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Chapter 1 Introducing Chemistry

1.1 What is chemistry?

Chemistry is the science which deals with the ____________, ___________, _____________

and reactions of substances.

What are substances made of? Common table salt: ____________ and ____________

Sugar : _________________, _______________ and _______________

Water : _________________ and ______________

Why do different substances have different properties?

Hydrogen will burn easily but not helium

How do different substances react?

When hydrogen reacts with oxygen, ______________ will be formed.

1.2 Laboratory safety

1. Do not run or play in the laboratory.

2. do not taste anything in the laboratory.

3. Do not eat or drink in the laboratory.

4. Do not wear loose clothing, or allow you hair or tie to dangle when conducting experiments.

5. Do not touch chemicals with bare bands, Use a spatula (刮勺) to transfer solid chemicals.

6. Do not smell gases directly – wave the gas towards your nose.

7. When you put a chemical into a test tube for heating, fill not more than one third ( ) of the

test tube. Do not point its mouth towards anyone when holding it for heating.

8. Do not pout chemicals into the sink. Put them into appropriate waste bottle.

9. Wear safety glasses when heating with a Bunsen burner.

10. Report all accidents and breakages to your teacher. If a chemical gets onto your skin or

clothing, wash the affected area with plenty of water.

11. Turn off the Bunsen burner when it is not in use.

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12. Always wash your hands thoroughly after experiments.

1.3 Hazard warning labels:

Hazard warning labels are used for labelling dangerous chemicals.

_________________

_________________

_________________

_________________

_________________

_________________

_________________

_________________

1.5 Common apparatus in the laboratory:

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1. 13.

2. 14.

3. 15.

4.. 16.

5. 17.

6. 18.

7. 19.

8. 20.

9. 21.

10. 22.

11. 23.

12.

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Chapter 2 The Atmosphere

2.1 Introduction

Our planet Earth provides us with plenty of natural resources:

Coal, _______________ and natural gas for our energy needs;

Metal such as _______________ for making cooking utensils and soft drink cans;

Sand and limestone for making _______________ and _______________.

_______________ for making computer chips

Some information about the Earth is listed below.

1. Age: 4.5 billion years

2. Shape and size : roughly spherical, about 6400 km in radius

3. Mass: 6 × 1024 kg

4. 70% covered by _______________, 30% covered by _______________, surrounded by

a gaseous layer (about 80 km thick) called the _______________.

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2.2 The atmosphere

The atmosphere can be divided into four layers

1. troposphere

2. stratosphere

3. mesosphere

4. ionosphere

Air is a mixture of gases –_______________ (21%), _______________ (78%) and other

gases (small amount of _______________, water vapour and noble gases).

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Elements are substances which cannot be broken down into anything simpler by chemical

methods.

Compounds are substances composed of two or more elements chemically joined together.

Class practice

Air contains mainly nitrogen and oxygen. It also contains other gases such as

water vapour, carbon dioxide, helium, neon argon, krypton and xenon.

Classify the constituents of air into elements and compounds.

2.3 Separation of oxygen and nitrogen from air

The method used by industry to separate the mixture of gases in the air is fractional

distillation of liquid air. Separation of air depends on the fact that different components in the

air have different _______________.

Class practice

If a mixture of water (boiling point 100oC) and ethanol (boiling point 78

oC) is

heated, which component will form vapour first?

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There are three stages in the fractional distillation of liquid air:

1. Purification

_______________, _______________ and _______________ in the air are

removed

2. Liquefaction of air

Purified air is compressed at a very high pressure and cooled down. Then the cooled,

compressed air is allowed to expand. During expansion, the temperature of air will

drop quickly. The compressing and expanding cycles are repeated until the

temperature of the air reaches _______________.

3. Fractional distillation of liquid air

Inside the fractionating column, different gases in air boil at different temperatures.

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Class practice

The table shows the boiling points of some of the gases found in air

Gases boiling points (oC)

Argon -186

Carbon dioxide -78

Helium -269

Krypton -153

Neon -246

Nitrogen -196

Oxygen -183

Xenon -109

1. Rearrange the gases into the order in which they would boil off during

fractional distillation of liquid air.

2. List the gases which would still be gaseous at -200oC

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2.4 Physical and chemical Properties

Any characteristic that can be used to describe or identify a substance is a property of the

substance. Each substance has its own set of properties.

Physical properties of a substance are properties that can be measured without the substance

changing into another substance.

Chemical properties of a substance are properties that describe its ability to form new

substance.

Class practice

Identify each of the following statements as describing a physical property or a

chemical property of the substance

a Pure metals are shiny and reflect

light.

b Water reacts with iron and air to

form rust.

c Water boils at 100oC.

d Milk turns sour if left too long at

room temperature.

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2.5 Physical and chemical changes

Matter can undergo two types of change: physical change and chemical change.

A physical change is a change in which _____________________________

_______________.

A chemical change is a change in which ______________________________

_______________.

Class practice

State whether each of the following is a physical change or a chemical change.

A magnesium ribbon

burns in air.

Sugar dissolves in water.

Water changes to ice in a

freezer.

Water is heated until it

boils.

Iron rusts.

2.6 Properties of oxygen

1. Physical properties of oxygen

Colourless, odourless

Slightly denser than air

Slightly soluble in water

2. Chemical properties of oxygen

Form oxides with many substances

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2.7 Test for oxygen

Method : test with a _______________

Result: If the gas is oxygen, ____________________________________________

2.8 Test for carbon dioxide

Method : test with _______________

Result: ________________________________________________________________

2.9 Test for hydrogen

Method : test with a _________________

Result: _________________________________________________________________

2.10 Test for water

Method : test with ______________________________

Result: _________________________________________________________________

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Complete the following concept map

soluble carbon dioxide radiation glowing splint

oxygen denser climate fractional distillation

lighter atmosphere ocean water vapour

combustion filtration burning splint evaporation

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Exercise

Fill in the blanks

1. The Earth is composed of the ________________ , ________________,

________________ and surrounded by the ________________.

2. The ________________ is a gaseous layer surrounding the Earth.

3. The major components of air are_______________(78%) and ________________(21%).

4. The method of separating the gases in air is called ________________________.

5. Air can be ________________ by cooling and compression.

6. Oxygen is a good supporter of ________________.

7. Oxygen relights a ________________ splint.

Multiple choice questions:

1. Which of the following is the correct composition of gases (by volume) in the

atmosphere?

A. 78% nitrogen, 21% oxygen, 0.93% argon, 0.03% carbon dioxide

B. 78% nitrogen, 21% oxygen, 0.93% carbon dioxide, 0.03% argon

C. 78% oxygen, 21% nitrogen, 0.93% argon, 0.03% carbon dioxide

D. 78% oxygen, 21% nitrogen, 0.93% carbon dioxide, 0.03% argon

2. Which of the following noble gases is the most abundant in air?

A. Argon

B. Helium

C. Krypton

D. Neon

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3. Which of the following gases in air is a (are) compound(s)?

(1) Argon

(2) Carbon dioxide

(3) Nitrogen

A. (1) only

B. (2) only

C. (1) and (3) only

D. (2) and (3) only

4. Which of the following statements about the fractional distillation of liquid

air are correct?

(1) Nitrogen boils off before oxygen.

(2) The process can be performed in school laboratory

(3) The air is liquefied by repeated cooling and compression.

A. (1) and (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

5. The boiling point information about certain components in a sample of

liquefied air is shown the table below,

Which of the following is correct for the fractional distillation of this sample?

Component Boiling point (oC)

Argon -186

Krypton -152

Nitrogen -196

Oxygen -183

A. Oxygen gas boils off first.

B. Nitrogen gas boils off first.

C. Argon gas boils off first.

D. Krypton gas boils off first.

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6. Oxygen

A. can only be found on Earth.

B. relights a burning splint.

C. is a flammable gas

D. is an odourless gas.

Questions:

1. Oxygen is used in many ways in our daily life. It can be obtained from the air separation

plant.

(a) Name the industrial process in the air separation plant that can obtain oxygen from

air.

____________________________________________________________________

(b) State the hazard warning label that should be shown on a jar of oxygen.

__________________________________

(c) State ONE physical property and ONE chemical property of oxygen.

____________________________________________________________________

(d) Suggest a test for identifying oxygen.

____________________________________________________________________

2. Classify each of the following statements as describing either a physical property or a

chemical property of the substance.

a. Sugar is soluble in water.

b. Magnesium burns in the air and forms a white solid.

c. Baking soda is a white powder.

d. Ammonia has an unpleasant smell.

e. Iron sinks in water.

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Chapter 3 Ocean

3.1 Introduction

Sea water covers over 70% of the surface area of the Earth. Sea water is a vast water solution

containing 3.5% by mass of dissolved solids. The main solute in sea water is common

salt –_______________.

A solution forms when one substance (__________) dissolves in another (______________).

A dilute solution contains a _________ amount of solute in a given volume of solution.

A concentrated solution contains a _________ amount of solute in a given volume of solution.

A saturated solution is a solution in which the solvent has dissolved the _____________

amount of the solute it can at a particular temperature.

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3.2 Extraction of common salt from sea water

(A) Decantation – a quick method for separating a much denser solid from a liquid.

Experimental set-up for decantation

(B) Filtration – for separating an insoluble solid from a liquid.

Experimental set-up for filtration

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Labeled diagram for filtration

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(C) Evaporation

The change of a liquid to a vapour which occurs at a temperature below the boiling

point is called _______________.

Experimental set-up for evaporation

Labeled diagram for evaporation (Direct heating)

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(D) Crystallization

Sea water is allowed to evaporate slowly at room temperature. The solution becomes more

and more _______________. Eventually, the solution becomes saturated. Further

evaporation of the solution will cause pure sodium chloride crystals to separate out. As

evaporation continues, the solid crystals slowly grow in size. The sodium chloride crystals

can be filtered from solution and then dried by _______________.

If the solution is evaporated quickly, the crystals formed are usually __________. If the

solution evaporated slowly, the crystals formed are usually ___________.

Labeled diagram for evaporation (Heating with a steam bath)

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3.3 Obtaining pure water from sea water

Distillation – The change of a vapour to a liquid is called condensation. The process of

evaporating a liquid and subsequently condensing the vapour is called distillation.

Experimental set-up for distillation

1. The bulb of the thermometer is placed near to the side-arm of the still head and can

record the temperature of the vapour which is distilled over and collected.

2. A few anti-bumping granules are added into the sea water before heating. This is to

ensure even boiling. Otherwise, the sea water may become so vigorously agitated (攪動)

that some of it may spurt(噴射) into the collecting vessel.

thermometer

Water out

Receiver adoptor

Test tube

Cool water

distillate

Water in

condenser

heating

Anti-bumping

granules

Pear shape flask

bulb

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Labeled diagram for distillation using simple apparatus:

Labeled diagram for distillation using quick-fit:

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3.4 Tests for sodium and chloride ions in common salt

1. Chemical analysis is a process to find the chemical identity or composition of a given

sample.

2. Flame test – some metals can be identified by the flame test.

(i) Dip a clean _______________ wire into concentrated hydrochloric acid.

(Concentrated hydrochloric acid is _______________.)

(ii) Dip the nichrome wire into the solid sample.

(iii) Put the end of the wire in the Bunsen flame and observe the colour of the flame.

(iv)

Flame colours of some metal compounds

Compound of Flame colour

Potassium Lilac

Sodium Golden yellow

Calcium Brick-red

Copper Bluish green

3. Silver nitrate test – test for chlorides

(i) Add some water to dissolve solid sample.

(ii) Add excess _______________ to the solution.

(iii) Add a few drops of _____________________________.

(iv) If chloride ions are present, __________________________________________

________________________________________________________________

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3.5 Electrolysis of sea water and uses of products

Electrolysis means ‘______________________________________’. It is usually carried out

by passing a direct electric current through an aqueous concentrated salt solution

(__________________).

Common uses of products obtained by the electrolysis of sea water

Electrolysis

of sea water

Manufacture of

ammonia

As rocket fuel Sterilizing

drinking water

Sterilizing swimming

pool water

Manufacturing of

hydrochloric acid

Manufacturing

of bleach Manufacture of

soaps and detergents

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Complete the following concept map.

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Exercise

Fill in the blanks:

1. The main dissolved substance in sea water is _________________ , which contains the

elements _________________ and _________________.

2. Common salt is extracted from sea water in some countries by _________________.

3. Pure common salt can be extracted from sea water by _________________ and then

_________________.

4. A _________________ solution is a solution in which the solvent has dissolved the

maximum amount of the solute it can at a particular temperature.

5. Distillation involves _________________ of a solution followed by

_________________ of the vapour formed.

6. In distillation, the pure liquid that distils over is called the _________________; the

solid left behind is called the _________________.

7. Sea water can be desalted by _________________.

8. Some metal give a characteristic flame colour to a non-luminous Bunsen flame. This

method of identification of metals is called the _________________.

9. Sodium compounds give a _________________ flame in the flame test.

10. Chloride ions in solution give a _________________ precipitate when acidified silver

nitrate solution is added.

11. Water turns dry cobalt chloride paper from _________________ to

_________________.

12. Water turns anhydrous copper(II) sulphate powder from _________________ to

_________________.

13. _________________ is a concentrated sodium chloride solution used in the chlor-alkali

industry.

14. By electrolysis of brine, the chemicals _________________, _________________ and

_________________ can be produced.

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Multiple choice questions

1. Which of the following elements are present in common salts?

A. Sodium and fluorine

B. Sodium and chlorine

C. Potassium and fluorine

D. Potassium and chlorine

2. Which of the following statements about seawater is INCORRECT?

A. Sea water is a solution of salts.

B. Common salt can be obtained from sea water by evaporation.

C. In chlor-alkali industry, sea water is electrolysed directly to form

hydrogen and chlorine.

D. Sea water is a mixture of compounds.

3. Which of the following statements about filtration is correct?

A. It can be used to remove salts from sea water.

B. Filtrate is the liquid passing through the filter paper.

C. Pure solution can be obtained from filtration.

D. Small crystals can be obtained after filtration.

4. Flame test

A. can be carried out to identify all compounds.

B. can be used to identify sodium compounds because sodium

compounds give out brick red flame in the test.

C. can be carried out in school laboratory.

D. can be used to test the purity of a given sample.

5. Which of the following is the correct observation when a drop of water is

added to anhydrous copper(II) sulphate crystal?

A. It turns from blue to pink.

B. It turns from white to blue.

C. It turns from blue to white.

D. None of the above

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6. Which of the following are the uses of hydrogen obtained from the

chlor-alkali industry?

(1) As rocket fuel

(2) Manufacture of ammonia

(3) Manufacture of soap

A. (1) and (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

7. Which of the following correctly describes the sequence of procedures to

separate sand, salt and water from a mixture of sand and salt solution?

A. Filtration, evaporation

B. Filtration, distillation

C. Crystallization, filtration

D. Crystallization, filtration, distillation

8. Some physical properties of a compound X are listed below:

Melting point: 90oC

Boiling point: 230oC

Solubility in water: soluble

Which of the following methods is the most suitable for obtaining X from a

solution of X in water?

A. Crystallization

B. Decantation

C. Filtration

D. Fractional distillation

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9. Which of the following compounds give characteristic flame colour flame

test?

(1) Potassium chloride

(2) Copper(II) chloride

(3) Calcium chloride

A. (1) and (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

10. Which of the following processes involve chemical changes?

(1) Mixing sea water with silver nitrate solution

(2) Evaporation of sea water

(3) Electrolysis of sea water

A. (1) and (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

11. Which of the following are the uses of chlorine obtained from the chlor-alkali

industry?

(1) As rocket fuel

(2) Manufacture of hydrochloric acid

(3) Sterilizing drinking water

A. (1) and (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

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The following table summarizes some common separation methods:

Separating process Method(s) of separation Example

Separating a much

denser insoluble solid

from a liquid

Separating coarse sand

from sea water

Separating an insoluble

tiny solid from a liquid

Separating mud from

muddy sea water

Separating a dissolved

solid from a solution

Obtaining common salt

from sea water

Separating solvent and

solute from a solution

Obtaining pure water and

salt from sea water

The following table shows the flame colours of some metal compounds:

Compound of Flame colour

Lilac

Sodium

Calcium

Bluish green

Questions

1. The following set-up is used to separate an insoluble solid from a liquid.

a) Name the process used.

______________________________

b) Name the material labeled X.

______________________________

c) Name the apparatus labeled Y.

______________________________

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d) Name the substance that passes through X and is collected in the beaker.

_____________________________________

e) Name the substance that remains on X.

___________________________________

f) Explain why the process can be used to remove mud particles from muddy water, but

cannot be used to remove sodium chloride from sea water.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

2. The following diagram shows the set-up for obtaining pure water from sea water.

a) Name the process used.

_____________________________________

b) Explain the principle of the process.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

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c) Name the apparatus labeled X.

_____________________________________

d) What is the purpose of adding anti-bumping granules into the sea water?

____________________________________________________________________

3. A student had a sample of sea water.

a) The student added dilute nitric acid, then silver nitrate solution to 5 cm3 of the sea

water.

i) Describe the expected observation for this test.

_____________________________________________________________

ii) Based on the above observation, name the species that is present in sea

water.

____________________________________________

b) The student evaporated some sea water to obtain a white solid.

i) Draw a labeled diagram of the set-up used for evaporation.

ii) Suggest how the student can show that the white solid contains sodium.

_____________________________________________________________

_____________________________________________________________

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4. You are given a mixture of sand and sodium chloride solution, and are asked to separate

sand, sodium chloride and water from the mixture.

a) Name the physical separation method you would use to separate sand from the

solution.

__________________________________________

b) Draw a labeled diagram for the experimental set-up of the above method.

c) Name the physical separation method you would use to separate sodium chloride and

water.

__________________________________________

d) Draw a labeled diagram for the experimental set-up of the above method.

e) After getting the sodium chloride, you have to test for the presence of sodium ions

and chloride ions in it. Suggest one test to show that sodium ions are present and

another test to show that chloride ions are present.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________