Download University of Crete, Materials Science, English 3 special Module 1

University of Crete, Materials Science, English 3 special
Module 1: Winter Semester 2008-2009, tutor: Ailamaki Katerina
Elements and the Periodic Table
Matter is anything that occupies space and has mass. Matter can be divided in terms of composition
into pure substances and mixtures. Pure substances, such as elements, cannot be chemically
separated or decomposed into simpler substances. On the other hand, a chemical combination of an
element is a compound. Mixtures are divided into two kinds: heterogeneous and homogeneous. The
former consists of discernible parts or phases whereas the latter is made up of components that cannot
be individually detected. Homogeneity can be found in solutions, which are uniform in composition.
In addition, it should be mentioned that the chemical elements are the building blocks of nature, since all
substances are combinations of these elements. Each element has a name and a symbol. In 1869,
Mendeleyev, a Russian chemist, in an attempt to arrange and classify them devised the periodic table,
a pattern used to show similarity in potential for combination of the elements.
However, before moving on to give a more detailed account of the periodic table, let us go through the
inner composition of elements. The elements are composed of tiny particles of matter called molecules,
which are made of even smaller fundamental particles called atoms. The entire world is made of atoms.
The concept of atoms first emerged in ancient Greece by Democritus in 400BC; the Greek word “atomo”
means indivisible or something that cannot be split. Later in 1804 the Englishman John Dalton,
formulated an atomic theory based on his experimentation. He claimed that all matter is made of
atoms, while all atoms of a single element have the same shape, size, weight, and behaviour. However,
atoms of each element are different from those of any other element. He also said that atoms are not
created or destroyed but rather form new combinations in chemical reactions.
Dalton thought that atoms were solid, but today atoms are believed to consist mainly of space, with a
dense nucleus at the centre. Each nucleus contains protons, which have a positive electric charge,
and neutrons, which have a neutral electric charge. The number of the protons in the nucleus is
called the atomic number. The nucleus is surrounded by electrons, which have a negative electric
charge. The number of protons equals the number of electrons in each atom, and therefore, the entire
atom has no charge, namely atoms are electrically neutral. Under certain circumstances they can
become charged. Most of the mass of an atom is concentrated in the nucleus, while the relative size of
an atom is approximately 10,000 times larger than its nucleus. The electrons surrounding the nucleus
are in motion in circular orbits and their distance from the nucleus is called an energy level or electron
shell. The outer most electron shell is known as the Valence shell.
In any group in the periodic table, each element has one or more energy levels than the element above
it. The distance from the centre of the nucleus to the outermost electron is called the atomic radius.
Therefore, as we move down through a particular group, the atomic radii of the elements increase. In
addition, as we move from the top to the bottom of a group, the ionization potential decreases. This is
the energy needed to remove an outer-shell electron from an isolated atom of an element. Eventually,
as we move down a group in the periodic table of atom’s ability to acquire additional electrons, generally
decreases.
The periodic table is a table of elements ranged in order of increasing proton number to show the
similarities of chemical elements with related electronic configurations. As you already know, an element
is a pure substance that contains only one type of atom. As was mentioned before, the original form of
the periodic table was proposed by Dimitri Mendeleyev in 1869 using relative atomic masses. He
predicted both the position and chemical properties of elements that had not been discovered, for
example Gallium and Germanium; we are still discovering elements today that fit into the table. In the
modern short form of the table, the lanthanides and actinides are not shown. The elements fall into
vertical columns, known as groups. Going down a group, the atoms of the elements all have the same
outer shell structure, but an increasing number of inner shells. Traditionally, the alkali metals were
shown on the left of the table and the groups were numbered IA to VIIA, IB to VIIB, and 0 for the noble
gases. All the elements in the middle of the table are classified as transition elements and the nontransition elements are regarded as main group elements. Because of confusion in the past regarding
the numbering of groups and the designations of subgroups, modern practice is to number the groups
across the table from 1 to 18. Horizontal rows in the table are periods. The first three are called short
periods; the next four (which include transition elements) are long periods. Within a period the atoms
of all elements have the same number of shells, but with a steadily increasing number of electrons in the
outer shell. The periodic table can also be divided into four blocks depending on the type of the shell
being filled: the s-block, the p-block, the d-block, and the f-block.
In brief, four separate groups of elements appear in large blocks: 1) main group elements or
representative elements, 2) noble gases, 3) transition elements, 4) inner transition elements. The 109
elements in the periodic table can also be divided into three general categories: metals, non-metals,
and metalloids (a cluster of elements that are neither metals nor non-metals).
There are certain general features of chemical behaviour shown in the periodic table. In moving down a
group, there is an increase in metallic character because of the increased size of the atom. In going
across a period, there is a change from metallic (electropositive) behaviour to non-metallic
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(electronegative) because of the increasing number of electrons in the outer shell. Consequently,
metallic elements tend to be those on the left and towards the bottom of the table; non-metallic elements
are towards the top and the right.
Overall, ninety two elements occur naturally, the rest are created under extreme conditions in the
laboratory. Unstable radioactive elements have their relative atomic masses in brackets.
Let us look at some element examples. As was mentioned above, the atom of each element is different
from the atom of every other element in the size and weight of its nucleus and the number of its
electrons. The simplest atom is that of the element hydrogen. Hydrogen is the lightest element, since it
has only one electron and one proton. In fact, the hydrogen atom, the most common atom in the
universe, is the basis on which our entire universe was formed. Oxygen has eight protons and eight
electrons. Uranium, one of the heaviest elements having more complicated atoms with a larger nucleus,
has 92 protons and 92 electrons.
Most substances are composed of two or more elements chemically combined as molecules to form
compounds; the most common being water. A molecule of water is composed of 3 atoms (2 of hydrogen
and 1 of oxygen/ with chemical formula: H2O). Some compounds, such as proteins, possess hundreds
of atoms of several elements in each of their molecules.
Finally, all life exists because atoms are continually moving, combining, separating, colliding, giving off
energy, and absorbing energy.
Chemical series of the periodic table
Alkali metals
Alkaline earth
metals
Lanthanides
Actinides
Transition
metals
Poor metals
Metalloids
Nonmetals
Halogens
Noble gases
Notes:Lanthanides are also known as "rare earth elements", a deprecated term. Regarding group
membership of these elements, see here. Alkali metals, alkaline earth metals, transition metals,
actinides, lanthanides, and poor metals are all collectively known as "metals". Halogens and noble
gases are also non-metals.
A.
COMPREHENSIVE AND CONVERSATIONAL QUESTIONS:
1. What is matter?
2. How are elements categorized?
3. Have all elements the same atoms in shape, size, weight and behavior?
4. What is atomic radius, and what is ionization?
5. Which is the lightest element and why?
6. What is the Periodic Table? Can you briefly describe it?
7. Are all elements in the periodic table natural elements?
PART B: VOCABULARY EXPLORATION
B1. Find the missing word
1. All substances are made from tiny particles called…………….
2. Groups of two or more atoms chemically bonded together are called
…………………..
3. Some substances contain only one type of atom. These are …………….
and they can not be broken down into simpler substances.
4. If a substance contains more than one type of atom, it is a …………….. . Its
different elements can not be separated easily, unlike the substances in a
mixture.
5. ………………… changes make new substances, but …………………changes
don’t.
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6. Atoms contain …………………, ……………………, and ……………………..
7. Protons are …………………… charged, while electrons are ………………
charged.
8. The part of the atom that has neither positive or negative charge is called
…………………….
9. The centre of an atom is called …………………
10. The electrons orbit the nucleus in ………………… or ……………………………..
B2. a. Match the following words with their equivalent explanation.
1.
2.
3.
4.
5.
6.
7.
8.
matter
solution
potential
fundamental
emerge
solvent
orbit
eventually
9.configuration
10.vertical
11.designation
12. dense
13.steady
14.representative
15.cluster
16.deprecate
a) a substance, especially a liquid, that can dissolve another substance
b)that can be developed in the future/ possible
c) finally
d) going from top to bottom
e) anything that occupies space and has mass
f) regular, not changing and not interrupted
g) basic
h) containing or including examples of all the different types of people or
things in a large group
i) a group of things of the same type that grow or appear close together
j) a liquid in which a substance is dissolved
k) to feel and express strong disapproval of sth
l) occur/ to appear or become known
m) thick, difficult to see through/ heavy in relation to its size
n)a name, title or description
o)a curved path around a planet or an object
p)the form or shape that the arrangement of a group of things produces/ or/ (in
computing) the equipment and programmes that form a computer system and the way
that these are set up to run
B3. Fill in the gaps with the appropriate word from the box. One word is
redundant.
lens, industry, appears, chains, evaporates, concentrating,
substance, sugars, pressure, properties, point, compounds,
organic, vital, quantities, fictional, fractional
In the late 18th century, a scientist called Joseph Priestley prepared oxygen by 1)
……………..the sun’s rays through a 2) ……….. on mercuric oxide. Oxygen had probably
been produced many times before, but Priestley was the first to recognize it. There is, in fact,
more oxygen on earth than any other single element. About 20% of the volume of atmosphere
is oxygen; nine tenths of the weight of water is oxygen; 65% of the weight of the human body
is oxygen. It is 3) ……………. to life because it is needed by the body cells of all animals. It is
also very useful in 4) …………….. . The method Priestley used produces only small 5)
……………… . The large amounts needed for industry are produced in a different way: Air is
put into containers under great 6) ………………… . This turns it into liquid and makes it very
cold. It is then gradually warmed up and each substance 7) …………….. at a different
temperature. The boiling 8) ………… of oxygen is -183oC. It is caught and stored in strong
steel cylinders as a pressure of 136 atmospheres. The process is known as
9)
……………distillation.
Carbon 10) ……………. in many forms and, like oxygen, it is an important element. Carbon
dioxide is needed by plants to make 11) …………. . The energy which is stored in plants by
this process is the basis of all forms of life. There are more carbon compounds than all other
chemical 12) ……………. together. This is because carbon atoms have special 13)
……………….. . They can connect to each other in rings and long 14) …………….. to form
very large molecules. They can also combine with most other elements. Wood, wool rubber,
oil, soap, alcohol and plastics are examples of carbon compounds in everyday use. Even
diamond, the hardest known natural 15) …………….. is a carbon compound. In addition, 18%
of the weight of the human body is carbon. Carbon chemistry is usually called 16)
………………. chemistry - the chemistry of life.
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B4. a. Complete the table making derivatives from the words provided.
VERB
NOUN
ADJECTIVE
1.
pigment
2. evaporate
3.
industry
4. collide
5.
fractional
6.absorb
7.
orbit
8.
discernible
9.emerge
10.
proposed
b. Find the opposites of the following words
1.divisible
2.former
3.composition
4.inner
5.decrease
6.soluble
7.steady
8.transitional
B5.Study the following list and translate the elements into Greek.
ALKALI METALS: (=
)
(Very reactive soft metals; all form ionic compounds with non-metals of the same
formula, for example: LiCl, NaCl, KCl. Reactivity increases down the group because
outer electron is further from the nucleus and is therefore easier to remove.)
Li = lithium
Rb = rubidium
Na = sodium
Fr = francium
K = potassium
ALKALINE EARTH METALS: (=
)
(They are called this because their compounds are commonly found in rocks and
minerals. Just like alkali metals, the reactivity increases down the group. They react
with water to give an alkaline solution.)
Be = beryllium
Ca = calcium
Mg = magnesium
Sr = strontium
Ba = barium
Ra = radium
SEMI-METALS/ METALLOIDS: (=
)
B = boron
Si = silicon
Ge = germanium
Te = tellurium
OTHER METALS:
Al = aluminium
Ga = gallium
In = indium
Sn = tin
NON-METALS: (
As = arsenic
Se = selenium
Sb = antimony
Ti = thallium
Pb = lead
Bi = bismuth
Po = polonium
)
C = carbon
N = nitrogen
O = oxygen
F = fluorine
P = phosphorus
S = sulphur
Cl = chlorine
Br = bromine
I = iodine
At = astatine
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NOBLE GASES: (=
He = helium
Ne = neon
Ar = argon
)
Xe = xenon
Kr = krypton
Rn = Radon
TRANSITION METALS: (=
)
(Are a block of dense metallic elements that have colored compounds, can often be
used as catalysts and have variable oxidation states. For example copper and nickel
are used in coinage, iron is used in construction industry, chromium compounds are
used as paint pigments and vanadium compounds can be used as catalysts.)
Sc = scandium
Os = osmium
Ti = titanium
Hf = hafnium
Pd = palladium
Fe = iron
Ir = iridium
Co = cobalt
Ta = tantalum
Pt = platinum
Sg = seaborgium
Ag = silver
Nb = niobium
W = tungsten
V = vanadium
Ni = nickel
Cu = copper
Zn = zinc
Au = gold
Re = rhenium
Hg = mercury
Cr = chromium
Y = yttrium
Hs = hassium
Mt
=
meitnerium
Ru = ruthenium
Tc = technetium
Mn
=
manganese
Uub = ununbium
Rf = rutherfordium
Uun = ununnilium
Cd = cadmium
Rh = rhodium
Bh = bohrium
Zr = zirconium
Db = dubnium
Mo = molybdenum
LANTHANIDES/ RARE EARTH: (=
ACTINIDES/ RARE EARTH: (=
)
)
PART C: GRAMMAR: present tenses
Theoretical background:
PRESENT TENSES: Present simple/ Present continuous
(notes taken from: “Advanced Grammar in Use” by Martin Hewings, CUP)
USE:
1. P.S. is used to describe things that are always true, or situations that exist now and
will go on indefinitely.
e.g. It takes me thirty minutes to get to University.
The word atom comes from a Greek word meaning ‘something that can not be split’.
2. P.C. is used to talk about particular actions or events that have begun but not ended
at the time of speaking. Time expressions such as at the moment, at present,
currently, just, still are used to emphasize that the action is happening now.
e.g. I am drawing a diagram to show you my experiment results.
3. P.S. is used to talk about habits of things that happen at regular basis. e.g. I leave
work at 5.30 most days.
4. However, P.C. is used to describe repeated actions that are happening at or around
the time of speaking.
e.g. I am hearing a lot of good reports about your work these days.
5. P.S. or P.C. can be used to describe something that we regularly do at a particular
time. Compare:
e.g. We usually attend the Chemistry lecture at 10 am.
(we start attending at 10 am)
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We are usually attending the Chemistry lecture at 10 am.
(we are already attending at 10 am)
6. P.C. is used to imply that a situation may / is temporary. Compare:
e.g. She teaches Maths in a school in Bonn.
(a permanent arrangement)
She is teaching Maths in a school in Bonn.
(implies that this is not or may not be permanent)
7. It is often preferred to use the P.S. rather than the P.C. with verbs describing state. e.g.
I really enjoy traveling.
Common state verbs are: agree, assume, believe, belong to, contain, cost, disagree,
feel, hate, have, hope, know, like, look, love, own, prefer, realize, regret, resemble,
smell, taste…
However, P.C. ca be used with some state verbs when the situation is temporary, for a
period of time around the present.
e.g. I consider him to be excellent researcher. (this is my view)
I am considering doing a PhD soon.
(This is something I am thinking about now)
8. P.C. is used when se talk about changes, developments, trends
e.g. I am beginning to realize how difficult it is to be an excellent University student.
9. For telling a story or a joke, for commentaries and giving instructions we often describe
the main events using the present (or past) simple, and longer, background events using
the present (or past) continuous.
e.g. She goes up to this man and looks straight into his eyes. She is carrying a bag full
of papers…..
10. P.C. is used to emphasize that something is done repeatedly and to show that we are
unhappy about it, including our own behavior. Words such as always, constantly,
continually, forever are use din this case.
e.g. They are constantly missing the laboratory work.
11. P.S. is used to report what we have heard or what we have read.
e.g. This newspaper article explains why unemployment has been rising more quickly.
Exercises:
Complete the sentences with appropriate verbs. Use the same verb for each
sentence in the pair. Use present simple or continuous.
1. a) It …………………… us a fortune at the moment to send our daughter to dance
classes.
b) It ………………….. us a fortune to fly first class to Japan.
2. a) I …………………….. sitting down at the end of a long day and reading a good
book.
b) It is a wonderful book. I ……………….. every moment of it.
3. a) We’ve always wanted a house in the country, but we ………………….
on where it should be.
b) When they agree with each other on so many important issues, I can’t understand
why they ……………………… now on this relatively minor matter.
4. a) With growing concerns about the environment, people……………. to use recycled
paper products.
b) He doesn’t like publicity, and ………………………..to stay firmly in the background.
5. a) - Can I speak to Dorothy? –She …………………. a shower. Can I take a message
for her?
b) My brother …………………. three children, all girls.
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Module 2: Winter Semester 2008-2009, English 3 special
Types of Materials
CLASSIFICATION OF MATERIALS:
Solid materials have been conveniently grouped into three basic classifications: metals,
ceramics, and polymers. This classification is based primarily on chemical makeup and
atomic structure. Most materials fall into one distinct grouping or another, although there are
some intermediates. In addition, there are three other groups of important engineering
materials: composites, semiconductors, and biomaterials. Composites consist of
combinations of two or more different materials, whereas semiconductors are utilised
because of their unusual electrical characteristics; biomaterials are implanted into the human
body. A brief explanation of the material types and representative characteristics is provided
next.
METALS:
Metallic materials are normally combinations of metallic elements. They have large numbers
of nonlocalized electrons, which means that these electrons are not bound to particular
atoms. Many properties of metals are directly attributable to these electrons. Metals are
extremely good conductors of electricity and heat and are not transparent to visible light, while
a polished metal surface has a lustrous appearance. Furthermore, metals are quite strong,
yet deformable, which accounts for their extensive use in structural applications. Many metals
we encounter in today’s world are mixtures (alloys). For example, the gold wedding band is a
copper-gold alloy and different colour golds are produced by mixing different metals with the
gold. Stainless steel is a mixture of iron, chromium and nickel, with a little carbon. Some
magnets are mixtures of iron, aluminium, nickel and cobalt. There is no end to the number of
metal alloys we can make. Not only do we have a choice of eighty metallic elements but we
also have a choice of the proportions we mix them in. This truly provides an infinite number of
possibilities.
CERAMICS:
Ceramics are compounds between metallic and non metallic elements. They are most
frequently oxides, nitrides, and carbides. The wide range of materials that falls within this
classification includes ceramics that are composed of clay minerals, cement, and glass.
Also, silica (SiO2) and alumina (Al2O3) are both ceramics. These materials are typically
insulative to the passage of electricity and heat, and are more resistant to high temperatures
and harsh environments than metals and polymers. Thus, they are used as thermal insulators
in fireplaces (firebricks) and in insulation for houses (fiberglass). With regard to mechanical
behaviour; ceramics are hard but very brittle.
POLYMERS:
Polymers include the familiar plastic and rubber materials. Many of them are organic
compounds that are chemically based on carbon, hydrogen, and other non metallic
elements. Furthermore, they have very large molecular structures. These materials
typically non magnetic, have low densities and may be extremely flexible. Polymers are
usually thermal and electrical insulators, although there are some recent developments in
conductive plastic. Many naturally occurring materials are polymeric such as wool, skin,
cotton, etc.
COMPOSITES:
A number of composite materials have been engineered and consist of more than one
material type. Fiberglass is a familiar example, in which glass fibres are embedded within a
polymeric material. A composite is designed to display a combination of the best
characteristics of each of the component materials. Fiberglass acquires strength from the
glass and flexibility from the polymer. Many of the recent material developments have
involved composite materials.
SEMICONDUCTORS:
Semiconductors have electrical properties that are intermediate between the electrical
conductors and insulators. Furthermore, the electrical characteristics of these materials are
extremely sensitive to the presence of minute concentrations of impurity atoms. These
concentrations may be controlled over very small spatial regions. The semiconductors have
made possible the advent of integrated circuitry that has totally revolutionised the
electronics and computer industries over the past few decades.
BIOMATERIALS:
Biomaterials are employed in components implanted into the human body for replacement
of diseased or damaged body parts. These materials must not produce toxic substances and
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must be compatible with body tissues, in other words they must not cause adverse biological
reactions. All of the above materials (metals, ceramics, polymers, composites, and
semiconductors) may be used as biomaterials. One example is that some biomaterials can be
utilised in artificial hip replacements.
ADVANCED MATERIALS
Materials that are utilised in high-technology (high-tech) applications are sometimes termed
as advanced materials. By high technology we mean a device or product that operates of
functions using relatively intricate and sophisticated principles, for example: electronic
equipment (CD players, etc.) computers, fiber-optic systems, spacecraft, aircraft, and military
rocketry. These advanced materials are typically either traditional materials whose properties
have been enhanced or newly developed being high-performance materials. Furthermore,
they may be of all materials types (e.g. metals, ceramics, and polymers) and are normally
relatively expensive. Application examples of these are the materials used for lasers,
integrated circuits, magnetic information storage, liquid crystal displays (LCD), and fiber
optics.
MATERIALS OF THE FUTURE
SMART MATERIALS:
They are a group of new and state- of-the-art materials that are now being developed, which
will have a significant influence on many of our technologies. The adjective “smart” implies
that these materials are able to sense changes in their environments and then respond to
these changes in predetermined manners – traits that are also found in living organisms. In
addition, this “smart” concept is being extended to rather sophisticated systems that consist of
both smart and traditional materials.
Components of a smart material or system include some type of sensor, that detects an input
signal, and an actuator, that performs a responsive and adaptive function. Actuators may be
called upon to change shape, position, natural frequency, or mechanical characteristics in
response to changes in temperature, electric and/ or magnetic fields.
Four types of materials are commonly used for actuators: 1) shape memory alloys, which
are metals that, after having been deformed, revert back to their original shapes when
temperature is changed; 2) piezoelectric ceramics, which expand and contract in response
to an applied electric field of voltage, while they generate an electric field when their
dimensions are altered; 3) magnetostrictive materials behave in analogy to piezoelectrics,
except that they are responsive to magnetic fields; and 4) electrorheological /
magnetorheological fluids are liquids that experience dramatic changes in viscosity upon
the application of electric and magnetic fields respectively.
Materials or devices that are employed as sensors include optical fibers, piezoelectric
materials, and microelectromechanical devices.
For example, one type of smart system is used in helicopters to reduce aerodynamic cockpit
noise that is created by the rotating rotor blades. Piezoelectric sensors inserted into the
blades, monitor blade stresses and deformations. Feedback signals from these sensors are
fed into a computer-controlled adaptive device, which generates noise-cancelling antinoise.
NANOTECHNOLOGY:
Until very recent times the general procedure utilised by scientists to understand the chemistry and
physics of materials has been “top-down”. This is achieved first by studying large and complex
structures, and then to investigate the fundamental building blocks of these structures that are smaller
and simpler.
However, with the use of scanning probe microscopes, which permit observation of individual atoms and
molecules, it has become possible to manipulate and move atoms and molecules to form new structures
and, thus, design new materials that are built from simple atomic level constituents. This ability to
carefully arrange atoms provides opportunities to develop mechanical, electrical, magnetic, and other
properties that are not otherwise possible. We call this the “bottom-up” approach, and the study of the
properties of these materials is termed “nanotechnology”. The “nano” prefix denotes that the dimensions
of these structural entities are on the order of a nanometer. In the future increasingly more of our
technological advances will utilise these nano-engineered materials.
( “Materials science and engineering- an introduction”, by Callister, W.D./
“Materials in today’s world”, by Thrower,
P.A.)
A. COMPREHENSIVE QUESTIONS:
1. In to which six categories are solid materials classified?
2. Which are the properties of metals, ceramics and polymers?
3. How are most composite materials designed?
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4.
5.
6.
7.
8.
Why are biomaterials created and what basic properties must they have?
Which materials are considered to be expensive and where are they applied?
Which materials resemble the characteristics of living organisms? Why?
What are a sensor and an actuator and where do we find them?
What is nanotechnology?
PART B: VOCABULARY EXPLORATION
B1. Match the words with their equivalent explanation.
a) become aware of, feel or detect
1. transparent
b) produce or cause
2. trait
c) make something look better, improve
3. advent
d) can be seen through
4. to sense
e) name or define
5. artificial
f) not real, imitation of something natural
6. to term
g) control and handle with skill
7. device
h) arrival or approach
8. to enhance
i) compartment of the pilot and crew of an aircraft
9. cockpit
j) hard but easily broken, fragile
10. viscosity
k) characteristic
11. intricate
l) particular type of matter or material
12. substance
m) thickness and stickiness
13. brittle
n) of many small parts joined in a complex way
14. to generate
o) thing made or adapted for a special purpose
15. to manipulate
B2. Fill in the table with the appropriate derivatives of the words given
VERB
NOUN
ADJECTIVE
1.
classification
2.
deformable
3.
application
4. compose
5.
resistant
6. adapt
7.
flexible
8. reduce
9.
convenient(-ly=adverb)
10.
integration
11.
attributable
12. imply
B3. Fill in the missing preposition.
1. His lecture is based ………… his current research.
2. She was busily employed ……… writing her dissertation.
3. This printer is compatible ………. most microcomputers.
4. Composites consist ……… two or more different materials.
5. The director responded ……. my letter with a phone call.
B4. Fill in the gaps with the words of the table. There is one extra word.
eventually, oxide layer, magnetic, stainless steel, reaction, ductile, crystalline,
bind-beams, opaque, deficiency, dull, wire, metals, brittle, conduct, copper, alloys
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Most elements are 1)…………………. . There are some common traditional metals such as
aluminium, copper, iron, gold, silver, platinum, etc. There are some rather rare metals such as
gadolinium, osmium, and holmium. Nowadays, many metals we encounter are mixtures or
2)…………………. . Metals are generally recognizable because they are 3)………………. and
have a shine or lustre. If they are 4) …………….. it is usually because the surface has been
oxidised by contact and 5) ……………….. with the air. If we scratch them we remove this
6) ……………………………. and reveal new shiny metal. There are considerable differences
between the strengths and stiffness of metals. Although some metals are brittle we know that
in the contrary many are quite 7) ……………. . For example, we can bend a copper
8) ……………… into any shape. However, we are aware that if we keep bending a metal, it
becomes hard and 9) …………………. so that it 10) ……………….. breaks. Steels are quite
strong and are used as 11) ………………….. in constructing large buildings. Steel is the
traditional of those metals which do not bend easily and carry a lot of weight. Moreover, there
are only three common metals (iron, nickel and cobalt) which are 12) ………………., but there
are some circumstances in which even those do not have this property. Finally, metals,
usually 13) ……………… heat and electricity well, although we know from cooking pans that
copper and iron conduct heat better than stainless steel, which is usually given an aluminium
or copper base to overcome this 14) …………………… . We do not usually make seats of
bare metal, while electrical wiring in our house is usually 15) …………………… while we
never think of using 16) ………………………… wires to conduct electricity.
PART C: GRAMMAR
PAST TENSES:
(notes taken from: “Advanced Grammar in Use” by Martin Hewings, CUP)
A) PRESENT PERFECT SIMPLE/ CONTINUOUS:
1. PPS is used when talking about an action or event of the past without
specifying precisely when (because we either don’t know or it is not important
to mention when). Its use suggests some kind of connection between what
happened in the past and the present time. Often we are interested in the way
that an event which happened in the past affects the situation that exists now.
e.g. I have finished my project work!
We can’t go ahead with the seminar, because very few people have
shown
any interest!
The connection with the present may also indicate that an event happened
recently with a consequence for the present.
e.g. I have found the journal you are looking for! Here it is, so stop
searching!
2. It is also used when we talk about how long an existing situation has lasted
even if we do not give precise length of time.
e.g. Prices of advanced materials have fallen sharply over the past six
months
3. It often shows that an action or event has been repeated a number of times
up to now. E.g. They have been to Chine three times now.
4. PPC is used to talk about a situation or activity that started in the past and
has been in progress for a period until now. (since, for)
e.g. The competition has been running every year since 1980.
5. The situation or activity may still be going on , or it may have just stopped
e.g. We’ve been discussing the proposals for a number of years now.
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6. It also can refer to a recent situation or activity and focuses on its present
results.
e.g. I haven’t seen Ross for a while! – No, he’s been working in Germany
7. It is used with How long questions and to say how long an action has been in
progress.
e.g. How long have you been waiting for me?
I have been trying to do this experiment properly for more than a week!
B) PAST SIMPLE/CONTINUOUS:
1. PS is used to indicate that an action took place at a specific time in the past; it
was completed and does not exist in the present at all.
e.g. Jane left her office two hours ago.
Democritus lived in 400 BC.
I stayed abroad to study for three years. (I am no longer staying there)
2. In news reports events are often introduced with present perfect, and then the
past simple is used to give the details.
e.g. “The US spacecraft Atlantis has returned safely to earth. It landed in
Florida this morning…”
3. PC is used for a temporary situation that existed in the past at or around a
particular time.
e.g. I was studying for the exams last night at 8 o’clock.
4. We often use past simple to talk about a completed past event and the past
continuous to describe the situation that existed at that time. The completed
situation might have interrupted the situation in progress or just occurred at the
time of the situation in progress.
e.g. When I was leaving it started raining.
5. Two past actions or event that went on over the same period of time are in PC.
e.g. Mary was studying at University when she was living in London.
6. We use past simple rather than past continuous when we are talking about
repeated actions or events in the past.
e.g. I went past her house every day when I lived in that area.
C) PAST PERFECT SIMPLE/ CONTINUOUS:
1. PAST P. S. is used when talking about a past situation or activity that took
place before another past situation or before a particular time in the past.
e.g. She has just realized that she had seen him before!
2. Also is used to express what we wanted or hoped to do, but we didn’t.
e.g. I had wanted to travel to new York , but it is not suggested now
because of terrorism.
3. PAST P. C. is used for an activity that happened over a period up to a
particular past time, or until shortly before it.
e.g. She had been suffering from flu during the interview.
4. Indicates duration and continuity of a past action.
e.g. They had been traveling for about 36 hours!
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Exercises:
C1. Narrate a short story of your past using all past tenses presented in this section.
(about 150 words)
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
C2. Put the verbs into the most appropriate past tense:
 Research ………. (show) that cycling can help patients overcome their illness.
 When he ……… (be) 13, his parents ………….. (move) to the United States.
 Just as I …………… (get) into my office the fire alarm …………(go) off.
 I ……………… (study) very hard for this exam! I hope I do well!
 She returned to the country where she ……………….. (live) for years before.
 The athletes were tired because they……….. (train) since early in the
morning
 By the time the seminar started, most of the audience ……………. (leave).
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13
Module 3: Winter Semester 2008-2009, English 3 special
The properties of Materials
Generally
speaking, properties of a substance are the characteristic ways in which a
substance behaves (reacts), which make it what it is and differentiates it from other
substances. It is usual to classify properties as either physical or chemical. Chemical
properties are concerned with the substance’s reactions. Lets provide the example of metals
that have various properties, the most important of which are: a) malleability (e.g. copper,
lead) for the ability to be rolled or hammered and pressed into a different shape when cold
without breaking easily, b) ductility (e.g. copper, tin, aluminium) for the ability to be stretched
into another shape, such as to be drawn into wires, without breaking, c) elasticity (e.g. alloys
of steel) for the ability to be deformed and stretched easily under stress and when the
stimulus of stress is removed to regain the original shape, and d) durability (e.g. chromium,
platinum, gold, aluminium) for the ability to resist corrosion, surface abrasion or penetration.
The following table provides a summary of physical and chemical properties:
PHYSICAL PROPERTIES
1. COLOUR
2. DENSITY
3. PHYSICAL STATE
4. BOILING POINT
5. MELTING POINT
6. CRYSTAL FORM
7. SOLUBILITY
8. HARDNESS
CHEMICAL PROPERTIES
1. a substance being metal or non-metal
2. gives acidic or basic oxides
3. has more than one valency
4. reacts with acids
5. is an oxidising or reducing agent
Similarly, when referring to materials, then properties are material traits expressed in terms of
the measured response to a specific imposed stimulus. Virtually all important properties of
solid materials may be grouped into six different categories: mechanical, electrical, thermal,
magnetic, optical, and deteriorative. For each there is a characteristic type of stimulus
capable of provoking different responses.
More specifically, mechanical properties relate deformation to an applied load or force;
examples include elastic modulus and strength. Modulus of elasticity, strength, ductility,
hardness, and toughness are useful properties to know in order to anticipate the mechanical
behaviour of various materials. They are summarised in table 1-1.Stress is a measure of an
applied mechanical load or force, normalised to take into account cross- sectional area. Two
different stress parameters are defined as engineering stress and true stress. Strain
represents the amount of deformation induced by a stress; both engineering and true strains
are used. Some of the mechanical characteristics of metals can be ascertained by simple
stress-strain tests. There are four test types: tension, compression, torsion and shear.
With sufficiently high stresses, ductile materials undergo a non- reversible yielding, or
permanent plastic deformation. Actually, the phenomenon of yielding occurs at the onset of
plastic or permanent deformation. Resilience is the capacity of a material to absorb energy
during elastic deformation. Ductile materials are normally tougher than brittle ones. Hardness
is a measure to the resistance of localised plastic deformation. In several popular hardnesstesting techniques (Rockwell, Brinell, knoop, and Vickers) a small indenter is forced into the
surface of the material, and an index number is determined on the basis of the size or depth
of the resulting indentation. For many metals, hardness and tensile strength are
approximately proportional to each other. Toughness is important in fracture and materials
failure and thus, it is the energy required for fracture. Measured mechanical properties (as
well as other properties) are not exact and precise quantities, in that there will always be
some scatter for the measured data. Typical material property values are commonly specified
in terms of averages, whereas magnitudes of scatter may be expressed as standard
deviations.
For electrical properties, such as electrical conductivity and dielectric constant, the stimulus
is an electric field. They have two prime sources: electron movements and charge
displacements. The ease with which a material is capable of transmitting an electric current is
expressed in terms of electrical conductivity or electrical resistance, which is counted and
expressed in ohms. On the basis of its conductivity, a solid material may be classified as a
14
metal, a semi-conductor, or an insulator. For most materials, an electric current results
from the motion of free electrons, which are accelerated in response to an applied electric
field. The number of these free electrons depends on the electron energy band structure of
the material. An electron band is just a series of electron states that are closely spaced with
respect to energy, and one such band may exist for each electron sub-shell found in the
isolated atom. By “electron energy band structure” is meant the manner in which the
outermost bands are arranged relative to one another and then filled with electrons. A
distinctive band structure type exists for metals, for semi-conductors, and for insulators. An
electron becomes free by being excited from a filled state in one band. In addition, the
electrical conductivity of semi-conducting materials is particularly sensitive to impurity type
and content, as well as to temperature. The addition of even minute concentrations of some
impurities enhances the conductivity drastically. Also two other electrical phenomena are the
following: a) ferroelectric materials are those that may exhibit polarization spontaneously, that
is, in the absence of any external electric field; b) piezoelectricity is the phenomenon whereby
polarization is induced in a material by the imposition of external forces.
The thermal behaviour of solids can be represented in terms of heat capacity and thermal
conductivity; these properties arise from internal energies that introduce atomic and electronic
movements. Thermal energy can influence mechanical properties and behaviour. Three
thermal properties will be mentioned here: a) thermal expansion, namely the ability of solid
materials to expand when heated and contract when cooled causes fractional change in
length which is proportional to the temperature change; thus, the constant of this
proportionality is the coefficient of thermal expansion; b) heat capability, which is the
quantity of heat required to produce a unit rise in temperature for one mole of a substance; c)
thermal conductivity is the transportation of thermal energy from high- to low-temperature
regions of a material. For solid materials the heat is transported by free electrons and by
vibrational lattice waves or phonons. The high thermal conductivities for relatively pure metals
are due to the large numbers of free electrons, and also the efficiency with which these
electrons transport thermal energy. In the contrary, ceramics and polymers are poor thermal
conductors because free electron concentrations are low. Also, porosity in ceramic materials
result in the reduction of thermal conductivity, therefore, many ceramics that are used for
thermal insulation are porous, such as drinking cups.
Magnetic properties demonstrate the response of a material to the application of a magnetic field.
Many of our modern technological devices rely on magnetism and magnetic materials; these include
electrical power generators, and transformers, electric motors, radio, television, telephones, computers,
and components of sound and video reproduction systems. Iron, some steels, and the naturally
occurring mineral lodestone are well-known examples of materials that exhibit magnetic properties. Not
so familiar, however, is the fact that all substances are influenced to one degree or another by the
presence of a magnetic field.
For optical properties, the stimulus is electromagnetic or light radiation; index of refraction and
reflectivity, as well as absorption and transmission of incident light are representative optical properties.
In other words, optical property is the material’s response to exposure to electromagnetic radiation and
to visible light. More specifically, metals appear opaque as a result of the absorption and the reemission
of light radiation within a thin outer surface layer. Non-metallic materials are either intrinsically
transparent, or opaque.
Finally, deteriorative characteristics indicate the chemical reactivity of materials, which will be
analysed in the handouts of week 3. Generally speaking however, corrosion refers to the phenomenon
of chemical or electrochemical attack on the surface of a metal, while degradation is a type of organic
chemical reaction during which a compound (e.g. A polymer) is gradually converted into a simpler one.
(adjusted from: “Materials science and engineering- an introduction”, by Callister, W.D, 2003;
“Materials science for engineers” by L.H.Van Vlack, 1970)
A. COMPREHENSIVE QUESTIONS
1.
2.
3.
4.
5.
Define the term “properties of substances”.
Define the term “properties of materials”
Into which important properties are solid materials categorized?
Define briefly each of the solid material properties.
What is stress and strain?
15
6. In how many ways can some of the mechanical traits of metals be identified?
7. Provide an example of a hardness-testing process.
8. What is meant by toughness as a material property?
9. On the basis of conductivity how are solid materials classified?
10. How does an electric current result?
11. In which stimuli id the electrical conductivity of semi-conductors particularly
sensitive?
12. Define the phenomena of ferroelectricity and piezoelectricity.
13. What properties of materials can be influenced by thermal energy?
14. Mention and define three thermal properties.
15. Are materials that exhibit magnetic properties important for modern industry?
Illustrate some examples.
PART B: VOCABULARY EXPLORATION
B1. Match the words with their equivalent explanation
1. valence
2. fraction
a) stimulation
3. fracture
c) making of a set of marks from cutting
b) can be pressed, beaten, pulled into fine
strands without being heated
into the edge or surface of sth
4. torsion
5. shear
6. resilience
7. refraction
8. opaque
9. emission
10. ductility
d) not transparent
e) giving off
f) slow destruction caused by chemical reaction
g) can be beaten or pressed into shapes easily
h) twisting
i) become twisted or break under pressure
j) quality of being springy back to original
form after being bent or stretched
k) scraping or wearing away a surface by
rubbing of
l) the bending of a ray or light
m) breaking into pieces/division
n) precise division of a number/ small part
o) unit of the combining power of atoms
11. corrosion
12.
13.
14.
15.
malleable
abrasion
indentation
excitation
B2. Word formation: Fill in the missing words in the table.
VERB
1.
NOUN
ADJECTIVE
reactor
2.
deteriorative
3. isolate
4.
provocation
5.
responding
6. anticipate
7.
Indenter, indentation
8.
9.
10.
failing
deviation
distinctive
B3. Find the opposites of the following words:
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ADVERB
1. density
2. brittle
3. opaque
4. formation
#
#
#
#
6. capable
7. accelerate
8. failure
9. emission
#
#
#
#
B4. Match the terms with their equivalent translation in Greek:
ENGLISH TERMS
1. to retard the ignition
2. internal combustion engine
3. ferroelectric
4. piezoelectric
5. phonon
6. lattice
7. integrated circuit
8. dislocation
9. ductile fracture
10. malleability
11. corrosion in metals
12. degradation in polymers
TRANSLATION IN GREEK
B5. Fill in the gaps with the most appropriate word. There is one extra word.
Bonds, conductivity, transparent, pressure, interatomic, refined,
properties, gem, thermal, crystal, covalent, refraction, reflection, grind
Diamond is a metastable carbon polymorph at room temperature and atmospheric
1)…………... Its 2)…………… structure is a variant of the zinc blend, in which carbon atoms
occupy all positions (both Zn and S). Thus, each carbon 3)…………….to four other carbons,
and those bonds are totally 4)………………. This is appropriately called the diamond cubic
crystal structure, which is also found for other Group IVA elements in the periodic table [e.g.,
germanium, silicon, and gray tin, below 13 ο C (55ο F)].The physical 5) ……………… of
diamond make it an extremely attractive material. It is extremely hard (the hardest known
material) and has a very low electrical 6)………………….; these characteristics are due to its
crystal structure and the strong 7)……………….covalent bonds. Furthermore, it has an
unusually high 8)……………… conductivity for a nonmetallic material, is optically
9)………………. in the visible and infrared regions of the electromagnetic spectrum, and has
a high index of 10)………………. Relatively large diamond single crystals are used as
11)…………. stones. Industrially, diamonds are utilized to 12)…………or cut other softer
materials. Techniques to produce synthetic diamonds have been developed, beginning in the
mid-1950s, which have been 13) ………….. to the degree that today a large proportion of the
industrial quality materials are man-made, in addition to some of those of gem quality.
PART C: GRAMMAR => expressing future
(notes taken from: “Advanced Grammar in Use” by Martin Hewings, CUP)
Simple Future is used to refer to remote future and for actions that are not
planned. E.g. I will go to England in two years.
S.F. is used to express a polite request or invitation.
E.g. Will you open the door please?
Also, it is used to express a last minute decision to do something.
17
E.g. I will answer the phone!!
Future Continuous is used to indicate an action which will be happening at
some moment or period in the future.
E.g. This time tomorrow I will be working in my office.
F.C. is also used for future events that are planned.
E.g. They will be staying with us again this summer.
Be going to + bare infinitive is also used to express planed actions for the
near future, or a prediction for the future that is based on present evidence.
E.g. I am going to get a new computer soon!
There is not a cloud in the sky! It is going to be a really
beautiful day!
Simple Present is used to express programmed actions in relation to a
schedule. E.g. Exams are next week according to Unit outline.
Present Continuous is also used to express personal plans for the near
future. E.g. When are you writing the test? – In the next few minutes.
Future Perfect Simple is used for an action which will have happened and
finished before some other future action happens. Expressions frequently
used with it are: by, by the time.
E.g. I will have finished the lecture by four o’clock.
By the time I finish though you will not have been very tired!
Future Perfect Continuous is used to indicate duration or continuity of an
action up to a time in the future.
E.g. When Easter comes, I will have been living here for two years.
EXERCISE: Make your own example sentences of expressing future in all afore
mentioned ways.
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Module 4: Winter Semester 2008-2009, English 3 special
CHEMICAL BONDING
THE STRUCTURE OF ATOMS:
As you already know, atoms have a nucleus composed by two types of particles, neutrons, which
have no electrical charge and therefore are neutral, and protons, which have a positive electrical
charge. This nucleus is surrounded by electrons which have a negative electrical charge. The number
of surrounding electrons is equal to the number of protons in the nucleus so that the atom is electrically
neutral because it contains equal numbers of electrons and protons. A simplified model of an atom
compares it to the solar system; electrons go round the nucleus in fixed orbits, just as the planets orbit
the sun. These orbits give rise to electron shells. The further away from the nucleus the larger the shell
and the larger the number of electrons which can be accommodated in it. For example: the first shell
can contain 2 electrons, corresponding to the two lightest elements, hydrogen and helium (H and He).
The second shell can contain 8 electrons, giving the elements lithium (Li), beryllium (Be), boron (B),
carbon (C), nitrogen (N), oxygen (O), Fluorine (F), and neon (Ne). The third shell can contain 18
electrons and the elements which correspond to the filling of this shell can be seen on the Periodic table.
The maximum number of electrons which can be accommodated in a shell is 2n2, where n is the
number of the shell, so the fourth shell could contain a maximum of 32 electrons.
However, nature keeps things simple - the first 8 electrons (e-‘s) in the shell are what make an atom
stable. If you look in the periodic table you will see that the right hand column contains what we call the
inert gases. These are gases which do not react with other elements to form compounds. With the
exception of helium, which can only have a maximum of two electrons in its one and only shell, they all
have eight electrons in their outer shell. Atoms which have eight electrons in their outer shell are very
stable and all atoms strive to achieve this state. In many respects the desire to have an outer shell of 8
electrons is sometimes called an octet, which is responsible for chemical bonding. The different types
of bond that exist between atoms are often due to the different ways the atoms decide to redistribute
their electrons to achieve the desired eight.
Finally, there are five main types of bond, and they are very instrumental in determining the properties
of materials, although sometimes their role is minor. We shall therefore describe them and some of their
major characteristics which affect the properties of materials.
METALLIC BONDS:
About eighty of the hundred or so elements are metals. What makes these elements metals is simply
the way the electrons hold the atoms together. Naturally, we call the bonds that hold these atoms
together metallic bonds. Metals are elements which have a tendency to release their electrons. In a
pure metal the electrons are therefore released from the outer electron shell, leaving a unit which has a
net positive charge because there is now no longer the same number of electrons surrounding the atom
as there are protons in the nucleus. We call this unit an ion; because it is positively charged we call it a
cation.
From a variety of experiments it is known that, on average, each atom releases approximately one
electron. A simple model of the metallic solid is therefore of a number of singly charged cations
surrounded by free electrons. One of the fundamentals of physics is that like charges (positive-positive
& negative-negative) repel each other, whereas unlike charges (positive-negative) attract each other. Of
course the cations are positively charged and the electrons are negatively charged which means that
there is an attraction between them. It is this attraction which holds the atoms together. This electrostatic
attraction between the cations and the electrons has certain characteristics, which are important in
determining the properties of metals.
The bond produced is quite strong. We cannot be too precise on this point because there are large
variations. The bond between the atoms in mercury is quite weak, a fact that is demonstrated by the fact
that mercury (Hg) is a liquid at room temperature. When materials are heated the energy goes into
making the atoms vibrate, and eventually this vibration energy is enough to break the bonds and the
material melts. At room temperature the bonds between mercury atoms have been broken. On the other
hand, the bonds in tungsten (W) are very strong. We use tungsten filaments in light bulbs and the
tungsten does not melt! In fact tungsten does not melt until its temperature reaches 3400 oC. The
electrons in a metal are instantaneously moving in all directions at the same time. It is important to
realize that they are free of the atoms or cations, even though they are what is holding the metal
together. We sometimes refer to them as sea of electrons or electron glue. When we put a voltage
across a piece of metal we put a force on the electrons which forces them to travel preferentially in one
direction. We call this electric current. This is simply why metals are electrical conductors.
Metallic bonds have no directionality. This is a really important concept which requires amplification.
Because the electrons act as a sort of glue, the metal atoms can arrange themselves in almost any way
they want to. The bonds do not point in any direction. There are several consequences of this glue
concept of which the two most important are the following: a) the atoms can pack closely; there is
nothing to stop them from getting as close as possible, which is something they want to do. As a
consequence metals are quite heavy or dense; b) the atoms can move over each other and change
19
positions relatively easily. This is the basic reason why metals can be formed by pressing, hammering
etc.
COVALENT BONDS:
While metal atoms share their electrons throughout the piece of metal, there are some materials in
which atoms share electrons with specific nearby atoms in order to achieve the stable octet (8) which
they wish to attain. For example, the carbon atom is element number 6, which means it has six
electrons, two in the first shell and four in the second. These four outer electrons are the valence
electrons. In diamond a carbon atom gets its octet by sharing these four electrons with four neighboring
atoms. Each pair of shared electrons between adjacent atoms constitutes what we call a covalent bond
(co-meaning “together”). Each atom has four bonds each of which contains two electrons 9 electron
pairs). Electrons are all negatively charged and therefore all four electron pairs repel each other. The
bonds are pushed as far away from each other as possible, with the result that there is an angle of
109.5o between them. This is what causes the four surrounding carbon atoms to be situated on the
corners of a tetrahedron with the other atom at the center.
From the above discussion you can see that covalent bonds are directional, namely, they place the
surrounding atoms in fixed positions. As a consequence the atoms in solids which are held together by
covalent bonds cannot stack as closely as they do in metals, and the resulting materials are usually not
as dense. Another result of this directional bonding is that it is difficult for the atoms to move past each
other, and the materials do not deform as easily as do metals. Since there are no free electrons,
materials with covalent bonds do not conduct electricity.
Finally, we must note that covalent bonds are very strong; in fact the strongest bonds known in nature
are covalent. Diamond is well recognized as a very hard, strong material, and the strength of the
covalent bond in graphite is taken advantage of in carbon/graphite fibers. Silicon and germanium also
have four outer electrons, and in the solid have the same atom arrangement (crystal structure) as do the
carbon atoms in a diamond, but the bonds are longer and not as strong as they are in diamond.
Covalent bonds are what hold the two atoms together in a molecule of oxygen (O2) or a molecule of
nitrogen (N2). They are also important in many ceramic materials, and are what hold the carbon atoms
together in long-chain polymer molecules. This is one reason why polymers are tough materials: the
chains are difficult to break because of the very strong covalent bonds between the carbon atoms
forming them.
IONIC BONDS:
Another way of achieving an octet of electrons in the outer electron shell is for atoms to exchange
electrons among themselves. The most common example is that of sodium chloride or common salt
(NaCl). Sodium (element number 11) has just one outer electron, while chlorine (element number 17)
has seven outer electrons. If the chlorine takes one electron from the sodium they then both have an
outer shell of eight electrons. Now the Na has lost an electron so has one more positive charge in the
nucleus than the number of electrons. This atomic entity is an ion (Na+) and, because it is positively
charged, it is called cation. The chlorine has one more electron than the number of positive charges on
the nucleus which produces an anion (Cl-) which is negatively charged. These positive and negative
charges attract each other (electrostatic attraction) and hence produce an ionic bond. In some respects
the bond produced is similar to a metallic bond. The ions can attract each other in any direction. The
electrons are in spherical shells around the atoms and there is therefore no preferred bonding direction.
The ions can therefore pack as closely as possible and they do. Ionic bonds are typically very strong
and are important in many ceramics.
To sum up, the three bond types considered so far (covalent, ionic, metallic) are known as the three
primary bonds. They are the strongest bonds and one or more of them is involved in holding together
the atoms in any useful solid material.
In addition to these three bonds there are some much weaker bonds between atoms and molecules and
these sometimes dictate the properties of a material, especially the strength. After all, a chain is only as
strong as its weakest link. These other bonds, which we call secondary bonds, are often the weak
points in materials.
HYDROGEN BONDS:
This secondary bond holds water molecules together in ice. Water consists of molecules of H 2O. The
molecule is angular (not straight) with the hydrogens making an angle of 105 O with the oxygen atom (the
three atoms form an isosceles triangle). The hydrogen atoms are covalently bonded to the oxygen
atoms but the electrons in the bonds are shifted somewhat towards the oxygen. This situation produces
what we call a polar molecule. Just as a magnet has magnetic poles with the north having an attraction
for the south, a polar molecule has electrical poles, positive and negative, with there being an attraction
between unlike poles in the same way that there is an attraction between positive cations and negative
anions on an ionic bond. This imbalance in charges is a permanent feature of the molecule, namely, it is
like a triangle with a positive charge on two corners and a negative charge on the other. This charge is
much smaller than the single electron charge such as there would be on a chlorine anion or a sodium
cation because the electron is not totally displaced as is the case in an ionic bond. The small charge
results from the fact that the electron favors the oxygen rather than the hydrogen. When two molecules
of water come together at a low temperature the positively charged ends of the molecule are attached
by the negative end of an adjacent molecule with the formation of a bond between them. Just like the
20
ionic bond, the hydrogen bond is the result of electrostatic attraction. However, it is much weaker
because the charges involved are much smaller. This is why solid ice melts at quite a low temperature.
The bonds between the molecules are quite weak. Another difference between the two sorts of
bonding is that ionic bonds hold ions together, while hydrogen bonds hold molecules together.
It has been mentioned that the water molecule contains an angle of 105O, which is not much different
from the angle between the corners of a hexagon (120 o). Therefore, when these water molecules are
joined together by hydrogen bonds to form ice these angles are slightly stretched to 120 o so that the
molecules arrange themselves into hexagons. This arrangement gives the ice crystals hexagon
symmetry and accounts for the shape of snowflakes. Each snowflake is unique and has the form of a
complex six-pointed star. Also, ice is lighter than water, since nearly all liquids become denser when
they freeze and he solid sinks to the bottom; this is not the case with water, which is why ice forms on
the top of a pond rather than sinks to the bottom! The hydrogen bonds are directional bonds because
they point in the direction of the hydrogen atoms in the molecule. This forces the adjacent molecules
into the arrangement of a hexagon with large space in the middle. This is what accounts for the lower
density of ice. In the liquid the molecules can pack more closely than the bonding allows them to in the
solid.
Finally, hydrogen bonds are common between molecules which contain hydrogen. They are often
important bonds between long chain polymer molecules. While they are not as strong as the primary
bonds, they are somewhat stronger than the bonds (van der Waals) which usually exist between
polymer molecules. The introduction of hydrogen bonding is therefore one possible way of strengthening
the polymer.
VAN DER WAALS BONDS:
They are the weakest of all chemical bonds. The only materials which have only van der Waals bonds
are the solid inert gases. They melt at very low temperatures and they cannot be considered useful
materials. Also, van der Waals bonds are more difficult to understand than are hydrogen bonds. They
are also the result of electrostatic attraction between polar molecules, but in this case the polarity of the
molecules is not permanent or fixed in direction as it is in water. It is always changing or fluctuating. For
example, neon is an inert gas with 10 electrons (first shell 2e, second shell 8e). At any one instant there
may be 4 electrons on one side of the atom and 6 on the other. A fraction of a second later the situation
may be reversed. This imbalance in the electron distribution gives rise to a dipole because the centers
of the positive charge in the nucleus and the negative charge of the surrounding electrons do not
coincide. However, the dipole is fluctuating. These fluctuating dipoles somehow change together so that
a bond is formed between the atoms of the molecules. The bond is obviously very weak and is nondirectional Van der Waals bonds are mostly important in polymers and in graphite.
MATERIALS WITH BOTH PRIMARY AND SECONDARY BONDS:
There are many important engineering materials which contain both primary and secondary bonds. For
example graphite contains both covalent and van der Waals bonds; it consists of layers of carbon atoms
held together by strong covalent bonds in a hexagonal chicken-wire arrangement; these layer planes
are held together by weak van der Waals bonds. The weak bonds between the layers allow them to
slide over each other easily, hence the lubricating property of graphite.
Polymers are materials which are based on chains of carbon atoms with strong covalent bonds between
the carbon atoms in the chain, but there are usually weak secondary bonds between adjacent chains, as
is the case with the polyethylene chain. Actually there are many instances where a solid contains two
different bonds but are not mentioned in this section.
(text taken and adjusted from: “Materials in today’s world” by P.A. Thrower,1996)
A. COMPREHENSIVE QUESTIONS:
1. What is chemical bonding? Why is it so important to study it (provide specific
examples)?
2. How many categories of chemical bonding do we have and how are called the
specific types of bonding that are classified under each category?
3. What are the main differences between the two general bond categories?
4. Describe each of the five specific bond types and mention the materials that contain
them.
5. Are there materials that combine different types of chemical bonding? Provide an
example.
PART B: VOCABULARY EXPLORATION
B1. Guess right! Fill in the gaps of the text with the appropriate given word!
sharing, non-directional, charges, distillation, involve, a sea of electrons,
directional, transfer, weak, differences, anions, attraction, hydrogen.
21
Let’s summarize some of the most important …………........ and characteristics of primary
bonds:
a) Ionic bonds …………….. the ……………. of electrons; covalent and metallic bonds
involve the ……………….. of electrons.
b) Covalent bonds are ……………………….; ionic and metallic bonds are
…………………………….
c) Metallic bonds involve attraction between cations and………….; ionic bonds involve
attraction between cations and …………………. Covalent bonds do not involve
electrostatic……………………...
Let’s make some general important points about chemical bonding:
a) Bonds other than covalent are really caused by positive and negative …………………
attracting each other.
b) Only covalent and ………………. bonds are directed.
c) No important engineering material has only hydrogen or van der Waals bond. Such a
material would be too ……………. to be of use.
B2. Translate the following words into Greek?
Inert gases
adjacent
octet
valence
filament
covalent
voltage
angular
bulb
fluctuating
B3. Fill in the gaps with the most appropriate word from the box.
Covalent, perpendicular, non-directional, conductor, crystal structure, plane, directed,
anisotropic, close packing, determines, valence, insulator
To a large extent the bonding 1)……………the way atoms pack together in solids. The atoms
in materials with 2)…………… bonds can pack more closely than those held together with
3)……….. bonds. This means that the easiest to consider are the pure metals (metallic
bonding) and solid inert gases (van der Waals bonding). In these cases the atoms are all the
same size and the bonds are non-directional so that the atoms can stack very close and
efficiently. We call the way they stack 4)……………. We already know that Silicon and
Diamond have their atoms bound together by 5)……….bonds and have a 6) …………..
Graphite has another type of crystal structure. Each carbon atom uses three 7)……….
electrons to form covalent bonds in a 8)……….. while the forth electron is allowed to move
freely through the crystal between the planes. Note that this electron cannot move across the
planes, which gives graphite the property of being able to conduct electricity along its layer
planes but not across them. It is therefore an electrical 9)………… in the planes but an
electrical 10)……….. in the 11)………….. direction. A material which shows different
properties in different directions is called 12)……………..
PART C: GRAMMAR => word formation
(notes taken from: “ English Vocabulary in Use – advanced” , by McCarthy, M. & O’Dell, F., 2002.,CUP.)
1. Prefixes: a) preposition- based prefixes: (over-, under-, up-, cross-),
b) less frequent prefixes: (con/com-, e-, a(d)-, pro-)
2. Suffixes: a) productive suffixes: (-able, -conscious, -esque, -free, -rich, -led,
-minded, -proof, -related, -ridden, -worthy),
b) different word classes: (-ly, -ant, -en)
3. Word-building and word-blending:
a) common well-established word parts: (auto-, bio-, cyber-, de-, -graph-, -gram,
-gress-, -ics, -phon-, -ology, pre-, post-, retro-, techno-, tele-),
b) blends: (heliport= helicopter+airport, smog= smoke+fog, motel= motor+hotel,
Chunnel= Channel+tunnel, guesstimate= guess+estimate,
Docusoap= documentary+soap opera, breathalyser= breath+analyser)
Consolidation: a) Tackle the examples provided in photocopies.
b)Look up a dictionary to find more prefixes, suffixes and word blends.
22
Module 5: Winter Semester 2008-2009, English 3 special
Corrosion and Degradation of Materials
(adjusted from: “Collins dictionary of basic chemistry and science facts”, 2001)
EXPLORATION OF THE TERMS:
Corrosion: It is chemical or electrochemical attack on the surface of a metal. Corrosion that
occurs through an electrochemical reaction is called electrolytic corrosion. Rusting is the
corrosion of iron or steel to form a hydrated iron (III) oxide Fe 2O3.x H2O.Rusting occurs only in
the presence of both water and oxygen. It is an electrochemical process in which different
parts of the iron surface act as electrodes in a cell reaction. At the anode, iron atoms dissolve
as Fe2+ ions: Fe(s)
Fe2+(aq) +2e
At the cathode, hydroxide ions are formed: O2(aq) + 2H2O(1) + 4e 4OH-(aq)
The Fe (OH)2 in solution is oxidised to Fe2O3. Rusting is accelerated by impurities in the iron
and by the presence of acids or other electrolytes in the water.
In other words, corrosion is a process whereby stone or metal is chemically eaten away.
Good examples are the weathering of limestone buildings by rainwater, which contain
dissolved acids, and, as aforementioned, the rusting of iron or steel due to oxidation in the
presence of air and moisture. Corrosion begins at the surface and often a surface layer is
formed that protects the rest of the material, e.g. the oxide coating on aluminium. A protective
layer is not formed in rusting; the rusting process goes through the iron and some steel until it
is all corroded. That is why rust is so damaging and causes great expense. Corrosion can be
prevented by means of sacrificial anodes, paint, and electroplating.
Degradation: It is a type of organic chemical reaction in which a compound is converted into
a simpler compound in stages.
DETERIORATIVE MECHANISMS OF MATERIALS:
(adjusted from:“Materials science and engineering- an introduction”, by Callister, W.D, 2003,look at pp.570-605)
To one degree or another, most materials experience some type of interaction with a large
number of diverse environments. Often, such interactions impair a material’s usefulness as a
result of the deterioration or its mechanical properties (for example ductility and strength),
other physical properties, or appearance. With knowledge of the types of and an
understanding of the mechanisms and causes of corrosion and degradation, it is possible to
take measures to prevent them from occurring. More specifically, deteriorative mechanisms
are different for the three material types. In metals, there is actual material loss either by
dissolution (corrosion) or by the formation of non-metallic scale or film (oxidation).
Ceramic materials are relatively resistant to deterioration, which usually occurs at elevated
temperatures or rather extreme environments; the process is frequently also called corrosion.
For polymers, mechanisms and consequences differ from those for metals and ceramics,
and the term degradation is most frequently used. Polymers may dissolve when exposed to a
liquid solvent, or they may absorb the solvent and swell; also electromagnetic radiation
(primarily ultraviolet) and heat may cause alterations in their molecular structure.
More specifically, metallic corrosion is ordinarily electrochemical, involving both oxidation and
reduction reactions. Oxidation is the loss of the metal atom’s valence electrons; the resulting
metal ions may either go into the corroding solution or from an insoluble compound. During
reduction, these electrons are transferred to at least one other chemical species. The
character of the corrosion environment dictates which of several possible reduction reactions
will occur.
Not all metals oxidise with the same degree of ease, which is demonstrated with a galvanic
couple; when in an electrolyte, one metal (the anode) will corrode, whereas a reduction
reaction will occur at the other metal (the cathode). The magnitude of the electric potential
that is established between anode and cathode is indicative of the driving force for the
corrosion reaction.
A number of metals and alloys passivate, or lose their chemical reactivity, under some
environmental circumstances. This phenomenon is thought to involve the formation of a thin
protective oxide film. Stainless steels and aluminium alloys exhibit this type of behaviour.
Metallic corrosion is sometimes classified into eight different forms: uniform attack, galvanic
corrosion, pitting, intergranular corrosion, selective leaching, erosion-corrosion, and stress
23
corrosion. The measures that may be taken to prevent, or at least reduce, corrosion include
material selection, environmental alteration, the use of inhibitors, design changes, application
of coatings, and cathodic protection. Oxidation of metallic materials by electrochemical action
is also possible in dry, gaseous atmospheres. An oxide film forms on the surface which may
act as a barrier to further oxidation if the volumes of metal and oxide film are similar.
Ceramic materials, being inherently corrosion resistant, are frequently utilised at elevated
temperatures and/or in extremely corrosive environments.
Polymeric materials deteriorate by non-corrosive processes. Upon exposure to liquids, they
may experience degradation by swelling or dissolution. With swelling, solute molecules
actually fit into the molecular structure. Scission, or the severance of molecular chain bonds,
may be included by radiation, chemical reactions or heat. This results in reduction of
molecular weight and deterioration of the physical and chemical properties of the polymer.
Finally, it is important to note that implant materials must be biocompatible with body tissue
and fluids, corrosion resistant, and also mechanically compatible with interfacing replacement
/ body components.
BIOLOGICAL DEGRADATION OF POLYMERS
(taken from: “An introduction to polymer science”, by Elias, H.G., 1997,VCH)
Most polymers cannot degrade naturally by light, oxygen, water, microorganisms, etc.,
because of their carbon chains and the lack of chrolophores. Even cellulose papers degrade
in landfills only very slowly. However, it is possible to produce biologically degradable
polymers but these polymers are unsuitable for long-lived goods. Biodegradable polymers for
short-lived good must lead to degradation products that are ecologically safe. They are thus
usually restricted to medical goods or agricultural materials. During biodegradation the energy
content of plastics is wasted. Such biodegradable synthetic polymers comprise:
Polyglycolide = PGL , Polylactide = PLT, polyε-caprolactone = PCL, and poly3hydroxybutyrate-co-hydroxyvalerate = PHB-HV
A. COMPREHENSIVE QUESTIONS:
1. Why material scientists must be aware of the corrosion and degradation of materials?
2.
Do all materials deteriorate in the same way? Explain in detail the different ways of corrosion.
3. What is oxidation?
4. Do all metals oxidise at the same degree of ease?
5. Which phenomenon is thought to involve the formation of a thin protective oxide film?
6. How metallic corrosion is usually classified?
7. Mention the measures that may be taken to prevent corrosion or degradation
to different material categories.
8. How must implant materials be in order to be applicable?
9. What is biological degradation of polymers?
10. Mention four biodegradable synthetic polymers.
PART B: VOCABULARY EXPLORATION
B1. Find the opposites of the following words:
1. passivate
2. include
3. compatible
4. reduce
5. swell
#
#
#
#
#
activate
exclude
incompatible
Increase, raise
detumesce
B2. Translate into Greek the following words:
1. solute = ………………………………
2. solvent = …………………………….
3. solution = ……………………………
4. limestone = …………………………
5. landfill = ……………………………..
6. intergranular = ……………………..
24
B3. Match the words with their equivalent explanation:
1. weathering
2. impair
3. erosion
a) the act of dividing by cutting or splitting
b) a thin layer covering something
c) Deterioration by the abrasive action of fluids, usually accelerated by the
presence of solid particles of matter in suspension. When deterioration is further
increased by corrosion, the term erosion-corrosion is often used .
4. rusting
5. scission
6. pitting
d) a compound whose molecules are composed of two identical monomers.
e) coarse-grained
f) cause a liquid to percolate/ The process by which soluble materials in
the soil, such as salts, nutrients, pesticide chemicals or contaminants, are
washed into a lower layer of soil or are dissolved and carried away by water.
7. granular
g) the formation of reddish-brown ferric oxides on iron by lowtemperature oxidation in the presence of water
8. leaching
9. coating
10. severance
11. swelling
12. dimer
h) the act of separation or cutting down
i) make worse, less effective or imperfect/ damage
j) abnormal protuberance or localized enlargement.
k) localized Corrosion taking the form of cavities at the surface.
l) The natural processes by which the actions of atmospheric and other
environmental agents result in the physical disintegration and chemical
decomposition of rocks and earth materials.
B4. Fill in the gaps with the most appropriate word from the box:
polymerization, monomer, reactions, distinguish, decrease, mass (2), lower,
In the polymer literature, degradation refers to a ………………(1) of the degree
of……………………(2), an uncontrolled change of constitution of monomeric units, or a
combination of both. Reactions that …………(3) degrees of polymerisation are reverse
polymerisation …………………(4). In analogy to polymerisations one can………………… (5)
four different types:
Chain scissions at random sites along the polymer chains with or without participation of low
molar …………(6) molecules.
Depolymerisation from the chain ends leading to ………………(7) with or without participation
of low molar …………(8) molecules.
B5. Match the following resembling terms with their definitions.
1.
2.
3.
4.
Degradation
Erosion
Wheathering
Corrosion
a)…….. displacement of solids (soil, mud, rock and other particles) usually by the agents of
currents such as, wind, water, or ice by downward or down-slope movement in response to
gravity or by living organisms.
b)…….. is the breaking down of rock and particles through processes where no movement is
involved.
c)………is breaking down of essential properties in a material due to chemical reactions with its
surroundings. In the most common use of the word, this means a loss of an electron of metals reacting
with water and oxygen. Weakening of iron due to oxidation of the iron atoms is a well-known example of
electrochemical ……………. This is commonly known as rust. This type of damage usually affects
metallic materials, and typically produces oxide(s) and/or salt(s) of the original metal. It also includes the
dissolution of ceramic materials and can refer to discoloration and weakening of polymers by the sun’s
ultraviolet light.
d) ………… is to change or to make something change to a simpler chemical form.
25
B6. Word formation: Fill in the missing words in the table:
VERB
1.
NOUN
ADJECTIVE
dissolution
2. accelerate
3.
inhibitor
4.
5.
6. erode
interacting
alteration
erosion
7.
erodent
biodegradable
8. restrict
9.
polymerization
10. apply
PART C: GRAMMAR => Relative sentences
(notes taken from: “Advanced Grammar in Use ” , by Hewings, M., 1999.,CUP.)
1. Relative pronouns: a) people: who/that, whom/who/that, whose
b) animals/things: which/that, whose/of which (formal)
Relative adverbs: a) time: when = (in/on which)*
b) place: where = (in/ at/on/to which)*
c) reason: why = (for which)*
2. a) Defining relative clause: It refers to the preceding noun. It gives essential
information about it and cannot be omitted, as this could obscure the meaning of the main
clause. It cannot be placed between commas: e.g. People are artists? ( too general )
but
People who paint are artists.
b) Non-Defining relative clause: It refers to the preceding noun and gives extra
information about it. Therefore, it can be omitted without cause confusion or changing the
meaning of the main clause, and must be between commas:
e.g. My sister, who is studying medicine, will be 27 next month.
3. Relatives with prepositions*: The proposition is put in front of whom or which
(formal English). However, it can be put at the end of the relative clause, thus whom
becomes who. In this case that (less formal) is more commonly used instead of who/
which. It is usual, though, to omit who/which/that in everyday speech and put the
preposition at the end of the relative clause.
e.g. That’s the man with whom I went to France. (formal)
That’s the man who/that I went to France with. (less formal)
That’s the man I went to France with. (informal)
Consolidation:
1. Study the photocopies provided and do the included exercises.
26
Module 6: Winter Semester 2008-2009, English 3 special
Mathematics – Chemical Formulae
Numerals in Chemistry:
Being involved with science means that one is able to recognise units and to talk
about figures and formulas. Study the following examples and how they are said in
English:
25%
42
83
106
1/2
1/3
2/3
1/4
8/14
10/6
32.4
7oC
7oF
60o
twenty five per cent
four squared
eight cubed
ten to the power of six
a half
one third
two thirds
one quarter
eight fourteenths/ eight over fourteen
ten over six (numerator/denominator)
thirty two point four (decimal number)
seven degrees Celsius or Centigrade
seven degrees Fahrenheit
at an angle of sixty degrees
The four basic processes of arithmetic:
Addition:
55 + 100 = 155
addends sum
Subtraction:
fifty-five plus a hundred
equals a hundred and a fifty
14 - 10 = 4
minuend - subtrahend = difference
Multiplication:
Division:
10 x 5 = 50
Factors(intensifier) product
10 : 5
fourteen minus ten
equals four
ten times five is fifty
or ten fives are fifty
= 2
dividend:divisor/factor=
[quotient=πηλίκο]remainder[υπόλοιπο διαίρεσης]
ten divided by
five equals
two
Rounding off:
Sometimes it is desirable to express fewer digits than the number of digits in a
measurement or a calculated result. This is achieved by rounding off the number to
the desired number of digits:
round 248.32 to one digit : 248.3 , round 0.0259 to two digits: 0.03
Geometric figures:
In organic chemistry, there are many compounds such as cycloalkanes that are
represented by polygons in skeletal drawings. Scientists need to refer to twodimensional or three dimensional shapes:
a square
an oval
a sphere
a cylinder
a rectangle
a triangle
a pyramid
a cube
a cone
an octagon
a pentagon
a hexagon
27
(s)heptagon
Conventions in Chemistry:
1. Two full arrows in opposite directions indicate a reaction that is proceeding in both
directions.
2. Two arrows with half heads facing opposite directions indicate a reaction in equilibrium. A
single arrow with heads on both sides indicates resonance structures, not a reaction.
3. Use common abbreviations in formulas but not in text.
4. Use the italic type for: axis (the y axis), planes (P), functions that describe variables (f(x)).
Reading chemical formulae:
Formulae are important in Chemistry because they provide a concise way to describe
the chemical make- up of a compound. The following equation is written showing the
formulas of the reactants and products separated by an arrow:
CH4 + 2O 2
CO 2 + 2H2O
This equation can be read in three ways:
1. C-H- four plus two-O-two react to give C-O-two plus two-H-two-O
2. Methane reacts with oxygen to produce/ to yield carbon dioxide and water.
3. One mole of methane and two moles of oxygen react to produce one
mole of carbon dioxide and two moles of water.
Translating mathematic terms from English to Greek:
1.function
2.constant
3.variable
4.plane
5.axis
6.equation
7.fraction
8.decimal
9.differential
10.coefficient
11.matrix
12.binary
13.eigenvalue
14.multinomial
15.naught
16.quadratic
17.integral
18.quartile
19.vector
20.tensor
21.component
22.gradient
23.slope
24.decimal
25.coordinates
26.tangent
27.osculation
28.bisector
EXERCISES:
1. Write the following formulae and figures in words. Use compound
names if you like: (C3H8 propane, CO2 carbon dioxide, H2O water, Fe2O3
iron (III) oxide, C2H4 ethylene, CO carbon monoxide)
C3H8 + 5O2
3CO2 + 4H2O
…………………………………………………………………………………………………
4Fe + 3O2
2Fe2 O3
…………………………………………………………………………………………………
C2H4 + 2O2
2CO + 2 H2O
…………………………………………………………………………………………………
Fe2O3 + 3CO
2Fe + 3CO2
…………………………………………………………………………………………………..
2. Write the following figures in words
a)
85.5% of the Greek population consumes antibiotics that have not been prescribed by a doctor
b) Ten amino acids result in more than 3.6 x 106 possible structures
c) X2 =3.6x107
d) X3/2 = 1.5x 108
28
3. Match the terms with their equivalent ones in Greek
1.Vector
differential
operations
2.Divergence of a
vector field
3.Gradient of
vector
a
4.Dyadic product
a) Απόκλιση
διανυσματικού
πεδίου
12. Latent variable
o) διανυσματικές
διαφορικές πράξεις
b) επίπεδη
διεπιφάνεια
c)
Αυθαίρετη
σταθερά
d) κοινό κλάσμα
13. Arbitrary
constant
14. Convex curve
p) Συστήματα
συντεταγμένων
q) Εφαρμοσμένα
μαθηματικά
r) λανθάνουσα
μεταβλητή
s)
εμβαδον
επιφάνειας
t) κυρτή καμπύλη
u) αντιμετάθεση /
συνδυασμός
v) Κλίση ταχύτητας
w)
περιφέρεια
κύκλου
x) Οξεία γωνία
15.Prependicular
bisector
16. Circumference
6. Velocity gradient
7. Plane interface
h) αριθμητικό
κατηγόρημα
i) Σημείο καμπής
j) δυαδικό γινόμενο
8. Acute angle
9. Applied maths
k) μεσοκάθετος
l)κινητό μέρος
19.Inflection point
20. permutation
10. arithmetical
predicate
11.crest
m) κλίση ενός
διανύσματος
n)στέψη
21. Area of a
surface
22.trough
5. Coordinate
systems
17. floating point
18. Vulgar fraction
y)κοίλωμα
4. Translate the following forms of an equation and an angle from Greek to
English and from English to Greek
An equation can be:
Συζυγής=
Γραμμική/
βαθμού=
Διώνυμη=
πρώτου
Τεταρτοβάθμια=
Δευτεροβάθμια=
Εκθετική=
Πεμπτοβάθμια=
Τριτιβάθμια=
Διαφορική=
Ολοκληρωματική=
Ανάστροφη=
Ρητή=
Βοηθιτική=
Ανάγωγη=
Υπερβατική=
Άρρητη=
An angle can be:
Right angle=
Obtuse angle=
Acute angle=
PART C: GRAMMAR => Modal Verbs
29
Re-entrant
angle=
Module 7: Winter Semester 2008-2009, English 3 special
Laboratory Environment and safety issues
Prelab Exercise: You are in you department’s laboratory. Locate the emergency eye-wash
station, safety shower, and fire extinguisher in your laboratory. Check your safety glasses or
goggles for size and transparency. Learn which reactions must be carried out in the hood.
Learn to use your laboratory fire extinguisher; learn how to summon help and how to put out a
clothing fire. Learn first aid procedures for acid and alkali spills on the skin. Learn to tell if
you laboratory hood is working properly. Learn which operations under reduced pressure
require special precautions. Check to see that compressed gas cylinders in your lab are
firmly fastened to benches or walls. Learn the procedures for properly disposing of solid
and liquid waste in your lab.
Important general rules:
Know the particular safety rules of your particular laboratory. Know the locations of
emergency eye washes and safety showers. Never eat, drink, or smoke in the lab. Don’t work
alone. Perform no unauthorised experiments and don’t distract your fellow workers. Eye
protection is extremely important. Safety glasses of some type must be worn at all times.
Contact lenses should not be worn because reagents can get under a lens and cause
damage to the eye before the lens can be removed. It is very difficult to remove a contact lens
from the eye after a chemical splash has occurred.
Ordinary prescription eyeglasses don’t offer adequate protection. Laboratory safety
glasses should be of plastic or tempered glass. If you don’t have such glasses, wear goggles
that afford protection from splashes and objects coming from the side as well as the front. Of
plastic safety glasses are permitted in your lab, they should have side shields.
Dress sensibly in the laboratory. Wear shoes, not sandals or cloth-top sneakers. Confine
long hair and loose clothes. Don’t wear shorts. Don’t use mouth suction to fill a pipette, and
wash your hands before leaving the lab. Don’t use a solvent to remove chemicals from skin.
This will only hasten the absorption of the chemical through the skin.
Working with flammable substances:
Flammable substances are the most common hazard of the organic laboratory; two factors
can make this lab safe: making the scale of the experiments as small as possible and not
using burners. Except for water, almost all of the liquids you will use in the lab will be
flammable. For example, diethyl ether (bp 35oC), the most flammable substance you will
usually use working with in a lab, has an ignition temperature of 160oC, which means that a
hot plate at that temperature will cause it to burn. Bulk solvents should be stored in and
dispensed from safety can. These and other liquids will burn in the presence of the proper
amount of their flammable vapours, oxygen, and a source of ignition (most commonly a flame
or spark). It is usually difficult to remove oxygen from a fire, although it is possible to put out a
fire in a beaker or a flask by simply covering the vessel with a flat object, thus cutting off the
supply of air. The best solution is to pay close attention to sources of ignition – open flames,
sparks, and hot surfaces. Remember the vapours of flammable liquids are always heavier
than air and thus will travel along bench tops and down drain troughs and will remain in
sinks. For this reason all flames within the vicinity of a flammable liquid must be
extinguished. Adequate ventilation is one of the best ways to prevent flammable vapours
from accumulating. Work in an exhaust hood when manipulating large quantities of
flammable liquids. A lab should be equipped with a carbon dioxide or dry chemical fire
extinguisher. When disposing of certain chemicals, be alert for the possibility of spontaneous
combustion. This may occur in oily rags; organic materials exposed to strong oxidizing
agents such as nitric acid, permanganate ion, and peroxides; alkali metals such as sodium;
or very finely divided metals such as zinc dust and platinum catalysts. Fires sometimes start
when these chemicals are left in contact with filter paper.
Working with hazardous chemicals:
If you do not know the properties or a chemical you will be with, it is wise to regard the
chemical as hazardous. The flammability of organic substances poses the most hazards in
the organic laboratory. There is the possibility that storage containers in the lab may
contribute to a fire. Large quantities of organic solvents should not be stored in glass. Use
safety cans. Do not store chemicals on the floor. You will need to contend with the
corrosiveness of many of the reagents you will handle. The danger here is principally to
30
the eyes. Proper eye protection is mandatory and even small-scale experiments can be
hazardous to the eyes. It takes only a single drop of a corrosive reagent to do lasting
damage. Handling concentrated acids and alkalis, dehydrating agents, and oxidizing agents
calls for commonsense care to avoid spills and splashes and to avoid breathing the often
corrosive vapours. Certain organic chemicals present problems with acute toxicity from short
duration exposure and chronic toxicity from long-term or repeated exposure. Exposure can
come about through ingestion, contact with the skin, or, most commonly, inhalation.
Currently, great attention is being focused on chemicals that are teratogens (chemicals that
often have no effect on a pregnant woman but cause abnormalities in a foetus), mutagens
(chemicals causing changes in the structure of the DNA, which can lead to mutations in
offspring), and carcinogens (cancer-causing chemicals).
Waste disposal and cleaning up:
Spilled solids should simply be swept up and placed in the appropriate solid waste container.
This should be done promptly because many solids are hygroscopic and become difficult if
not impossible to sweep up in a short time. This is particularly true of sodium hydroxide and
potassium hydroxide. Spilled acids should be neutralized. Use sodium carbon or, for larger
spills, cement or limestone. Use sodium bisulfate for bases. If the spilled material is very
volatile, clear the area and let it evaporate, provided there is no chance of igniting flammable
vapours. Unless you are sure the spilled liquid is not toxic, wear gloves when using paper
towels or a sponge to remove the liquid.
In the not-too-distant past it was common practice to wash all unwanted liquids from the
organic laboratory down the drain and to place all solid waste in the trash basket. This was
never a wise practice, and now, for environmental reasons, this is no longer allowed by law.
Organic reactions usually employ a solvent and often involve the use of a strong acid, a
strong base, an oxidant, a reductant, or a catalyst. None of these should be washed down
the drain or placed in the wastebasket. We will place the material we finally classify as waste
in containers labelled for non-hazardous solid waste, organic solvents, halogenated organic
solvents, and hazardous wastes of various types.
Non- hazardous waste encompasses such solids as papers, corks, sand, alumina, and
sodium sulphate. These ultimately will end up in a sanitary landfill (the local dump). Any
chemicals that are leached by rainwater from this landfill must not be harmful to the
environment. Because hazardous wastes are often incompatible (oxidants with reductants,
cyanides with acids, ete.), several different containers may be provided in the laboratory for
these, e.g. for phosphorus compounds, heavy metal hydroxides. The kinds of hazardous
waste that can be disposed of have become extremely limited in recent years, and much of
the waste undergoes various kinds of treatment at the disposal site (e.g. neutralization,
incineration, reduction) to put it in a form that can be safely buried in a secure landfill or
flushed to a sewer. There are relatively few places for approved disposal of hazardous waste;
and it now costs more to dispose of most hazardous chemicals than it does to purchase them
new. The law states that a material is not a waste until the laboratory worker declares it a
waste. The area of waste disposal is changing rapidly. Many different laws apply- local, state,
and federal. What may be permissible to wash down the drain or evaporate in the hood in
one jurisdiction may be illegal in another, so before carrying out an experiment check with
your university waste disposal officer.
Gloves:
Be aware that protective gloves in the organic laboratory may not offer much protection. Polyethylene
and latex rubber gloves are very permeable to many organic liquids. An undetected pinhole can mean
long-term contact with reagents. Disposable polyvinyl chloride (PVC) gloves offer reasonable protection
from contact with aqueous solution acids, bases, and dyes, but no one type of glove is useful as
protection against all reagents. It is for this reason that no less than 25 different types of chemically
resistant gloves are available from laboratory supply houses. It is probably safer no to wear gloves
and immediately wash your hands with soap and water after accidental contact with any harmful reagent
or solvent than to wear inappropriate or defective gloves.
Laboratory equipment:
The pictures that follow display some of the most common equipment used in a lab.
(text adjusted from: “Organic experiments”, by Fieser,L & Williamson,K., 1998.)
31
A. TEXT COMPREHENSION EXERCISES:
A1. Read the text first and then discuss the following issues.
1. How well do you know your department lab? With the help of the first paragraph
check whether you can locate and use emergency equipment in your lab.
2. Mention ten of the most important safety rules of your lab.
3. Have you ever worked with flammable substances? What problems did you face and
what should one know to protect themselves when working with them?
4. Make a list with the most important things one should know when working with
hazardous chemicals.
5. Is there a university waste disposal officer in your academic environment? How useful
is the existence of a person like that? How do you usually deal with waste disposal
and lab cleaning up issues?
A2. Say whether the following statements are true or false.
1. Compressed cylinders in a lab are not necessary to be firmly fastened on benches or walls.
2. It is advisable to perform unauthorised experiments.
3. Ordinary prescription glasses are not as protective as goggles.
4. Solvents facilitate the absorption of spilled chemicals through the skin and thus avoid them.
5. Making a small scale experiments and avoiding burners does not make an organic lab
safe.
6. Disposition of certain chemicals can cause spontaneous combustion when they are in contact with
oily rags, oxidising agents and alkali metals, or finely divided metals and filter paper.
7. Safety cans should not be used instead of glass containers for large quantities of organic solvents.
8. Scientists should be aware of the fact that certain organic chemicals cause acute or chronic toxicity
according to the duration of exposure to them.
9. Washing all unwanted liquids from the organic lab down the drain and to place all solid waste in the
trash basket is allowed by law for environmental reasons.
10. There should always be a cautious selection from a variety of gloves used in a lab and still safety is at a risk.
PART B: VOCABULARY EXPLORATION
B1. Find the synonyms and the opposites of the provided words.
Words:
1. ultimately
2. adequate
3. tempered glass
4. manipulate
5. dehydrate
Synonyms:
Words:
1. confine
2. inhalation
3. effective
4. appropriate
5. authorised
Opposites:
B2. Complete the table with the derivatives of the words given.
VERB
1. cork
2.
3.
4. dispose
5.
NOUN
ADJECTIVE
exposure
ventilatory
extinguished
B3. Look at your notes and list as much similar laboratory equipment of the items provided
below:
1. flask =
2. funnel =
3. pipette =
32
4. adapter =
B4. Match the words with their equivalent explanation
a) chemicals causing changes in the structure of the DNA
1. ignition
b) porous/ that can be entered and spreaded to every part by liquids or gas
2. vicinity
3. combustion
c) things done in advance ot prevent danger or problems
4. mutagen
d) making percolate through soil, ore, ash, etc.
5. mutation
e) substances used to cause a chem. reaction or to detect other substances
6.permeable
f) alteration/ new organisms result from such a change
7. precautions
g) in the surrounding district
8. leaching
h) the act of burning completely
9. reagents
i) causing sth to catch fire/ electrical mechanism in a petrol engine
10. incinerate (v.) j) process or burning/ chemical process in which substances combine with
oxygen in air producing heat and light
B5. Do you know how we say the following lab equipment in English? Look at
the pictures and fill in the table:
Greek
English
Greek
English
1.δοχείο ζέσης
10.συγκρατητής
2.φιάλη
11.χωνί
3.λύχνος
12.υδροβολέας
4.δοκιμαστικός σωλήνας
13.σωήνας με βαθμούς για
χημικές αναλύσεις/ προχοϊδα
5.σιφώνιο/σταγονόμετρο
6.ογκομετρικός κύλινδρος
7.σφιγκτήρας
14.ράβδος
15.αντλία
16.συμπυκνωτής,
ψυκτήρας,
συγκεντρωτικός φακός
8.διάφραγμα
9. λαβίδa/τσιμπίδα
17.χοάνη χυτηρίου, χωνευτήρι μετάλ.
18. έμβολο
B6. Fill in the gaps with the most appropriate word from the table, except for one.
Pasteur pipette, burners, Graduated cylinders, syringes, capillary tube, suction, pumps, graduated,
calibration, gauges, plunger, tongs.
1)....................... are calibrated containers used to measure volumes in the range of 2 to 500
mL, depending on the size of the cylinder. Beakers, Erlenmeyer flasks, and conical vials may
also bear 2) ..................... marks.
The 3).................. is comprised of a glass barrel, drawn out at one end to form a tip through
which liquid is pulled with the aid of a latex 4)...............bulb. Quantitative volumetric
measurements are possible with 5)................... pipettes, of which there are a number of styles
and sizes.
Plastic or glass 6).................. are often used to deliver liquids into reaction mixtures. The
needles on them are either fixed or demountable. With the demountable style, needles having
various 7)............... can be affixed to the barrel.
Dispensing 8)................... and automatic pipettes are devices used for accurately and quickly
dispensing liquids. They are commonly used when quantities greater than about 0.5mL must
be dispensed. The 9)................... is made of Teflon, which allows using the unit with corrosive
liquids and organic solvents.
Many different types of heating devices can be used to determine the melting point of a solid.
But most equipment utilizes a 10).....................to contain the sample so that only a small
amount of the sample is required. Such tubes have one sealed end and are commercially
available.
Most chemistry labs are supplied with natural gas for use with various types of 11)..............,
which provide the convenience of a rapid and reasonably inexpensive source of heat.
PART C: GRAMMAR => Conditionals
33
Module 8: Winter Semester 2008-2009, English 3 special
Nuclear Chemistry: Fission, Fusion, Diffusion
(taken from: “Collins dictionary of basic chemistry and science facts”, 2001)
Fusion is another term for melting. The “latent heat” of fusion is that energy needed to turn one mole(a
mole is the mass of an element or compound which contains the same number of atoms or molecules)
of solid into a liquid at its melting point. Fusion is also the coming together, in some nuclear reactions, of
two atoms to form a single atom. This is the opposite of fission and can involve the release of enormous
quantities of energy. Hydrogen bombs are fusion weapons. Fusion is used in an uncontrolled way in the
hydrogen atomic bomb. Effective ways of controlling this have not yet been developed; however, it
promises to be cheap and clean source of power in the future. That is, attempts are being made to use
fusion reactions to generate electricity. Nuclear fusion= the joining of two or more light atomic nuclei to
make a more massive one whose mass is slightly lower than the combined masses of he particles is
made from. This process involves a large transfer of mass to energy. Much of the energy from the sun
and other stars comes from fusion.
Fission is the process of breaking or splitting into parts. If a molecule is split into two or more parts it is
said to undergo fission. This occurs when the large unstable nucleus of an atom splits into two smaller
stable nuclei of similar size, together with other smaller particles such as neutrons. The total mass of the
products is less than that of the starting material. The difference in mass appears as energy. For
example, in nuclear reactions the fission of a large atom, for example uranium into smaller ones, such
as barium and krypton, releases enormous amounts of energy. Thus, the fission of uranium-235
provides the energy in a nuclear power station.
Diffusion is the complete mixing of two or more different substances that comes about from the natural
movements of the particles of the substance. Diffusion occurs rapidly in gases because the molecules in
the gases are moving about randomly at high speed because of the thermal energy they possess.
Diffusion occurs at a faster rate when the temperature is raised. The less dense a gas is, the greater is
its rate of diffusion. Diffusion occurs at a lower rate in liquids and solutions and yet more slowly in solids.
In more detail, diffusion is the way in which fluid particles spread from a source through the space
available. Fore example, if a gas with a distinct odor (such as hydrogen sulphide) is released from a
bottle in the corner of a room it takes very little time before people all over the room will be able to smell
it. According to the principles of diffusion, the process continues unceasingly until the concentration of
the gas molecules is equal in all parts of the room; in other words, until a state of equilibrium has been
reached, and there is no further change, if conditions remain constant. Diffusion in liquids is not as fast
as in gases, because the particles move at slower speed and collide more often. Diffusion is part of the
evidence for kinetic model of matter.
NUCLEAR FUSION
(taken from: “English for Chemistry” by K. Katsaboxaki, 2005)
There is nothing new about nuclear energy. Man didn’t invent it. In fact, without knowing it, man
has been enjoying its benefits since the beginning of recorded time, and before. In its common form,
though, we do not call it nuclear energy. We call it solar energy. It is the energy that comes from the
sun. The energy the earth derives from the sun comes from a type of nuclear reaction called nuclear
fusion, in which two small nuclei combine to form a larger nucleus. The smaller nuclei are “fused”
together, you might say. Fusion processes are, in general, more energetic than fission reactions. The
fusion of one gram of hydrogen in the above reaction yields about five times as much energy as the
fission of an equal mass of uranium-235. So far man has been able to produce only one kind of fusion
reaction, and that has been the explosion of hydrogen bomb.
Much research effort is being made to develop nuclear fusion as a source of useful energy. It has
several advantages over a fission reactor. It presents energy given per quantity of fuel. The isotopes
required for fusion are far more abundant than those needed for fission. Perhaps the biggest advantage
is that fusion yields no radioactive waste, removing both the need for extensive disposal systems and
the danger of accidental release of radiation to the atmosphere.
The main obstacle to overcome before energy can be obtained from fusion is the extremely high
temperature required to start and sustain the reaction. There is no problem on the sun, where
temperatures are more than one million degrees. On earth, no substance known can hold the reactants
at the required temperature. Experiments are now in progress on “magnetic containment”, in which the
fuel is suspended in a magnetic field. The only way now known to reach the necessary temperature in a
hydrogen bomb is to explode a small fission bomb first. New research is investigating “energy pellets”
that react when struck by a laser or ion beam. Even if the technological obstacles to energy from fusion
are overcome, time remains a serious problem. Only the most optimistic predictions foresee an
operating plan in this century.
34
WHY STUDY DIFFUSION IN MATERIALS SCIENCE
(adjusted from: “Materials science and engineering- an introduction”, by Callister, W.D, 2003.)
Materials of all types are often heat treated to improve their properties. The phenomena that
occur during a heat treatment almost always involve atomic diffusion. Often an enhancement of diffusion
rate is desired; on occasion measures are taken to reduce it. Heat-treating temperatures and times, and/
or cooling rates are often predictable using the mathematics of diffusion and appropriate diffusion
constants (a component of a relationship between variables that does not change its value). An example
of this is the “case hardening” of a steel gear. That is, its outer surface layer was selectively hardened
by a high-temperature heat treatment by diffusing excess carbon or nitrogen from the surrounding
atmosphere into its outer surface layer.
Generally, many reactions and processes that are important in the treatment of materials rely on the
transfer of mass either within a specific solid (ordinarily on a microscopic level) or from a liquid, a gas, or
another solid phase. This is necessarily accomplished by diffusion, the phenomenon of material
transport by atomic motion. This phenomenon may be demonstrated with the use of a diffusion
couple, which is formed by joining bars of two different metals together so that there is intimate contact
between the two faces. For example, copper and nickel can be heated for an extended period at an
elevated temperature (but below the melting temperature of both metals), and cooled to room
temperature. Chemical analysis will reveal a condition where pure copper and nickel are at the
extremities of the couple, separated by an alloyed region. Concentrations of both metals vary with
position. This result indicates that copper atoms have migrated or diffused into the nickel, and that nickel
has diffused into copper. This process, whereby atoms of one metal diffuse into another, is termed
inter-diffusion, or impurity diffusion.
Diffusion mechanisms: From an atomic perspective, diffusion is just the stepwise migration of atoms
from lattice site to lattice site. In fact, the atoms in solid materials are in constant motion, rapidly
changing positions. For an atom to make such a move, two conditions must be met: a) there must be an
empty adjacent site, and b) the atom must have sufficient energy to break bonds with its neighbour
atoms and then cause some lattice distortion during the displacement. This energy is vibrational in
nature. At a specific temperature some small fraction of the total number of atoms is capable of diffusive
motion, by virtue of the magnitudes of their vibrational energies. This fraction increases with rising
temperature. Several different models for this atomic motion have been proposed; of these possibilities
two dominate for metallic diffusion:
Vacancy diffusion: Is termed the mechanism which involves the interchange of an atom from a normal
lattice position to an adjacent vacant lattice site, or vacancy. This process necessitates the presence of
vacancies, and the extent to which vacancy diffusion can occur in a function of the number of these
defects that are present; significant concentrations of vacancies may exist in metals at elevated
temperatures. Since diffusing atoms and vacancies exchange positions, the diffusion of atoms in one
direction corresponds to the motion of vacancies in the opposite direction. Both self-diffusion (that
occurs for pure metals during which all atoms exchanging positions are of the same type) and interdiffusion occur by this mechanism; for the latter, the impurity atoms must substitute for host atoms.
Interstitial diffusion: It involves atoms that migrate from an interstitial position to a neighbouring one
that is empty. This mechanism is found for inter-diffusion of impurities such as hydrogen, carbon,
nitrogen, and oxygen, which have atoms that are small enough to fit into the interstitial positions. Host or
substitutional impurity atoms rarely form interstitials and do not normally diffuse via this mechanism. In
most metal alloys, interstitial diffusion occurs much more rapidly than diffusion by the vacancy mode,
since the interstitial atoms are smaller and thus more mobile. Furthermore, there are more empty
interstitial positions than vacancies. Hence, the probability of interstitial atomic movement is greater than
vacancy diffusion.
A. COMPREHENSIVE QUESTIONS:
1.
2.
3.
4.
5.
6.
7.
8.
9.
What is meant by fission reaction?
What is a fusion reaction?
How does a fusion reaction differ from a fission reaction?
What prevents scientists from obtaining energy from fusion?
What is diffusion in general?
Why do we study diffusion in materials science?
What is inter-diffusion or impurity diffusion and what a self-diffusion?
List the conditions needed for an atomic diffusion.
What are vacancy and interstitial diffusion?
35
PART B: VOCABULARY EXPLORATION
B1. Match the words with their equivalent explanation:
1.yield
2.abundant
a)throwing away after use
b) in between/ term for referring to the space between other structures.
In crystallography, it refers to the open spaces within the crystal lattice.
3. disposal
4. obtain
5.suspend
6. lattice
7. interstitial
8. stepwise
9. fraction
10. adjacent
c) gradually
d) A small part or item forming a piece of a whole/The quotient
of two rational numbers.
e) neighboring
f) plentiful/ existing in large quantities
g) net
h) create, make, produce
i) to get something by making an effort/ exist(formal)
j) to float in liquid or air without moving/ to officially delay something
B2.Word formation: Fill in the missing words in the table:
VERB
1.
NOUN
ADJECTIVE
disposal
2. suspend
3.
elevated
4.reveal
5.
fusion
B3. You are provided with the definition; find the term and its synonyms
DEFINITION
TERM
SYNONYMS
A nuclear reaction in which nuclei combine to form more
massive nuclei with the simultaneous release of energy./
The state of being combined into one body.
A nuclear reaction in which a massive nucleus splits into
smaller nuclei with the simultaneous release of energy.
Reproduction of some unicellular organisms by division of
the cell into two more or less equal parts.
the intermingling of molecules in gases and liquids as a
result of random thermal agitation.
B4. Translate into Greek the following terms:
1. fusion
6. suffusion
2. fission
7.effusion =>
3. diffusion
8. transfusion
4. impregnation
9. dissemination
5. infusion
10. divergence
PART C: GRAMMAR => Passive Voice
C1. Turn the following sentences into passive
36
1. We will not advance the problem in this article.
6. Figure 9 is indicating the context of friction model.
………………………………………………………
…………………………………………………………
2. The equation demonstrates two important
7.Researchers had been addressing this problem for years
…………………………………………………………………
8.By next year we will have attempted to do more research
…………………………………………………………………
9. The surface dissipation of energy dissipates friction.
…………………………………………………………………
10. The value depended on the significance of principles
…………………………………………………………………….
parameters.
……………………………………………………………….
3. The professor has expanded the definition.
………………………………………………………
4. Water vapor can modify the ambient
temperature.
………………………………………………………
5.He had avoided the difficulty by identifying the
quantity A
………………………………………………………………
Module 9: Winter Semester 2008-2009, English 3 special
Environmental issues
What is Ecology?
No living thing or group of living things exists in isolation. All organisms both plants and
animals, need energy and materials from the environment in order to survive, and the lives of
all kinds of living species affect the lives of others. Ecology is the study of the relationships
between living species and between them and their environment. As scientific discipline
Ecology is relatively new. Ecologists study species in their natural context but they also carry
out laboratory studies and experiments. Fieldwork involves the collection of information to see
what happens to particular species- such as population numbers, diet, form, size, and
behaviour, and their physical environment- such as the composition of rocks, soil, air, and
water. The data can be used to identify patterns and trends, and some of these can be
tested in the laboratory. It was in 1866 when a German biologist and evolutionist Ernst
Haackel (1834-1919) used the word “oecology” to denote the study of organisms and their
interactions with the world around them. He based it on the Greek word “οίκος” meaning
household and Haackel clearly saw the living world as a community in which each species
had a role to play. The modern spelling of ecology was first used in 1893. Although Ecology is
not primarily about solving environmental issues, ecologists are already proposing ways of
meeting human needs that are sympathetic to the environment, and drawing attention to
ecological implications of just about everything that humans do, but to solve the problems ,
people must want to use this knowledge.
Natural decomposition and recycling
In every ecosystem there is always waste material consisting of dead plant material, animal
waste and droppings and dead animals. Collectively this is called detritus. The larger
animals that are able to tackle this material directly are called detritivores. These organisms
are able to digest quite large pieces of detritus and turn this into their own droppings. This
renders the material more easily digested by smaller decomposers such as fungi and
bacteria, which break it down even further into simple chemicals. Some of the most familiar
detritivores are woodlice, worms, slugs and snails and millipedes.
Bacteria are normally associated with diseases, but they are also important in
decomposition. They survive in moist or wet conditions, because their bacterial cells can
grow quickly, and some grow in anaerobic conditions, where there is little oxygen. Like fungi,
bacteria produce enzymes to digest the waste material so that their cells can absorb it. It has
been estimated that about 90% of all primary production in an ecosystem passes through the
decomposition cycle. This is an important process, since without the carbon dioxide that
decomposition releases, all plant life would die out. Today, modern sewage treatment plants
make use of natural decomposers. More specifically, the sewage is passed over beds of
bacteria and protozoa that break down the organic content of the waste into its constituent
chemicals. These can then be removed from the liquid, leaving the water in a much cleaner
state, free from organic material.
Human Ecology and human impact on the environment
With the development of tools, the use of fire, and increasing communication skills, humans
moved up the trophic pyramid to become hunters and later cultivators. Gradually, the
deliberate cultivation of crops changed everything, enabling human beings to increase the
37
productivity of the land and escape the tyranny of the food chain. This single development
makes humans ecologically different from all other species. It opened up the possibility of a
tremendous population increase and has changed the face of the Earth itself.
Since the industrial revolution of the 18th and 19th centuries, human impact on the
environment has been enormous. The burning of fossil fuels has polluted vast areas and
significantly altered the atmosphere. Industrial technology has brought millions of people from
rural areas into new towns and cities, and advantages in mechanization have dramatically
reduced the number of people needed to work the land. The use of fertilisers and pesticides
had increased agricultural production and fed the growing human population, but they have
had dire effects. The consequences of these rapid changes could not be predicted. Now the
science of ecology has made it possible to assess how human actions affect the
environment, and look for ways to reduce and repair the damage that is being done.
Pest problems
In modern intensive agriculture, crops of a single plant species are often grown over
enormous areas of land. This practice creates a particular problem. Such a concentration of
food allows some pest species, such as the “cabbage white butterfly”, to reproduce on a vast
scale, since food is virtually unlimited. The solution has been to spray the crop with
pesticides. As a result, pest species build up a resistance to the pesticides, human food
crops carry potentially harmful chemicals, and non-biodegradable chemicals gradually
infiltrate the environment. Ecological studies have now led to the development of biological
methods of control.
Wastes
Many complex manufactured chemicals, including plastics and some metals, can not be
broken down by decomposers. They remain in the environment permanently locking away the
natural resources that went to make them. More serious still is the dumping of poisonous
chemicals, and there are many examples of hazardous waste leaking into the environment
and harming both the ecosystem and people. It is believed by many that until such materials
can be disposed of safely, they should not be made.
Polymers and recycling
Most polymers cannot degrade naturally by light, oxygen, water, microorganisms, etc.,
because of their carbon chains and the lack of chrolophores. Even cellulose papers degrade
in landfills only very slowly. However, it is possible to produce biologically degradable
polymers but these polymers are unsuitable for long-lived goods. Biodegradable polymers for
short-lived goods must lead to degradation products that are ecologically safe. They are thus
usually restricted to medical goods or agricultural materials. During biodegradation the energy
content of plastics is wasted. Such biodegradable synthetic polymers comprise:
Polyglycolide = PGL , Polylactide = PLT, polyε-caprolactone = PCL, and poly3hydroxybutyrate-co-hydroxyvalerate = PHB-HV
Plastics can be recycled in three different ways: a) as materials by remelting or reshaping, b)
as raw materials by degradation to monomers or petrochemicals, c) as energy providers by
incineration.
Water pollution
Are you worried about pollution in our rivers, lakes and seas? It is not possible to get
absolutely pure water in nature because it is so good at dissolving things. This is often useful
to us, but also makes it easy to pollute water.
Eutrophication:
Sometimes too many fertilizers are added to the soil. Some fertilizer is washed down
through the soil by rain and it is leached out of the soil. The dissolved fertilizer drains from
the fields into rivers. Tiny plants, called algae, thrive on the fertilizer. They start to cover the
surface of the water. This cuts off light to other living things in the river. When the algae die
bacterial decompose them. The bacteria multiply quickly with so much food. They use up
much of the oxygen dissolved in the water so that fish and other water animals can not get
enough oxygen and soon they die. This chain of events is called eutrophication.
Thermal pollution:
Besides its use as a solvent, water is also used in industry as a coolant. It transfers energy
away from a reaction. This raises the temperature of the water. An example is its use to
38
transfer energy in power stations. The water is not polluted when it is passed into a nearby
river. However, it is warmer than the river water. This can affect the delicate balance of life in
the river. Remember that the aquatic animals rely on oxygen gas dissolved in the water. But
as we know, the higher the temperature, the less soluble a gas becomes on water. So not as
much oxygen dissolves in the warmer water and animals die.
Other waste:
Chemical discharged from factories can also pollute water, although rules are much stricter
now. Finding pesticides in our drinking water is another problem which water companies
have to tackle. Pesticide residues can get into waterways from crop spraying in nearby
fields. Our drinking water is now checked for acceptable levels of pesticides.
Also, oil floats on water and does not dissolve in it. Fuel oil contains sulfur, so when oil is
burnt in industry sulfur dioxide is formed. This combines with water particles in the
atmosphere and falls as rain, which is dilute sulfuric acid. In some countries, such as
Sweden, the soil does not contain enough of the alkalis that are needed to neutralize this
acid. So the fish in Scandinavian lakes and rivers are poisoned by high acid concentration in
the water.
Lead in water:
Lead is a toxic metal, which like other heavy metals tends to accumulate in organs once it
gets inside your body. It is particularly dangerous for children under the age of 6 because it
hinders development of the brain. So no wonder lead water pipes have been banned! Before
we realized just how poisonous lead is, plumbers used lead because it is such malleable
material that it can be bent into shapes easily. Lead pipes in old houses should have been
replaced by modern plastic pipes by now. Lead is not very soluble in water but a little does
dissolve, and that is enough to cause problems. You get more lead ions in your water if water
is of low pH (acidic) or if the water is hot.
Water filters:
More and more people are using filters for their drinking water as an extra safety measure.
The filters contain carbon, impregnated with silver. The silver is an excellent bactericide. A
filter contains only about 0.07% silver. Carbon absorbs organic compounds. Some filters
also include an ion-exchange resin that gets rid of metal ions. However, some calcium ions in
your water will bring health benefits. The best filters absorb: heavy metals, such as lead,
copper, cadmium, chromium, etc., bad smells and tastes, chlorine, most calcium and
magnesium ions (removing about 60%), as well as killing 99% of bacteria.
(text taken from: “Ecology”, by Pollock, S., 1993/ “New chemistry for you” by Lawrie Ryan,2006/
“An introduction to polymer science”, by Elias, H.G., 1997,VCH)
A. COMPREHENSIVE QUESTIONS
1. What is the discipline of Ecology and what its role regarding environmental issues?
2. What is the difference between detritivores and decomposers?
3. Describe the function of modern sewage treatment plants.
4. Describe the gradual development of human impact on the environment.
5. How has the pest problem been created?
6. Why most polymers cannot degrade naturally? Where are mostly biodegradable
polymers used? Mention three ways that plastics can be recycled.
7. Why all lead water pipes must be replaced?
8. Why is lead a dangerous substance for people?
9. What is filters’ composition?
10. What benefits do people get from using water filters?
PART B: VOCABULARY EXPLORATION
B1. Find the synonyms and the opposites of the provided words.
Words:
1. alter
2. assess
3. species
Synonyms:
Words:
1. rural
2. composition
3. hazardous
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Opposites:
4. moist
5. accumulate
4. potential
5. dilute
B2. Complete the table with the derivatives of the words given.
VERB
1.
2.
3. digest
4.
5. incinerate
NOUN
resin
ADJECTIVE
cultivated
Evolutionist, evolution
B3. Match the words with their equivalent explanation
1. thrive on
a) remains
b) caused to be filled in every part with
2. accumulate
another substance/ saturate
c) waste that remains after something has
been destroyed, used or finished
3. residue
4. impregnate
5. pesticides
6. detritus
7. slug (n.)
8. leaching
9. dire (adj.)
10.drain (v.)
11. incineration
d) making percolate through soil, ore, ash, etc.
e) similar to snail but without shell
f) very severe or serious
g) to let a liquid flow away from something
h) the act of burning completely
i) live from
j) chemical substance used to kill insects
12. resin
l) gather
k) transparent sticky substance produced by
some plants and trees , often used for making
paints, glue and plastic
PART C: GRAMMAR => Prepositions
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