Lesson1. Physical changes.
Chemists divide the changes into two types: physical and chemical.
If a change doesn’t make any new substances, it is a physical change. Most physical
changes are quite easy to reverse.
1. Changes of state are physical changes.
solid
liquid
gas
2. Thermal expansion and contraction are physical changes.
(For example, steel bridges are longer in the summer than in the winter. It’s because steel expands
when it is heated and contracts when it is cooled.)
3. Mixing substances (e.g. dissolving) is a physical change.
Glossary:
physical changes – фізичні явища
steam – (водяна) пара
condense, v – конденсувати(ся)
reverse, v–обертатися у протилежному напрямі
to put something under pressure – піддавати тиску
expand, v - розширюватися
thermal
expansion – температурне розширення
contract, v – стискатися, звужуватися, скорочуватися
thermal contraction – температурне стискання
release, v – вивільняти, випускати
rust, v – іржавіти
ferment, v - бродити(про сік)
fermentation - бродіння
steel - сталь
Lesson2. Chemical changes.
If a change makes new substances, it is a chemical change or a chemical
reaction. The substances that are mixed are called the reactants. And the new
substances which result are called products. So, in chemical reactions substances react
to form new substances.
Chemical changes are usually very difficult to reverse.
Recognizing chemical reactions.
There are a few ways of recognizing chemical reactions:
1. Energy changes.
2. Change in appearance.
3. When a reaction produces a gas ,we can often see or hear fizzing as bubbles of
gas escape.
Describing chemical reactions.
Chemical reactions can be described by word equations,for example:
magnesium + oxygen → magnesium oxide
“Magnesium reacts with oxygen to form magnesium oxide”.
sodium + chlorine → sodium chloride
“Sodium reacts with chlorine to form sodium chloride”.
iron +sulphur → iron sulphid
“Iron reacts with sulphur to form iron sulphide”.
Word equations give us information about the reactants and products. There is another
kind of equation which gives us more detail about a chemical reaction. It’s a chemical (or
symbol) equation.
Glossary:
a chemical change = a chemical reaction
react, v - реагувати
a chemical reaction – хімічна реакція
a reactant– реагент, вихідна речовина
a product– продукт реакції, кінцева речовина
recognize, v - розпізнавати
fizzing – шипіння (з виділенням бульбашок)
an equation – рівняння
sodium chloride – натрій хлорид
iron sulphide – ферум сульфід
Lesson 3. Chemical equations.
iron +sulphur → iron sulphide
This is a word equation for the reaction between iron and sulphur. It shows that iron
reacts with sulphur to form iron sulphide. The chemical equation for the same reaction
is as follows:
Fe +S → FeS
It shows the formula of each substance in the reaction. This equation also tells us that
1 atom of iron reacts with 1 atom of sulphur. They make iron sulphide which contains
1 iron atom and 1 sulphur atom. These atoms are chemically bonded together in iron
sulphide. The new compound, iron sulphide, is not like iron and sulphur at all. It has
totally different properties. It is also difficult to get the iron and sulphur back from the
iron sulphide. This is characteristic of a chemical reaction.
The number of atoms on either side of a chemical equation must be equal, as no new
atoms can be made or destroyed in a chemical reaction.And the mass of reactants
must be equal to the mass of products. So, each side of an equation must balance.
Let’s take the following equation as an example.
Na +Cl2 → NaCl
This equation is not balanced. There are two atoms of chlorine on the left-hand side
(reactants), but one atom of chlorine on the right-hand side (products). Let’s balance
the equation. We need one more chlorine atom on the right-hand side. Unfortunately,
we can’t simply change the formula of sodium chloride to NaCl2 , but we can change
the number of NaCl ‘s made in the reaction. So, we put 2 in front of the NaCl.
Na +Cl2 → 2NaCl
In doing this, we need one extra Na atom on the left-hand side. Put another 2 in front
of the Na and you get
2Na +Cl2 → 2NaCl
Now the equation is balanced. If you count the atoms on either side of the equation,
they are equal.
Glossary:
balance, v
Model: It’s a chemical equation for the reaction between ……….and ........... We know
that the number of atoms on either side of a chemical equation must be equal. This
equation is not balanced, as there ...........atom(s) of ………on the left-hand side, but
………..atom(s) of………. on the right-hand side. We can’t change the formulas of
reactants and products, so we put ….. in front of the……. To balance the number of
……….atoms, we put ….. in front of the ……on the …..-hand side. This is the
balanced equation.
Lesson4.Balancing
chemical equations.
Glossary:
bromine (Br)
iodine (I)
lead (Pb)
Lesson 5. Oxygen.
To characterize oxygen as the type of atom we’ll use the Periodic Table.
Symbol - O
The atomic number -8
Period – 2
Group – VI
Relative atomic mass – 16
the number of protons - 8
the number of electrons- 8
the charge of the nucleus 8+
Oxygen is a non-metal.
Occurence of oxygen on the earth
Oxygen is one of the most abundant chemical elements on the Earth.
1) in the earth’s crust - 53%(SiO2, Al2O3, etc)
It is the most abundant chemical element in the earth’s crust (measured by atomic
percent there is 53% of oxygen). It can be found in compounds with silicon,
aluminium and other chemical elements in various rocks and minerals (SiO2, Al2O3)
2) in the oceans(H2O, etc)
It can be found combined with other chemical elements, for example, with hydrogen in
the oceans (H2O).
3) in the air
It can be found as an element (проста речовина) -oxygen gas - in the air
4) in living things
Living organisms contain oxygen combined with other chemical elements in different
compounds.
The chemical element oxygen occurs as two elements (прості речовини) – oxygen
gas and ozone.
Oxygen gas consists of molecules. Each molecule contains two atoms of oxygen. So,
the formula of oxygen gas is O2.
Oxygen gas -O2
Physical properties of oxygen gas
Standard state
State
Colour
odour
Taste
density
Solubility in water
gas
colourless
odourless
1.4 g/l
slightly soluble in
water
-183º C
- 219ºC
(boiling point)
liquid
solid (crystals)
pale blue
blue
odourless
odourless
-
Oxygen gas is a colourless and odourless gas without taste. Its density is 1.4 g/l.
Oxygen gas is slightly soluble in water. At a temperature of -183º C oxygen gas
condenses into pale blue liquid. So, the boiling point of oxygen is -183º C. At a
temperature of - 219ºC liquid oxygen turns to a blue solid.
Glossary:
abundant – поширений
the earth’s crust – земна кора
rocks – гірські породи
occur, v – зустрічатися, траплятися
occurrence – поширення
colourless
odourless
Lesson 6. Laboratory preparation of oxygen gas.
Laboratory preparation of oxygen is based on chemical changes (chemical
reactions).
In many chemical reactions there are two or more reactants, but to produce oxygen
gas in the laboratory you need only one reactant. Of course it should be a substance
containing oxygen atoms, for example mercury (II) oxide.
tº
1) 2HgO → 2Hg + O2
mercury (II)
oxide
As you see there is only one reactant in this equation – mercury (II) oxide. In the
reaction this substance splits up into two simpler substances – mercury and oxygen
gas.Such a reaction is called decomposition.
So, a chemical reaction in which one substance splits into two or more simpler
substances is called decomposition.
Mercury oxide in this reaction splits up when it is heated. So, the decomposition in
this reaction is caused by heating. Decomposition caused by heating is thermal
decomposition.As for the thermal decomposition of mercury oxide, this reaction is not
usually used for laboratory preparation of oxygen, because the mercury vapour formed
is very toxic. So, it’s very dangerous to prepare oxygen gas by this reaction. Oxygen
gas is usually prepared in the laboratory by thermal decomposition of other oxygencontaining substances such as potassium permanganate.
tº
2) 2KMnO4 →K2MnO4 + MnO2 + O2
potassium
permanganate
There are some more substances that break down on heating to give oxygen gas:
tº
3) 2KNO3 →2KNO2 + O2
potassium
nitrate
tº
2NaNO3 →2NaNO2 + O2
sodium
nitrate
tº, MnO2
4) 2KClO3 → 2KCl+ 3O2
potassium
chlorate
This thermal decomposition is not simply breakdown on heating. This reaction must
be catalysed by manganese dioxide, MnO2. We say that MnO2 catalyses the reaction.
It is a catalyst that is a substance which speeds up a chemical reaction but is
chemically unchanged.
There are two more decomposition reactions which can be used to prepare oxygen gas
in the laboratory. They are not caused by heating, so they are not thermal
decompositions. The first reaction needs the catalyst MnO2.
MnO2
5) 2H2O2 → 2H2O + O2
And the second reaction is caused by electricity:
6) H2O → 2H2+ O2
Thus, oxygen gas can be prepared in the laboratory by (thermal) decomposition
of some oxygen-containing substances.
Glossary:
decomposition – реакція розкладу
thermal decomposition – термічний розклад
an oxygen-containing substance – оксигеновмісна речовина
vapour - пара
manganese - манган
potassium permanganate – калій перманганат
potassium nitrate – калій нітрат
sodium nitrate - натрій нітрат
potassium chlorate – калій хлорат
manganese dioxide – манган діоксид
to catalyse a reaction – каталізувати (прискорювати) хімічну реакцію
a catalyst – каталізатор
Lesson 7. Industrial production of O2.
Unlike laboratory preparation, industrial production of oxygen gas is based on
physical changes.
Industrially, oxygen is produced by separating it from nitrogen and other components
of the air. As you know the air is a mixture of gases. To separate the mixture fractional
distillation is used.
Distillationis a way of separating a liquid from its mixtures. If we have a mixture
containing one liquid, we can distil the mixture. At first, we heat the mixture, so that
the liquid evaporates. Then we make the vapour condense into a liquid using a
condenser. And at last we collect the liquid. To separate a mixture of two or more
liquids that have different boiling points, fractional distillation is used.
Industrial oxygen gas is produced by fractional distillation of liquid air. This process
uses the fact that the normal boiling point of oxygen is -183°C, while the normal
boiling point of nitrogen is -196°C. So, to produce oxygen gas, they make the air liquid
by cooling it to about -200°C. Then they heat the liquid air. Nitrogen will boil at 196°C and turn into gas, at -183°C oxygen gas will be collected.
Glossary:
fractional distillation – фракційна дистиляція
Lesson 8.Chemical properties of oxygen.
Oxygen is one of the most reactive non-metals. It reacts with a lot of elements and
compounds.
1. Reactions of oxygen with elements(metals and non-metals):
tº
C + O2 → CO2
tº
S + O2 → SO2
tº
4P + 5O2 →2P2O5
tº
2Mg + O2 → 2MgO
4Na + O2 → 2Na2O
tº
2Cu + O2 → 2CuO
All these reactions take place on heating, so in the equations we put the “tº” symbol
above the arrows.
Oxygen reacts with elements to form an oxide.
An oxide is a compound consisting of two chemical elements, one of which is oxygen.
2. Reactions of oxygen with compounds:
tº
2CO + O2 → 2CO2
tº
CH4 + 2O2 → CO2+ 2H2O
tº
2H2S + 2O2 → SO2+ 2H2O
Oxygen reacts with compounds to form oxides.
Thus, oxygen reacts with elements (metals and non-metals) and compounds to
form oxides.
When substances combine with oxygen, they are oxidized.The products of the
reactions are oxides. The reactions are called oxidation reactions. So, oxidation is
the addition of oxygen to produce oxides. Many oxidation reactions produce hot
gases, which can usually be seen as flames. These reactions are examples of burning
or combustion. Burning is an oxidation reaction that gives out heat and light. Not all
oxidation reactions can be called burning. For example, the reaction of copper with
oxygen doesn’t give out heat and light. So, it’s not burning. There are a lot of
oxidation reactions which take place slowly and without heating. For example,
oxidation of aluminium is not burning:
4Al + 3O2 → 2Al2O3
Other examples of oxidation reactions which are not burning reactions are rusting,
fermentation and numerous reactions in human bodies and animals.
Glossary:
Oxidation - окиснення
oxidize, v -окиснювати
reactive– хімічно активний
Lesson 9. Test.
Lesson 10. The composition of atmosphere.
Air is mainly a mixture of 2 gases – nitrogen and oxygen. The composition of air
varies from place to place. However, we can talk about the composition of a typical
sample of air.
The composition by volume of a typical sample of air
Gas
Percentage volume
nitrogen
78%
oxygen
21%
carbon dioxide
0.03%
noble gases (argon, neon, helium, krypton, 1%
zenon)
water vapour
variable (0-4%)
impurities or pollutants
variable
(e.g. H2S, SO2, etc)
Some factors affecting the composition of air are: respiration, photosynthesis, decay,
volcanic activity, radioactive decay, human activity.
Respiration by all living things
Photosynthesis (the way plants build up
their food using the sunlight)
Decay (when living things die)
Volcanic activity
Radioactive decay
Human activity involving burning of
fossil fuels
Oxygen is taken in and carbon dioxide
given out to the atmosphere
Carbon dioxide is taken in and oxygen is
given out to the atmosphere
Carbon dioxide is released
Water vapour, carbon dioxide and other
impurities (sulfur dioxide and hydrogen
sulfide) are released
Helium is formed
Carbon dioxide and water vapour are
produced as well as other pollutant gases
such as sulfur dioxide and oxides of
nitrogen
Volcanic activity
Human activity
Oxygen takes up 1/5 of air. It can be proved experimentally by measuring the
percentage of oxygen in air.
Glossary:
a sample – зразок, проба
percentage volume – об’єм у відсотках, об’ємна частка у відсотках
noble
gases – інертні (благородні) гази
argon - аргон
krypton-криптон
zenon – ксенон
to vary – змінюватися, різнитися
variable, n– змінна величина; adj. - непостійний, змінний
impurities = pollutants – домішки; речовини, що забруднюють
to affect - впливати
to contribute to – сприяти, робити внесок
respiration - дихання
photosynthesis
decay – розкладання, розпад, гниття
radioactive decay – радіоактивний розпад
Experiment
an apparatus – апарат, пристрій
to estimate – приблизно підраховувати, визначати
asyringe - шприц
copper turnings - мідна стружка
a plunger - штовхач (шприца)
to decrease - зменшувати(ся)
a Bunsenburner – горілка Бунзена
to take readings - вимирювати, знімати показання приладу
a value – значення, величина
the percentage reduction – зменшення у відсотках
the residual gas - газ, що залишився
to increase – збільшувати(ся)
Lesson 11.The atmospheric pollution.
The major pollutants of air are sulfur dioxide (SO2), oxides of nitrogen (NO and
NO2), carbon monoxide (CO).”
1. Where do the pollutants come from?
2. Why are they dangerous?
3. What problems do they cause?
SO2
1. The main source of SO2 is burning fossil fuels in power stations. Coal and fuel
from oil contain 2% sulfur.
coal
sulfur
sulfur dioxide
When they are burnt, the sulfur is turned into sulfur dioxide.
S + O2 → SO2
2. SO2 is a colourless gas with a strong irritating smell. It reacts with water to form
sulfurous acid.
SO2+ H2O → H2SO3
The sulfurous acid then reacts with oxygen to form sulfuric acid.
2H2SO3+ O2 → 2H2SO4
3. The smoke with SO2 produces long-term fogs and causes serious health
problems (coughing, chest pains, shortness of breath, bronchitis, lung cancer).
Another major problem is acid rain, which causes damage to:
soil, tree roots, lakes and rivers, stonework and buildings, humans and
metalwork.
Oxides of nitrogen: NO and NO2.
1. About 30-40% of the oxides of nitrogen in the air come from car exhausts. The
temperatures in the car engine are high enough for nitrogen and oxygen to combine
together to form nitrogen monoxide and nitrogen dioxide.
N2 + O2 → 2NO
2NO + O2 → 2NO2
Other sources of nitrogen oxides are power stations, factories and fires.
2. Nitrogen dioxide is a highly toxic brown gas.
Oxides of nitrogen react with water to form acids.
3. Health problems and acid rain.
CO
1. Much of CO comes from car exhausts. It is produced by incomplete
combustion of petrol in the car engine.
2. CO is a very poisonous gas. The fact that it is colourless and odourless makes it
more dangerous, since it gives no warning of its presence.
3. CO can cause severe health problems and death, even in very small amounts.
For example, exhaust fumes of a motor-car in an enclosed space as a garage.
Glossary:
sulfur dioxide – сульфур діоксид
oxides of nitrogen – оксиди нітрогену
carbon monoxide – карбон моноксид
fossil fuels–викопні палива
H2SO3 sulfurous acid– сульфітна кислота
H2SO4 sulfuric acid – сульфатна (сірчана) кислота
car exhausts–вихлопні гази
incomplete combustion– неповне згоряння
Lesson 12.The uses of oxygen, nitrogen and carbon dioxide.
Glossary:
combustion of fuels– горіння палив
welding - зварювання
a hydrocarbon - вуглеводень
to go off = to spoil (about food) - псуватися
a tissue – тканина (біол.)
crude oil – сира нафта
to put out a fire - гасити пожежу
a fire extinguisher - вогнегасник
to sublime = to turn from a solid into a gas without forming a liquid
Table. Uses of oxygen gas, nitrogen gas and carbon dioxide gas.
Gas
O2
N2
CO2
Uses
Oxygen is used
1) for breathing
2) for burning
Specific examples
3) in many industrial processes
Nitrogen is used
1) as an unreactive gas for keeping
oxygen in the air away from different
things
2) for fast freezing
1)
2) Burning natural gas in a
cooker
Burning fuels in power stations
Welding
3) making steel
1) to stop food from going off
To prevent fires on ships
carrying oil
2) to freeze foods quickly
To freeze tissues in hospitals
Carbon dioxide is used
1) by plants for photosynthesis
1) -
2) for putting out fires
2) in fire extinguishers
3) for making fizzy (carbonated) drinks 3) 4) as “ dry ice”
Burning natural gas in a cooker
4) smoky effects
To keep ice cream
Burning fuels in power stations
Welding
Liquid nitrogen in the laboratory
smoky effects
Lesson13.Iron.
To characterize iron as a type of atom, we’ll use the Periodic Table.
Iron
Symbol - Fe
The atomic number - 26
Period – 4
Group – 8
Relative atomic mass – 56
The charge of the nucleus - 26+
The number of protons - 26
The number of electrons - 26
Iron is a metal.
Iron can lose two or three electrons to form ions. If it loses 2 electrons, it forms Fe2+
ions.
Fe – 2e → Fe2+
If it loses 3 electrons, it forms Fe 3+ ions.
Fe – 3e → Fe3+
Iron is the second abundant metal in the Earth’s crust (the first is aluminium). It
occurs in many compounds, but is usually extracted from its ores: iron oxides (Fe2O3
and Fe3O4).
Fe3O4
Fe2O3
The formula of iron as a substance is Fe.
Physical properties of iron
State
solid
Colour silver-grey
Luster
shiny(lustrous)
Density high (7.9 g/cm3)
Melting point high (1538 ºC)
a good conductor of electricity and heat
malleable
ductile
magnetic (can be attracted to a magnet)
capable of forming alloys (mixtures with other metals)
Glossary:
An alloy
A magnetic metal
Lesson14. Chemical properties of iron.
1.Iron reacts with most non-metals on heating.
t°
3Fe + 2O2 → Fe3O4
t°
Fe + S →FeS
t°
2Fe + 3Cl2 → 2FeCl3
2. Iron reacts with water (steam) on heating.
t°
3Fe + 4H2O→ Fe3O4+ 4H2
Unfortunately, iron has a property that causes a lot of problems:
2. Rusting (corrosion) of iron.
Rusting is a reaction of iron with oxygen in the air and water to make a red power,
called rust.
This powder is hydrated iron (III) oxide Fe2O3·H2O.
4Fe + 6H2O + 3O2 →4Fe(OH)3
Rusting takes place in ordinary conditions. The rusting of iron and steel causes a lot of
damage as many common objects in the modern world, such as motor cars,
engineering tools, bridges, etc., are made from iron and steel.
To prevent rusting we should keep oxygen in the air and water away from
different things made from iron and steel.
We can do this by coating the iron or steel with:
1. Paint
2. Oil or grease
3. Plastic
4. Another metal which is more resistant to corrosion, for example zinc, tin or
chromium.
Different objects can be protected from rusting in different ways. The method used
depends on how much metal there is, and what the metal is used for.
Beginnings
Endings
Large objects such as bridges and ships protected with paint.
are usually
Oiling
bicycle chains at regular intervals helps
to stop them rusting.
If a metal object needs to be protected
it can be coated in coloured plastic.
from rust and look attractive,
Old gas and water pipes which are
a new high-density plastic.
rusting can be coated inside with
Steel cans that are used for storing food coated with a thin layer of tin, which is
are
non-toxic.
Car bumpers, bicycle handlebars, taps
chromium.
and kettles are coated outside with
Glossary:
Rusting – іржавіння
To rust – іржавіти
To corrode – іржавіти
Oil – мастило
Grease – мастило
Zinc – цинк
Tin – олово, біла жерсть
Rust - іржа
Corrosion – корозія, іржавіння
To coat – покривати шаром (фарби тощо)
To oil – мастити, змащувати
Resistant to corrosion - стійкий до корозії
Chromium - хром
Lesson15.Materials from the Earth.
As you already know a material is a substance which an object can be made of. But
this definition is not complete, as materials are substances that can be used for
makingobjects or doing something. Many of our materials come from inside the
Earth, from the seas or from the atmosphere around us.
Gases from air.
Oxygen, nitrogen, argon, neon, etc. These gases can be used, for example, as raw
materials in chemical industry.
Metals from the Earth.
Some of the materials can be used just as they are. Others have to be refined or
purified before we can use them, as in many cases we need pure materials.
Lumps of pure gold can be found in rocks. We can also find copper, silver and
platinum as the metals in nature. It is possible because these metals are unreactive, so
they don’t often form compounds.
The other metals are combined with various substances. This means that they are
found in rocks in compounds, chemically bonded to other elements. Rocks that
contain metal compounds are called ores.The metal compound is separated from
bits of sand and rock. We say that the ore is purified. Then the metal is separated from
other elements. It is separated chemically, because elements in a compound are
chemically bonded together. It’s not a mixture. So, the metal is chemically separated
from other elements. We say that the metal is extracted. All these processes can be
shown schematically.
Extracting metals from their ores:
Mining an ore
↓
Purification of the ore
(the metal compound is separated from rock)
↓
Extraction of the metal
(the metal is chemically separated from its compound)
There are three main methods of extracting pure metals from their ores:
electrolysis, reduction and roasting in air.These methods are based on chemical
changes as we have to separate an element from its compound. The method used
depends on the metal.
1.Electrolysis is used for extracting very reactive metals, for example sodium and
aluminium.
2. Less reactive metals such as iron and lead are extracted using reduction.
3CO + Fe2O3 → 2Fe + 3CO2
In this reaction the iron oxide is reduced to iron.
3. Other metals such as copper are extracted from their ores by roasting them in
air.
Cu2S + O2→ 2Cu + SO2
Minerals. Rocks contain important materials called minerals. Some rocks, for
example granite, are used for building. Others are processed to produce useful
substances. For example rock salt can be processed to make sodium and chlorine.
Calcium carbonate is an ingredient in cement. Examples of rocks: granite, rock salt,
calcium carbonate.
granite
Fossil fuels. Most of the fuel we use in our homes, cars, and factories comes from the
Earth. The fuels that come from the Earth are called fossil fuels. The fossil fuels are
coal, crude oil and natural gas.
Coal
Crude oil
Natural gas (methane)
is mined and then burnt at power stations
to produce electricity and heat
is extracted from its deposits, very often
from the rocks beneath the sea, and then
refined to produce petrol and other fuels.
is piped to power stations and homes
Glossary:
a raw material - сировина
to refine - очищувати
to purify - очищувати
purification – очищення, очистка
pure materials
a lump - шматок
rocks - гірські породи
an ore - руда
to mine– видобувати (руду), виконувати гірничі роботи
to extract – добувати, видобувати
extraction - видобування
electrolysis - електроліз
reduction - відновлення
to be reduced to – бути відновленим до
roasting - випалювання
granite - граніт
rock salt - кам’яна сіль
calcium carbonate – кальцій карбонат
coal - вугілля
deposits - родовища
Lesson16.Extraction and uses of iron.
Lesson 17.Revision-consolidation.