8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng http://slidepdf.com/reader/full/tieng-anh-b4-danh-cho-sinh-vien-khoa-hoa-hoc-nguyen-tat-thang 1/128 TRÖÔØNG ÑAÏI HOÏC ÑAØ LAÏT GIAÙO TRÌNH TIEÁNG ANH B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc) NGUYEÃN TAÁT THAÉNG 2002
128
Embed
Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 3 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
III. Review on vocabulary:..................................................................................................... 75
IV. Grammar – Preposition .................................................................................................... 75
Unit Ten: IONIC AND COVALENT BONDS ........................................................................... 79
I. Vocabulary in Context ........................................................................................................ 80
II. Vocabulary in new context: ............................................................................................... 80
III. Comprehension Question ................................................................................................. 81
Unit Eleven: CHEMICAL REACTIONS ................................................................................... 94
I. Vocabulary in context ......................................................................................................... 95
II. Vocabulary in new context ................................................................................................ 95
III. Reading comprehension................................................................................................... 96
Unit Twelve: OXIDATION AND REDUCTION..................................................................... 101
I. Vocabulary in context ....................................................................................................... 101
II. Comprehension questions................................................................................................ 102
III. Grammar review ............................................................................................................ 102 Unit Thirteen COMPOUNDS................................................................................................... 106
I. Vocabulary........................................................................................................................ 107
II. Comprehension questions................................................................................................ 108
III. Review on Vocabulary:.................................................................................................. 109
IV. Review on Grammar: ..................................................................................................... 110
Unit Fourteen: MIXTURES ..................................................................................................... 112
I. Vocabulary........................................................................................................................ 113
II. Comprehension questions................................................................................................ 114
III. Grammar review ............................................................................................................ 114
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 22 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
If you do not get good score on the TOEFL exam this weekend, you can ….. it
next month
FURTHER READINGSThe Nature of the Problem
The understanding and prediction of the properties of matter at the atomic level
represents one of the great achievements of twentieth-century science. The theory
developed to describe the behavior of electrons, atoms and molecules differs
radically from familiar Newtonian physics, the physics governing the motions of
macroscopic bodies and the physical events of our everyday experiences. The
discovery and formulation of the fundamental concepts of atomic physics in the
period 1901 to 1926 by such men as Planck, Einstein, de Broglie and Heisenbergcaused what can only be described as a revolution in the then-accepted basic
concepts of physics.
The new theory is called quantum theory or quantum mechanics. As far as we
now know this theory is able to account for all observable behavior of matter and,
with suitable extensions, for the interaction of matter with light. The proper
formulation of quantum mechanics and its application to a specific problem requires
a rather elaborate mathematical framework, as do proper statements and applications
of Newtonian physics. We may, however, in this introductory account acquaint
ourselves with the critical experiments which led to the formulation of quantummechanics and apply the basic concepts of this new mechanics to the study of
electrons.
Specifically the problem we set ourselves is to discover the physical laws
governing the behavior of electrons and then apply these laws to determine how the
electrons are arranged when bound to nuclei to form atoms and molecules. This
arrangement of electrons is termed the electronic structure of the atom or molecule.
Furthermore, we shall discuss the relationship between the electronic structure of an
atom and its physical properties, and how the electronic structure is changed during
a chemical reaction.
Rutherford's nuclear model for the atom set the stage for the understanding of the
structure of atoms and the forces holding them together.
From Rutherford's alpha-scattering experiments it was clear that the atom
consisted of a positively-charged nucleus with negatively-charged electrons
arranged in some fashion around it, the electrons occupying a volume of space many
times larger than that occupied by the nucleus. (The diameters of nuclei fall in the
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 23 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
range of l × 10-12
→ 1 × 10-13
cm, while the diameter of an atom is typically of the
order of magnitude of 1 × 10-8
cm.) The forces responsible for binding the atom,
and in fact all matter (aside from the nuclei themselves), are electrostatic in origin:the positively-charged nucleus attracts the negatively-charged electrons. There are
attendant magnetic forces which arise from the motions of the charged particles.
These magnetic forces give rise to many important physical phenomena, but they
are smaller in magnitude than are the electrostatic forces and they are not
responsible for the binding found in matter.
During a chemical reaction only the number and arrangement of the electrons are
changed, the nucleus remaining unaltered. The unchanging charge of the atomic
nucleus is responsible for retaining the atom's chemical identity through any
chemical reaction. Thus for the purpose of understanding the chemical propertiesand behavior of atoms, the nucleus may be regarded as simply a point charge of
constant magnitude for a given element, giving rise to a central field of force which
binds the electrons to the atom.
Rutherford proposed his nuclear model of the atom in 1911, some fifteen years
before the formulation of quantum mechanics. Consequently his model, when first
proposed, posed a dilemma for classical physics. The nuclear model, based as it was
on experimental observations, had to be essentially correct, yet all attempts to
account for the stability of such a system using Newtonian mechanics ended in
failure.
According to Newtonian mechanics we should be able to obtain a complete
solution to the problem of the electronic structure of atoms once the nature of the
force between the nucleus and the electron is known. The electrostatic force
operative in the atom is well understood and is described by Coulomb's law, which
states that the force between two particles with charges e1 and e2 separated by a
distance R is given by:
There is a theorem of electrostatics which states that no stationary arrangement of
charged particles can ever be in electrostatic equilibrium, i.e., be stable to any
further change in their position. This means that all the particles in a collection of
postively and negatively charged species will always have resultant forces of
attraction or repulsion acting on them no matter how they are arranged in space.
Thus no model of the atom which invokes some stationary arrangement of the
electrons around the nucleus is possible. The electrons must be in motion if
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 24 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
electrostatic stability is to be preserved. However, an electron moving in the field of
a nucleus experiences a force and, according to Newton's second law of motion,
would be accelerated. The laws of electrodynamics state that an accelerated charged particle should emit light and thus continuously lose energy. In this dynamical
model of the atom, all of the electrons would spiral into the nucleus with the
emission of light and all matter would collapse to a much smaller volume, the
volume occupied by the nuclei.
No one was able to devise a theoretical model based on Newtonian, or what is
now called classical mechanics, which would explain the electrostatic stability of
atoms. The inescapable conclusion was that the classical equations of motion did not
apply to the electron. Indeed, by the early 1900's a number of physical phenomena
dealing with light and with events on the atomic level were found to be inexplicablein terms of classical mechanics. It became increasingly clear that Newtonian
mechanics, while predicting with precision the motions of masses ranging in size
from stars to microscopic particles, could not predict the behavior of particles of the
extremely small masses encountered in the atomic domain. The need for a new set
of laws was indicated
Questions
What do we – human being benefit from the understanding and prediction of the
properties of matter at the atomic level?
What does the quantum theory or quantum mechanics concern about?
What are the main differences between Newtonian mechanics and quantum
mechanics?
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 32 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
UNIT FOUR: PROPERTIES OF ATOMS
The behavior of substances is determined by the behavior of the atoms that make
up those substances. Scientists judge the behavior of atoms by identifying the
characteristics and properties of different atoms.
THE ATOMIC NUMBER refers to the number of protons an atom has. Since all
atoms of the same element have the same number of protons, they share the same
atomic number. Helium atoms, for example, have two protons, and so the atomic
number for helium is 2. Natural elements have atomic numbers that range
successively up to 92, which is the atomic number for uranium. Plutonium, which
also occurs in nature, has an atomic number of 94. Elements that have higher atomicnumbers must be created in a laboratory.
THE MASS NUMBER is the sum of the protons and neutrons in an atom.
Isotopes of the same element have different mass numbers, depending on the
number of neutrons each isotope contains. For example, the nucleus of protium, the
most common hydrogen isotope, consists of a single proton and so has the mass
number of 1. Deuterium, another hydrogen isotope, has a mass number of 2, because
its nucleus consists of a proton and a neutron.
ATOMIC MASS is the mass of an atom expressed in atomic mass units (amu).
Atomic mass units are extremely small-one amu equals 1/12 the mass of an atom ofthe element carbon 13. The mass of most atoms in amu is almost identical to the
mass number. Electrons do not affect an atom's atomic mass because they have
virtually no mass.
ELECTRIC CHARGE. Atoms are normally electrically neutral. But they can
lose or gain electrons through chemical reactions or in a collision with an electron or
another atom. This gain or loss of electrons produces an electrically charged atom
called an ion. An atom that loses electrons becomes a positive ion; one that gains
electrons is called a negative ion. The gain or loss of electrons is called ionization.
VALENCE is the capacity of an atom to combine with another atom, forming a
molecule. Atoms combine through the exchange of electrons -they either lose, gain,
or share electrons with another atom. Valence refers to the number of electrons
involved when atoms combine. If an atom tends to lose electrons to other atoms, it
has a positive valence. If an atom tends to gain electrons, its valence is negative.
Chlorine, for example, tends to gain one electron from another atom and so has a
valence of –1.
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 33 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
I. Vocabulary in context
electrically neutral - atomic mass - create - mass number - electrons - atomicvalence - negative ion - number - behavior - atomic mass unit - positive ion
1. The behavior of the atoms that make up a substance determine the
…………..of that substance.
2. The number of protons in an atom is called the …………………..
3. Scientist can ………………..elements.
4. The sum of the protons and neutrons in an atom is called the ………………...
5.
Amu is the abbreviation of …………………………6. The unit of ………………….is expressed in amu.
7. The atomic mass of an atom is not affected by ………………….which have
virtually no mass.
8. Although atoms are normally …………………………., they may lose or gain
electrons.
9. An atom becomes a …………………..when it loses electrons, and
……………. when it gains electrons.
10.
The capacity of an atom to combine with another atom to from a molecule iscalled …………….
II. Comprehension questions1. How can scientists judge the behavior of atom?………………………………...
…………………………………………………………………………………..
2. What is the atomic numbers? …………………………………………………..
…………………………………………………………………………………..
3. Can we create new elements? How? ……………………………………………
…………………………………………………………………………………..
4. Do all isotopes of the same element have the same mass number? Why? ……..
…………………………………………………………………………………..
5. What is the unit of the atomic mass? …………………………………………...
…………………………………………………………………………………..
6. Do electrons affect the atomic mass of an atom? Why? ………………………..
…………………………………………………………………………………..
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 39 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
UNIT FIVE: ELEMENTS AND SYMBOLS OF ELEMENTSChemical elements, the most basic of substances, can be defined in either of two
ways. An element is (1) a substance that cannot be broken down chemically into a
simpler substance, or (2) a substance that contains only one kind of atom.
All chemical substances are either elements or compounds, which are
combinations of elements. For example, hydrogen and oxygen are elements, and
water is a compound of hydrogen and oxygen. A few elements occur naturally in
their pure form. They include carbon, sulfur, and certain metals, such as gold and
silver. But nearly all other elements - apart from the gases in the atmosphere - occur
in combination as compounds.
There are currently 103 officially named and recognized elements. Some
elements do not occur naturally and must be created in a laboratory. Since 1964,several groups of scientists have claimed to have created six new elements, but none
of the claim has yet been accepted officially.
The names of elements come from different sources. Some of these names come
from Greek or Latin words. Bromine, for example, gets its name from the Greek
word for stench. Many artificially created elements are named in honor of a place or
individual. Einsteinium, an element created in a laboratory, was named in honor of
the physicist Albert Einstein.
Each element has a symbol that consists of one or two letters. Chemists use these
symbols as abbreviations for elements. The symbols are universally recognized, andso provide an international language for chemists.
In some cases, the first letter of an element's name is used as its symbol. For
example, C is the symbol for carbon. If the names of two or more elements begin
with the same letter, two letters of a name are used for all but one of the elements.
The second letter is written in lower case. The symbol for calcium is Ca, and the
symbol for helium is lie. Some symbols come from an old word for the element.
Sodium, for example, has the symbol Na, which comes from the Latin word for
sodium, natrium.
Chemists use the symbols for elements to write formulas for compounds. Theformulas tell which elements and how many atoms of each are in a compound.
Chemical reactions can be illustrated by placing the formulas in a particular series.
There are only a few more than one hundred elements. Of those, only eighty-
three are not naturally radioactive, and of those, only fifty or so are common enough
to our experience to be useful for general knowledge.
It would serve you well to know the elements. If you were to attempt to read
anything without knowing your letters, you would be in trouble. Let’s say you still
have a hard time telling the difference between a ‘b’ and a ‘d’. Your fluency in
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 40 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
reading would be ruined by having to look up the difference every time you
encountered one of those letters. Similarly, you should know your elements well
enough so that if you read or hear about one of them, you instantly know what theyare. Learn how to spell the names of the elements. Learn the symbols. Some of the
symbols have one letter, some have two, but each element symbol has one and only
one upper case letter in it.
I. Vocabulary in context formulas - pure forms – elements - honor - element - Greek or Latin – substance
- common - letters - compounds - create - elements - atoms
1. An ………….is a …………………that cannot be broken down chemically
into a simpler substance
2.
All chemical substances exist in two states: ………….or …………………..
3. There are only a few elements that exist naturally in their …………………...
4. Scientists can ……………some elements in a laboratory.
5. Scientists name elements by using words from …………………….
6. Some elements are named in ……………….of a place or individual
7. The symbol for an element contains one or two ………………...
8. Symbols are used to write ………………..for compounds.
9.
By looking at the formulas, we can recognize which ……………and how
many ………….. of each are in a compound.
10. Only a few more than fifty elements are ………….to our experience to be
useful for our general knowledge.
II. Vocabulary in new contextChemical symbols - Symbols - formulas -Chemical elements -
hundred - formulas
1.
……………………are substances that cannot be decomposed or broken into
more simpler/simpler substances by ordinary chemical means
2. More than 1 …………….chemical elements are known to exist in the
universe.
3. …………….for the elements may be used merely as abbreviations for the
name of the element, but
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 46 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
elements are not soluble in water. The lightest of the alkali metals are very common
in the earth’s crust. Francium is both rare and radioactive.
Group II (2) elements, beryllium, magnesium, calcium, strontium, barium, andradium, all have two electrons in the outside ring, and so have a valence of two.
Also called the alkaline earth metals, Group 2 elements in the free form are slightly
soft metals. Magnesium and calcium are common in the earth’s crust.
Group 3 elements, boron, aluminum, gallium, indium, and thallium, are a mixed
group. Boron has mostly non- metal properties. Boron will bond covalently by
preference. The rest of the group are metals. Aluminum is the only one common in
the earth’s crust. Group 3 elements have three electrons in the outer shell, but the
larger three elements have valences of both one and three.
Group 4 elements, carbon, silicon, germanium, tin, and lead, are not a coherent
group either. Carbon and silicon bond almost exclusively with four covalent bonds.
They both are common in the earth’s crust. Germanium is a rare semi-metal. Tin
and lead are definitely metals, even though they have four electrons in the outside
shell. Tin and lead have some differences in their properties from metal elements
that suggest the short distance from the line between metals and non-metals (semi-
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 47 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
metal weirdness). They both have more than one valence and are both somewhat
common in the earth’s crust.
Group 5 is also split between metals and non-metals. Nitrogen and phosphorusare very definitely non-metals. Both are common in the earth’s crust. In the rare
instances that nitrogen and phosphorus form ions, they form triple negative ions.
Nitride (N-3) and phosphide (P-3) ions are unstable in water, and so are not found in
nature. All of the Group 5 elements have five electrons in the outer shell. For the
smaller elements it is easier to complete the shell to become stable, so they are non-
metals.
Group VII (6 or 16) elements, oxygen, sulfur, selenium, and tellurium, have six
electrons in the outside shell. We are not concerned with polonium as a Group 6
element. It is too rare, too radioactive, and too dangerous for us to even consider in a
basic course. Tellurium is the only element in Group 6 that is a semi-metal. There
are positive and negative ions of Tellurium. Oxygen, sulfur, and selenium are true
non-metals. They have a valence of negative two as an ion, but they also bond
covalently. Oxygen gas makes covalent double-bonded diatomic molecules. Oxygen
and sulfur are common elements. Selenium has a property that may be from semi-
metal weirdness; it conducts electricity much better when light is shining on it.
Selenium is used in photocells for this property.
On some charts you will see hydrogen above fluorine in Group VII (7 or 17).
Hydrogen does not belong there any more than it belongs above Group 1. Fluorine,
chlorine, bromine, and iodine make up Group 7, the halogens. We can forget aboutastatine. It is too rare and radioactive to warrant any consideration here. Halogens
have a valence of negative one when they make ions because they have seven
electrons in the outer shell. They are all diatomic gases as free elements near room
temperature. They are choking poisonous gases. Fluorine and chlorine are yellow-
green, bromine is reddish, and iodine is purple as a gas. All can be found attached to
organic molecules. Chlorine is common in the earth’s crust. Fluorine is the most
active of them, and the activity decreases as the size of the halogen increases.
Questions:
1. How was the periodic table formed?
2. How is the table organized?
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 49 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
UNIT SIX : MOLECULESAlthough they are made up of atoms, molecules are still considered one of the
basic units of matter. That is because a molecule is the smallest particle into which a
substance can be divided and still have the chemical identity of the original
substance. If the substance were divided further, only atoms of chemical elements
would remain. For example, a drop of water contains billions of water molecules. If
one water molecule were separated from the rest, it would still behave like water.
But if that water molecule were divided, only atoms of the elements hydrogen and
oxygen would remain.
THE STRUCTURE OF MOLECULESMolecules are made up of atoms held together in certain arrangements. The
forces that hold the atoms of a molecule together are called chemical bonds. Atoms bond by sharing electrons - some atoms give up electrons, some take on electrons,
and in some bonds the electrons orbit the nucleus of two atoms.
Each atom in a molecule consists of a positively charged nucleus surrounded by
negatively charged electrons. When atoms bond, these charges balance each other,
forming an electrically neutral molecule. In some molecules, positive and negative
charges are spread evenly throughout it. In polar molecules, however, more positive
charge collects at one place in the molecule and more negative charge collects at
another place. Some polar molecules are magnetic because of the way the electrons
are unevenly distributed within the molecule.Scientists show the composition of molecules by using the symbols for elements
in chemical formulas. For example, a water molecule consists of two hydrogen
atoms and one oxygen atom. Therefore, the chemical formula for water is written as
H2O.
Molecules are measured by their molecular mass, which equals all the atomic
masses of the atoms in a molecule. The molecular mass of carbon dioxide (CO2) can
be found by adding the atomic mass of one atom of carbon, which is 12, and the
masses of the 2 oxygen atoms, which are about 16 each. The molecular mass of
carbon dioxide, therefore, is about 44.
I. Vocabulary in Context
Chemical bonds - Molecular mass - electrons - polar molecules -
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 53 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
2. I know you country has good university. Does the United have good
universities too?
…………………………………………………………………………………
3. I know you lost your wallet. Did you lose your keys too?
…………………………………………………………………………………
4. I know she goes to school. Does she have a full time job too?
…………………………………………………………………………………
5. I know he bought a coat. Did he buy a new pair of shoes too?
…………………………………………………………………………………
WORD STUDYSuffix –ly: Sometimes we can add the suffix –ly to an adjective to make an
adverb.
Here is an example:
Slow + -ly = slowly
Please speak slowly so I can understand
Add the suffix –ly to each adjective. Then choose the best adverb for each
sentence:Accidental ………accidentally………
Inexpensive …………………………..
Careful ………………………………
Silent ………………………………..
Thoughtless …………………………
Similar ………………………………
1. Brian …………………told his friend that he didn’t like the color of her newcar. Then he was sorry for what he said. He didn’t think about it before he said.
2. Always read the directions ………………….before you take a test so you
don’t make any careless mistakes.
3. Loud talking is not allowed in the library. You must work ………………so
other people can study too.
4. Julia ………………..knocked her glass off the table, and it broke. She didn’t
mean to do it.
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 55 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
UNIT SEVEN: THE VARIETY OF MOLECULESMolecules occur in an incredible number of shapes and sizes. This variety plays
an important role in the chemical properties that different substances show. Liquids
freeze and gases condense at certain temperatures, partly because of the makeup of
their molecules.
A molecule's size depends on the size and number of its atoms. Molecules
consist of as few as one or as many as millions of atoms. Specific names are given
to molecules with particular numbers of atoms. A molecule consisting of two atoms
of the same element, like oxygen (O2), is a diatomic molecule. A molecule made up
of three atoms, like ozone (O3), is a triatomic molecule.
Forces within a molecule determine its shape. Molecules take the shape thatforms the strongest bonds and provides the least amount of strain among its atoms.
Some molecular shapes are simple. An ammonia molecule, for example, takes the
shape of a tetrahedron. It consists of three hydrogen atoms attached to a nitrogen
atom. Other shapes are more complicated. Many protein molecules form long
helixes. A benzene molecule has six carbon atoms arranged in a ring with six
hydrogen atoms attached.
MOLECULES IN COMBINATIONMolecules are held together by forces called van der Waals forces, which are
usually weaker than those that hold the atoms of a molecule together. The force between molecules depends on the distance between them. Molecules attract each
other when they are widely separated; they repel when close together.
In a solid, the forces that attract and repel are balanced. The molecules in a solid
vibrate but do not move about to different parts of the solid. But if the solid's
temperature is raised, the molecules vibrate more rapidly. Eventually, the energy of
these vibrations becomes greater than the van der Waals forces that hold the
molecules in place. The solid then melts and becomes a liquid - a change of phase.
In a liquid, molecules move about easily, but they still have some force thatattracts them to one another called surface tension. Surface tension pulls the
molecules on the surface toward the molecules in the body of the liquid and
prevents the liquid from flying apart. The liquid acts as if it has a thin skin on it.
The molecules in a gas move about rapidly, and the attractive forces have little
effect on them. Gas molecules move freely through the available space. When they
collide, repelling forces send them apart again, so gases will always fill a container
completely.
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 56 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
Sometimes, when two kinds of molecules come near enough to each other they
react to form one or more new molecules. Two molecules of the same kind may also
combine to form a larger molecule. The process by which many small moleculescombine to form large molecule is called polymrization. Certain conditions, such as
the presence of ultraviolet light or nuclear radiation, can cause large molecules to
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 64 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
because they are attached to one another. Solids can have molecular energy due to
vibration and rotation. Picture a class of second graders glued to their seat. Each
student can jump up and down and sideways and turn the chair around, but theycan’t move out of place. Another useful mental picture is a junkyard for springs.
The springs have all been tied to each other in one enormous mass. Each spring can
twist and vibrate, but it can’t get loose from its neighbor.
It is now necessary to change from being able to see and understand each atom
or molecule to our larger world. Solids show a definite shape and a definite volume.
Unless forces are used that are not commonly found near the earth’s surface, solids
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 70 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
SOLID BASICS
Solids can be made up of many things. They can have elements or compoundsinside. They can also be made up of mixtures, or combinations of differentelements and compounds. Most of the solids you see are mixtures. Most rocks
are mixtures of many elements and compounds. Concrete is a good example of a
man-made solid mixture.
Characteristics Of Solids
First let's explain that characteristicsare the traits or features that something
might have. One characteristic of a solidis that it might be hard. That idea is
pretty straight forward.
One of the main characteristics ofsolids is that they hold their own shape. So if you put a solid in a container it
won't change its shape... No matter how much you move or slide it around. You
can even grind a solid up so that it fills up a container. If you look at the powderunder a microscope you will still see little tiny solids that you couldn't change.
You know that liquids are different because if you put a liquid into a container it
will fill it up as much of the container as it can.
In the same way that a solid holds its shape the atoms inside of a solid are not
allowed to move around much. This is a physical characteristic
of all solids. It happens no matter how small the pieces are. The
atoms in liquids and gases move around in all directions. Thesolid atoms and molecules are trapped in their places. The
atoms still spin and the electrons still move but the entire atomdoesn't go anywhere. They just kind of jiggle in place.
So You Want To Be A Solid
Obviously not everything is a solid. If you look around you'll see solids,
liquids, and especially gases (remember the air around you). Sometimes liquidsfeel a physical need to become a solid. Then look out! Phase changes are about to
happen.
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 71 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
Scientists use something called a FREEZING POINT to measure when aliquid turns into a solid. There are physical effects that can change the freezing
point. Pressure is one of those effects. When the pressure surrounding asubstance goes up the freezing point also goes up. That means it's easier to freezethe substance at higher pressures. When it gets colder, most solids shrink in size.
There are a few which expand but most shrink.
Crystals
If a solid is made up of pure elements or compounds
something special happens. It can freeze into a very specificstructure. This structure is called a CRYSTAL LATTICE. A
crystal lattice is a very exact organization of atoms whichcreates a specific place for every molecule or atom in the solid.
It is very neat and very compact. A great example of a crystal
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 72 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
UNIT NINE: A COMPOUND'S IDENTITYA compound is a substance that is made up of at least two different elements
and, therefore, two different kinds of atoms. Compounds are distinctive in that they
always have the same composition by weight. No matter what part or how much of
a compound you isolate, it will always have the same ratio between elements that
the original compound has. Water, for example, is a compound that consists of
molecules that have one atom of oxygen and two atoms of hydrogen. Therefore, in
any sample of water, there will always be twice as many hydrogen atoms as oxygen
atoms.
Every compound can be described by a particular chemical formula, which
shows the ratio between the elements that make up the compound. Chemists write
formulas using the symbols for chemical elements. Chemical formulas show themakeup of one unit of a compound; these units generally occur as molecules or ions.
The composition of simple molecules can be shown in a formula by combining
the symbols for the elements that the compound contains. Hydrogen fluoride, for
instance, is made up of molecules that contain one atom of hydrogen and one atom
of fluorine. Its formula can be written as HF.
Many molecules have more than one atom of the same element. Formulas for
these molecules include numbers written just below the symbols as subscripts. The
subscripts indicate the number of atoms included in a molecule. For example.
carbon dioxide is a compound that contains one carbon (C) atom and two oxygen(O) atoms. The formula for carbon dioxide is written CO2.
Formulas for compounds that consist of ions show the symbols of elements
whose atoms exist as ions in the compound. The compound sodium chloride, or
common table salt, has equal amounts of sodium (Na) and chlorine (Ct) atoms that
occur as ions. The formula for sodium chloride is written NaCl.
HOW COMPOUNDS ARE FORMEDA compound is formed when atoms of one element bond with atoms of another
element. Atoms tend to bond as a means of becoming more stable. A stable atom is
one that has the maximum amount of electrons in its outer shell. Therefore, atoms bond through the exchange of electrons, which are either transferred from one atom
to another or shared by more than one atom.
The capacity of an atom to combine with another atom is referred to as its
valence. Atoms of an element are assigned a valence number, which generally
equals the number of electrons that an atom needs to fill or release from its
outermost shell. Atoms that tend to lose electrons have a positive valence, and those
that tend to gain electrons have a negative valence. However, an atom of a certain
element may combine in a number of different ways with different elements. Thus,
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 80 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
Nearly all elements in their natural states are joined by covalent bonds.
Hydrogen, for example, normally consists of covalently bonded molecules. An
ordinary hydrogen molecule (H2) has two atoms that share electrons, so that twoelectrons revolve around each nucleus. Covalent compounds are often joined by
bonds that are much more complicated. Some individual molecules are held together
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 84 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
………………………………………………………………………………
g. That’s the house. I was born in it.
………………………………………………………………………………
h. Where is the lady? She ordered the fish.
………………………………………………………………………………
i. Do you know the children? They live in that house.
………………………………………………………………………………
j. The clothes come from Marks & Spencer. They are good quality.
………………………………………………………………………………
Further readings
STRUCTURE AND BONDING
1. Why do atoms bond together?
Some atoms are very reluctant to combine with other atoms and exist in
the air around us as single atoms. These are the Noble Gases and have very stable
electron arrangements eg 2, 2.8 and 2.8.8 and are shown in the diagrams below.
(atomic number) and electron
arrangement.
All other atoms therefore, bond to become electronically more stable, that is to become like Noble Gases in electron arrangement. Atoms can do this in two ways:
COVALENT BONDING - sharing electrons to form molecules with covalent
bonds, the bond is usually formed between two non-metallic elements in a
molecule.
OR
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 89 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
It is possible for many atoms to link up to form a giant covalent structure. This
produces a very strong 3-dimensional covalent bond network. This illustrated by
carbon in the form of diamond. Carbon can form four single bonds to four otheratoms etc. etc. This type of structure is thermally very stable and they have high
melting and boiling points. They are usually poor conductors of electricity
because the electrons are not usually free to move as they can in metallic structures.
Also because of the strength of the bonding in the structure they are often very hard
and will not dissolve in solvents like water.
3. Ionic Bonding
Ionic bonds are formed by one atom transferring electrons to another atom to
form ions. Ions are atoms, or groups of atoms, which have lost or gained electrons.
The atom losing electrons forms a positive ion (a cation) and is usually a metal.
The overall charge on the ion is positive due to excess positive nuclear charge
(protons do NOT change in chemical reactions).
The atom gaining electrons forms a negative ion (an anion) and is usually a non-
metallic element. The overall charge on the ion is negative because of the gain, and
therefore excess, of negative electrons.
The examples below combining a metal from Groups 1 (Alkali Metals), 2 or 3, with
a non-metal from Group 6 or Group 7 (The Halogens)
Example 1
A Group 1 metal + a Group 7 non-metal eg sodium + chlorine è sodium chlorideNaCl or ionic formula Na
+Cl
-
In terms of electron arrangement, the sodium donates its outer electron to a chlorine
atom forming a single positive sodium ion and a single negative chloride ion. The
atoms have become stable ions, because electronically, sodium becomes like neon
and chlorine like argon.
Na (2.8.1) + Cl (2.8.7) è Na+ (2.8) Cl
- (2.8.8)
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 90 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
ONE combines with ONE to form
Example 2
A Group 2 metal + a Group 7 non-metal eg magnesium + chlorine è magnesium
chloride MgCl2 or ionic formula Mg2+
(Cl-)2
In terms of electron arrangement, the magnesium donates its two outer electrons to
two chlorine atoms forming a double positive magnesium ion and two single
negative chloride ions. The atoms have become stable ions, because electronically,
magnesium becomes like neon and chlorine like argon.
Mg (2.8.2) + 2Cl (2.8.7) è Mg2+
(2.8) 2Cl- (2.8.8)
ONE combines with TWO to form
see *
(* NOTE you can draw two separate chloride ions, but in these examples a number
subscript has been used, as in ordinary chemical formula)
Example 3
A Group 3 metal + a Group 7 non-metal e.g. aluminium + fluorine è aluminium
fluoride AlF3 or ionic formula Al3+
(F-)3
In terms of electron arrangement, the aluminium donates its three outer electrons tothree fluorine atoms forming a triple positive aluminium ion and three single
negative fluoride ions. The atoms have become stable ions, because electronically,
aluminium becomes like neon and also fluorine.
Al (2.8.3) + 3F (2.8.7) è Al3+
(2.8) 3F- (2.8)
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 91 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
ONE combines with THREE to form
Example 4
A Group 1 metal + a Group 6 non-metal eg potassium + oxygen è potassium oxide
K2O or ionic formula (K+)2O
2-
In terms of electron arrangement, the two potassium atoms donates their outer
electrons to one oxygen atom. This results in two single positive potassium ions toone double negative oxide ion. All the ions have the stable electronic structures
2.8.8 (argon like) or 2.8 (neon like)
2K (2.8.8.1) + O (2.6) è 2K+ (2.8.8) O
2- (2.8)
TWO combine with ONE to form
Example 5
A Group 2 metal + a Group 6 non-metal eg calcium + oxygen è calcium oxide CaO
or ionic formula Ca2+
O2-
In terms of electron arrangement, one calcium atom donates its two outer electrons
to one oxygen atom. This results in a double positive calcium ion to one double
negative oxide ion. All the ions have the stable electronic structures 2.8.8 (argonlike) or 2.8 (neon like)
Ca (2.8.8.2) + O (2.6) è Ca2+
(2.8.8) O2-
(2.8)
ONE combines with ONE to form
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 94 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
UNIT ELEVEN: CHEMICAL REACTIONSChemical reactions are constantly carried out in our lives. The digestion of food,
the burning of fuel - even the development of photographic film - all involve
chemical reactions. Understanding and predicting chemical reactions is an important
way in which scientists apply the concepts of chemistry to everyday life.
A chemical reaction is a process in which one substance is chemically converted
into a different substance. In all chemical reactions, bonds between atoms are
broken and new ones are formed. Thus, the molecular or ionic structure of the
substance a chemical reaction creates is always different from the structure of the
original substance.
All the changes we witness, however, are not chemical reactions. There are also
physical changes and nuclear reactions. In a physical change, the substanceundergoing change has the same chemical formula as the resulting substance. The
melting of ice, for example, is a physical change, because the structure of the water
molecules remains the same. In a nuclear reaction, an atom is transformed into
another type of atom as a result of changes in the composition of its nucleus.
A chemical equation is a way to describe what goes on in a chemical reaction, the
actual change in a material.
CHEMICAL EQUATIONS demonstrate what occurs in chemical reactions.
These equations consist of chemical formulas and symbols that describe the
substances that are involved in the reaction. For example, the following is thechemical equation for the rusting of iron:
4Fe(s) + 3O2(g)→ 2Fe2O3(s)
This equation states that four atoms of solid iron (Fe[s]) react with three
molecules of oxygen gas (O2[g]) to form two units of solid rust (Fe2O3[s]).
Experiments that have been performed on this reaction have proven that iron and
oxygen always react in these proportions.
All chemical reactions have at least one product and at least one reactant. In the
rusting of iron, rust is the product , or result, of the reaction. Iron and oxygen are the
reactants, the substances that undergo chemical change.
The Total number of atoms and the kinds of atoms do not change in a chemical
reaction. The number of atoms in the reactants is the same as the number of atoms in
the products. In this way, chemical equations are similar to mathematical equations.
Both sides— of the arrow, in a chemical equation—must balance. Thus, in the
equation for the rusting of iron, the reactants contain a total of 10 atoms: 4 atoms of
iron and 6 atoms of oxygen. Likewise, the product contains 10 atoms. But the
formula of the product is very different from the formulas of the reactants.
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 100 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
Conditions Of Chemical Reactions
Some chemical reactions occur spontaneously - that is, when two reactants are
simply placed together. The rusting of iron is a spontaneous reaction. Spontaneousreactions occur only when the products are more chemically stable than are the
reactants. Rust, therefore, is more stable than iron or oxygen.
Many chemical reactions, however, do not occur spontaneously. They require
certain conditions. One of the most common conditions that contributes to chemical
reactions is the presence of heat. Heat, a form of energy, can cause substances to
become more reactive, or less stable. Solid rust, as demonstrated in the equation
shown previously, is fairly stable. But when rust is heated in combination with
certain other materials, it becomes metallic iron. This reaction also reveals an
important chemical principle - most reactions are reversible. In other words,
products can be changed back into reactants.
Chemical reactions proceed at different rates, according to different conditions.
Heal, for example, tends to increase the speed of many chemical reactions. Certain
substances, called catalysts, can also accelerate the speed of a chemical reaction.
The process in which a substance increases the speed of a reaction is called
catalysis.
Unlike reactants, catalysts remain unchanged by chemical reactions. In most
cases, there are several possible sequences of steps by which a reaction occurs.
Catalysts participate in some or all of these steps, creating a chemical pathway along
which the entire reaction can proceed more rapidly. In this way, catalysis can lower
the amount of energy needed to cause a chemical reaction.
An example of catalysis is the effect that nitric oxide (NO) has on the
decomposition of ozone (O3) in the upper atmosphere of the Earth. Ordinarily,
ozone decomposes slowly as oxygen atoms and ozone molecules combine and
produce oxygen molecules (O2). The presence of nitric oxide, however, causes the
oxygen molecules to be created rapidly.
Catalysts are used widely in industry to speed up chemical reactions that would
otherwise take place too slowly. Many useful substances, including gasoline and
ammonia, are created through processes that use catalysts, such as platinum and palladium.
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 101 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
UNIT TWELVE: OXIDATION AND REDUCTIONThere is an extraordinary range of possible chemical reactions, some that take
place naturally every day, and others that must be created in a laboratory. Among
the most common - and important in our day-to-day lives - are two related reactions,
called oxidation and reduction. Many essential processes that take place in plants
and animals depend on a whole series of interdependent oxidation and reduction
reactions.
Originally, the term oxidation referred to any chemical process in which a
substance combines with oxygen. Scientists learned, however, that the type of
reaction they were describing could take place, in some cases, without oxygen.
Today, oxidation refers to any chemical reaction in which a substance loses
electrons. Reduction refers to any reaction in which a substance gains electrons.Since the electrons released during oxidation must be captured by another
substance, oxidation is always accompanied by reduction. This combined transfer of
electrons is often called the redox process. The formation of water is an example of
the redox process. Water molecules are formed when oxygen and hydrogen gases
combine. During the reaction of these gases, hydrogen atoms lose an electron.
Therefore, they have been oxidized. The oxygen atoms, on the other hand, gain two
electrons – one from each of two hydrogen atoms. The oxygen atoms have
undergone reduction. Thus, the formation of water involves both oxidation and
reduction.
The rusting of iron is a common example of oxidation. Another example is the
combustion of fuels such as natural gas. Oxidation also takes place within the
human body, as inhaled oxygen reacts with molecules of food lo produce energy,
water, and carbon dioxide.
Many important processes rely on reduction. Metal plating, for example, occurs
when metal ions are reduced - gain electrons - to form neutral atoms. When a piece
of copper is placed in a solution containing positive silver ions, the silver ions pick
up electrons from copper atoms, and a coating of silver forms on the copper.
I. Vocabulary in context oxidized - Oxidation - reductions - Redox process - oxidation
1. Any chemical reaction in which a substance loses electrons is called
………………………….
2. Any chemical reaction in which a substance gains electrons is called
………………….
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 106 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
UNIT THIRTEEN COMPOUNDSChemical compounds may be divided into one of two groups, organic
compounds and inorganic compounds. These two groups can be split up into a few
smaller groups of compounds, each denned by its atomic structure. Acids and bases
are two important groups of compounds. Isomer is a term used to describe different
compounds that have the same molecular formula.
Organic compounds
All basic substances that make up living organisms are called organic
compounds. Carbon atoms make up the foundation of organic compounds. Most
other substances that contain carbon, particularly synthetic substances such as
plastics, are also considered organic compounds. The study of compounds that
contain carbon is called organic chemistry.
Carbon forms more compounds than any other element except hydrogen. The
basic reason for this is that carbon atoms have the ability to form an incredible
variety of chemical bonds with other carbon atoms and atoms of other elements.
Scientists have identified several million organic compounds.
Many important organic chemicals used in industry are obtained from plant and
animal sources. For example, coal, oil, and natural gas are produced from the
remains of organisms that lived millions of years ago. Other organic compounds
present in living matter include ammo acids, sugars, and nucleic acids.
Originally, scientists believed that carbon-containing compounds could only be
found from living sources. In the early 1800's, however, scientists learned that
organic compounds could be created artificially. Nearly all the plastics and synthetic
fibers we use every day are organic substances, as are such materials as artificial
sweeteners, pesticides, and many useful drugs.
In addition to their ability to form many types of bonds, carbon atoms can also
link together into very long chains. These long chains form gigantic molecules
called polymers. Polymers make up many important organic compounds. Some
polymers, such as starch and wool, occur naturally. Starch is formed by plants from
a simple sugar called glucose, and wool is a variety of protein. Other polymers aresynthetic. Nylon and polyethylene, a tough plastic material, are examples of
synthetic polymers. Rubber, another polymer, occurs naturally. But more than half
The rubber used today is made synthetically.
Inorganic compounds
Compounds that do not contain living matter are called inorganic compounds.
With a few exceptions, such as the gas carbon dioxide, inorganic compounds do not
have carbon atoms. Most inorganic compounds occur in rocks and minerals.
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 107 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
Many inorganic compounds are ionic substances that occur as solids. They
include salts and many minerals. Nonmetal elements, such as boron, nitrogen,
oxygen, and silicon, make up a wide variety of inorganic compounds.Although they do not contain living matter, inorganic compounds can be found
in living organisms. Blood, for example, contains coordination compounds, an
important class of inorganic compounds. Coordination compounds contain a central
metal atom surrounded by a nonmetal atom or molecule. Blood contains a
coordination compound made up of iron atoms that are each surrounded by nitrogen
and oxygen atoms.
Acids
Among the most common and important compounds are acids. Acids share
certain recognizable properties. For example, they turn litmus paper red, and theytend to corrode metals. Acids also have a sour taste. We come into contact with
acids every day. Citric acid is found in citrus fruits such as oranges, and sulfuric
acid is commonly used as the fluid in automobile batteries.
Chemists use several definitions to describe the behavior of acids. They are often
defined as compounds that produce hydrogen ions when dissolved in water. Acids
can also be defined more generally as compounds that can donate a proton when
they combine with any other substance.
Acids vary in strength. The strength of an acid is measured by the number of
hydrogen ions it produces wit dissolves in water. Stronger acids produce morehydrogen ions. Hydrochloric acid, which helps digestion in the human stomach, is
an example of a strong acid. Acetic acid, which is found in vine a weak acid.
ORGANIC ACIDS contain carbon atoms. They are often obtained from living
matter. Organic acids are used in the manufacture of detergents, foods, and soaps.
Amino acids, which are the building blocks of proteins, are common organic acids.
Others include ascorbic acid, which is vitamin C; and acetylsalicylic acid, or aspirin.
INORGANIC ACIDS do not, in general, contain carbon atoms. They tend to be
stronger than organic acids. They are used in plastics and synthetic fibers. Inorganic
acids are also used in the refining of petroleum. Nitric acid and hydrochloric acidare common inorganic acids.
3. The number of electrons in the outer shell of an element’s atom determines
its chemical behavior.----------------------------------------------------------------------------------------------------------------------------------------
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 112 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
UNIT FOURTEEN: MIXTURES
Many substances consist of combinations of compounds. These substances are
called mixtures. Unlike compounds, mixtures vary in composition from sample to
sample. For example, spaghetti sauce is a mixture. Some samples of it may be
composed of more tomato, some may have more spices, and others may have more
water. However, they are all spaghetti sauce.
There are two basic types of chemical mixtures, solutions and suspensions. A
solution is a mixture of two or more individual substances that cannot be separated
by a mechanical means, such as filtration. A suspension is a mixture whose
substances can be separated by filtration. Also, it is possible to recognize a
suspension as a combination of two different substances. The different substances in
tomato sauce, for example, can be recognized as separate from each other. Asolution generally appears as one substance.
Solutions
Solutions occur in three forms. There are liquid solutions, solid solutions, and
gaseous solutions.
LIQUID SOLUTIONS are formed when a solid, gas, or liquid is dissolved in a
liquid. Examples include water mixed with alcohol, and sugar dissolved in tea. Two
liquids that have the ability to form a solution are described as miscible. This ability
depends on the chemical properties of the liquids and on physical conditions such as
tempera lure and atmospheric pressure. Some liquid mixtures are more misciblethan others. Water and alcohol are completely miscible because any amount of the
two substances produces a solution. Oil and water, on the other hand, are not
miscible because one will not dissolve in the other.
Gases and solids that dissolve in liquid are described as soluble. The substance
that is dissolved is called the solute, and the substance that dissolves it is the solvent .
Water is the most common solvent. Other common solvents include acetone and
alcohol. In most cases, a solvent and the substance it dissolves have similar
molecular structure. For instance, oil dissolves in gasoline.
A given volume of solvent at a particular temperature can dissolve only a certainamount of solute. For example, a particular amount of water can dissolve only a
certain amount of salt. Any additional salt remains undissolved in the water. A
substance's ability to dissolve in another is called its solubility. The solubility of
most solids depends on the chemical properties of the substances and on the
temperature of the liquid solution. For gases, solubility also depends on pressure.
Solvents have many industrial and scientific applications. They are used in the
production of cleaning fluids and such coatings as inks and paints. Solvents are also
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 113 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
important in the manufacture of nylon, polyethylene, and many other synthetic
fibers.
SOLID SOLUTIONS usually occur as solid forms of liquid solutions. A mixtureof melted copper and zinc, for example, is a liquid solution that cools to form brass,
a solid solution. When melted silver and copper are mixed and cooled, another solid
solution—sterling silver—is produced.
GASEOUS SOLUTIONS result from the mixture of gases. Air, for instance, is a
mixture of nitrogen and oxygen, plus smaller amounts of argon and carbon dioxide.
Gaseous solutions are completely miscible - any amount of one gas in a solution can
dissolve in any amount of the other. Physical conditions do not affect the ability of
gases to form a solution.
SuspensionsThe chemical definition of a suspension is a mixture in which the particles of a
substance separate from a liquid or gas slowly. These particles consist of many
atoms or molecules, so that they can generally be visually recognized. The particles
can be thought of as "Heating" in the mixture.
There are several types of suspensions. They include: (1) a solid in a gas, such as
dust and smoke; (2) a liquid in a gas, such as fog and aerosols; (3) a solid in a liquid,
such as muddy or soapy water; (4) a gas in a liquid, such as foam; and (5) a liquid in
a liquid, such as latex or water-based paints.
Colloids are suspensions that contain extremely small particles. The particles inmost colloids can only be seen through an electron microscope. An example of a
common colloid is homogenized milk, which has tiny particles of suspended fat.
Colloids also include such familiar products as paint and ink. Blood and many other
that / the force / hold / together / ionic compounds / is called / an ionic bond.-----------------------------------------------------------------------------------------------------------------------------------------------
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 117 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
Concrete And Salt Water
Two classic examples of mixtures are concrete and salt water. You can see them
both being made everyday. Concrete is a mixture of lime (CaO)/cement, water,
sand, and other ground-up rocks and solids. All of these are mixed together.
Workers then pour the concrete into a mold and the concrete turns into a solid
(because of the cement solidifying) with the separate pieces inside. While the
cement hardening might be a chemical reaction... The rocks and gravel are held in
place by physical forces and used for added strength. The rocks and gravel are not
chemically bonded to the cement. The gravel is also not evenly distributed, there are
still pieces here and there. The concentrations change from area to area. Salt water is
a little different. First, it's a liquid. Second, it's an ionic solution. the salt is broken
up into sodium (Na) and chloride (Cl) ions in the water.
Now you might be wondering why concrete and salt water are not new
compounds when they are all mixed together. The special thing is that the basic
parts can still be removed by physical forces. You can take the solid concrete and
grind it up again. The individual components can then be separated and you can start
all over. Salt water is even easier. All you have to do is boil the water off and the
salt is left over, just like when you started.
The thing to remember about mixtures is that you start with some pieces,
combine them, and then you can do something to pull those pieces apart again. You
wind up with the same molecules (in the same amounts) that you started with.
SOLUTIONS
Before we dive into solutions let's separate solutions from mixtures. Solutions are
groups of molecules that are mixed up in a completely even distribution. Hmmm. Not the easiest way to say it. Scientists say that solutions are HOMOGENEOUS
systems. A mixture can have a little higher concentration on one side of the liquid
than the other. Solutions have an even concentration throughout the system.
An example: Sugar in water vs. Sand in water. Sugar dissolves and is spread
throughout the glass of water. The sand sinks to the bottom. The sugar-water could
be considered a solution. The sand-water is a mixture.
Can anything be in a solution?
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng
Tieáng Anh B4 (Daønh cho Sinh vieân Khoa Hoaù Hoïc - 118 -
Nguyeãn Taát Thaéng Khoa Ngoaïi Ngöõõ
Pretty much. Solutions can be solids dissolved in liquids. They could also be gases
dissolved in liquids (like carbonated water). They can be gases in other gases and
liquids in liquids. If you mix things up and they stay at an even distribution, it is asolution. You won't find solid-solid solutions, they are usually considered to be
mixtures.
Solutes, Solvents And Concentration
A simple solution is basically two substances that are going to be combined. One of
them is called the SOLUTE. A solute is the substance to be dissolved (sugar). The
other is a SOLVENT. The solvent is the one doing the dissolving (water). As a rule
of thumb there is usually more solvent than solute.
So what happens? How do you make that solution? Mix the two and stir. It's thatsimple. Science breaks it into three steps. When you read the steps, remember...
Solute=Sugar, Solvent=Water, System=Glass.
(1) The solute is placed in the solvent and the concentrated solute slowly breaks into
pieces.
(2) The molecules of the solvent begin to move out of the way and they make room
for the molecules of the solute. Example: The water has to make room for the sugar
molecules.
(3) The solute and solvent interact with each other until the concentration of the two
substances is equal throughout the system. The concentration of sugar in the water
would be the same from a sample at the top, bottom or middle of the glass.
Can anything change a solution?
Sure. All sorts of things can change the concentrations of substances in solution.
Scientists use the word SOLUBILITY. Solubility is the ability of the solvent
(water) to dissolve the solute (sugar). You may have already seen the effect of
TEMPERATURE. Usually when you heat up a solvent it can dissolve more solid
materials (sugar) and less gas (Carbon dioxide). Next on the list of factors is
PRESSURE. When you increase the surrounding pressure you can usually dissolve
more gases in the liquid. Think about your soda can. They are able to keep the fizzinside because the contents of the can are under higher pressure. Last is the
STRUCTURE of the substances. Some things dissolve easier in one kind of
substance than another. Sugar dissolves easily in water, oil does not. So... Water has
a low solubility when it comes to oil.
8/19/2019 Tiếng Anh B4 (Dành cho sinh viên khoa hoá học) - Nguyễn Tất Thắng