Po Kok Sec. School Chemistry S. 3 First Semesterfile.pokok.edu.hk/~chem/notes/S3_Chem_1st.pdf · 1 Po Kok Sec. School Chemistry S. 3 First Semester Date Content Grade Correction (

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Po Kok Sec. School

Chemistry

S. 3

First Semester

Date Content Grade Correction

(/×)

Chapter One:

Introducing Chemistry

Chapter Two:

The atmosphere

Exercise for Chapter Two

Chapter Three:

Fractional distillation

Exercise for Chapter Three

Chapter Four:

Oceans

Exercise for Chapter Four

Chapter Five:

Simple Chemical Analysis

Chapter Six:

What does common salt contain?

Exercise for Chapter Five & Six

Name: ___________________

Class: ( )

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Po Kok Sec. School Name:

S.3 Chemistry Class: ( )

Chapter One Introducing Chemistry Date

Learning Objectives:

After studying this chapter, you should be able to:

state what chemistry is about

explain how important chemistry is to our daily lives

list guidelines for observations in chemistry experiments

understand the importance of laboratory safety

know common hazard warning labels

name common laboratory apparatus

Vocabularies The following table show basic English terms used in this chapter. Write all their Chinese terms down in

the right column.

1. Chemistry 6. apparatus

2. Observation 7. Bunsen burner

3. Laboratory 8. test tube

4. Safety rules 9. boiling tube

5. hazard warning

labels 10.

Dropper

1.1 What is chemistry about?

?? Chemistry is a branch of science.

‘Science’ means knowledge gathered systematically from observations and

experiments.

Chemistry is the study of substances, about their compositions, structures,

properties and the changes among them.

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1.2 Chemistry in our lives today Chemistry is so important to us……..

Chemistry plays a major role in each of them! Class Practice 1.1

The photos below are some commodities or facilities in our daily lives which are affected by or related to chemistry. Write down the names of chemicals in them. The first one has been done for you as an example.

(a) Clothing (b) Food (C) Housing polyester, nylon,

dyes

(D) Transport

(E) Medical care

(F) Entertainment

4

1.3Working in chemistry laboratory Observation in chemistry includes four activities:

Seeing with eyes Smelling with nose

Feeling with hands Hearing with ears

Activity 1.1

Add a small piece of magnesium ribbon to a test tube containing dilute sulphuric acid. What changes can you observe?

(1)

(2)

(3)

(4)

(5)

For all the experiments you will do in this course, try your best to:

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Class Practice 1.2 – Laboratory safety rules

Match the following rules to “We should” and “We should not”. 1. keep all exits and passages clear

2. do experiments without teacher’s permission.

3. follow the instructions given by the teacher.

4. enter the laboratory without teacher’s permission.

5. wear safety goggles when heating or mixing substances.

6. tie back long hair and fasten school ties when doing experiments.

7. keep an eye on our experiments.

8. report all accidents to the teacher at once.

9. eat, drink, play or run about in the laboratory.

10. keep the laboratory clean and tidy.

11. point the mouth of a test tube towards anyone when heating. We should We should NOT

Class Practice 1.3 Identify the safety rules (choose from a list) that students have not observed in the laboratory.

1

Student 1: He should not run about in the laboratory.

2

Student 2:

3

Student 3:

4

Student 4:

5

The door of the laboratory:

6

Student 6:

6

Classification of hazardous chemicals

Activity 1.2 Studying hazard warning labels Your teacher will show you reagent bottles containing the chemicals below. Study the hazard warning label(s) on each reagent bottle. Suggest the hazardous nature of each chemical.

Chemicals Hazardous Nature

a Dilute ammonia

b Ethanol

c Dilute hydrochloric acid

d Concentrated sodium hydroxide solution

e Methanol

f Concentrated nitric acid

Common laboratory apparatus

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Class Practice 1.3 Name the apparatus in the following figures.

(a) ______________________ (b) ______________________ (c) ______________________ (d) ______________________ (e) ______________________

(f) ______________________

(g) ______________________ (h) ______________________ (i) ______________________ (j) ______________________ (k) ______________________ (l) ______________________ (m) ______________________ (n) ______________________

(o) ______________________ (p) ______________________ (q) ______________________

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(r) _______________ (s) _______________ (t) _______________

(u) _______________ (v) ______________

(w) ______________

(x) ______________________ (y) ______________________ (z) ______________________ (aa) ______________________ (bb) ______________________ (cc) ______________________

(dd) ______________________ (ee) ______________________ (ff) ______________________

(gg) ______________________

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Chapter Two: The atmosphere Date



appreciate that the Earth’s crust, the oceans and the atmosphere are major sources of useful

chemicals.

state the composition of clean air

state the uses of gases separated from air.

demonstrate how to carry out a test for oxygen and carbon dioxide.


the right column.

1. Earth 6. Oxygen

2. Atmosphere 7. Carbon dioxide

3. resources 8. Noble gas

4. Composition 9. Argon

5. nitrogen 10. Water vapour

2.1 The Earth We all live on the Earth.

The Earth’s crust, the ocean and the atmosphere

provide us with all the resources we need.

resources

The atmosphere

The

oceans

The

Earth’s

crust

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Resources obtained from the Earth

2.2 The atmosphere and air The atmosphere is a gaseous layer (about 80 km thick)

surrounding the Earth.

This layer contains a mixture of gases called air.

Composition of air

From the atmosphere:

Nitrogen, oxygen and

other gases

From the ocean:

Sodium chloride, bromine

and magnesium

From the Earth’s crust::

Coal, petroleum and

natural gas

Metals

Wood

Rocks

1% other gases (noble gases

0.93%, carbon dioxide 0.03% and

small amounts of water vapour)

Oxygen

21%

Nitrogen

78%

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Class Practice 2.1 A) Match each of the gases listed on the left column with its uses.

∙(i)

to fill some food packages

∙ (ii) to store living cells at a very

low temperature.

(a)

(b)

(c)

Oxygen∙

Nitrogen∙

Carbon dioxide∙

∙(iii) to cut metals when mixed with gas fuel. (Supporter of burning)

∙(iv) to help patients who have

breathing problems.

∙(v) to put out fire (as fire

extinguishers).

∙(vi) to keep ice-cream cakes

frozen.

B) Making sentences:

e.g.

1. Oxygen is used to cut metals when mixed with gas fuel.

2. Oxygen is used to

3. Nitorgen is used to

4. Nitorgen

5.

6.

(A. Gas)+is used to + (B. verb + noun.)

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Class Practice 2.2

Noble gases (貴氣體) are a group of unreactive and colourless gases. They include helium

(氦), argon(氬), neon(氖), etc.

1. Helium is used to ____________________________

2. Argon __________________________________

3. Neon __________________________________

2.3 Testing for gases in the air Oxygen, carbon dioxide, nitrogen and water vapour are common gases in the air. What are the

properties of these gases? How can we test for these gases? Let us find out in the following

experiments.

Experiment 2.1 Title: Tests for oxygen, carbon dioxide and nitrogen Aim: To find out the properties of oxygen, carbon dioxide and nitrogen, and learn how to test for

them Apparatus and Chemicals:

Test tubes filled with oxygen ×5, test tubes filled with carbon dioxide×5, Test tubes filled with nitrogen ×5, test

tube racks, wooden splints, matches or lighter, limewater

Safety precaution: Wear safety goggles.

EYE PROTECTIONMUST BE WORN

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Procedure: 1. (a) Look at the oxygen in the test tubes. (b) Records its colour in the table on the result part. 2. (a) Remove the stopper of a test tube of oxygen. Fan the gas towards your nose and

smell it. [Caution: DO NOT breathe in the gas directly] (b) Records its smell in the table on the result part. 3. (a) Prepare a burning splint. Put it quickly into another test tube of oxygen. (b) Observe what happens to the splint and record the observation in the table on the

result part.

4. (a) Prepare a glowing splint. Put it quickly into another test tube of oxygen. (b) Observe what happens to the splint and record the observation in the table on the

result part.

5. (a) Add about 2cm3 of lime water into another test tube of oxygen. Stopper the test tube

and shake it gently. (b) Observe what happens to the lime water and record the observation in the table on the

result part.

6. Repeat steps 1 to 5, using carbon dioxide in place of oxygen. 7. Repeat steps 1 to 5, using nitrogen in place of oxygen.

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Results:

Observation Test result

Oxygen Carbon dioxide Nitrogen

1. colour of gas

2. smell of gas

3. change of burning splint

4. change of glowing splint

5. colour change of limewater

Conclusions:

1. Oxygen can ___________________________

2. Carbon dioxide can __________________________

3. There is ____________________________ for nitrogen.

Questions: 1. Can we identify oxygen by looking at its colour? Why?

2. Can we identify carbon dioxide by using burning splint and glowing splint? Why?

Experiment 2.2 Title: Liquid nitrogen ice cream (Demonstration) Aim: To find out the properties of liquid nitrogen. Apparatus and Chemicals:

Whipping cream, fruits, steel plate and bowl

Safety precaution: Wear safety goggles and safety cloth.

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Exercise for Chapter Two Date

A. Concepts maps

Complete the concept map using the following words:

carbon dioxide, limewater, glowing splint, nitrogen, noble gases, oxygen, water vapour

B. Fill in the blanks

1. A gaseous layer surrounding the Earth is called ____________________.

2. The major components of air are ________________ and ____________________ .

3. Oxygen relights a ________________________________ .

4. Carbon dioxide can turn limewater ___________________________- .

C. 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% carbon dioxide, 0.03% argon

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

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

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

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

A. Argon B. Helium

C. Krypton D. Neon

3. Oxygen

A. can only be found on Earth. B. relights a burning splint.

C. is a flammable gas. D. is an odourless gas.

air

Tested by a

relighting Tested by

21% 78% 0.03% 0.9%

small

amount

of

turns milky.

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4. Which of the following is NOT a use of oxygen?

A. Assisting breathing of firemen. B. Filling the airships and party balloons.

C. cutting and welding of metals. D. supporting the combustion of fuel.

5. Which of the following is NOT a use of carbon dioxide?

A. it is used in soft drinks. B. it can be used to make fire extinguishers.

C. it is used to fill advertising lights. D. it is used as a refrigerant

D. Structured questions.

1. The bar chart shows the percentage composition of the atmosphere on Mars.

State THREE ways in which the atmosphere on Earth today is different from that on Mars.

(i) The atmosphere on Earth contains less ________________________________________

(ii) The atmosphere on Earth ___________________________________________________

(iii) ________________________________________________________________________

2. Air can be dissolved in water. The dissolved air can be driven out for collection using a special set-up.

In an experiment, 50cm3 of such dissolved air had been collected. The dissolved air was passed back

and forth over some heated copper turnings. Afterwards, the volume of dissolved air left was 33cm3.

(a) Name the two most abundant gases in air .

________________________________________________________________________

(b) Which gas in air did react with the heated copper turnings?

________________________________________________________________________

(c) What volume of this gas was present in 50cm3 of dissolved air.

________________________________________________________________________

(d) Calculate the approximate percentage of this gas in dissolved air.

________________________________________________________________________

(e) What is the percentage of this gas in the atmosphere?

________________________________________________________________________

(f) Suggest one reason for the difference between the answers in (e) and (f).

________________________________________________________________________

0

20

40

60

80

100

Carbon dioxide Nitrogen Other gases

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Chapter Three: Fractional distillation Date



describe the process involved in fractional distillation of liquid air, and understand the

concepts and procedures involved.


the right column.

1. Separation 6. argon

2. Boiling point 7. vapour

3. Fractional distillation 8. column

4. Purification 9. alcohol

5. liquefaction 10. condenser

3.1 Separation of oxygen and nitrogen from air The gases in air are useful in many ways.

We can separate the gases in air by fractional distillation (分餾) of liquid air.

The components of air can be separated according to their differences in boiling points (沸點):

Gas Boiling points

Nitrogen -196∘C

Argon -186∘C

Oxygen -186∘C

Stage of fractional distillation:

Stage Action

1. Purification Dust, water vapour and carbon dioxide in the air are

removed.

2. Liquefaction of air The air is liquefied (液化) by repeated cooling and

compression. It gets very cold (-200C) and some turns

to liquid.

3. Separation of liquid air The liquid air is pumped into a fractionating column and

then warmed up bit by bit very slowly.

Different gases in air boil at different temperatures, we

can collect them one by one.

During fractional distillation, nitrogen boils off as a gas first. Argon follows and then oxygen.

Class Practice 3.1 1. Explain why the water vapour and carbon dioxide in the air have to be removed before

liquefaction.

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2. Complete the diagram using the following words:

Purification, liquefaction, Fractionating column, nitrogen gas, Argon gas, Oxygen gas

An air separation plant.

3.2 Fractional distillation Fractional distillation is also used to separate alcohol from water, in order to purify alcoholic

beverages.

Beer and wine produced after fermentation of grains and grapes contain less than 15% alcohol. It is

due to the fact that a high concentration of alcohol kills the yeast that are responsible for proceeding

fermentation. In such a condition, fractional distillation is used to purify alcohol and make stronger

alcoholic drinks.

Wine (alcohol = 12~15%) Brandy (alcohol = 35~60%)

(b.p. -196C)

(b.p. -186C)

(b.p. -183C)

Air in

Liquid

air

Fractional distillation

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Experiment 3.1 (Demonstration) Title: Fractional distillation of alcoholic beverage Aim: To purify alcohol from the mixture of water and alcohol. Apparatus and Chemicals:

Quick fit of fractional distillation, 15% alcohol solution (stained), evaporating dish and lighter

Safety precaution: Wear safety goggles. Introduction:

The boiling point of alcohol is 78C while the boiling point of water is 100C. The following set-up of

fractional distillation in the laboratory can be used:

Questions and discussion: 1. Which one will be boiled off at gas first when the mixture of alcohol and water are heated by Bunsen

burner? Why?

2. What is the use of condenser in the above set-up?

3. A fractional distillation setup includes an additional column called fractionating column that is

typically packed with glass beads or pieces of ceramic.

What is the use of the fractionating column in the above set-up?

4. How do we show that the major component of distillate is alcohol?

15% alcohol

solution (stained)

distillate

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Exercise for Chapter Three Date

A. Fill in the blanks

1. The method of separating the gases in air is called ______________________ of liquid air.

2. Air can be _______________________ by cooling and compression.

3. Fractional distillation of liquid air bases on the different __________________________ of the

components of air.

B. Multiple choice questions

1. The components of air can be separated by fractional distillation according to their differences in

A. cooling point. B. melting points.

C. boiling points. D. freezing points

2. Which of the following substances has the lowest boiling point?

A. Oxygen. B. Nitrogen.

C. Argon. D. Water

3. Which of the following constituents in the air are separated by fractional distillation of liquid air?

(1) Nitrogen.

(2) Carbon dioxide.

(3) Argon.

A. (1) and (2) only. B. (1) and (3) only.

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

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 table below gives some information about certain components in a sample of liquefied air.

Component Boiling point (∘C)

Argon -186

Nitrogen -196

Oxygen -183

In what order are these components distilled out when the sample undergoes fractional distillation?

A. Nitrogen, oxygen, argon. B. Nitrogen, argon, oxygen.

C. Oxygen, argon, nitrogen. D. Oxygen, nitrogen, argon.

6. Which of the following statements about the fractional distillation of liquid air are correct?

A. Oxygen boils at -183∘C

B. Nitrogen boils at a higher temperature than oxygen

C. Nitrogen gas is collected at the lower part of fractionating column.

D. Fractional distillation can not be used to separate nobles gases

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C. Structured questions.

1. The table below gives some information about three components in a sample of liquefied air: Component Argon Oxygen Nitrogen

Boiling point (∘C) -186 -183 -196

a) Upon heating the liquefied air, which component will boil first? Explain briefly.

b) Both oxygen and nitrogen can be obtained from the fractional distillation of liquid air.

i) Give a reason why they can be obtained separately by fractional distillation.

ii) Where does the fractional distillation of liquid air occur in industry?

iii) Does the fractional distillation involve chemical change? Explain briefly.

iv) Suggest a test to distinguish between nitrogen and oxygen. Describe briefly.

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Chapter Four: Oceans Date



state the composition of sea water.

describe how common salt can be extracted from sea water.

Evaluate the methods of physical separation including evaporation, filtration,

crystallization and distillation.


the right column.

1. Composition 6. filtration

2. Sodium chloride 7. evaporation

3. salt 8. Crystallization

4. Soluble 9. Concentrated

5. Insoluble 10. crystals

4.1 Composition of sea water 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 dissolved solids are different salts. The main one is common salt – sodium chloride.

The salts are brought to the sea mainly by rivers.

The salt composition of sea water may vary slightly according to location and depth.

The Dead Sea has an unusually high salt content which

enables one to float effortlessly.

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4.2 Extraction of common salt from sea water When we leave sea water to dry in the sun, the water evaporates and leaves behind the common salt.

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

evaporation(蒸發).

Common salt is obtained from sea water by evaporation.

Experiment 4.1 Title: Extracting common salt from sea water by evaporation Aim: To extract common salt from sea water. Apparatus and Chemicals:

Stand and ring, filter funnel, glass rod, beaker (100cm3), 2 beakers (250cm3), tripod and wire gauze, Bunsen burner, heat-resistant mat, evaporating dish, measuring cylinder (10cm3), filter paper, 50cm3 of sea water (obtained from a sandy each)

Safety precaution: Wear safety goggles. Procedure: 1. Pour the muddy sea water into a filter funnel fitted with a piece of filter paper. Collect the

filtrate in an evaporating dish.

Filtration 2. a) Compare the sea water before filtering and after filtering (the filtrate obtained in

step (1). b) Observe also carefully what is left in filter paper. c) Record your observations in Table of result part. 3. a) Arrange the evaporation set-up as shown in the following figure.

Evaporation b) Place about 5cm3 of the filtrate obtained in step 2 on the evaporating dish of the

set-up. c) Heat the set-up with a Bunsen burner until the water on the dish dries up. 4 a) Observe the appearance of the product obtained. b) Record your observations.

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Results:

Observations Results

Comparing the sea water before filtration and after filtration

Remain on the filter paper after filtration

Change occurring on the evaporation dish when direct heating.

Colour and state of substance remaining on the evaporating dish after the filtrate dries up.

Conclusions: 1. Filtration can remove_____________impurities from a liquid, like _____________from sea

water in this experiment.

2. Filtration cannot remove _____________ impurities from a liquid, like _____________in

sea water in this experiment.

3. To isolate the solute of a solution, the method of _____________needs to be used.

4. To extract common salt from sea water, the method of _____________followed by

_____________has to be used.

Questions: 1. Rock salt is another source of common salt. It contains some insoluble impurities such as

sand and clay. Suggest how you can obtain pure common salt from rock salt.

2. The following set-up is used to indirectly heat the evaporating dish over a steam bath. What is the advantage and disadvantage of this heating method comparing to direct heating on a wire gauze? .

Advantage: Disadvantage:

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Crystallization (結晶法)

Many solids exist as crystals (晶體).

Crystallization is the process of forming crystals — another method for separating a solute from

a solution.

There are two common techniques of crystallization.

By cooling a hot concentrated solution The solution was heated to remove some of the solvent. The solution becomes more

concentrated.

A hot solvent can usually dissolve more solute than a cold one.

When the hot and concentrated solution cools, the solvent cannot hold all the solutes.

The extra solutes then separate out as crystals.

Slow evaporation of a solution at room temperature

We can also obtain crystals by evaporating a solution at room temperature.

Sea water is allowed to evaporate slowly at room temperature.

As the solvent evaporates, the remaining solution becomes more concentrated and finally

becomes saturated.

Further evaporation makes the extra solutes separate out as crystals.

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Experiment 4.2 (Demonstration) Title: Growing copper (II) sulphate crystals Aim: To prepare copper (II) sulphate crystals. Apparatus and Chemicals:

2 beakers (100cm3), watch glass, spatula, glass rod, filter funnel, stand and clamp, thread, paper, well-shaped copper(II) sulphate crystal, copper(II) sulphate (15g), water

Safety precaution: Wear safety goggles. Copper (II) sulphate is harmful. Procedure: 1. Prepare a saturated solution of copper(II) sulphate by following the steps below. a) Place 50 cm3 of water in a beaker. b) Add a spatula measure of copper(II) sulphate.

c) Stir with a glass rod.

d) Add some more copper(II) sulphate, one spatula measure at a time. Stir after each addition.

e) Continue adding copper(II) sulphate until some solids remain in the beaker. 2. Filter the saturated solution into another beaker.

3 Suspend a well-shaped copper(II) sulphate crystal in the solution.

4 Cover the beaker with a piece of paper. 5 Leave the beaker in a warm place until the next lesson. 6 Look at the beaker again in the next lesson. Describe what you see. 7 Pick out the crystal formed on the thread. Draw its shape. 8 Record your observations in the result part.

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Results and Observations: 1. What will be observed in the next lesson?

2. Drawing of the crystal formed on the thread.

Conclusion:

As the water evaporates from a saturated solution, the solvent cannot hold all the solutes. The extra solutes then separate out as ___________________ . This process of forming crystals is called _________________ .

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Exercise for Chapter Four Date A. Concepts maps

Complete the concept map using the following words:

Concentrated solution, crystals, dilute solution, insoluble, saturated, soluble, solution

B. Fill in the blanks

1. A solution in which the solvent has dissolved a large amount of the solute in a given volume of

solution is called ______________________ solution.

2. Pure common salt can be extracted from sea water by filtration and then ________________.

3. The process of forming crystals is called ________________________.

C. Multiple choice questions

1. Which of the following correctly describes the sequence of procedures to separate sand, salt and water

form a mixture of sand and salt solution?

A. Filtration, evaporation B. Filtration, distillation

C. Crystallization, filtration D. Crystallization, filtration, distillation

2. 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.

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3. Some properties of a substance X are listed below:

Melting Point: 90∘C

Boiling Point: 230∘C

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

4. Which of the following combinations is correct?

Method Uses

A. Fractional distillation Obtaining salt from salty water

B. Crystalization Obtaining salt from salty water

C. Filtration Obtaining oxygen from liquid air

D. Evaporation Obtaining oxygen from liquid air


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

a) Name the process used..

b) Name the material labelled X.

c) Name the apparatus labelled Y.

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 common salt from sea water. (Hints: comparing the size of mud particles, common

salt and holes on filter paper.)

30



Chapter Five: Simple Chemical Analysis Date



Describe chemical tests used to show the presence of ions.


the right column.

1. Chemical analysis 6. Nichrome wire

2. Compound 7. Calcium

3. Cation 8. Sodium

4. Anion 9. Potassium

5. Flame test 10. Copper

5.1 Chemical Analysis Chemical Analysis is a process to find the chemical identity or composition of a given sample.

Detecting Insecticides, Chemical Contaminants, & Residues in Food.

Pollution investigation from site survey and sampling to Chemical analysis.

Usually, compounds are made of cations and anions. Methods, which show the presence of cations

(ions with positive charge) and anions (ions with negative charge) in the compounds respectively, are

used to identity unknown compound.

Ionic Compound = Cations + Anions

31

Experiment 4.1 Title: Flame test (Test for cations) Aim: To test for the presence of cations in compounds Introduction: Some cations (metal ions/metal compounds) give a brightly coloured flame when

burnt in a Bunsen flame. The colour of the flame may be used to identify the type of cation in the compound

Apparatus and Chemicals: Bunsen burner, heat-resistant mat and lighter, nichrome wire, 4 watch glasses, conc. Hydrochloric acid in test tube, sodium carbonate solid, sodium chloride solid, calcium carbonate solid, calcium chloride solid, copper(II) chloride solid, copper(II) carbonate solid, potassium carbonate solid, potassium chloride solid.

Safety precaution: Wear safety goggles. If you are spill any acid on your skin or clothes, wash it off immediately with plenty of water. The laboratory must be well-ventilated.

Conc. hydrochloric acid is very corrosive. Procedure: 1. Light a Bunsen burner. Half open the air hole of the burner to obtain a blue flame. 2. a) Clean the end of a nichrome wire by dipping it into concentrated hydrochloric acid

and then heat it in the Bunsen flame. b) Observe the colour of the flame. If the flame is still coloured, repeat step 2a.

3. a) Put 1 spatula measure of solid sample onto a clean watch glass. b) Dip the nichrome wire into concentrated hydrochloric acid and then into the solid. c) Put the end of the wire in the Bunsen flame again. Record the colour of the flame. 4. a) Repeat the test with other compounds and the common salt obtainedfrom sea

water. Clean the nichrome wire after testing each compound. b) Record your observations. 5. Record the colour of the flames of various compounds. Results:

Compound Colour of flame

Calcium carbonate

Calcium chloride

Sodium carbonate

Sodium chloride

Potassium carbonate

Potassium chloride

Copper(II) carbonate

Copper(II) chloride

Nichrome wire

Concentrated

hydrochloric acid

32

Conclusions: 1. Complete the following table.

Compound containing Colour of flame

Calcium ion

Sodium ion

Potassium ion

Copper(II) ion

Questions: 1. Suggest how you would show the presence of calcium ion s in a solid sample.

Experiment 4.2 Title: Testing for anions Aim: To test for the presence of anions in compounds Apparatus and Chemicals:

Test tubes in rack and with brush, dropper, spectula, delivery tube, 100cm3 beaker, deionized water, dilute nitric

acid,silver nitrate solution,sodium chloride solution,potassium chloride solution,sodium carbonate solid,copper(II)

carbonate solid,limewater

Safety precaution: Wear safety goggles. If you spill any acid on your skin or clothes, wash it off

immediately with plenty of water. Dilute nitric acid is corrosive. Silver nitrate solution can cause black stains on your skin. Handle with care.

Procedure: A. Testing for carbonate ions 1. a) Your teacher will give you some solids of the following compounds:

sodium carbonate copper(II) carbonate sodium sulphate

b) Using a spatula, put some solids into a test tube respectively. 2. Arrange the set-up as shown in the following figure. Pour 2cm3 of dilute nitric acid into

solid samples. Test the gas given off with lime water.

3. Record your observations in the following table.

Compounds Gas given off (/)

Observation of lime water What is the gas?

sodium carbonate

copper(II) carbonate

sodium sulphate

dilute nitric

acid

lime

water

33

4. Conclusions

B. Testing for chloride ions 1. a) Your teacher will give you solutions of the following compounds:

sodium chloride potassium chloride sodium sulphate

b) Pour 2cm3 of each solution into a test tube respectively.

2. Add 2 cm3 of dilute nitric acid into each test tube.

Is any gas given off? Do they contain carbonate ions? _____________________________________

3. Make sure the sample without carbonate ions. Then, add a few drops of silver nitrate

solution. Record your observation in the following table.

Solution of Observations

Sodium chloride

Potassium chloride

Sodium sulphate

4. Conclusion:

dilute nitric

acid

silver nitrate

solution

34



Chapter Six: What does common salt contain? Date Learning Objectives:


Describe chemical tests used to show the presence of ions in common salt.


the right column.

1. Common salt 6. Chloride

2. Carbonate 7. Silver nitrate

3. Nitric acid 8. Concentrated

4. Lime water 9. Hydrochloric acid

5. Carbon dioxide 10. Sodium chloride

Experiment 6.1 Title: What does common salt contain? Aim: To perform chemical tests for common salt. Apparatus and Chemicals:

Bunsen burner, heat-resistant mat and lighter, nichrome wire, watch glass, conc. Hydrochloric acid in test tube, common salt, Test tubes in rack and with brush, dropper, spectula, delivery tube, 100cm3 beaker, deionized water,

dilute nitric acid,silver nitrate solution.

Safety precaution: Wear safety goggles. If you are spill any acid on your skin or clothes, wash it off immediately with plenty of water. The laboratory must be well-ventilated. Conc. hydrochloric acid is corrosive. Silver nitrate solution can cause black stains on your skin. Handle with care.

Procedure: A. Testing for cations 1. Light a Bunsen burner. 2. Clean the end of a nichrome wire by dipping it into concentrated hydrochloric acid and

then heat it in the Bunsen flame.

3. Put 1 spatula measure of common salt onto a clean watch glass. 4. Dip the nichrome wire into concentrated hydrochloric acid and then into the solid.Put the

end of the wire in the Bunsen flame again.Record the colour of the flame. Results and observations:

Testing Observations

Cations Flame test

Conclusions 1. Common salt from sea water contains ___________________ ions.

Concentrated

hydrochloric acid

Nichrome wire

35

Procedure: B1. Testing for anions (carbonate ions) 1. Arrange the set-up as shown in the following figure. Pour 2cm3 of dilute nitric acid into

common salt. Test the gas given off with lime water.

3. Record your observations. B2. Testing for anions (chloride ions) 1, Using a spatula, put some common salt powder into a test tube. Dissolve the solid in

deionized water. 2. Add a few drops of dilute nitric acid to the test tube.

3. If there is no any reaction occurred when dilute nitric acid is added, then add a few drops

of silver nitrate solution. Record your observation.. Results and observations:

Testing Observations

Anions Addition of nitric acid

Addition of acidified

silver nitrate solution

Conclusions 1. Common salt from sea water contains _____________________ ions. 2. Results of above test show that common salt is ______________________ Question: (a) Which anion does the common salt from sea water contain? Explain your answer.

(b) Write the word equation of the chemical reaction involved.

silver nitrate

solution dilute nitric

acid

dilute nitric

acid

lime

water

36



Exercise for Chapter Five & Six Date

A. Fill in the blanks

1. Ionic compound is made up of ________________ and _________________.

2. Some metals give a characteristic flame colour to a non-luminous Bunsen flame. This method of

identification of metals is called the ______________________ .

3. Complete the following table which shows the flame colours of some metal compounds:

Compound of Flame colour

Potassium ions

Sodium ions

Calcium ions

Copper ions

4. Chloride ions in solution give a ____________________ precipitate when acidified silver nitrate

solution is added.

B. Multiple choice questions

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

A. Sodium and fluorine B. Sodium and chlorine

C. Potassium and fluorine D. Potassium and chlorine

2. The element sodium is usually found in fireworks, since

A. sodium is an essential substance to ignite fireworks.

B. sodium burns with a golden yellow flame.

C. sodium makes fireworks explode violently.

D. burning sodium gives the sound of explosion.

3. Steps of a flame test for sodium are shown below.

(1) Heat the nichrome wire with a small, non-luminous Bunsen flame.

(2) Dip the tip of the nichrome wire into concentrated hydrochloric acid.

(3) Dip the tip of the nichrome wire into the sample under test.

(4) Put the tip of the nichrome wire at the lower part of the Bunsen flame.

Which of the following sequences to perform a flame test is correct?

A. (4)(2)(3)(1)(2) B. (2)(4)(2)(3)(1)

C. (2)(1)(2)(3)(4) D. (3)(2)(4)(2)(1)

4. Which of the following is the flame colour of sodium chloride?

A. Golden yellow B. Greenish yellow

C. Lilac D. Brick-red

5. Which of the following elements can be identified easily by flame test?

A. Phosphorus B. Calcium

C. Chlorine D. Sulphur

37

6. Which of the following methods can be used to test for the presence of chloride ions in sea water?

A. Heat the sea water to see if white residue forms.

B. Add acidified silver nitrate solution to sea water, and see if white precipitate forms.

C. Add oil to sea water to see if two liquid layers form.

D. Heat sea water to detect the smell of chlorine.

7. When acidified silver nitrate solution is added to magnesium chloride solution, a white precipitate is

formed. The white precipitate is

A. magnesium nitrate. B. silver chloride.

C. silver metal. D. magnesium metal.


1. Suppose a student collected a certain substance and would like to test whether it is common salt.

(a) What is the chemical name of common salt?

(b) The student would first like to test for the presence of sodium ions. Name the test he should adopt.

(c) Briefly outline the procedures of this test, and how he could determine the presence of sodium ions.

(d) State two safety precautions he should pay attention to while he is conducting the above experiment.

(e) Next he would like to test for the presence of chloride ions and has prepared a sample of silver

nitrate solution and excess dilute nitric acid. Why is excess dilute nitric acid needed?

(f) The student added sea water into the above sample. What is the expected result?

(g) Write the word equation of the chemical reaction involved.

(h) Suggest a method to separate the newly formed chloride compound from the solution.

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Po Kok Sec. School Chemistry S. 3 First Semesterfile.pokok.edu.hk/~chem/notes/S3_Chem_1st.pdf · 1 Po Kok Sec. School Chemistry S. 3 First Semester Date Content Grade Correction (