English in Chemistry 2
Nguyen Tuyet Phuong - Nguyen Dinh Hiep - Tran Thu Phuong
Lesson 1-1 (Listening)
Review of laboratory glassware
Listen and watch the video clip, then answer the following questions.
1. Which are three basic glassware in laboratory?
2. What are beakers used for?
3. What are the differences between beakers and Erlenmeyer flasks?
4. Which (among the three basic ones) is used to measure a liquid volume fairly accurately?
5. Why test tube rack must be used to keep test tubes?
6. What are test tubes used for?
7. When do you use crucible tongs in laboratory?
8. What is used to take and transfer some powder, solid or crystals?
9. Are you allowed to heat watch glass?
10. Tell something about the basic idea of a filter funnel use?
11. Why must you use a glass rod to stir solution instead of metallic one?
12. Tell a function of pipet.
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English in Chemistry 2
Nguyen Tuyet Phuong - Nguyen Dinh Hiep - Tran Thu Phuong
BASIC CHEMISTRY LAB EQUIPMENT
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English in Chemistry 2
Nguyen Tuyet Phuong - Nguyen Dinh Hiep - Tran Thu Phuong
Lesson 1-2 (Reading)
IUPAC nomenclature of inorganic compounds
In chemical nomenclature, the IUPAC nomenclature of inorganic chemistry is a systematic method
of naming inorganic chemical compounds, as recommended by the International Union of Pure and
Applied Chemistry (IUPAC). It is published in Nomenclature of Inorganic Chemistry. Ideally, every
inorganic compound should have a name from which an unambiguous formula can be determined.
The names "caffeine" and "3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione" both signify the same
chemical. The systematic name encodes the structure and composition of the caffeine molecule in
some detail, and provides an unambiguous reference to this compound, whereas the name
"caffeine" just names it. These advantages make the systematic name far superior to the common
name when absolute clarity and precision are required. However, for the sake of brevity, even
professional chemists will use the non-systematic name almost all of the time, because caffeine is a
well-known common chemical with a unique structure. Similarly, H2O is most often simply
called water in English, though other chemical names do exist.
1. Single atom anions are named with an -ide suffix: for example, H− is hydride.
2. Compounds with a positive ion (cation): The name of the compound is simply the cation's
name (usually the same as the element's), followed by the anion. For example, NaCl
is sodium chloride, and CaF2 is calcium fluoride.
3. Cations which have taken on more than one positive charge are labeled with Roman
numerals in parentheses. For example, Cu+ is copper(I), Cu2+ is copper(II). An older,
deprecated notation is to append -ous or -ic to the root of the Latin name to name ions
with a lesser or greater charge. Under this naming convention, Cu + is cuprous and Cu2+ is
cupric. For naming metal complexes see the page on complex (chemistry).
4. Oxyanions (polyatomic anions containing oxygen) are named with -ite or -ate, for a lesser or
greater quantity of oxygen, respectively. For example, NO2− is nitrite, while NO3− is nitrate.
If four oxyanions are possible, the prefixes hypo- and per- are used: hypochlorite is ClO−,
perchlorate is ClO4−.
5. The prefix bi- is a deprecated way of indicating the presence of a single hydrogen ion, as in
"sodium bicarbonate" (NaHCO3). The modern method specifically names
the hydrogen atom. Thus, NaHCO3 would be pronounced sodium hydrogen carbonate.
Positively charged ions are called cations and negatively charged ions are called anions. The cation
is always named first. Ions can be metals or polyatomic ions. Therefore the name of the metal or
positive polyatomic ion is followed by the name of the non-metal or negative polyatomic ion. The
positive ion retains its element name whereas for a single non-metal anion the ending is changed
to -ide.
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Example: sodium chloride, potassium oxide, or calcium carbonate.
When the metal has more than one possible ionic charge or oxidation number the name
becomes ambiguous. In these cases the oxidation number (the same as the charge) of the metal
ion is represented by a Roman numeral in parentheses immediately following the metal ion name.
For example in uranium(VI) fluoride, the oxidation number of uranium is 6. Another example is the
iron oxides. FeO is iron(II) oxide and Fe2O3 is iron(III) oxide.
An older system used prefixes and suffixes to indicate the oxidation number, according to the
following scheme:
Oxidation state Cations and acids Anions
Lowest
Highest
hypo- -ous
hypo- -ite
-ous
-ite
-ic
-ate
per- -ic
per- -ate
hyper- -ic
hyper- -ate
Thus the four oxyacids of chlorine are called hypochlorous acid (HOCl), chlorous acid (HOClO),
chloric acid (HOClO2) and perchloric acid (HOClO3), and their respective conjugate bases are the
hypochlorite, chlorite, chlorate and perchlorate ions. This system has partially fallen out of use, but
survives in the common names of many chemical compounds: the modern literature contains few
references to "ferric chloride" (instead calling it "iron(III) chloride"), but names like "potassium
permanganate" (instead of "potassium manganate(VII)") and "sulfuric acid" abound.
Naming simple ionic compounds
An ionic compound is named by its cation followed by its anion. See polyatomic ions for a list of
possible ions.
For cations that take on multiple charges, the charge is written using Roman numerals in
parentheses immediately following the element name. For example, Cu(NO3)2 is copper(II) nitrate,
because the charge of two nitrate ions (NO3−) is 2 × (−1) = −2, and since the net charge of the ionic
compound must be zero, the Cu ion has a 2+ charge. This compound is therefore copper(II) nitrate.
In the case of cations with a +4 oxidation state, the only acceptable format for the Roman numeral
4 is IV and not IIII.
The Roman numerals in fact show the oxidation number, but in simple ionic compounds (i.e.,
not metal complexes) this will always equal the ionic charge on the metal.
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List of common ion names
Monatomic anions:
HSO3− hydrogen sulfite (or bisulfite)
Cl− chloride
HCO3− hydrogen carbonate (or bicarbonate)
S2− sulfide
CO32− carbonate
P3− phosphide
PO43− phosphate
Polyatomic ions:
HPO42− hydrogen phosphate
NH4+ ammonium
H2PO4− dihydrogen phosphate
H3O+ hydronium
CrO42− chromate
NO3− nitrate
Cr2O72− dichromate
NO−2 nitrite
BO33− borate
ClO− hypochlorite
AsO43− arsenate
ClO2− chlorite
C2O42− oxalate
ClO3− chlorate
CN− cyanide
ClO4− perchlorate
SCN− thiocyanate
SO32− sulfite
MnO4− permanganate
SO42− sulfate
Naming hydrates
Hydrates are ionic compounds that have absorbed water. They are named as the ionic
compound followed by a numerical prefix and -hydrate. The numerical prefixes used are listed
below (see IUPAC numerical multiplier):
1. mono-
6. hexa-
2. di-
7. hepta-
3. tri-
8. octa-
4. tetra-
9. nona-
5. penta-
10. deca-
For example, CuSO4·5H2O is "copper(II) sulfate pentahydrate".
Naming molecular compounds
Inorganic molecular compounds are named with a prefix (see list above) before each element. The
more electronegative element is written last and with an –ide suffix. For example, H2O (water) can be
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called dihydrogen monoxide. Organic molecules do not follow this rule. In addition, the prefix monois not used with the first element; for example, SO2 is sulfur dioxide, not "monosulfur dioxide".
Sometimes prefixes are shortened when the ending vowel of the prefix "conflicts" with a starting
vowel in the compound. This makes the name easier to pronounce; for example, CO is "carbon
monoxide" (as opposed to "monooxide").
Common exceptions
There are a number of exceptions and special cases that violate the above rules. Sometimes the prefix
is left off of the initial atom: S2O7 is known as sulfur heptoxide, but it should be called disulfur
heptoxide. S2O3 is called sulfur sesquioxide (sesqui- means 1 1⁄2).
The main oxide of phosphorus is called phosphorus pentoxide. It should actually be diphosphorus
pentoxide, but everyone knows that there are two phosphorus atoms (P 2O5) needed in order to
balance the oxidation numbers of the five oxygen atoms. However, people have known for years that
the real form of the molecule is P4O10, not P2O5, yet it is not normally called tetraphosphorus
decaoxide.
In writing formulas, ammonia is NH3 even though nitrogen is more
Likewise, methane is written as CH4 even though carbon is more electronegative.
Read the text and answer the following questions
1.
What does IUPAC mean? What is it used for in chemistry nomenclature?
2.
What does a systematic name encode?
3.
What is advantage of the systematic name?
4.
What is the systematic name of ¨caffeine¨?
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electronegative.
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Nguyen Tuyet Phuong - Nguyen Dinh Hiep - Tran Thu Phuong
5.
Name 3 examples of anion named with an –ide suffix.
6.
How are positively charged ions and negatively charged ions called?
7.
Which order is used to name a compound formed by a metal/positive ion and a nonmetal/negative ion?
8.
How to name a compound whose metal has multiple ionic charges or oxidation numbers?
9.
How is a name of an inorganic molecular compound written?
10. *Provide IUPAC names of following inorganic compounds: NaH, AlCl3, FeBr3, KHCO3, Ca(ClO2)2,
CuO, Zn(NO3)2, Na2Cr2O7, MgSO4.7H2O, CuCl2.6H2O, CO2.
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English in Chemistry 2
Nguyen Tuyet Phuong - Nguyen Dinh Hiep - Tran Thu Phuong
Lesson 2-1 (Listening)
THERMOCHEMICAL CONVERSION OF BIOMASS TO BIOFUEL VIA PYROLYSIS
Listen and complete the text.
The (1)………………………………….. conversion process uses heat and break down biomass into
intermediates, such as (2)…………….. or bio-oil, which can be (3)…………………… into fuel and other
products. One type of thermochemical conversion process is (4)……………………….. a method that
uses heat to (5)………………….. biomass in the absence of oxygen. Here’s one example of a pyrolysis
conversion process.
Wood material such as forest (6)…………………. is a common feedstock for the pyrolysis
process. For best results, (7)……………………… particles are less than two millimeters in size and have
less than 10% (8)……………………. content by weight. The process of pyrolysis (9)…………………. the
biomass at moderate temperatures in the absence of (10)……………….. This produces vapors that are
condensed into liquid bio-oil. (11)……………… is also produced during the pyrolysis process. Cleanup
and stabilization of the bio-oil make it more (12)……………………..for storage, downstream
processing, and end use. (13)…………………… consist of filtering out particles and ash before the biooil is (14)……………………… into a liquid. (15)……………………….. typically involves mild hydro-treating, a
process that uses hydrogen to remove contaminants such as sulfur, (16)…………………., or in the case
of bio-oils, oxygen. Hydro-treating (17)……………………… with high hydrogen pressures in the
presence of catalysts. Oxygen is eliminated mostly as water, along with some (18)………………………..
Other processes to remove oxygen are also being examined. Eliminating oxygen creates a less
reactive bio-oil with lower acidity. The less reactive bio-oil may be (19)……………… longer and is
more suitable for use as a fuel oil. The less (20)………………… bio-oil may be more readily accepted
into current infrastructure, by achieving (21)………………………. compatibility with infrastructure
materials, such as pipes, reactors, and tanks. Mild hydro-treating is usually followed by more
severe (22)……………………….., which is required for the bio-oil to be suitable for use in conventional
petroleum refinery at several insertion points. Then, using technologies employed by existing
refineries today, the bio-oil goes through a (23)…………………………. process, which tailors the
molecule sizes to be in the desired range of gasoline, (24)………………………, or jet fuel. The
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department of energy is supporting development of innovative (25)……………………………. that result
a higher quality bio-oil that lowers subsequent upgrading costs, allows for longer storage, and
improves
commercial viability.
Advancing these
technologies will
help
bring
clean,
(26)……………………….. transportation fuels to market place that can be used in place of petroleum.
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English in Chemistry 2
Nguyen Tuyet Phuong - Nguyen Dinh Hiep - Tran Thu Phuong
Lesson 2-2 (Reading)
THERMOCHEMISTRY
Introduction
Thermochemistry is a branch of chemistry concerned with the heat effects that accompany
chemical reactions. To understand the relationship between heat and chemical and physical
changes, we must start with some basic definitions. We will then explore the concept of heat and
the methods used to measure the transfer of energy across boundaries. Another form of energy
transfer is work, and, in combination with heat, we will define the first law of thermodynamics. At
this point, we will establish the relationship between heats of reaction and changes in internal
energy and enthalpy. We will see that the tabulation of the change of internal energy and change
in enthalpy can be used to calculate, directly or indirectly, energy changes during chemical and
physical changes. Finally, concepts introduced in this chapter will answer a host of practical
questions, such as, why natural gas is a better fuel than coal and why the energy value of fats is
greater than that of carbohydrates and proteins.
Some terminology
Most of the systems we will examine will be small and we will look, particularly, at the transfer of
energy (as heat and work) and matter between the system and its surroundings. The surroundings
are the part of the universe outside the system with which the system interacts. An open system
freely exchanges energy and matter with its surroundings. A closed system can exchange energy,
but not matter, with its surroundings. An isolated system does not interact with its surroundings.
The remainder of this section says more, in a general way, about energy and its relationship to
work. Energy is the capacity to do work. Work is done when a force acts through a distance.
Moving objects do work when they slow down or are stopped. Thus, when one billiard ball strikes
another and sets it in motion, work is done. The energy of moving object is called kinetic energy
(the word kinetic means “motion” in Greek). We can see the relationship between work and
energy by comparing the units for these two quantities.
The bouncing ball suggests something about the nature of energy and work. First, to lift the ball to
the starting position, we have to apply a force through a distance (to overcome the force of
gravity). The work we do is “stored” in the ball as energy. This stored energy has the potential to
do work when released and is therefore called potential energy. Potential energy is energy
resulting from condition, position, or composition; it is an energy associated with forces of
attraction or repulsion between objects.
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All the energy originally invested in the ball as potential energy (by raising it to its initial position)
eventually appears as additional kinetic energy of the atoms and molecules that make up the ball,
the surface and the surrounding air. This kinetic energy associated with random molecular motion
is called thermal energy.
In general, thermal energy is proportional to the temperature of a system, as suggested by the
kinetic theory of gases. The more vigorous the motion of the molecules in the system, the hotter
the sample and the greater is its thermal energy. However, the thermal energy of a system also
depends on the number of particles present, so that a small sample at a high temperature (for
example, a cup of coffee at 75 oC) may have less thermal energy than a larger sample at a lower
temperature (for example, a swimming pool at 30 oC). Thus, temperature and thermal energy must
be carefully distinguished. Equally important, we need to distinguish between energy changes
produced by an action of forces through distances – work – and those involving the trasfer of
thermal energy – heat.
Heat
Heat is energy transferred between a system and its surroundings as a result of a temperature
difference. Energy that passes from a warmer body (with a higher temperature) to a colder body
(with a lower temperature) is transferred as heat. At the molecular level, molecules of the warmer
body, through collisions, lose kinetic energy to those of the colder body. Thermal energy is
transferred – “heat flows” – until the average molecular kinetic energies of the two bodies become
the same, until the temperatures become equal. Heat, like work, describes energy in transit
between a system and its surroundings.
Not only can heat transfer cause a change in temperature but, in some instances, it can also
change a state of matter. For example, when a solid is heated, the molecules, atoms, or ions of the
solid move with greater vigor and eventually break free from their neighbors by overcoming the
attractive forces between them. Energy is required to overcome these attractive forces. During the
process of melting, the temperature remains constant as a thermal energy transfer (heat) is used
to overcome the forces holding the solid together. A process occuring at a constant temperature is
said to be isothermal. Once a solid has melted completely, any further heat flow will raise the
temperature of the resulting liquid.
Although we commonly use expressions like “heat is lost”, “heat is gained”, “heat flows”, and “the
system loses heat to the surroundings”, you should not take these statements to mean that a
system contains heat. It does not. The energy content of a system is a quantity called the internal
energy. Heat is simply a forming which quantity of energy may be transferred across a boundary
between a system and its surroundings.
It is reasonable to expect that the quantity of heat, q, required to change the temperature of a
substance depends on
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
How much the temperature is to be changed

The quantity of substance

The nature of the substance (type of atoms or molecules)
Historically, the quantity of heat required to change the temperature of one gram of water by one
degree Celcius has been called the calorie (cal). The calorie is a small unit of energy, and the unit
kilocalorie (kcal) has also been widely used. The SI unit for heat is simply the basic SI energy unit,
the joule (J).
Heat of reaction and calorimetry
Another type of energy that contributes to the internal energy of a system is chemical energy. This
energy associated with chemical bonds and intermolecular attractions. If we think of a chemical
reaction as a process in which some chemical bonds are broken and others are formed, then, in
general, we expect the chemical energy of a system to change as a result of a reaction.
Furthermore, we may expect some of this energy change to appear as heat. A heat of reaction,
qrxn, is the quantity of heat exchanged between a system and its surroundings when a chemical
reaction occurs within the system at constant temperature. One of the most common reactions
studied is the combustion reaction. This is such a common reaction that we often refer to the heat
of combustion when describing the heat released by a combustion reaction.
If a reaction occurs in an isolated system, that is, one that exchanges no matter or energy with its
surroundings, the reaction produces a change in the thermal energy of the system – the
temperature either increases or decreases. Imagine that the previously isolated system is allowed
to interact with its surroundings. The heat of reaction is the quantity of heat exchanged between
the system and its surroundings as the system is restored to its initial temperature. In actual
practice, we do not physically restore the system to its initial temperature. Instead, we calculate
the quantity of heat that would be exchange in this restoration. To do this, a probe (thermometer)
is placed within the system to record the temperature change produced by the reaction. Then, we
use the temperature change and other system data to calculate the heat of reaction that would
have occurred at constant temperature.
Two widely used terms related to heats of reaction are exothermic and endothermic reactions. An
exothermic reaction is one that produces a temperature increase in an isolated system or, in nonisolated system, gives off heat to the surroundings. For the exothermic reaction, the heat of
reaction is a negative quantity (qrxn< 0). In an endothermic reaction, the corresponding situation is
a temperature decrease in an isolated system or a gain of heat from the surroundings by a nonisolated system. In this case, the heat of reaction is a positive quantity (q rxn>0). Heats of reaction
are experimentally determined in a calorimeter, a device for measuring quantities of heat. Two
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types of calorimeters, which are called bomb calorimeter and “coffee-cup” one, are treated as
isolated system.
The First Law of Thermodynamics
The absorption or evolution of heat and the performance of work require changes in the energy of
a system and its surroundings. When considering the energy of a system, we use the concept of
internal energy and how heat and work are related to it.
Internal energy, U, is the total energy (both kinetic and potential) in a system, including
translational kinetic energy of molecules, the energy associated with molecular rotations and
vibrations, the energy stored in chemical bonds and intermolecular attractions, and the energy
associated with electrons in atoms. Internal energy also includes energy associated with the
interactions of protons and neutrons in atomic nuclei, although this component is unchanged in
chemical reactions. A system contains only internal energy. A system does not contain energy in
the form of heat or work. Heat and work are the means by which a system exchanges energy with
its surroundings. Heat and work exist only during a change in the system. The relationship between
heat (q), work (w), and changes in internal energy ( U) is dictated by the law of conservation of
energy, expressed in the form known as the first law of thermodynamics.
U= q + w
An isolated system is unable to exchange either heat or work with its surroundings, so that
Uisolated system = 0, and we can say
The energy of an isolated system is constant.
In using the aforementioned equation we must keep these important points in mind.

Any energy entering the system carries a positive sign. Thus, if heat is absorbed by the
system, q > 0. If work is done on the system, w > 0

Any energy leaving the system carries a negative sign. Thus, if heat is given off by the
system, q < 0. If work is done by the system, w < 0

In general, the internal energy of a system changes as a result of energy entering or leaving
the system as heat and/ or work. If, on balance, more energy enters the system than leaves,
U is positive. If more energy leaves than enters, U is negative.

A consequence of Uisolated
conserved.
system
= 0 is that Usystem= -Usurroundings,, that is, energy is
Enthalpy (H) and Internal Energy (U) changes in a Chemical Reaction
We have noted that the heat of reaction at constant pressure, H, and the heat of reaction at
constant volume, u, are related by the expression
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u= H -P  V
(a)
The last term in this expression is the energy associated with the change in volume of the system
under a constant external pressure. To assess just how significant pressure-volume work is,
consider the following reaction.
2 CO(g) + O2(g)  2 CO2(g)
If the heat of this reaction is measured under constant-pressure conditions at a constant
temperature of 298 K, we get – 566.0 KJ. To evaluate the pressure-volume work, we begin by
writing
P  V = P(Vf– Vi)
Then we can use the ideal gas equation to write this alternative expression.
P  V= RT (nf – ni)
Here, nf is the number of moles of gas in the products (2 mol CO2) and ni is the number of moles of
gas in the reactants ( 2 mol CO + 1 mol O2). Thus,
P  V =0.0083145 kJ mol-1K-1 x 298 K x [ 2 – ( 2 + 1 ) ]mol = -2.5kJ
The change in internal energy is
u
= H -P  V
= -566.0 KJ – ( -2.5 kJ )
= - 563.5 kJ
This calculation shows that the PV term is quite small compared to H and that u and H are
almost the same. An additional interesting fact here is that the volume of the system decreases as
a consequence of the work done on the system by the surroundings.
In the combustion of sucrose at a fixed temperature, the heat of combustion turns out to be the
same, whether at constant volume (qv) or constant pressure (qp). Only heat is transferred between
the reaction mixture and the surroundings; no pressure – volume work is done. This is because the
volume of a system is almost entirely determined by the volume of gas 12 mol O 2 (g) occupies the
same volume as 12 mol CO2 (g). There is no change in volume in the combustion of sucrose: qp= qv.
Thus, the result of the example can be represented as
C12H22O11 (s) + 12O2 (g)  12CO2 (g) + 11H2O (l) H= -5.65 X103kJ (1)
That is, 1 mol C12H22O11 (s) reacts with 12 mol O2 (g) to produce 12 mol CO2 (g), 11 mol H2O (1), and
5.65 x 103 kJ of evolved heat. Strictly speaking, the unit for H should be kilojoules per mole,
meaning per mole of reaction. “One mole of reaction” relates to the amounts of reactants and
products in the equation as written. Thus, reaction (1) involves 1 molC12H22O11 (s), 12 mol O2 (g), 12
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mol CO2 (g), 11 mol H2O (1), and -5.65 x 103 kJ of enthalpy change per mol reaction. The mol-1 part
of the unit of H is often dropped, but there are times we need to carry it to achieve the proper
cancellation of units.
In summary, in most reactions, the heat of reaction we measure is H. In some reactions, notably
combustion reactions, we measure u (that is, qv). In reaction (1), u = H, but this is not always
the case. Where it is not, a value of H can be obtained from u by the method illustrated in the
discussion of expression (a), but even in those cases, H and u will be nearly equal. In this text, all
heats of reaction are treated as H values unless there is an indication to the contrary.
You may be wondering why the term H is used instead of u, q, and w. It’s mainly a matter of
convenience. Think of an analogous situation from daily life – buying gasoline at a gas station. The
gasoline price posted on the pump is actually the sum of a base price and various taxes that must
be paid to different levels of government. This breakdown is important to the accountants who
must determine how much tax is to be paid to which agencies. To the consumer, however, it’s
easier to be given just the total cost per gallon or liter. After all, this determines what he or she
must pay. In thermochemistry, our chief interest is generally in heats of reaction, not pressurevolume work. And because most reactions are carried out under atmospheric pressure, it’s helpful
to have a function of state, enthalpy, H, whose change is exactly equal to something we can
measure: qp.
Answer the following questions.
1. What is the subject of thermochemistry?
2. Name the types of energy transfer mentioned in the reading passage?
3. How to determine energy variations during chemical and physical changes?
4. According to the reading passage, is it true that coal is a better fuel than natural gas?
5. According to the reading passage, what does the term surroundings mean?
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6. What kind of system that able to interact with its surroundings without restraint?
7. What can’t a closed system exchanged with its surroundings?
8. Can an isolated system exchange matter with its surroundings?
9. According to the reading passage, what does energy mean?
10. In what case that work is considered to be done?
11. What can we say when one billiard balls strikes another and sets it in motion?
12. Define a way to give a ball potential energy?
13. According to the reading passage, what is the terminology for the energy of moving objects?
14. What is potential energy associated with?
15. What is thermal energy?
16. What is the relationship between thermal energy and the temperature of a system?
17. On what parameters does the thermal energy of a system depend?
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18. Why may a cup of coffee at 71oC have less thermal energy than a swimming pool at 32oC?
19. What is the change in term of thermal energy of a system when the motion of the molecules in
the system?
20. What are the differences between work and heat?
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Lesson 3-1 (Listening)
HOW TO SPEED UP CHEMICAL REACTIONS?
Listen and watch the video clip, then answer the following questions.
1. What does the video clip describe about?
2. According to the video clip, to which are chemical reactions matched up with?
3. Which problem does Harriet need to solve?
4. What does she think back?
5. Why did Harriet and Harold sprint directly one to another?
6. Was it a small collision? Why?
7. What did the collision of Harriet and Harold result to?
8. How many characteristics must the collisions have? What are they?
9. What are the two missions of Harriet and the teacher?
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10. Tell the first way the teacher proposed?
11. How can the chemist explain the case related to the first way?
12. What did the teacher propose for the second and third ways?
13. What is the third way analogous to in chemical reactions?
14. How does Harriet increase the total area of particles?
15. What is a matchmaker compared in chemical reactions?
16. What are the functions of chemical catalysts?
17. To sum up, which process must be considered if a chemist wants to make chemical reactions
occur?
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English in Chemistry 2
Nguyen Tuyet Phuong - Nguyen Dinh Hiep - Tran Thu Phuong
Lesson 3-2a (Reading)
Why Do Some Batteries Last Longer When Stored in a Refrigerator?
The Chemical Basics
The conversion of chemical energy of a cell/battery into electrical energy is known as the process
of discharge. All batteries have characteristics that lead to a slow loss of charge over time (known
as battery self-discharge). Additionally, some battery components can deteriorate over time (such
as occurs with the corrosion of zinc in zinc-carbon batteries) or volatilize (such as occurs with the
loss of water through evaporation). As any of the reactions are characterized by a reaction rate,
then the rate constant for the reaction can exhibit a temperature dependence. If the reaction
mechanism involves a single rate-determining step, then the rate constant for that elementary
step will behave according to the Arrhenius law. This law gives a quantitative expression to relate
the increase in a reaction rate with higher temperature. In general, the higher the storage
temperature, the worse the capacity retention. Thus, for some batteries, self-discharge and
deterioration reactions can be slowed considerably by storing the battery at low temperature
when not in use. Nickel metal hydride (NiMH) batteries have a self-discharge rate of only 0.8 %/day
at 20 °C but a self-discharge rate of 6 %/day at 45 °C. The shelf-life of primary (nonrechargeable)
batteries such as the zinc-carbon or alkaline-manganese systems can be significantly extended by
storage at lower temperatures.
The Chemical Details
In 1887 the Swedish chemist Svante Arrhenius suggested that before a chemical reaction could
occur, there must be some minimum kinetic energy possessed jointly by the molecules undergoing
collision. If (two) molecules collide with less than this critical amount of energy, they will recoil
without undergoing chemical change. If this added potential energy were greater than some
critical amount known as the "activation energy (Ea)", then reactants proceed to products. Initially,
Arrhenius empirically derived the temperature dependence of rate constants.
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His relationship of the rate constant k with temperature T in Kelvin involved a constant A known as
the pre-exponential factor and the activation energy Ea:
k = Ae -Ea/RT
Ink = lnA - Ea/RT.
Read the text and answer the following questions
1. What could cause the process of discharge of a cell/battery?
2. Which law will the rate constant for the elementary step behave according to if the
reaction mechanism involves a single rate-determining step?
3. What does that law express?
4. What did Arrhenius’ suggest explaining the process of discharge of a cell/battery?
5. Regarding the text, what is an advice for using some cells/batteries?
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Lesson 3-2b (Reading)
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Read the text and answer the following questions
1. Why are enzymes exceedingly attractive to chemical companies?
2. What is a disadvantage of most enzymes?
3. What are extremozymes?
4. Describe a process of cloning the DNA from a mix of extremophiles?
5. Which bacterium is commonly used to express the gene (DNA fragments) into? Why?
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English in Chemistry 2
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Lesson 4-1 (Listening)
WHAT IS CHEMICAL EQUILIBRIUM
Listen and complete the paragraphs
Say two people are walking down the street, and they bump into each other. They’ll just shake it
off and walk on. Sometimes that happens with (1)…………………………… too. They just bounce off
each other, and that’s that. But what if two people were to (2)…………………………… each other, and
during that (3)……………………., one person’s arm got severed and reattached to the other person’s
face? Now that sounds really weird, but it’s similar to one of the many ways that molecules can
(4)…………………… with each other.
Two molecules can join and become one. One can (5)……………………….… and become two.
Molecules can switch parts. All these changes are (6)………..………………….…, and we can see them
happening around us. For example, when firewords explode, or iron rusts, or milk goes bad, or
people are born, grow old, die, and then (7)………………………... But chemical reactions don’t just
happen willy nilly! Everything has to be right. First, the molecules have to hit each other in the right
(8)……………………..…. And second, they have to hit each other hard enough, in other words, with
enough (9)…………………. Now you’re probably thinking that a reaction just happens in one direction
and that’s it. Sometimes that’s true. For example, things can’t unburn or (10)……………………..… But
most reactions can happen in both directions, (11)……………………..…………..……. There’s no reason
that our face-arm guy can’t bump into armless girl, reattaching that arm back to its original socket.
Now let’s zoom out a bit. Now let’s say that you’ve got a thousand people on the street, and all of
them start with their limbs normally (12)……………………. At the beginning, every collision is a chance
for Person A to (13)…………………………. an arm to Person B’s face. And so at the beginning, more
and more people end up with arms attached to their faces or arms missing. But as the number of
people with arm-faces and (14)……………………………… grows, collisions between those people
become more likely. And when they bump into each other, guess what? Normal-appendage people
are (15)………………….….. Now the number of limb transfers per second forward will
(16)………………….………..…. and then fall, and the number of limb transfers per second backward will
(17)………………….……………. and then rise. Eventually they’ll meet, they’ll be the same. And when
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that happens, the number of people in each state stops (18)……………………, even though people are
still bumping into each other and exchanging limbs. Now how many people do you think there are
in each state? Half and half, right? No, well, maybe. It depends. It could be 50/50, but it could be
(19)…………………… or 15/85 or anything. We chemists have to get our little, gloved hands dirty – ah,
well, we’re in a lab so not really dirty- to figure out what the actual (20)……………….……..… of
molecules is. Even though each of limb transfers is a pretty dramatic event for the people involved,
if we zoom out, we see population numbers that don’t change. We call this nirvana
(21)………………………, and it doesn’t just happen with chemical (22)……………………. Things like gene
pools and highway traffic show the same pattern. It looks pretty still from 30,000 feet, but there is
lots of crazy stuff happening on the ground, you just need to zoom in to see it.
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Lesson 4-2 (Reading)
Altering equilibrium condition: Le Châtelier’s principle
At times, we want only to make qualitative statements about a reversible reaction: the direction of
a net change, whether the amount of a substance will have increased or decreased when
equilibrium is reached, and so on. Also, we may not have the data needed for a quantitative
calculation. In these cases, we can use a statement attributed to the French chemist Henri Le
Châtelier (1884). Le Châtelier’s principle is hard to state unambiguously, but its essential meaning
is stated here:
When an equilibrium system is subjected to a change in temperature, pressure, or concentration of
a reacting species, the system responds by attaining a new equilibrium that partially offsets the
impact of the change.
As we will see in the examples that follow, it is generally not difficult to predict the outcome of
changing one or more variables in a system at equilibrium.
Effect of Changing the Amounts of Reacting Species on Equilibrium
Let’s return to reaction
Suppose we start with certain equilibrium amounts of SO2, O2 and SO3, as suggested by Figure a.
Now let's create a disturbance in the equilibrium mixture by forcing an additional 1.00 mol SO3 into
the 10.0 L flask (Figure b). How will the amounts of the reacting species change to re-establish
equilibrium?
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According to Le Châtelier’s principle, if
the system is to partially offset an action
that
increases
the
equilibrium
concentration of one of the reacting
species, it must do so by favoring the
reaction in which that species is
consumed. In this case, this is the
reverse reaction-conversion of some of
the added SO3 to SO2 and O2. In the new equilibrium, there are greater amounts of all the
substances than in the original equilibrium, but the additional amount of SO 3 is less than the 1.00
mol that was added.
Another way to look at the matter is to evaluate the reaction quotient immediately after adding
the SO3.
Adding any quantity of SO3 to a constant-volume equilibrium mixture makes Qc larger than Kc. Anet
change occurs in the direction that reduces [SO3], that is, to the left, or in the reverse direction.
Notice that reaction in the reverse direction increases [SO2] and [O2], further decreasing, the value
of Qc.
Effect of Changes in Pressure or Volume on Equilibrium
There are three ways to change the pressure of a constant-temperature equilibrium mixture.
1. Add or remove a gaseous reactant or product. The effect of these actions on the equilibrium
condition is simply that caused by adding or removing a reaction component, as described
previously.
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2. Add an inert gas to the constant-volume reaction mixture. This has the effect of increasing the
total pressure, but the partial pressures of the reacting species are all unchanged. An inert gas
added to a constant-volume equilibrium mixture has no effect on the equilibrium condition.
3. Change the pressure by changing the volume of the system. Decreasing the volume of the
system increases the pressure, and increasing the system volume decreases the pressure. Thus, the
effect of this type of pressure change is simply that of a volume change.
Effect of Temperature on Equilibrium
Raising the temperature of an equilibrium mixture shifts the equilibrium condition in the direction
of the endothermic reaction. Lowering the temperature causes a shift in the direction of the
exothermic reaction.
Effect of a Catalyst on Equilibrium
Adding a catalyst to a reaction mixture speeds up both the forward and reverse reactions.
Equilibrium is achieved more rapidly, but the equilibrium amounts are unchanged by the catalyst.
We now have two thoughts about a catalyst to reconcile:
- A catalyst changes the mechanism of a reaction to one with a lower activation energy.
- A catalyst has no effect on the condition of equilibrium in a reversible reaction.
Answer the following questions.
1. Where is Henri Le Châtelier from?
2. What is Henri Le Châtelier’s occupation?
3. What could happen when an equilibrium system is subjected to a change according to Le
Châtelier’s principle?
4. According to Le Châtelier’s principle, what would a system do in order to partially neutralize an
action that increases the equilibrium concentration of one of the reacting species?
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5. How many moles of SO2 are there in the flask when the system reaches an equilibrium after the
adding of 1.00 mole of SO3?
6. How many approaches are there to influence the pressure of a constant-temperature
equilibrium mixture? What are they?
7. Is it true that the pressure of a constant-temperature equilibrium mixture remains unchanged
after adding or removing a gaseous product?
8. How about the variation in partial pressures of the reacting species after adding of an inert gas
to a constant-volume reaction mixture?
9. Is it correct that adding an inert gas to a constant-volume equilibrium mixture has an effect on
the equilibrium condition?
10. How would the pressure of a system be when its volume is reduced?
11. In an exothermic reaction, what would happen to the system when lowering the temperature?
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Lesson 5-1 (Listening)
WHAT IS THE BRØNSTED – LOWRY THEORY
Listen and watch the video clip, then answer the following questions.
1. What is the Arrhenius theory of acids and bases?
2. How can we test for an acid solution? How does colour change?
3. What happens when hydrogen chloride dissolves in water? Write down the chemical reaction.
4. What happens to the proton (H+)?
5. What is another name of hydronium ion (H3O+)?
6. According to Brønsted-Lowry, hydrogen chloride and water are acids or bases? Why?
7. Why does ammonia (NH3) act as a base even though it does not release hydroxide ion?
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8. Write down the chemical reaction when ammonia dissolves in water. Which substance is acting
as an acid? Which is acting as a base? Why?
9. Does a base according to Brønsted-Lowry theory need to turn red litmus paper to blue?
10. What is the only requirement for a Brønsted-Lowry base/acid?
11. Based on Brønsted-Lowry theory, water acts as a base or an acid?
12. How do we call subtances that cac act as either an acid or a base?
13. In conclusion, according to the Brønsted-Lowry theory, an acid is a sunstance that associates to
(13)………………………..….. or (14)…………………..… protons, a Brønsted-Lowry bases is a substance
that (15)……………………….. protons. Therefore, an acid-base reaction according to this theory
involves the (16)…………………………. of a proton.
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Lesson 5-2 (Reading)
Why Does Disappearing Ink Disappear
Disappearing ink or invisible ink - chances are, you've been fascinated by the gradual fading
of color when a message written with seemingly standard ink dissipates right before your
eyes. Why should a chemist not be fooled by the disappearing ink in a magician's bag of
tricks?
The Chemical Basics
Whether for a class demonstration, a practical joke, or perhaps a clandestine activity,
disappearing ink is a fascinating substance. What is the secret to its action? One
formulation of disappearing ink contains a common acid-base indicator, that is, a substance
that by its color shows the acid or basic nature of a solution. One acid-base indicator that
shifts from a colorless hue under acidic conditions to a deep blue color in alkaline solutions
is thymolphthalein. If the indicator starts off in a basic solution, perhaps containing sodium
hydroxide, the typical blue color of an ink is perceived. How does the ink color disappear?
This behavior is dependent upon the contact of the ink with air. Over time, carbon dioxide
in the air combines with the sodium hydroxide in the ink solution to form a less basic
substance, sodium carbonate. The carbon dioxide also combines with water in the ink to
form carbonic acid. The indicator solution responds to the production of acid and returns to
its colorless acid form. A white residue (sodium carbonate) remains as the ink dries.
The Chemical Details
Thymolphthalein (Fig. 6.2.1) (also known as 2',2"-dimethyl-5,5-diisopropylphenolphthalein)
is an acid-base indicator that is colorless in its acidic form and deep blue in its basic form.
The equilibrium between the acidic and basic forms of the indicator may be represented as:
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The acidic form of the indicator (HIn) retains the hydrogen on each hydroxyl group; the
conjugate base form of the indicator (In-) contains one ionized hydroxyl group ( - O- ) . The
pKa value for the acid ionization is 9.9; thus, Ka = 10-9.9 = 1.3 x 10-10. A discernible color
change is noted when the pH of an aqueous solution of the indicator is in the range of 9.4
to 10.6.
Disappearing ink can be prepared by first dissolving solid thymolphthalein in ethanol,
adding water, and then adjusting the pH with sodium hydroxide solution. The deep blue
color of the basic form of the indicator is readily apparent. Applying the ink to paper
increases its exposure to carbon dioxide in air. Two chemical reactions occur. Carbon
dioxide and sodium hydroxide react to form the salt sodium carbonate. Carbon dioxide and
water also combine to form carbonic acid:
The partial ionization of carbonic acid produces hydronium ion, H+, driving the indicator
equilibrium to the weak acid form. A colorless solution results. As the water in the ink
evaporates, the white residue of sodium carbonate remains.
Read the text and answer the following questions.
1.
What is the other name of disappearing ink?
2.
When is disappearing ink commonly used?
3.
What does disappearing ink mainly contain?
4. What is the name of the substance that shows the acid or basic nature of a solution by its
color?
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5.
When does thymolphthalein shift from a colorless to a deep blue color?
6.
Why does the indicator have the typical blue color?
7.
What is the important step to make ink color disappear?
8.
What happens when carbon dioxide in the air combines with water in the ink?
9. How many forms does thymolphthalein have? What are they? Describe the color of each form.
10. Which form retains the hydrogen on each hydroxyl group?
11. Which form contains one ionized hydroxyl group?
12. If the pH of an aqueous solution of the indicator is less than 9.4, which color can be observed?
13. How to prepare disappearing ink?
14. Sodium hydroxide solution is used to adjust the pH of the aqueous solution of the indicator.
Why?
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15. “Applying the ink to paper increases its exposure to carbon dioxide in air”. What does this
sentence mean?
16. How many reactions occur when the ink is applied to paper?
17. Which reaction produces carbonic acid?
18. How is hydronium ion produced?
19. This hydronium ion drives the indicator equilibrium to the right or to the left?
20. What can be observed after the water in the ink evaporates?
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Lesson 6-1 (Listening)
THE CHEMISTRY OF COLD PACKS
Listen and complete the text.
So you just strained a muscle and the inflammation is unbearable. You wish you have something
ice-cold to dull the pain, but to use an ice pack, you would have had to put it in the freezer hours
ago. (1)………………………….., there’s another option.
A cold pack can be left at room temperature until the moment you need it, then just snap it as
instructed and within seconds you’ll feel the chill. But how can something go from room
temperature to near (2)…………………… in such a short time? The answer lies in chemistry. Your cold
pack contains water and a (3)……………………… compound, usually ammonium nitrate, in different
compartments separated by a barrier. When the barrier is broken, the solid dissolves causing
what’s known as an (4)………………………… reaction, one that absorbs heat from its surroundings. To
understand how this works, we need to look at the two driving forces behind chemical processes:
energetics and (5)…………………………. These determine whether a change occurs in a system and
how energy flows if it does. In chemistry, energetics deals with the (6)……………………… and repulsive
forces between particles at molecular level. This scale is so small that there are more water
molecules in a single glass than there are known stars in the universe. And all these trillions of
molecules are constantly moving, (7)…………………….. and rotating at different rates. We can think of
temperature as a measurement of the average motion or kinetic energy of all these (8)…………………,
with an increase in movement meaning an increase in temperature and vice versa.
The flow of (9)……………….. in any chemical transformation depends on the relative strength of
particle interactions in each of a substance’s chemical states. When particles have a strong mutual
attractive force, they move rapidly towards one another, until they get so close, that
(10)……………………… forces push them away. If the initial attraction was strong enough, the particles
will keep vibrating back and forth in this way. The stronger the attraction, the faster their
movement, and since heat is essentially (11)…………………….., when a substance changes to a state in
which these interactions are stronger, the system heats up. But our cold packs do the opposite
which means that when the solid dissolves in water, the new interactions of solid particles and
water molecules with each other are weaker than the separated interactions that existed before.
This makes both types of particles slow down on average, cooling the whole solution. But why
would a (12)…………………………. change to a state where the interactions were weaker? Wouldn’t
the stronger pre-existing interactions keep the solid from dissolving? This is where entropy comes
in. Entropy basically describes how objects and energy are distributed based on random motion. If
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you think of the air in a room, there are many different possible arrangements for the trillions of
particles that compose it. Some of these will have all the (13)………………. molecules in one area, and
all the (14)……………………. molecules in another. But far more will have them mixed together, which
is why air is always found in this state. Now if there are strong attractive forces between particles,
the probability of some (15)……………………………….. can change even to the point where the odds
don’t favor certain substances mixing. Oil and water not (16)………………….. is an example. But in the
case of ammonium nitrate, or other substance in your cold pack, the attractive forces are not
strong enough to change the odds, and random motion makes the particles composing the solid
separate by (17)……………………….. into the water and never returning to their solid state. To put it
simply, your cold pack gets cold because random motion creates more configurations where the
solid and water mix together, and all of these have even (18)………………………..particle interaction,
less over all particle movement, and less heat than there was inside the unused pack. So while the
(19)…………………….. that can result from entropy may have caused your injury in the first place, it’s
also responsible for that comforting cold that soothes your pain.
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Nguyen Tuyet Phuong – Nguyen Dinh Hiep – Tran Thu Phuong
Lesson 6-2 (Reading)
What are the Red or Silver Liquids in Thermometers
We are accustomed to the rise and fall of the liquid in a thermometer as temperatures increase
and decrease, respectively. Why do these liquids respond to temperature in this fashion, and what
are the identities of these materials?
The Chemical Basics
The invention of the thermometer is generally credited to Galileo. His instrument, built near the
end of the sixteenth century, relied on the expansion of air with an increase of heat. Traditional
liquid-in-glass thermometers were devised in the 1630s and are standard equipment today in
research settings, medical practice, and meteorological measurement.
Many common thermometers contain a liquid confined within a narrow capillary tube. The liquid
height varies with the surrounding temperature. In actuality, the volume of the liquid is responding
to temperature, and the liquid tries to expand equally in all directions. By confining the liquid in a
tube, the only direction for ready expansion is along the length of the narrow tube. Thus,
expansion in that direction (i.e., liquid height) can be used as a measure of the ambient
temperature. Most liquids expand in volume as their temperature increases, and, because the
extent of expansion is generally constant over a range of temperatures, the amount of expansion
can be quantified and calibrated. In particular, two liquids exhibit a consistent and measurable
expansion at commonly measured temperatures - liquid mercury and ethanol (also known as ethyl
alcohol). Daniel Gabriel Fahrenheit (1686-1736), a German physicist and maker of scientific
instruments, is credited for inventing the alcohol thermometer in 1709 and the mercury
thermometer in 1714 (as well as developing the temperature scale that bears his name). These
liquids permit common temperatures to be readily measured, such as the boiling and freezing of
water. Why are these particular measurements possible? Mercury has a higher boiling point than
water, and ethanol has a lower freezing point than water. The silvery color of mercury facilitates
viewing the liquid level in a thermometer, but the colorless appearance of ethanol generally is
modified with a red dye to enhance distinguishing the liquid level.
The Chemical Details
The useful temperature ranges for mercury and ethanol-filled thermometers depend on the
temperature ranges over which these materials remain as liquids. Mercury exhibits freezing and
boiling points at atmospheric pressure (i.e., normal freezing and boiling points at 1 atm) of -38.9
and 356.6 °C. Thus, a mercury thermometer is advantageous when high-temperature conditions
are likely. Ethanol, with normal freezing and boiling points of - 114.1 and 78.3 °C, respectively, is
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convenient as a thermometer liquid when temperatures below the freezing point of water are to
be measured. The equation relating the volume change of a material to a change in temperature is
given by:
for Vo at an initial T of 0 °C and where fl is the volume expansion coefficient or the coefficient of
cubical expansion or the coefficient of thermal expansion. The units of β are reciprocal
temperature, for β is defined as the increase in volume per unit volume per degree celsius rise in
temperature. Mercury has an average value for of 1.8169041 x 10-4 °C-1 over the temperature
range of 0 to 100 °C and 1.81163 x 10-4 °C-1 over the temperature range of 24-299°C. The volume
expansion coefficient β for ethanol averages 1.04139 x 10-3 °C-1 over the temperature range of 0-80
°C, a larger value allowing for finer calibrated thermometers. An important point to note is that any
expansion or contraction of the thermometer container itself (usually glass) is generally ignored
when calibrating household thermometers because liquids generally have a substantially larger
coefficient of thermal expansion than do solids. As an example, Corning 790 glass exhibits a cubical
expansion coefficient of 2.4 x 10-6 °C-1. Pyrex glass contains borosilicate glass, a type of glass that is
exceptionally resistant to heat, expanding only about one-third as much as common silicate glass.
As a consequence, Pyrex is often used to make chemical apparatuses, including thermometers.
Read the text and answer the following questions.
1.
How does the liquid in a thermometer respond as temperatures increase and decrease?
2.
Who invented the thermometer?
3.
What did the thermometer rely on?
4.
What were devised in the 1630s?
5.
The thermometer are standard equipment today in in which field?
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6.
What do common thermometers contain?
7.
How to make the liquid expands in the only direction?
8.
How do most liquids respond as their temperature increases?
9.
Why can the amount of expansion be quantified and calibrated?
10. What kind of liquid s exhibit a consistent and measurable expansion at commonly measured
temperatures?
11. Why are mercury and ethanol chosen for making thermometer?
12. What is Daniel Gabriel Fahrenheit credited for?
13. What is the name of the temperature scale?
14. Why are mercury and ethanol chosen for making thermometer?
15. Why is ethanol in a thermometer generally modified with a red dye?
16. Mercury and ethanol which are filled in thermometers must be in which state?
17. Why is an ethanol thermometer useful when temperatures below the freezing point of water
are measured?
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18. Any expansion or contraction of the thermometer container itself (usually glass) is generally
ignored when calibrating household thermometers. Why?
19. What does Pyrex glass contain? How does this material respond to heat, comparing with
common silicate glass?
20. What is Pyrex often used to make?
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English in Chemistry 2
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Lesson 7-1 (Listening)
ELECTROLYSIS OF MOLTEN COMPOUNDS
Listen and answer the questions.
1. What are ionic compounds formed from?
2. Why cannot ionic solid conduct electricity or undergo electrolysis?
3. Tell the way to make it conduct.
4. Which compound is mentioned as the first example?
5. What are the positive and negative electrodes called?
6. Describe the reaction at cathode for the first example. What is produced at the cathode?
7. Which reaction happens at anode? And what is finally produced at the anode?
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8. Which materials are the electrodes usually made from?
9. Which compound is taken as the second example?
10. Describe what happen at the cathode and anode for the second example.
11. Complete the summary: Electrolysis will cause any molten ionic compound to ...........................
into its ……………………………………
12. The process of electrolysis is actually very useful and in which area is it used a lot?
13. Which example is introduced at last?
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Lesson 7-2 (Reading)
Read and translate the lesson (team-work)
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888
Chapter 20
Electrochemistry
The glass electrode was devised in 1906 by German biologist Max Cremer,
and it was the prototype for a large number of membrane electrodes that are
selective for a particular ion, such as the ions K+, NH4 +, Cl-, and many others.
Such electrodes are known collectively as ion-selective electrodes, and they have
many applications in environmental chemistry and biochemistry.
20-5
Batteries are vitally
important to modern society.
Annual production in
developed nations has been
estimated at more than
10 batteries per person
per year.
Cell phones, laptop
computers, and many other
devices rely heavily on
rechargeable batteries.
Advances in electrochemistry
and engineering are leading
to the development of
batteries that weigh less, last
longer, and provide more
power for portable electronic
devices.
*
Insulation
Graphite rod
(cathode)
MnO2 and carbon
black paste
making contact
with cathode
+
NH4Cl/ZnCl2
paste (electrolyte)
Zinc metal can
(anode)
FIGURE 20-14
The Leclanché (dry) cell
The chief components of the
cell are a graphite (carbon)
rod serving as the cathode, a
zinc container serving as the
anode, and an electrolyte.
Batteries: Producing Electricity Through
Chemical Reactions
A battery is a device that stores chemical energy for later release as electricity.
Some batteries consist of a single voltaic cell with two electrodes and the
appropriate electrolyte(s); an example is a flashlight cell. Other batteries consist of two or more voltaic cells joined in series fashion plus to minus to
increase the total voltage; an example is an automobile battery. In this section,
we will consider three types of voltaic cells and the batteries based on them.
Primary cells. The cell reaction in a primary cell is not reversible. When
the reactants have been mostly converted to products, no more electricity
is produced and a battery employing a primary cell(s) is dead.
Secondary cells. The cell reaction in a secondary cell can be reversed
by passing electricity through the cell (charging). A battery employing
secondary cells can be used through several hundred or more cycles of
discharging followed by charging.
Flow batteries and fuel cells. Materials (reactants, products, and
electrolytes) pass through the battery, which is simply a converter of
chemical energy to electric energy. These types of batteries can be run
indefinitely as long as they are supplied by electrolytes.
The Leclanché (Dry) Cell
The most common form of voltaic cell is the Leclanché cell, invented by the
French chemist Georges Leclanché (1839 1882) in the 1860s. Popularly called a
dry cell, because no free liquid is present, or flashlight battery, the Leclanché cell
is diagrammed in Figure 20-14. In this cell, oxidation occurs at a zinc anode
and reduction at an inert carbon (graphite) cathode. The electrolyte is a moist
paste of MnO 2 , ZnCl2 , NH 4Cl, and carbon black (soot). The maximum cell
voltage is 1.55 V. The anode (oxidation) half-reaction is simple.
Oxidation: Zn1s2 ¡ Zn2+1aq2 + 2 e -
The reduction is more complex. Essentially, it involves the reduction of MnO2
to compounds having Mn in a +3 oxidation state, for example,
Reduction: 2 MnO21s2 + H 2O1l2 + 2 e - ¡ Mn 2O31s2 + 2 OH -1aq2
An acid base reaction occurs between NH 4 + (from NH 4Cl) and OH -.
NH 4 +1aq2 + OH -1aq2 ¡ NH 31g2 + H 2O1l2
A buildup of NH 31g2 around the cathode would disrupt the current because
the NH 31g2 adheres to the cathode. That buildup is prevented by a reaction
between Zn2+ and NH 31g2 to form the complex ion 3Zn1NH 32242+, which crystallizes as the chloride salt.
Zn2+1aq2 + 2 NH 31g2 + 2 Cl -1aq2 ¡ 3Zn1NH 3224Cl21s2
The Leclanché cell is a primary cell; it cannot be recharged. This cell is
cheap to make, but it has some drawbacks. When current is drawn rapidly
from the cell, products, such as NH 3, build up on the electrodes, causing the
voltage to drop. Also, because the electrolyte medium is acidic, zinc metal
slowly dissolves.
20-5
Batteries: Producing Electricity Through Chemical Reactions
889
A superior form of the Leclanché cell is the alkaline cell, which uses NaOH or
KOH in place of NH 4Cl as the electrolyte. The reduction half-reaction is the
same as that shown above, but the oxidation half-reaction involves the formation of Zn1OH221s2, which can be thought of as occurring in two steps.
Zn1s2 ¡ Zn2+ 1aq2 + 2 e Zn2+1aq2 + 2 OH -1aq2 ¡ Zn1OH221s2
Zn1s2 + 2 OH -1aq2 ¡ Zn1OH221s2 + 2 e -
The advantages of the alkaline cell are that zinc does not dissolve as readily in
a basic (alkaline) medium as in an acidic medium, and the cell does a better
job of maintaining its voltage as current is drawn from it.
The Lead Acid (Storage) Battery
Secondary cells are commonly encountered joined together in series in the
lead acid battery, or storage battery, which has been used in automobiles
since about 1915 (Fig. 20-15). A storage battery is capable of repeated use
because its chemical reactions are reversible. That is, the discharged energy
can be restored by supplying electric current to recharge the cells in the
battery.
The reactants in a lead acid cell are spongy lead packed into a lead grid at the
anode, red-brown lead(IV) oxide packed into a lead grid at the cathode, and an
electrolyte solution consisting of dilute sulfuric acid (about 35% H 2SO 4 , by
mass). In this strongly acidic medium, the ionization of H 2SO 4 does not go to
completion. Both HSO4 -1aq2 and SO4 2-1aq2 are present, but HSO 4 -1aq2 predominates. The half-reactions and overall reaction are
Reduction:
° is an intensive property
Ecell
The voltage of a dry cell
battery does not depend on
the size of the battery all of
those pictured here are 1.5 V
batteries. Although these
batteries deliver the same
voltage, the total energy output
of each battery is different.
You can think of
the half-reactions as
occurring in two steps:
(1) oxidation of Pb(s) to
Pb2+1aq2 and reduction
of PbO21s2 to Pb2+1aq2,
followed by (2) precipitation of PbSO41s2 at each
electrode.
PbO21s2 + 3 H +1aq2 + HSO4 -1aq2 + 2 e - ¡ PbSO41s2 + 2 H 2O1l2
Pb1s2 + HSO4 -1aq2 ¡ PbSO41s2 + H +1aq2 + 2 e -
Oxidation:
Overall: PbO21s2 + Pb1s2 + 2 H +1aq2 + 2 HSO4 -1aq2 ¡ 2 PbSO41s2 + 2 H 2O1l2
Ecell = EPbO2>PbSO4 - EPbSO4>Pb = 1.74 V - 1- 0.28 V2 = 2.02 V
(20.24)
e
Discharge
e
Charge
Discharge
e
PbO2 cathode
Pb anode
H2SO4(aq)
FIGURE 20-15
A lead acid (storage) cell
The composition of the electrodes is described in the text. The cell reaction that occurs
as the cell is discharged is given in equation (20.24). The voltage of the cell is 2.02 V. In
this figure, two anode plates are connected in parallel fashion, as are two cathode plates.
The battery shown in this figure is the good battery used to charge a dead battery.
e
Charge
890
Chapter 20
Electrochemistry
In spite of its usefulness
and ability to deliver a strong
current, the lead storage
battery is also a pollution
hazard. All batteries should
be disposed of properly and
should not be dumped in
land fills or garbage
disposal sites.
Lead-acid storage batteries
are also used to power golf
carts, wheelchairs, and
passenger carts in airport
terminals.
When an automobile engine is started, the battery is at first discharged.
Once the car is in motion, an alternator powered by the engine constantly
recharges the battery. At times, the plates of the battery become coated with
PbSO41s2 and the electrolyte becomes sufficiently diluted with water that the
battery must be recharged by connecting it to an external electric source. This
forces the reverse of reaction (20.24), a nonspontaneous reaction.
2 PbSO41s2 + 2 H 2O1l2 ¡ Pb1s2 + PbO21s2 + 2 H +1aq2 + 2 HSO 4 -1aq2
Ecell = - 2.02 V
To prevent the anode and cathode from coming into contact with each other,
causing a short circuit, sheets of an insulating material are used to separate
alternating anode and cathode plates. A group of anodes is connected together
electrically, as is a group of cathodes. This parallel connection increases the
electrode area in contact with the electrolyte solution and increases the currentdelivering capacity of the cell. Cells are then joined in a series fashion, positive
to negative, to produce a battery. The typical 12 V battery consists of six cells,
each cell with a potential of about 2 V.
The Silver Zinc Cell: A Button Battery
Rechargeable silver
oxide batteries have been
developed and provide
alternatives to lithium-ion
batteries.
The cell diagram of a silver zinc cell (Fig. 20-16) is
Zn1s2, ZnO1s2 KOH1satd2 Ag2O1s2, Ag1s2
The half-reactions on discharging are
Reduction: Ag2O1s2 + H 2O1l2 + 2 e - ¡ 2 Ag1s2 + 2 OH -1aq2
Oxidation:
Overall:
Zn1s2 + 2 OH -1aq2 ¡ ZnO1s2 + H 2O1l2 + 2 e Zn1s2 + Ag 2O1s2 ¡ ZnO1s2 + 2 Ag1s2
(20.25)
Because no solution species is involved in the cell reaction, the quantity of
electrolyte is very small and the electrodes can be maintained very close
together. The cell voltage is 1.8 V, and its storage capacity is six times greater
than that of a lead acid battery of the same size. These characteristics
make batteries, such as the silver zinc cell, useful in button batteries. These
miniature batteries are used in watches, hearing aids, and cameras. In addition, silver zinc batteries fulfill the requirements of spacecraft, satellites,
missiles, rockets, space launch vehicles, torpedoes, underwater vehicles, and
life-support systems. On the Mars Pathfinder mission, the rover and the cruise
system were powered by solar cells. The energy storage requirements of the
lander were met by modified silver zinc batteries with about three times
the storage capacity of the standard nickel cadmium rechargeable battery.
The Nickel Cadmium Cell: A Rechargeable Battery
The nickel cadmium cell (or nicad battery) is commonly used in cordless electric
devices, such as electric shavers and handheld calculators. The anode in this
cell is cadmium metal, and the cathode is the Ni(III) compound NiO(OH)
Zn anode (+)
Metal
cathode (*)
A rechargeable
nickel cadmium cell, or
nicad battery.
FIGURE 20-16
A silver zinc button
(miniature) cell
Insulation
Zinc/electrolyte
Ag2O paste
Separator (porous)
20-5
Batteries: Producing Electricity Through Chemical Reactions
supported on nickel metal. The half-cell reactions for a nickel cadmium battery during discharge are
Reduction: 2 NiO1OH21s2 + 2 H 2O1l2 + 2 e - ¡ 2 Ni1OH221s2 + 2 OH -1aq2
Oxidation:
Overall:
Cd1s2 + 2 OH -1aq2 ¡ Cd1OH221s2 + 2 e -
Cd1s2 + 2 NiO1OH21s2 + 2 H 2O1l2 ¡ 2 Ni1OH221s2 + Cd1OH221s2
This cell gives a fairly constant voltage of 1.4 V. When the cell is recharged by
connection to an external voltage source, the reactions above are reversed.
Nickel cadmium batteries can be recharged many times because the solid
products adhere to the surface of the electrodes.
In primary cells the positive and negative electrodes are known as the
cathode, where reduction takes place, and the anode, where oxidation takes
place. In rechargeable systems, however, we have either a charging mode or a
discharging mode, and so depending whether electrons are flowing out of the
cell or flowing into the cell, the notion of the anode and the cathode changes.
On the discharge of a nicad battery, the NiO(OH) electrode is the cathode
because reduction is taking place, but on the charge, it is the anode because
oxidation is taking place (the reverse reaction). In discharge mode the
NiO(OH) electrode electrons are removed from the electrode because of the
reduction process, and so this electrode is positively charged. In the charging
mode electrons are being removed from this electrode by the oxidation
process; this is the anode and it is positively charged. Therefore, regardless of
charging or discharging, the NiO(OH) electrode is positive.
The negative electrode, the cadmium electrode in a nicad battery, is the
anode on discharging (oxidation) and the cathode (reduction) on charging. In
both charging and discharging, the anode is the electrode from which electrons exit the battery, and the cathode is the electrode at which electrons enter
the battery.
In summary, when dealing with rechargeable batteries, it is better to speak
of the positive and negative electrodes and avoid the terms cathode and anode.
The Lithium-Ion Battery
Lithium-ion batteries are a type of rechargeable battery now commonly used
in consumer electronics, such as cell phones, laptop computers, and MP3 players. In a lithium-ion battery, the lithium ion moves between the positive and
negative electrodes. The positive electrode consists of lithium cobalt(III) oxide,
LiCoO2, and the negative electrode is highly crystallized graphite. To complete the battery an electrolyte is needed, which can consist of an organic solvent and ions, such as LiPF6. The structure of LiCoO2 and graphite electrodes
is illustrated in Figure 20-17. In the charging cycle at the positive electrode,
lithium ions are released into the electrolyte solution as electrons are removed
from the electrode. To maintain a charge balance, one cobalt(III) ion is oxidized to cobalt(IV) for each lithium ion released:
LiCoO21s2 ¡ Li 1l - x2CoO21s2 + xLi +1solvent2 + x e -
At the negative electrode, lithium ions enter between the graphite layers and
are reduced to lithium metal. This insertion of a guest atom into a host solid
is called intercalation, and the resulting product is called an intercalation
compound:
C1s2 + xLi +1solvent2 + x e - ¡ Li xC1s2
In the operation of a lithium-ion battery the source of the electrons is the
oxidation of the Co(III) to Co(IV). The lithium ion takes these electrons to the
graphite electrode during charging and returns them to the positive electrode
during discharge.
891
892
Electrochemistry
Chapter 20
Positive electrode
Negative electrode
c ha
rge
Li
Co
O
Li
h
disc
arge
Li
LiCoO2
Graphite
FIGURE 20-17
The electrodes of a lithium-ion battery
The layered graphite electrode is shown with lithium ions (violet) intercalated. The
LiCoO2 is shown as a face-centered cubic lattice, with the oxygen atoms (red)
occupying the corners and the faces, the cobalt atoms (pink) occupying half of the
edges, and the lithium atoms occupying half of the edges and the central octahedral
hole. This arrangement leads to planes of oxygen, cobalt, oxygen, lithium, oxygen,
cobalt, and oxygen atoms, as indicated in the figure.
Output
Anode
e
e
Cathode
H2(g)
O2(g)
H2(g)
O2(g)
Electrolyte
KOH(aq)
FIGURE 20-18
A hydrogen oxygen
fuel cell
A key requirement in fuel
cells is porous electrodes that
allow for easy access of the
gaseous reactants to the
electrolyte. The electrodes
chosen should also catalyze
the electrode reactions.
Many other lithium batteries exist that use many different materials for the
positive electrode, while graphite is the most common negative electrode. A
major development is in the use of conducting polymers as the electrolyte,
which has led to a whole range of lithium-ion polymer batteries. The development
of new batteries based on lithium ions is currently an area of great interest.
Fuel Cells
The three types of cells considered in the remainder of this section fall into the
third category mentioned on page 888; they are found in flow batteries.
For most of the twentieth century, scientists explored the possibility of converting the chemical energy of fuels directly to electricity. The essential
process in a fuel cell is fuel + oxygen ¡ oxidation products. The first fuel cells
were based on the reaction of hydrogen and oxygen. Figure 20-18 represents
such a fuel cell. The overall change is that H 21g2 and O 21g2 in an alkaline
medium produce H 2O1l2.
Reduction: O21g2 + 2 H 2O1l2 + 4 e - ¡ 4 OH -1aq2
Oxidation:
Overall:
2 5H 21g2 + 2 OH -1aq2 ¡ 2 H 2O1l2 + 2 e -6
2 H 21g2 + O21g2 ¡ 2 H 2O1l2
(20.26)
° 2>OH- - E H
° 2O>H2 = 0.401 V - 1- 0.828 V2 = 1.229 V
° = EO
E cell
The theoretical maximum energy available as electric energy in any electrochemical cell is the Gibbs energy change for the cell reaction, ¢G°. The maximum
energy release when a fuel is burned is the enthalpy change, ¢H°. One of the
measures used to evaluate a fuel cell is the efficiency value, e = ¢G°>¢H°. For
the hydrogen oxygen fuel cell, e = - 474.4 kJ> - 571.6 kJ = 0.83.
20-5
Batteries: Producing Electricity Through Chemical Reactions
893
The day is fast approaching when fuel cells based on the direct oxidation of
common fuels will become a reality. For example, the half-reaction and cell
reaction for a fuel cell using methane (natural gas) are
Reduction: 2 5O21g2 + 4 H + + 4 e - ¡ 2 H 2O1l26
Oxidation:
CH 41g2 + 2 H 2O1l2 ¡ CO21g2 + 8 H + + 8 e CH 41g2 + 2 O21g2 ¡ CO21g2 + 2 H 2O1l2
Overall:
¢H° = - 890 kJ
¢G° = - 818 kJ
e = 0.92
(20.27)
Although methane fuel cells are still in the research stage, an automobile engine
is currently under development in which (1) a liquid hydrocarbon is vaporized;
(2) the vaporized fuel is partially oxidized to CO(g); (3) in the presence of a catalyst, steam converts the CO(g) to CO21g2 and H 21g2; and (4) H 21g2 and air are
fed through a fuel cell, producing electric energy.
A fuel cell should actually be called an energy converter rather than a battery.
As long as fuel and O 21g2 are available, the cell will produce electricity. It does
not have the limited capacity of a primary battery or the fixed storage capacity
of a secondary battery. Fuel cells based on reaction (20.26) have had their most
notable successes as energy sources in space vehicles. (Water produced in the
cell reaction is also a valuable product of the fuel cell.)
This Toyota prototype is a
fuel-cell-powered electric car
producing hydrogen from
gasoline.
Fuel cells are
environmentally friendly.
Oxygen and hydrogen are
readily available. Hydrogen,
although dangerous, can
now be transported safely
by the use of special
materials that can adsorb
large volumes.
Air Batteries
In a fuel cell, O21g2 is the oxidizing agent that oxidizes a fuel such as H 21g2 or
CH 41g2. Another kind of flow battery, because it uses O 21g2 from air, is
known as an air battery. The substance that is oxidized in an air battery is
typically a metal.
One heavily studied battery system is the aluminum air battery in which
oxidation occurs at an aluminum anode and reduction at a carbon air cathode.
The electrolyte circulated through the battery is NaOH(aq). Because it is in the
presence of a high concentration of OH -, Al3+ produced at the anode forms
the complex ion 3Al1OH244-. The operation of the battery is suggested by
Figure 20-19. The half-reactions and the overall cell reaction are
3 5O 21g2 + 2 H 2O1l2 + 4 e - ¡ 4 OH -1aq26
Reduction:
4 5Al1s2 + 4 OH -1aq2 ¡ 3A11OH244-1aq2 + 3 e -6
Oxidation:
Overall: 4 A11s2 + 3 O21g2 + 6 H 2O1l2 + 4 OH -1aq2 ¡ 43A11OH244-1aq2
(20.28)
The battery is kept charged by feeding chunks of Al and water into it. A
typical air battery can power an automobile several hundred miles before
refueling is necessary. The electrolyte is circulated outside the battery, where
Al1OH231s2 is precipitated from the 3Al1OH244-1aq2. This Al1OH231s2 is collected and can then be converted back to aluminum metal at an aluminum
manufacturing facility.
NaOH(aq) out
Air in
Air cathode
(carbon)
Air out
Air in
Al anode
Air cathode (carbon)
Air out
FIGURE 20-19
NaOH(aq) in
A simplified aluminum air battery
English in Chemistry 2
Nguyen Tuyet Phuong – Nguyen Dinh Hiep – Tran Thu Phuong
Lesson 8-1 (Listening)
The sounds of science presents (The lab safety song)
Listen and complete the song below.
The laboratory is a wondrous place where (1)………………………………….. are put to test.
There are so many tools at our disposal to (2)………………….. science at its best.
Pipettes and (3)……………………………... What’s this for?
Acids, bases, salts galore! Bunsen burners scale and more.
We’re going to have so much fun, and we’ve only just begun, cause we have so many gadgets to
explore.
Now wait just a minute my young(4) …………………………………. before we begin, we must be alert.
There are so many (5)…………………………. in the lab, and it’s best if we do not get hurt.
Equipment may appear robust but (6)…………………….. can break and (7)……………………… can rust.
So safety goggles are a must.
And many fluids look the same, so we (8)………………………………. them by name,
Be aware of open flames,
And we always work with someone whom we trust.
Oh there once was a famous monster Jeffrey, who accidentally left tea on his lab desk late one
night.
And then he made a wonderful (9)……………………… before he spilled his hot tea which ended in
catastrophe!
So remember to keep (10)……………………… and (11)………………….. away, just make it a part of your
lab routine
And your desk holds many sensitive (12)……………………………. It’s crucial that you keep it clean!
So waft, don’t smell those toxic scents,
(13)…………………….. is our best defense. Most of all use common sense.
You know that shoes with open toes are at risk to be exposed to burns and glass, who knows?!
Please don’t track in all that sand and don’t touch that with bare hands.
1
English in Chemistry 2
Nguyen Tuyet Phuong – Nguyen Dinh Hiep – Tran Thu Phuong
Gloves are a concern, to avoid a nasty burn.
You’ll soon learn to (14)………………………….. and can you clean up all that hair?
Come on, safety is a serious affair!
I’m not unsafe. It’s not fair.
I can’t help that I shed purple hair. Alas!
I wish I had a second chance…
Everybody makes mistakes.
Be careful next time for all our sakes!
The (15)…………………………………. is a wondrous place where experiments are put to test.
There are so many (16)………………….. at our disposal to study science at its best.
It’s (17)…………………………….. that we all take care
Stay alert and be aware
Cause safety is a duty (18)…………………………..!
It’s instrumental to identify potential things as they come by, cause plans can often go away!
And we must be prepared!
2
English in Chemistry 2
Nguyen Tuyet Phuong – Nguyen Dinh Hiep – Tran Thu Phuong
Lesson 8-2 (Reading)
HEAVY METALS AND CANCER
Read and translate the lesson (team-work)
Atomic absorption spectroscopy (AAS) has been used to reveal an appreciable difference in the
pattern of metal ions distributed throughout the blood plasma of cancer patients compared with
control volunteers.
Blood is a widely used biological sample in trace metal research, partly because it is so easy to
obtain samples but moreover because it is the medium by which toxic and non-toxic trace metal
ions are transported through the body. A study of trace metals in blood can, therefore, provide
direct evidence of their metabolism. Chemist Munir Shah of the Quaid-i-Azam University, in
Islamabad, Pakistan, working with biochemists Qaisara Pasha and Salman Malik have focused on
these qualities in an investigation of plasma trace metal concentrations in cancer patients with
perhaps surprising results.
"The role of different trace metals in the normal vital activities and initiation of some diseased has
long been known," the researchers point out, "however, until recently clinical recognition was
limited to very few of the trace metals." It is now assumed that almost all the chemical elements
have some involvement whether positive or detrimental in a wide range of physiological processes
to varying degrees. "Moreover," the team adds, "any changes in the environment as well as in the
human body itself can trigger changes in trace metal composition of any organ or tissue." The
consequences of such change might be linked to the emergence of a disease state.
One such disease state in which trace metal levels could play a role is cancer. Until recently, cancer
has been considered a purely genetic disease, or rather group of diseases. In which some agent,
whether endogenous or exogenous, initiates runaway cell replication or otherwise disrupts the
normal process of cell death, leading to the growth of a tumour or the spread of cancerous cells
through the lymph system or blood.
Shah points out that, diet has become an increasingly well-recognized factor in cancer incidence,
and he suggests that it may be possible to glean significant insights into cancer from an analysis of
food consumption patterns. Many studies suggest that rather than being a simple problem of gene
damage, cancer is a disease with multiple interwoven causes. As such, the researchers say, "the
role of trace metals in the development and inhibition of cancer has a complex character and raises
many questions."
Previous researchers have tried to uncover a relationship between the presence of trace metals in
the body and the development of human cancers. Given that so many trace metals underpin the
functions of a huge range of enzymes and proteins involved in cell signalling, lifecycles, replication,
and cell death, it would be odd if trace metals did not have a key role to play in cancer.
3
English in Chemistry 2
Nguyen Tuyet Phuong – Nguyen Dinh Hiep – Tran Thu Phuong
Of course, metals such as cadmium, are known to be mammalian mutagens, damaging DNA, and
high levels have been linked to prostate, renal and lung cancers. Similarly, the researchers add,
raised concentrations of lead have been associated with stomach, small intestine, large intestine,
ovary, renal, lung, myeloma, and leukaemia.
Other metals, including chromium and zinc have been observed to speed up tumour growth in
animal models. In humans, these metals have been associated with the more rapid progression of
breast, colon, rectum, ovary, lung, pancreas, bladder cancers, and leukaemia. Shah and colleagues
also point out that nickel too is a mutagen and has been linked to lung and nasal cancer as are
antimony and cobalt.
There are several trace metals that are essential to life. Iron and copper, for instance, play a crucial
role in various metabolic processes. However, there is some evidence of the carcinogenicity of iron
and significantly raised plasma levels of copper have also been associated with malignancy. The
link perhaps being that these metals can trigger hydroxyl radical formation with attendant DNA
damage.
The team has used flame AAS and a multivariate principal component analysis to estimate the
comparative distribution of trace metals in the plasma of cancer patients and healthy volunteers.
They analysed aluminium, antimony, cadmium, calcium, cobalt, chromium, copper, iron, lead,
lithium, magnesium, manganese, molybdenum, nickel, potassium, sodium, strontium, and zinc.
They found that in the plasma of cancer patients the mean concentrations of the essential metals
(Ca, Fe, K, Mg, Na, and Zn) were significantly lower in the healthy volunteers. Similarly, the average
concentrations of Cd, Cr, Cu, Mn, Mo, Ni, Pb, Sb, and Sr were much higher in the cancer patients.
The analysis revealed several close correlations between specific pairs of metals in the cancer
patients: Fe-Mn, Ca-Mn, Ca-Ni, Ca-Co, Cd-Pb, Co-Ni, Mn-Ni, Mn-Zn, Cr-Li, Ca-Zn and Fe-Ni, whereas
this coupling pattern was very different in the controls.
"The study indicates appreciably different patterns of metal distribution and mutual relationships
in the plasma of cancer patients in comparison with controls," the researchers conclude. Further
studies are now needed to determine how and why such marked changes in trace metal
concentrations are observed in cancer patients. Metabolism in cancer patients is obviously
changed significantly by specific trace metals but whether that is a cause or an effect remains to be
seen.
Article by David Bradley
4