statements are trite (T) or false (F). 1. Organic

compounds

are

classified

according

to

their

structural

formulas, the spatial arrangement of the atoms. 2. The word `fat' is derived from the Greek language. 3. Acyclic compounds can be either saturated or unsaturated fatty compounds. r 

4. An aliphatic compound of `normal structu e' is one which has a  branched-chain structure. 5. Heterocyclic compounds consist of hydrocarbons arranged in a ring. 6. Iso cyclic compounds with alternating double carbon-carbon bonds are aromatic compounds.

Gap-filling Complete the passage with appropriate words below.

chains

aromatic

heterocyclic

ring

aliphatic

hydrogen atoms

structure

hydrocarbons heterocycles

Organic compounds are classified according to their (1) this classification  being based on the character of the carbon skeleton of (2),i.e., the sequence of  carbon atoms linked to one another. Tran Huu Hai

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Compounds that contain atoms other than carbon are regarded as derivatives of hydrocarbons, in which (3)

are

repla ced

by

such

atom s

ca lled

heteroatoms. An exception is made for such structure in which the heteroatom closes the (4) of carbon atoms into a (5). Such cyclic or ring compounds are classified as a special class of compounds termed (6) Some of the classes of substances studied in organic chemistry include (7) compounds, chains of carbon which may be modified by functional groups; (8) hydrocarbons, compounds containing one or more benzene rings; (9) compounds, which include non-carbon atoms as parts of a ring structure and polymers, which are long (10) of repeating groups or so-called monomers.

The Formation of Nouns and Verbs from Adjectives The regular formation of nouns and verbs from the adjectives given is as follows. Adjective weak 

Verb weaken

Noun weakness

tough

toughen

toughness

soft

soften

softness

hard

harden

hardness

rough

roughen

roughness

coarse

Coarsen

coarseness

 bright

 brighten

 brightness

  Non-regular verb and noun formation is dealt with in the following table. Where no verb exists (as with resilient), the construction make something 

resilient  may be used. Adjective Tran Huu Hai

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Strong

strengthen

Strength

Brittle

embrittle

Brittleness

Smooth

smooth

Smoothness

make something

Resilience

Flexible

resilient make

Flexibility

Elastic

something flexible

Elasticity

Pliable

make something

Pliability

Rigid

elastic make

Rigidity

Ductile

something pliable

Ductility

Malleable

make something rigid

malleability

hot

make something

heat

ductile make

warmth

resilient

warm cool cold

something malleable

coolness

heat

cold/coldness

warm cool cool

Complete the sentences with the right form of the word in brackets and then trans late them into  Vietnamese. 1. When aluminium (hot) to 659.70°C, it melts. 0

2. When water (cool) to 0 C, it freezes. 3. When water (hot) to 100°C, it vaporizes. 0

4. When ice (hot) to 0 C, it melts. 5. When liquid steel (cool), it solidified. 6. When steel (hard), it becomes brittle. 7. When rubber (vulcanize), it becomes tougher. Tran Huu Hai

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8. When copper (hot), it becomes more ductile. 9. When glass (tough), it becomes more resilient. 10.When blue copper sulphate crystals (hot), they turn white.

Complete the passage with the appropriate words given above. Medium and high carbon steel are not very hard, so they must he (1). They 0

are (2) slowly to a high temperature (above 700 C), and then rapidly (3) or  quenched. Fully (4) steel is extremely brittle and has poor shock resistance. The (5) of hardened steel can be reduced. The quality of the steel can be inc rea sed by tempering.

Vocabu lary in Con text There are two major ways of finding the meanings of new words. One is to read with a dictionary in one hand and the reading book in the other. If you use only this dictionary method of finding the meanings of new words, you are likely to become very good at using a dictionary, but you do not develop skills for figuring word meanings for yourself. Another method is finding clues to meanings of new words in context. If you learn a new word in context, you learn it in a meaningful g

situation. Lookin for context clues helps you pay attention to the full meaning of se nt en ce s. (Adapted from Zukovski, Jonhston and others. Between the Lines, p.2)

Here are some examples of new words you can learn in context. In dry milling, the entire corn kernel or other starchy grain is first ground into flour, which is referred to in the industry as "meal" and processed without separating out the various component parts of the grain. The meal is slurried with water to form a "mash." Enzymes are added to the mash to convert the starch to dextrose, a simple sugar. Ammonia is added for PH control and as a Tran Huu Hai

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nutrient to the yeast.

The mash is processed in a high-temperature cooker to reduce bacteria levels ahead of fermentation. The mash is cooled and transferred to fomenters where yeast is added and the conversion of sugar to ethanol and carbon dioxide (CO 2 ) begins. Meal is defined in the context of the relative clause in the same sentence. Mash is defined in the context of the purpose of an action. Dextrose is

defined by the phrase between commas that follows the word. Fomenters is defined in the context of the relative clause in the same sentence.

State how you can guess at the meanings of the words in bold. 1.

Water is a colorless liquid   but it can be solidified   by very low temperature or freezing. The fact that different liquids boil at different temperatures Seri’s the basis for a separating method known as fractional distillation.

2.

All metals expand, increase in volume, when they are heated.

3.

The presence of water vapor in the air can he observed by its condensation on the cold surface; on the outside of a glass of icy tea, for 

example.

Now, read this passage and explain the meanings of  the words underlined.

Air is the commercial source for many of the gas it contains. It is separated into its components by fractional distillation of liquefied air. Before air is liquefied, water vapor and carbon dioxide are removed, because these substances are solidified when cooled and would clog the pipes of the air liquefaction plant. The dry, CO 2  _free air is compressed to about 200 Tran Huu Hai

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atmospheres. This compression causes the air to become warm, and the heat is removed by passing the compressed air through radiators. The cooled, compressed a ir is then allowed to expand rapidly. The rapid expansion causes the air to become cold, so cold that some of it condenses. By the alternative compressing and expanding of air, most of it can be liquefied.

Language Use Study the sentence below. 

It was observed that the temperature continued to fall for a short time

without any ice forming.

This is another way of saying: 

The temperature continued to fall a short time, but no ice was formed.  In

the same way, we can re-phrase this sentence as: 

The temperature continued to fall for a short time, without any ice being

formed

Study these situations, and then re-phrase the sentences using without. 1. A metal wire wa s stretched 5 cm, but it didn't break. 2.

Mercury was cooled to -20°C, but it didn't freeze.

3.

Sand was added to water and the mixture was heated gently for a long time, but the sand did not dissolve.

4.

Some aluminium was placed in water and left for some time, but no reaction was observed.

5.

A current was passed through a wire for a period of time, but no heating effect was detected.

6.

A substance was heated for a short time, but no rise in temperature was observed.

7. Various substances were placed in dilute hydrochloric acid, hut no gas was seen to he evolved. Tran Huu Hai

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8.

Some ammonium chloride was heated, but no ammonia was smelt.

9.

A lighted splint was held over the top of a test-tube of gas, but no explosion was heard.

10. A suspended magnet was brought near to a coil of wire, but no effect was noticed on the magnet.

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Unit 3 Natural Rubber and Vulcanization Pre-Reading 1. What do you know about rubber? 2. In what climate do rubber trees grow'?

Fig la   Natural rubber   Natural rubber (NR) in the form of liquid resin secreted from the inner hark of the

  Hevea brusiliensis tree, is known as latex. Latex is not tree sap. It consists of  isoprene molecules (Fig la). Poly isoprene or rubber is formed through a natural   polymerization in the tree (Fig 1 b). The liquid latex dries into a thermoplastic material. The structure is an amorphous mass of coiled and kinked chains with constant thermally induced motion of the atoms and chains. Rather than stretch when heated, rubber shrinks because the thermal

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Fig lb   Natural rubber  agitation causes the chains to entangle and draw up. The structure provides the

resistance for rubber to spring back into shape when compressed or stretched. When a tensile load is applied, the structure changes as the chains straighten (bond straightening) and stretch (bond lengthening), and crystallinity is achieved in varying degrees depending on the a mount of stress. With increased crystallinity comes a greater strength, increased rigidity, and increased hardness. The structural changes in rubber make it good for tires   because the portion of the tire under high stress is crystalline and provides support for the vehicle it is carrying, while at the same time the portions of the tire not under high stress are still resilient and absorb shock from bumps in the road. The problem with natural rubber is that it is too soft and has too many reactive sites (double bonds) which cause rapid oxidation and dry rot. It is also somewhat   plastic and will not recover from high stress. In 1839, Charles Goodyear  discovered through the addition of sulfur to natural rubber compounds that it was  possible to increase hardness and reduce

Fig 2 Vulcanized rubber 

susceptibility to oxidation and reaction with other chemicals. The sulfur  Tran Huu Hai

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vulcanizes the rubber or changes it into a thermosetting polymer by linking together the molecular chains at their double bond s (Fig 2). Two sulfur a toms   per pair of isoprene mers are needed, and with 5% of the mer pairs crosslinked a flexible resilient rubber exists. Further cross-linking increases hardness. Vulcanization of only sulfur to rubber requires several hours and temperatures around 145°C. However, accelerators and activators added to the compound will result in vulcanization within minutes. Vulcanized natural rubber has excellent flexural strength or deformability, tensile strength, and abrasion resistance, but it is attacked by petroleum oil, greases, and gasoline. Its value in auto tires comes from low heat buildup. NR  has superior overall engineering capabilities compared to synthetics. The choice of a synthetic rubber over natural rubber or of one synthetic over  another boils down to specific properties required, price, and processibility. Because natural rubber comes from a renewable source and because it has excellent properties, natural rubber science and technology continue to make strides. Deproteinized natural rubber is an example of developments in improving this natural elastomer. By removal of ingredients with an affinity for water such as protein, polyols, and inorganic salts, fatigue resistance and other mechanical properties are enhanced.

Comprehension Questions Make a summary of the text by transferring the information into the table below.  

Natural rubber

Vulcanized rubber 

Language Use Tran Huu Hai

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The Participle Used as an Adjective Study the sentences below. The latex which has been dried is dispatched to ether countries. can be rephrased as: - The dried latex is dispatched to other countries.

Elliptical Adverb Clauses When adverb clause and main clause have the same subject, the subject and verb BE in adverb clause may be omitted. Study the sentences below. When hea ted, water turns into a steam. can be rephrased as: When wate r is heated, it turns into s team.

The Adverbial Clause of Condition: if, provided, unless  Additional Reading: Synthetic Rubber Even with the improved properties obtained through vulcanization, natural rubber has poor resistance to aging. It is attacked by ultraviolet light, oxygen, and heat because it still has many reactive sites. Due to these shortcomings

and

because

the

rubber

tree

grows

only

in

special

environments that were vulnerable to political sanctions, the search for a substitute produced several synthetic rubbers in the early to mid part of the Tran Huu Hai

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twentieth century. The number of synthetic rubbers has grown to include many special  purpose elastomers. Improvements in synthetic elastomers have also   brought improvement in the additives and fillers for natural rubber (NR). Almost identical to NR is synthetic poly isoprene, except that it has greater  stretching ability. Synthetic rubbers have the same raw materials used in  plastics. Starting with crude oil and natural gas, many formulations are possible. Styrene, the monomer for styrene-butadiene rubber (SBR), is derived from coal as vinyl benzene, CH 2 =C H 2 , a product of benzene and ethylene. Butadiene is derived from petroleum. The hydrocarbon is obtained in fraction of cracking petroleum used for olefins, polymers, or gasoline. The 1-butene is separated and catalytically dehydrogenated in the vapor phase to produce butadiene. There is a complexity of synthetic-rubber production, which produces the raw synthetic rubber or  crumb that is shipped to the processors who will make semi finished or finished products. During the final processing, the vulcanizing is preceded by masticating or kneading; the crumb or rubber    bales are ground up to soften them. In some instances, vulcanizing is achieved in the final shaping of the parts as with tire manufacture, and in other cases the products are placed under steam heat and pressure in an

autoclave.

Fig 3. Synthetic Rubber  Tran Huu Hai

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Thermoplastic Rubbers or Elastoplastics Ordinary vulcanized rubber does not melt on heating, and therefore cannot he recycled. Because of this disposal of used tyres is a major problem. Scientists have been trying to solve this problem by making thermoplastic rubber, this is made by mixing the small–molecule building blocks of a   plastic with the building block of rubber. Thermoplastic rubber has the elastic properties of rubber, as well as the properties of a thermoplastic. This means it can be remelted and moulded into different shapes.

Exercise Unit 3 Natural Rubber and Vu lcanization Pre-Reading 1. What do you know about rubber? 2. In what climate do rubber trees grow'?

Rubber

Latex being collected from a tapped rubber tree Tran Huu Hai

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Rubber is an elastic hydrocarbon  polymer  that naturally occurs as a milky colloidal

suspension, or  latex, in the sap of some plants. It can also be synthesized.

Explanation The major commercial source of natural latex used to create rubber is the Para rubber  tree,   Hevea brasiliensis (Euphorbiaceae). This is largely because it responds to wounding by producing more latex. Henry Wickham gathered thousands of seeds from Brazil in 1876 and they were germinated in Kew Gardens, England. The seedlings were sent to Colombo, Indonesia, Singapore and British Malaya. Malaya was later to  become the biggest producer of rubber. Liberia is another rubber-producing country. Other plants containing latex include figs ( Ficus elastica ), euphorbias, and the common dandelion. Although these have not been major sources of rubber, Germany attempted to use such sources during World War II when it was cut off from rubber supplies. These attempts were later supplanted by the development of synthetic rubber . Synthetic rubber  is made through the  polymerization of a variety of  monomers to  produce polymers. These form part of a broad study covered by   polymer science and rubber technology. Its scientific name is polyisoprene.

Collection

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A woman in Sri Lanka in the process of harvesting rubber. In places like Kerala, where coconuts are in abundance, the shell of half a coconut is used as the collection container for the latex. The shells are attached to the tree via a short sharp stick and the latex drips down into it overnight. This usually produces latex up to a level of half to three quarters of the shell. The latex from multiple trees is then  poured into flat pans, and this is mixed with formic acid, which serves as a coagulant. After a few hours, the very wet sheets of rubber are wrung out by putting them through a press before they are sent onto factories where vulcanization and further processing is done.

Chemical makeup Aside from a few natural product impurities, natural rubber is essentially a polymer of  isoprene units, a hydrocarbon diene monomer . Synthetic rubber can be made as a   polymer of isoprene or various other monomers. Rubber is believed to have been named by Joseph Priestley, who discovered in 1770 that dried latex rubbed out pencil marks. The material properties of natural rubber make it an elastomer  and a thermoplastic.

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History In its native Central America and South America, rubber has been collected for a long time. The Mesoamerican civilizations used rubber mostly from Castilla elastica. The Ancient Mesoamericans had a ball game using rubber balls ( see: Mesoamerican

ballgame), and a few Pre-Columbian rubber balls have been found (always in sites that were flooded under fresh water), the earliest dating to about 1600 BC. According to Bernal Díaz del Castillo, the Spanish Conquistadores were so astounded by the vigorous bouncing of the rubber balls of the Aztecs that they wondered if the balls were enchanted by evil spirits. The Maya also made a type of temporary rubber shoe  by dipping their feet into a latex mixture. Rubber was used in various other contexts, such as strips to hold stone and metal tools to wooden handles, and padding for the tool handles. While the ancient Mesoamericans did not have vulcanization, they developed organic methods of processing the rubber with similar results, mixing the raw latex with various saps and juices of other vines, particularly   Ipomoea alba, a species of  Morning glory. In Brazil the natives understood the use of rubber to make waterresistant cloth. A story says that the first European to return to Portugal from Brazil with samples of such water-repellent rubberized cloth so shocked people that he was  brought to court on the charge of witchcraft. When samples of rubber first arrived in England, it was observed by Joseph Priestley, in 1770, that a piece of the material was extremely good for rubbing out  pencil marks on paper (see eraser ), hence the name. The para rubber tree initially grew in South America, where it was the main source of  what limited amount of latex rubber was consumed during much of the 19th century. About 100 years ago, the Congo Free State in Africa was a significant source of natural rubber latex, mostly gathered by forced labor. The Congo Free State was forged and ruled as a personal colony by the Belgian King Leopold II. After repeated efforts (see Henry Wickham) rubber was successfully cultivated in Southeast Asia, where it is now widely grown. Tran Huu Hai

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In India commercial cultivation of natural rubber was introduced by the British Planters, although the experimental efforts to grow rubber on a commercial scale in India were initiated as early as 1873 at the Botanical Gardens, Kolkata. The first commercial Hevea plantations in India were established at Thattekadu in Kerala in 1902.

Properties

Rubber latex

Rubber exhibits unique physical and chemical properties. Rubber's stress-strain behavior exhibits the Mullins effect, the Payne effect and is often modeled as hyperelastic. Rubber strain crystallizes.

Why does rubber have elasticity? In most elastic materials, such as metals used in springs, the elastic behavior is caused  by  bond distortions. When force is applied, bond lengths deviate from the (minimum energy) equilibrium and strain energy is stored electrostatically. Rubber is often assumed to behave in the same way, but it turns out this is a poor description. Rubber is a curious material because, unlike metals, strain energy is stored thermally, as well as electrostatically. In its relaxed state rubber consists of long, coiled-up polymer chains that are interlinked at a few points. Between a pair of links each monomer can rotate freely about its neighbour. This gives each section of chain leeway to assume a large number  Tran Huu Hai

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of geometries, like a very loose rope attached to a pair of fixed points. At room temperature rubber stores enough kinetic energy so that each section of chain oscillates chaotically, like the above piece of rope being shaken violently. When rubber is stretched the "loose pieces of rope" are taut and thus no longer able to oscillate. Their kinetic energy is given off as excess heat. Therefore, the entropy decreases when going from the relaxed to the stretched state, and it increases during relaxation. This change in entropy can also be explained by the fact that a tight section of chain can fold in fewer ways (W) than a loose section of chain, at a given temperature (nb. entropy is defined as S=k*ln(W)). Relaxation of a stretched rubber   band is thus driven by an increase in entropy, and the force experienced is not electrostatic, rather it is a result of the thermal energy of the material being converted to kinetic energy. Rubber relaxation is endothermic. The material undergoes adiabatic cooling during contraction. This property of rubber can easily be verified by holding a stretched rubber band to your lips and relaxing it. Stretching of a rubber band is in some ways equivalent to the compression of an ideal gas, and relaxation in equivalent to its expansion. Note that a compressed gas also exhibits "elastic" properties, for instance inside an inflated car  tire. The fact that stretching is equivalent to compression may seem somewhat counter-intuitive, but it makes sense if rubber is viewed as a one-dimensional gas. Stretching reduces the "space" available to each section of chain. Vulcanization of rubber creates more disulphide bonds between chains so it makes each free section of chain shorter. The result is that the chains tighten more quickly for  a given length of  strain. This increases the elastic force constant and makes rubber  harder and less extendable. When cooled below the glass transition temperature, the quasi-fluid chain segments "freeze" into fixed geometries and the rubber abruptly loses its elastic properties, though the process is reversible. This is a property it shares with most elastomers. At very cold temperatures rubber is actually rather brittle; it will break into shards when Tran Huu Hai

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struck or stretched. This critical temperature is the reason that winter tires use a softer  version of rubber than normal tires. The failing rubber  o-ring seals that contributed to the cause of the Challenger disaster  were thought to have cooled below their critical temperature. The disaster happened on an unusually cold day.

Current sources of rubber Close to 21 million tons of rubber were produced in 2005 of which around 42% was natural. Today Asia is the main source of natural rubber, accounting for around 94% of  output in 2005. The three largest producing countries (Indonesia, Malaysia and Thailand) together accounts for around 72% of all natural rubber production. Hypoallergenic rubber can be made from Guayule. Early experiments in the development of  synthetic rubber led to the invention of  Silly Putty.  Natural rubber is often vulcanized, a process by which the rubber is heated and sulfur ,  peroxide or bisphenol are added to improve resilience and elasticity, and to prevent it from  perishing. Vulcanization greatly improved the durability and utility of rubber  from the 1830s on. The successful development of vulcanisation is most closely associated with Charles Goodyear . Carbon black is often used as an additive to rubber  to improve its strength, especially in vehicle tires.

Uses The use of rubber is wide spread, ranging from household to industrial products, entering the production stream at the intermediate stage or as final products. Tires and tubes are the largest consumers of rubber, accounting for around 56% total consumption in 2005. The remaining 44% are taken up by the general rubber goods (GRG) sector, which are all products except tires and tubes.

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Other significant users of rubber are hoses, belts and dampners for the automobile industry in what is known as the "under the bonnet" products. Gloves (medical, household and industrial) are also large consumers of rubber, although the type of  rubber used is that of the concentrated latex. Of particular importance is condom manufacture, a most valuable product which, when used properly, may prevent the spread of sexually-transmitted diseases and significantly reduce the number of  unwanted pregnancies. Significant tonnage of rubber is used as adhesives in many manufacturing industries and products, although the two most noticeable are the paper  and the carpet industry. Additionally, rubber produced as a fiber has significant value for use in the textile industry because of its excellent elongation and recovery properties. For these   purposes, manufactured rubber fiber is made as either an extruded round fiber, or  rectangular fibers that are cut in strips from extruded film. Because of its low dye acceptance, its hand and appearance, the rubber fiber is either covered by yarn of  another fiber or directly woven with other yarns into the fabric. In the early 1900’s, for  example, rubber yarns were used in foundation garments. While rubber is still used in textile manufacturing, its low tenacity limits its use in lightweight garments because latex lacks resistance to oxidizing agents and is damaged by aging, sunlight, oil and   perspiration. Seeking a way to address these shortcomings, the textile industry has turned to Neoprene, a type of synthetic rubber as well as another more commonly used elastomer fiber, spandex (also known as elastane), because of their superiority to rubber in both strength and durability. Rubber is also commonly used to make rubber   bands and balloons, althought latex can be used as well.

Vocabu lary in Con text   Define the context clues in the following sentences to guess at the meaning of the underlined words. Rather than stretch when heated, rubber shrinks because the thermal agitation causes the chains to entangle and draw up. Tran Huu Hai

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To  shrink  means:………………………………………

The structure provides the resistance for rubber to spring back into shape when compressed or stretched. To   spring

hack into shape means:……………………

Vulcanization of only sulfur to rubber requires several hours and temperatures "

around 145 C. However, accelerators and activators added to the compound will result in vulcanization within minutes.

 Accelerators means:……………………………………

4. The choice of a synthetic rubber over natural rubber or of one synthetic over another boils down to specific properties required, price,

and processibility. To boil down to something  means:…………………

True or False Read the following sentences and decide whether they are true or false. Isoprene is formed through a natural polymerization in the tree.  The problems with natural rubber are solved by vulcanization.  The structural changes in rubber do not make it good for tires. It is necessary, for certain purpose, to make use of the latex itself as raw material.  The higher crystallinity of rubber, the greater its strength. Tran Huu Hai

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Vulcanization

can

be

speeded

up

by

adding

accelerators

and

activators to the rubber. Vulcanized rubber  resists petroleum oil, greases and gasoline. If deproteinized, natural rubber produces improvement in elastomer.

Comprehension Questions Answ er the ques tions be low. What's the structure of latex? Why is natural rubber  vulcanized? Why do the structural changes in rubber make it good for tires'? Make a summary  of  the text by transferring the information into the table below. Natural rubber

Vulcanized rubber

Language Use The Participle Used as an Adjective Study the sentences below.

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 The latex which has been dried is dispatched to ether countries. can be rephrased as:  The dried latex is dispatched to other countries. Rewrite these  sentences as shown above.

 The industrial areas which were developing were too far from the rubber plantations.  The  plantations which were established had to be in countries with a hot, humid climate.   The industry which is growing requires both natural and synthetic rubber in large quantities. Synthetic rubber  is produced by a process which is complicated.   The needs for rubber  which were growing were satisfied after synthetic rubber was produced. Supplies of  natural rubber which were required in industry were never sufficient.

Elliptical Adverb Clauses When adverb clause and main clause have the same subject, the subject and verb BE in adverb clause may be omitted. Study the sentences below. When heated, water turns into a steam. can be rephrased as: Tran Huu Hai

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When water is heated, it turns into steam.

Interpret the following adverb clauses. If carried out carefully, the experiment can give reliable data. When shown this chart, pay attention to the figures. The structure provides the resistance for rubber to spring hack into shape when compressed or stretched. If evaporated, a mass of greenish crystals will be obtained. When further heated, the liquid water boils forming the gaseous water. When examined, it will be found that the rod has diminished in mass.

The Adverbial Clause of Condition: if, provided, unless Use the correct verb form to m ake the sentences, then translate them into Vietnamese. Provided a liquid had evaporated into a closed space, its gaseous molecules (leave) the liquid surface. Unless he helps me, I (be able) to finish this work in time. If we did not know the nature of radioactive elements, it (he difficult) to deal with them. Provided the relative pressure of water is higher in the atmosphere, vapour  (condensate).

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Provided the temperature is kept constant, the volume of a given amount of  gas (be) inversely proportional to its pressure and directly to its absolute temperature. If liquid boiled, nitrogen (escape) from the solution more rapidly than oxygen as its boiling point is lower than that of oxygen.

 Additional Reading Synthetic Rubber Synthetic rubber is any type of artificially made  polymer  material which acts as an

elastomer . An elastomer is a material with the mechanical (or material) property that it can undergo much more elastic deformation under stress than most materials and still return to its previous size without permanent deformation. Synthetic rubber serves as a substitute for  natural rubber  in many cases, especially when improved material  properties are needed.   Natural rubber coming from latex is mostly polymerized isoprene with a small   percentage of impurities in it. This will limit the range of properties available to it. Also, there are limitations on the proportions of  cis and trans double bonds resulting from methods of  polymerizing natural latex. This also limits the range of properties available to natural rubber, although addition of  sulfur  and vulcanization are used to improve the properties. However, synthetic rubber can be made from the polymerization of a variety of  monomers including isoprene (2-methyl-1,3-butadiene), 1,3- butadiene, chloroprene (2chloro-1,3-butadiene), and isobutylene (methylpropene) with a small percentage of  isoprene for  cross-linking. Furthermore, these and other monomers can be mixed in various desirable proportions to be copolymerized for a wide range of physical, mechanical, and chemical properties. The monomers can be produced pure and addition of impurities or additives can be controlled by design to give optimal Tran Huu Hai

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 properties. Polymerization of pure monomers can be better controlled to give a desired  proportion of  cis and trans double bonds. The expanded use of motor vehicles, and particularly motor vehicle tires tires,, starting in the 1890s, created increased demand for rubber. Political problems that resulted from great fluctuations in the cost of natural rubber led to enactment of the Stevenson Act in 1921. This act essentially created a cartel which supported rubber prices by regulating   production (see OPEC OPEC), ), but insufficient supply, especially due to wartime shortages, also led to a search for alternative forms of synthetic rubber. In 1879, Bouchardt created one form of synthetic rubber, producing a polymer of  isoprene in a laboratory. Scientists in England and Germany developed alternate methods for creating isoprene polymers from 1910-1912. The first large-scale commercial production occurred in Germany during World War I, as a result of shortages of natural rubber. However, it used a different form of synthetic rubber based on a polymer of  butadiene,  butadiene, building on the laboratory work of the Russian scientist Sergei Lebedev. Lebedev. This early form of synthetic rubber was again replaced with natural rubber after the war ended, but investigations of synthetic rubber continued, leading to the 1933 invention which German scientists designated "Buna S". S". This type of synthetic rubber, a copolymer of butadiene and styrene styrene,, still represents about onehalf of total world production. Dr. Waldo Semon of the B.F. Goodrich Company developed Koroseal in 1935, and  Ameripol (from AMERican POLymer) in 1940, while Russian researchers created Sovprene

[1]

.

By 1925 the price of natural rubber had increased to the point that many companies were exploring methods of producing synthetic rubber to compete with natural rubber. In the United States, the investigation focused on different materials than in Europe. Building on the early laboratory work of  Nieuwland of  Nieuwland,, the DuPont company began the commercial sale of  Neoprene of  Neoprene in 1931, and Thiokol began the sale of that brand of  rubber, based on ethylene dichloride in 1930. The production of synthetic rubber in the United States expanded greatly during World War II, since the Axis Powers controlled Tran Huu Hai

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nearly all the world's supply of natural rubber once Japan conquered Asia. Additional refinements to the process of creating synthetic rubber continued after the war, and the quantity of synthetic rubber exceeded the production of natural rubber by the early 1960s. 

Butyl rubber 



Elmer Keiser Bolton



Polybutadiene

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Unit 4: SOAP History of soap

Soap is a surfactant cleaning compound used for personal or minor  cleaning. It usually comes in solid moulded form, termed bars. In somewhat recent years, the use of thick liquid

soap has become increasingly

widespread, especially from dispensers in public washrooms.

The origins of personal cleanliness date back to prehistoric times. Since water is essential for life, the earliest people lived near water and knew something about its cleansing properties - at least that it rinsed mud off  their hands. A soap-like material material found in clay cylinders during the excavation

of 

ancient Babylon is evidence that soapmaking was known as early as 2800 B.C. Inscriptions on the cylinders say that fats were boiled with ashes, which is is a method method of making making soap, but do not refer to the purpose of the "soap." Such materials were later used as hair styling aids. Records show that ancient Egyptians bathed regularly. The Ebers Papyrus, a medica l document from about 1500 B.C., describes combining animal and vegetable oils with alkaline salts to form a soap-like material used for treating skin diseases, as well as for washing At about the same time, Moses gave the Israelites detailed laws governing personal cleanliness. Tran Huu Hai

He

also

related

cleanliness

to

health

and

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religious

purification.

Biblical accounts suggest that the Israelites knew

that mixing ashes and oil produced a kind of hair gel.

The early Greeks bathed for aesthetic reasons and apparently did not use soap. Instead, they cleaned their bodies with blocks of clay, sand, pumice and ashes, then anointed themselves with oil, and scraped off the oil and dirt with a metal instrument known as a strigil. They also used oil with ashes. Clothes were washed without soap in streams.

Soap

got

its

name, according

to

an

ancient Roman

legend,

from

Mount Sapo, where animals were sacrificed. Rain washed a mixture of  melted animal fat, or allow, and wood ashes down into the clay soil along the Tiber River. Women found that this clay mixture made heir wash cleaner with much less effort. The ancient Germans and Gauls are also credited with discovering a substance called soap, made of tallow and ashes, that they used to tint their hair  red. Soapmaking was an established craft in Europe by the seventh century. Soapmaker

guilds

guarded

their

trade

secrets

closely. Vegetable and

animal oils were used with ashes of plants, along with fragrance. Gradually Tran Huu Hai

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more varieties of soap became available for shaving and shampooing, as well as bathing and laundering.

The chemistry of soap

Surfactants are classified by their ionic (electrical charge) properties in water: 1. anionic (negative charge) 2. nonionic (no charge) 3. cationic (positive charge) 4. amphoteric (either positive or negative charge). Soap is an anionic surfactant. Other anionic as well as nonionic surfactants are the main ingredients in today's detergents. Now let's look closer  at

the

chemistry

of surfactants. Soaps are water-soluble sodium or 

  potassium salts of fatty acids. Soaps are made from fats and oils, or their  fatty acids, by treating them ch emically with a strong al kali. Fats and Oils

The fats and oils used in soapmaking come from animal or plant sources. Each fat or oil is made up of a distinctive mixture of several different triglycerides. In a triglyceride molecule, three fatty acid molecules are attached to one Tran Huu Hai

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molecule of glycerine. There are many types of triglycerides; each type consists of its own particular combination of fatty acids. Fatty acids are the components of fats and oils that are used in making soap. They are weak  acids composed of two parts: A carboxylic acid group consisting of one hydrogen (H) atom, two oxygen (O) atoms, and one carbon (C) atom, plus a hydrocarbon chain attached to the carboxylic acid group. Generally, it is made up of a long straight chain of carbon (C) atoms each carrying two hydrogen (H) atoms. 4.4 Alkali

An alkali is a soluble salt of an alkali metal like sodium or potassium. Originally, the alkalis used in soapmaking were obtained from the ashes of    plants, but they are now made commercially. Today, the term alkali describes a substance that chemically is a base (the opposite of an acid) and that reacts with and neutralizes an acid. The common alkalis used in soapmaking are sodium hydroxide (NaOH), also called caustic soda; and potassium hydroxide (KOH), also called caustic potash. How Soaps are Made

Saponification of fats and oils is the most widely used soapma king process. This method involves heating fats and oils and reacting them with a liquid alkali to produce soap and water (neat soap) plus glycerine. The other  major soapmaking process is the neutralization of fatty acids with an alkali. Fats and oils are hydrolyzed (split) with a high-pressure steam to yield crude fatty acids and glycerine. The fatty acids are then purified by distillation and neutralized with an alkali to produce soap and water (neat soap). When the alkali is sodium hydroxide, a sodium soap is formed. Tran Huu Hai

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Sodium soaps are

"hard"

soaps.

When

the

alkali

is potassium

hydroxide, a potassium soap is formed. Potassium soaps are softer and are found in some liquid hand soaps and shaving creams. The carboxylate end of the soap molecule is attracted to water. It is called the hydrophilic (water-loving) end. The hydrocarbon chain is attracted to oil and grease and repelled by water. It is known as the hydrophobic (water-hating) end. How Water Hardness Affects Cleaning Action

Although soap is a good cleaning agent, its effectiveness is reduced when used in hard water. Hardness in water is caused by the presence of mineral salts - mostly those of calcium (Ca) and magnesium (Mg), but sometimes also iron (Fe) and manganese (Mn). The mineral salts react with soap to form an insoluble precipitate known as soap film or scum.Soap film does not rinse away easily. It tends to remain behind and produces visible deposits on clothing and makes fabrics feel stiff. It also attaches to the insides of bathtubs, sinks and washing machines. Some soap is used up by reacting with hard water minerals to form the film. This reduces the a mount of soap available for cleaning. Even when clothes are washed in soft water, some hardness minerals are introduced by the soil on clothes. Soap molecules are not very versatile and cannot be adapted to today's variety of  fibers, washing temperatures and water conditions. 4.7 Products

Soaps and detergents found in the home can be grouped into four general categories:

personal

cleansing,

laundry,

cleaning. Within each category are Tran Huu Hai

dishwashing

different

product

and

household

types

formulated

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with ingredients selected to perform a broad cleaning function as well as to deliver properties specific to that product. Knowing the different   products and their ingredients helps you select the right product for the cleaning job.

Personal

liquid soaps and

Cleansing

Products

i nclude

b ar

soaps,

gels,

heavy duty hand cleaners. These products get their 

cleaning action from soap, other surfactants or a combination of the two. The choice of cleaning agent helps determine the product's lathering characteristics, feel on the skin and rinsability. Bar soaps or gels are formulated for cleaning the hands, face and   body. Depending on the other ingredients, they may also moisturize the skin and/or kill or inhibit Specialty

bars

bacteria

that

can

cause

odor

or

disease.

include transparent/translucent soaps, luxury soaps and

medicated soaps. Liquid soaps are formulated for cleaning the hands or body, and feature skin conditioners. Some contain antimicrobial agents that kill or inhibit   bacteria that can cause odor or disease. Heavy duty hand cleaners are available as bars, liquids, powders and pastes. Formulated for removing stubborn, greasy dirt, they may include an abrasive. Laundry and

Laundry

Aids

are

available

as

liquids, powders,

Detergents

gels,

sticks,

sprays, pumps, sheets and bars. They are formulated to meet a variety of soil and stain removal, bleaching, fabric softening and conditioning, and disinfectant needs under varying water, temperature and use conditions. Laundry detergents are either general   purpose or light duty. General purpose detergents are suitable for all washable fabrics. Liquids work best on oily soils and for pretreating soils and stains. Powders are especially effective in lifting out clay and groundin dirt. Light duty detergents are used for hand or machine washing lightly soiled items and delicate fabrics. Tran Huu Hai

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Laundry aids contribute to the effectiveness of laundry detergents and   provide special functions. Bleaches (chlorine and oxygen) whiten and brighten fabrics and help remove stubborn stains. They convert soils into colorless,

soluble

particles

that

can

be

removed

by detergents and

carried away in the wash water. Liquid chlorine bleach (usually in a sodiu m hypochlorite solution) can also disinfect and deodorize fabrics. Oxygen (color-safe) bleach is more gentle and works safely on almost all washable fabrics.Bluings contain a blue dye or pigment taken up by fabrics in the wash or rinse. Bluing absorbs the yellow part of the light spectrum, counteracting the natural yellowing of many fabrics. Boosters enhance the soil

and

stain

removal,

brightening,

buffering

and

water

softening

  performance of detergents. They are used in the wash in addition to the detergent. Enzyme presoaks are used for soaking items before washing to remove difficult stains and soils. When added to the wash water, they increase cleaning power. Fabric softeners, added to the final rinse or  dryer, make fabrics softer and fluffier; decrease static cling, wrinkling and drying time; impart a pleasing f ragrance and make ironing easier. Prewash soil and stain removers are used to pretreat heavily soiled and stained garments, especially those made from synthetic fibers. Starches, fabric finishes and sizings, used in the final rinse or after drying, give body to fabrics, make them more soil-resistant and make ironing easier.

Water softeners, added to the wash or rinse, inactivate hard water minerals. Since detergents are more effective in soft water, these products increase cleaning power. Dishwashing Products include detergents for hand and machine dishwashing as well as some specialty products.They are available as liquids, gels, powders and solids. Hand dishwashing detergents remove food soils, hold soil in suspension and   provide long-lasting suds that indicate how much cleaning power is left in the wash Tran Huu Hai

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water. Automatic dishwasher detergents, in addition to removing food soils and holding them in suspension, tie up hardness minerals, emulsify grease and oil, suppress foam caused by protein soil and help water sheet off dish surfaces. They produce little or no suds that would interfere with the washing action of the machine. Rinse agents are used in addition to the automatic dishwasher detergent to lower surface tension, thus improving draining of the water from dishes and utensils. Better draining minimizes spotting and filming and enhances drying. Film removers remove build-up of hard water film and cloudiness from dishes and the interior of the dishwasher. They are used instead of an automatic dishwasher detergent in a separate cycle or together  with the detergent. Lime and rust removers remove deposits of lime and/or rust from the interior of the dishwasher. They are used when no dishes or other dishwasher    products are present. Household Cleaners are available as liquids, gels, powders, solids, sheets and pads for use on painted, plastic, metal, porcelain, glass and

other surfaces, and on washable floor coverings. Because no single product can  provide optimum performance on all surfaces and soils, a broad range of products has  been formulated to clean efficiently and easily. While all-purpose cleaners are intended for more general use, others work best under highly specialized conditions.

All-

  purpose cleaners penetrate and loosen soil, soften water and prevent soil from redepositing on the cleaned surface. Some also disinfect. Abrasive cleansers remove heavy accumulations of soil often found in small areas. The abrasive action is provided   by small mineral or metal particles, fine steel wool, copper or nylon particles. Some also disinfect. Specialty cleaners are designed for the soil conditions found on specific surfaces, such as glass, tile, metal, ovens, carpets and upholstery, toilet bowls and in drains. Glass cleaners loosen and dissolve oily soils found on glass, and dry quickly without streaking. Glass and multi-surface cleaners remove soils from a variety of  smooth surfaces. They shine surfaces without streaking. Tub, tile and sink cleaners remove normal soils found on bathroom surfaces as well as hard water deposits, soap scum, rust stains, and/or mildew and mold. Some also treatsurfaces to retard soiling; some also disinfect. Metal cleaners remove soils and polish metalware. Tarnish, the Tran Huu Hai

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oxidation of metal, is the principal soil found on metal ware. Some products also   protect cleaned metal ware against rapid retarnishing. Oven cleaners remove burnedon grease and other food soils from oven walls. These cleaners are thick so the product will cling to vertical oven surfaces. Rug shampoos and upholstery cleaners dissolve oily and greasy soils and hold them in suspension for removal. Some also treat surfaces to repel soil. Toilet bowl cleaners prevent or remove stains caused by hard water and rust deposits, and maintain a clean and pleasant-smelling bowl. Some products also disinfect. Drain openers unclog kitchen and bathroom drains. They work by producing heat to melt

fats, breaking them down into simpler substances that can be rinsed away, or by oxidizing

hair and other materials. Some use bacteria to prevent grease build-up which leads to drain clogging.

Manufacturing Soap and detergent

Manufacturing consists of a broad range of processing and packaging operations. The size and complexity of these operations vary from small plants employing a few   people to those with several hundred workers. Products range from large-volume types

like

laundry detergents that are used on a regular basis to lower-volume

specialties for less frequent cleaning needs. Cleaning products come in three principal forms: bars, powders and liquids. Some liquid products are so viscous that they are gels. The first step in manufacturing all three forms is the selection of raw materials. Raw materials are chosen according to many criteria, including their human and environmental safety, cost, compatibility with other ingredients, and the form and  performance characteristics of the finished product. While actual production processes may vary from manufacturer to manufacturer, there are steps which are common to all   products of a similar form. Let's start by looking at bar soap manufacturing and then we'll review the processes used to make powder and liquid detergents. Traditional bar  Tran Huu Hai

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soaps are made from fats and oils or their fatty acids which are reacted with inorganic water-soluble bases. The main sources of fats are beef and mutton tallow, while palm, coconut and palm kernel oils are the principal oils used in soap making. The raw materials may be pretreated to remove impurities and to achieve the color, odor and   performance features desired in the finished bar. The chemical processes for making soap, i.e., sap ammonification of fats and oils and neutralization of fatty acids, are described in the Chemistry section. Soap was made by the batch kettle boiling method until shortly after World War II, when continuous processes were developed. Continuous processes are preferred today because of their flexibility, speed and economics. Both continuous and batch processes produce soap in liquid form, called neat soap, and a valuable by-product, glycerine (1). The glycerine is recovered by chemical treatment, followed by evaporation and refining. Refined glycerine is an important industrial

material used in foods, cosmetics, drugs and many other products. The next processing step after sap ammonification or neutralization is drying. Vacuum spray drying is used to convert the neat soap into dry soap pellets (2). The moisture content of the pellets will vary depending on the desired properties of the soap bar. In the final processing step, the dry soap pellets pass through a bar soap finishing line. The first unit in the line is a mixer, called an amalgamator, in which the soap pellets are blended together with fragrance, colorants and all other ingredients (3). The mixture is then homogenized and refined through rolling mills and refining plodders to achieve thorough blending and a uniform texture (4). Finally, the mixture is continuously extruded from the plodder, cut into bar-size units and stamped into its final shape in a soap press (5). Some of today's   bar soaps are called "combo bars," because they get their cleansing action from a combination of soap and synthetic surfactants. Others, called "syndet bars," feature surfactants as the main cleansing ingredients. The processing methods for  manufacturing the synthetic base materials for these bars are very different from those used in traditional soap making. However, with some minor modifications, the finishing line equipment is the same. Tran Huu Hai

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Powder detergents

Powder detergents are produced by spray drying, agglomeration, dry mixing or  combinations of these methods. In the spray drying process, dry and liquid ingredients are first combined into a slurry, or thick suspension, in a tank called a crutcher (1). The slurry is heated and then pumped to the top of a tower where it is sprayed through nozzles under high pressure to produce small droplets. The droplets fall through a current of hot air, forming hollow granules as they dry (2). The dried granules are collected from the bottom of the spray tower where they are screened to achieve a relatively uniform size (3).

After the granules have been cooled, heat sensitive

ingredients that are not compatible with the spray drying temperatures (such as bleach, enzymes and fragrance) are added (4). Traditional spray drying produces relatively low density powders. New technology has enabled the soap and detergent industry to reduce the air inside the granules during spray drying to achieve higher densities. The higher density powders can be packed in much smaller packages than were needed  previously.

Agglomeration, which leads to higher density powders, consists of blending dry raw materials with liquid ingredients. Helped by the presence of a liquid binder, rolling or  shear mixing causes the ingredients to collide and adhere to each other, forming larger  Tran Huu Hai

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  particles. Dry mixing or dry blending is used to blend dry raw materials. Small quantities of liquids may also be added.

4.10 Liquid detergents

Both batch and continuous blending processes are used to manufacture liquid and gel cleaning products. Stabilizers may be added during manufacturing to ensure the uniformity and stability of the finished product. In a typical continuous process, dry and liquid ingredients are added and blended to a uniform mixture using in-line or  static mixers. Recently, more concentrated liquid products have been introduced. One method of producing these products uses new high-energy mixing processes in combination with stabilizing agents.

Packing

The final step in the manufacture of soaps and detergents is packaging. Bar soaps are either wrapped or cartooned in single packs or multi packs. Detergents, including Tran Huu Hai

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household cleaners, are packaged in cartons, bottles, pouches, bags or cans. The selection of packaging materials and containers involves considerations of product compatibility and stability, cost, package safety, solid waste impact, shelf appeal and ease of use.

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