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Chemistry Workbook

Original material © Cambridge University Press 2016

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Richard Harwood and Ian Lodge

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Cambridge IGCSE®

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Physical Science

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Chemistry Workbook

Original material © Cambridge University Press 2016

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NOTICE TO TEACHERS IN THE UK It is illegal to reproduce any part of this work in material form (including photocopying and electronic storage) except under the following circumstances: (i) where you are abiding by a licence granted to your school or institution by the Copyright Licensing Agency; (ii) where no such licence exists, or where you wish to exceed the terms of a licence, and you have gained the written permission of Cambridge University Press; (iii) where you are allowed to reproduce without permission under the provisions of Chapter 3 of the Copyright, Designs and Patents Act 1988, which covers, for example, the reproduction of short passages within certain types of educational anthology and reproduction for the purposes of setting examination questions.

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Example answers and all questions were written by the authors.

Original material © Cambridge University Press 2016

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Contents v vi

C1 The particulate nature of matter C1.1 Changing physical state C1.2 Plotting a cooling curve

1 1 3

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C2 Experimental techniques C2.1 Diffusion, solubility and separation C2.2 Chromatography at the races

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Introduction Periodic table

7 7 10

C3 Atoms, elements and compounds C3.1 Atomic structure C3.2 The first four periods C3.3 The chemical bonding in simple molecules C3.4 The nature of ionic lattices

12 12 13 15 16

C4 Stoichiometry

17

Formulae of ionic compounds Making magnesium oxide – a quantitative investigation The analysis of titration results Calculating formula masses A sense of proportion in chemistry Finding the mass of 5 cm of magnesium ribbon Reacting volumes of gases

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C4.1 C4.2 C4.3 C4.4 C4.5 C4.6 C4.7

iii

17 19 22 24 26 27 29

C5 Electricity and chemistry C5.1 The nature of electrolysis C5.2 Making and ‘breaking’ copper chloride

31 31 33

C6 Energy changes in chemical reactions C6.1 Energy diagrams C6.2 The collision theory of reaction rates C6.3 The influence of surface area on the rate of reaction C6.4 Finding the rate of a reaction producing a gas

36 36 38 39 43

C7 Acids, bases and salts C7.1 Acid and base reactions – neutralisation C7.2 Types of salt C7.3 Descaling a coffee machine C7.4 Thermochemistry – investigating the neutralisation of an acid by an alkali

46 46 47 48 50

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54 54 56 58

C9 Metals C9.1 The reactivity series of metals C9.2 Energy from displacement reactions C9.3 Metals and alloys

59 59 61 64

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C8 The Periodic Table C8.1 Trends in the halogens C8.2 Displacement reactions of the halogens C8.3 Group I: The alkali metals

66 66 69

C11 Organic chemistry C11.1 Families of hydrocarbons C11.2 Unsaturated hydrocarbons (the alkenes) C11.3 The alcohols as fuels C11.4 Essential processes of the petrochemical industry C11.5 Addition polymerisation

72 73 74 76 79 81

C12 Analysis C12.1 Titration analysis C12.2 Chemical analysis C12.3 Planning a controlled experiment C12.4 Chemical testing and evaluation C12.5 Experimental design

82 82 84 88 91 94

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iv

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C10 Air and water C10.1 Atmospheric pollution, industry and transport C10.2 Clean water is crucial

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Glossary

Introduction This workbook contains exercises designed to help you develop the skills needed for success in Cambridge IGCSE Physical Science.

AO1 Knowledge with understanding AO2 Handling information and problem solving AO3 Experimental skills and investigations.

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The examination tests three different Assessment Objectives, or AOs for short. These are:

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In the examination, about 50% of the marks are for AO1, 30% for AO2 and 20% for AO3. Just learning your work and remembering it is therefore not enough to make sure that you get the best possible grade in the exam. Half of all the marks are for AO2 and AO3. You need to be able to use what you’ve learned in unfamiliar contexts (AO2) and to demonstrate your experimental skills (AO3).

This workbook contains exercises to help you to develop AO2 and AO3 further. There are some questions that just involve remembering things you have been taught (AO1), but most of the questions require you to use what you’ve learned to work out, for example, what a set of data means, or to suggest how an experiment might be improved.

These exercises are not intended to be exactly like the questions you will get on your exam papers. This is because they are meant to help you to develop your skills, rather than testing you on them.

There’s an introduction at the start of each exercise that tells you the purpose of it – which skills you will be working with as you answer the questions.

v

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For some parts of the exercises, there are self-assessment checklists. You can try marking your own work using these.

This will help you to remember the important points to think about. Your teacher should also mark the work and will discuss with you whether your own assessments are right.

The exercises cover both Core and Supplement material of the syllabus. The Supplement material can be identified by the Supplement bar in the margin (as shown). This indicates that the exercise is intended for students who are studying the Supplement content of the syllabus as well as the Core.

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II

a = relative atomic mass

X

b

X = atomic symbol b = proton (atomic) number

F

9

Ne

Helium 4 10

He

Group

8

2

VIII / 0

O

Neon 20 18

VII

7

Ar

VI

N

Fluorine 19 17

Argon 40 36

V

6

Cl

Kr

IV

C

Chlorine 35.5 35

III

H

5

S

Oxygen 16 16

Br

1

Hydrogen 1

B

Sulfur 32 34

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I

a

P

Nitrogen 14 15

Se

4

Carbon 12 14

Phosphorus 31 33 30

3

Key

Si

As

Zn

Be

Boron 11 13

Silicon 28 32 29

Li

Al

Ge

Cu

Beryllium 9 12

Aluminium 27 31 28

Mg

Ga

Ni

Lithium 7 11

22

27

Na

Ti

Co

25

21

26

Mn

Sc Fe

24

Krypton 84 54

Cr

Xe

V

I

Bromine 80 53

23

Selenium 79 52

Magnesium 24 20

Te

Ca

Arsenic 75 51

Sodium 23 19

Sb

K

Germanium 73 50 Iron 56 44

Sn Ru

Gallium 70 49

Manganese 55 43

In Tc

Zinc 65 48

Chromium 52 42

Cd

Mo

Copper 64 47

Vanadium 51 41

Ag

Nb

Zr

Titanium 48 40

Y

Scandium 45 39

Nickel 59 46

Calcium 40 38

Pd

Sr

Cobalt 59 45

Potassium 39 37

Rh

Rb

Xenon 131 86

–

Rn

Technetium

Iodine 127 85

Rhodium 103 77

At

Ir

Tellurium 128 84

Ruthenium 101 76

Po

Os

Antimony 122 83 75

Bi

Re

Tin 119 82

Molybdenum 96 74

Pb

W

Indium 115 81

Niobium 93 73

Tl

Ta

Zirconium 91 72

Cadmium 112 80

Hf

Yttrium 89 57 *

Hg

La

Silver 108 79

Strontium 88 56

Au

Ba

Platinum 195 110

Palladium 106 78

Rubidium 85 55

Ds

Pt

Cs

Indium 192 109

Radon 222 118

Mt

Uuo

Osmium 190 108

Astatine 210 117

Hs

Uus

Rhenium 186 107

Polonium 209 116

Bh

Lv

Tungsten 184 106

Bismuth 209 115

Sg

Uup

Tantalum 181 105

Fl

Db

Lead 207 114

Rf

Hafnium 179 104

Thallium 204 113

Lanthanum 139 † 89

Uut

Ac

Mercury 201 112

Barium 137 88

Cn

Ra

Gold 197 111

Caesium 133 87

Rg

Fr

Ununoctium

Meitnerium 268

Eu

63

Gd

64

Bk

Terbium 159 97

Tb

65

Cf

Dysprosium 163 98

Dy

66

Es

Holmium 165 99

Ho

67

Fm

Erbium 167 100

Er

68

–

Md

Thulium 169 101

Tm

69

–

No

Ytterbium 173 102

Yb

70

Lr

Lutetium 175 103

Lu

71

Lawrencium 262

–

62

Gadolinium 157 96

–

Hassium 265

Sm

Cm

Ununpentium Livermorium

61

Europium 152 95

Nobelium 259

–

Bohrium 264

Pm

Am

Mendelevium 258

Flerovium

60

Samarium 150 94

Fermium 257

–

Seaborgium 263

Nd

Pu

Einsteinium 252

–

59

Promethium 145 93

Californium 251

Darmstadtium Roentgenium 281 273 Dubnium 262

Pr

Np

Berkelium 247

Rutherfordium 261

Original material © Cambridge University Press 2016

Ununseptium

Actinium 227

Ununtrium

Radium 226

Copernicium

Francium 223

Praseodymium

U

Neodymium 144 92

Curium 247

58

141 91

Americium 243

Ce

*58–71 Lanthanoid series

Pa

Plutonium 244

Cerium 140 90

Neptunium 237

Th

†90–103 Actinoid series

Uranium 238 Protactinium 231

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Thorium 232

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The Periodic Table

C1: The particulate nature of matter DEFINITIONS TO LEARN

physical state: the three states of matter are solid, liquid and gas condensation: the change of state from gas to liquid freezing: the change of state from liquid to solid at the melting point

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melting: the change of state from solid to liquid boiling: the change of state from liquid to gas at the boiling point of the liquid evaporation: the change of state from liquid to gas below the boiling point sublimation: the change of state directly from solid to gas (or the reverse)

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crystallisation: the formation of crystals when a saturated solution is left to cool

Exercise C1.1 Changing physical state

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The graph shows the heating curve for a pure substance. The temperature rises with time as the substance is heated.

Temperature / ÂşC

This exercise will develop your understanding of the kinetic model and the energy changes involved in changes of physical state.

1

D

115

C B

17

A 0

0

Time

a What physical state(s) is the substance in at points A, B, C and D? A

C

B

D

b What is the melting point of the substance? c What is its boiling point?

d What happens to the temperature while the substance is changing state?

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Cambridge IGCSE Physical Science

e The substance is not water. How do we know this from the graph?

Complete the passage using the words given below. different

diffusion

gas

spread

particles

diffuse

random

lattice

vibrate

temperature

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f

in a liquid and a

The kinetic model states that the

are in constant motion. In a gas, the particles are far apart from each other and their motion is said to be

. The particles in a solid are held in fixed positions in a regular

positions.

about their fixed

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. In a solid, the particles can only

Liquids and gases are fluid states. When particles move in a fluid, they can collide with each other. When they collide, they bounce off each other in mixed, the different types of particle

directions. If two gases or liquids are

out and get mixed up. This process is called

.

2

particles that have a lower mass move faster than those with higher

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At the same

mass. This means that the lighter particles will spread and mix more quickly; the lighter particles are said to faster than the heavier particles.

g Use the data given for the substances listed below to answer the questions that follow on their physical state at a room temperature of 25 °C and atmospheric pressure.

Substance sodium

Melting point / °C

Boiling point / °C

98

883

−71

−62

ethanol

−117

78

cobalt

1492

2900

nitrogen

−210

−196

propane

−188

−42

16

118

radon

ethanoic acid

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C1: The particulate nature of matter

i

Which substance is a liquid over the smallest range of temperature?

ii

Which two substances are gaseous at −50 °C? and Which substance has the lowest freezing point?

iv

Which substance is liquid at 2500 °C?

v

A sample of ethanoic acid was found to boil at 121 °C at atmospheric pressure. Use the information in the

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table to comment on this result.

Exercise C1.2 Plotting a cooling curve

This exercise presents data obtained practically for plotting a cooling curve. It will help develop your skills in handling the data and interpreting what changes the different regions of the curve represent. Examples of sublimation are also discussed.

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A student, carried out the following data-logging experiment as part of a project on changes of state. An organic crystalline solid was melted by placing it in a tube in a boiling water bath. A temperature sensor was placed in the liquid.

computer

3

temperature sensor

bath of boiling water

magnetic stirrer

The temperature change was followed as the liquid was allowed to cool down. The data shown in the table below are taken from the computer record of the temperature change as the liquid cooled down to room temperature.

Time / min

0

0.5

1.0

1.5

2.0

2.2

2.4

2.6

2.8

3.0

3.5

4.0

4.5

5.0

Temperature / °C 96.1 89.2

85.2

82.0

80.9

80.7

80.6

80.6

80.5

80.3

78.4

74.2

64.6

47.0

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Cambridge IGCSE Physical Science

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4

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a On the grid below, plot a graph of the temperature change taking place in this experiment.

b What change is taking place over the second minute of the experiment?

c Why does the temperature remain almost constant over this period of time? Give your explanation in terms of what is happening to the organisation of the molecules of the substance.

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C1: The particulate nature of matter

d What change would need to be made to carry out the experiment using a compound with a melting point greater than 100 °C?

e A similar experiment was carried out to demonstrate the cooling curve for paraffin wax.

In the space below, sketch the shape of the graph you would expect to produce.

ii

Explain why the curve is the shape you have drawn.

f

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i

5

Sublimation occurs when a substance passes between the solid and gaseous states without going through

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the liquid phase. Both carbon dioxide and water can sublime under certain conditions of temperature and pressure.

‘Dry ice’ is the solid form of carbon dioxide used in commercial refrigeration. At atmospheric pressure it has a ‘sublimation point’ of –78.5°C. i

What difference can you see between solid carbon dioxide and water ice at atmospheric pressure?

ii

If you gently shake a carbon dioxide fire extinguisher, you will feel the presence

CO2

of liquid within the extinguisher. What conditions within the extinguisher mean that the CO2 is liquid in this case?

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Cambridge IGCSE Physical Science

iii

Complete the following paragraph about a particular type of frost using the words listed below. surrounding

liquid

colder

white

crystals

ice

Hoar frost is a powdery

humid

frost caused when solid

air. Water vapour is deposited on a surface as fine ice

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6

phase.

without

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going through the

than the

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air. The solid surface on which it is formed must be

forms from

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Cambridge IGCSE Physical Science

Exercise C12.3 Planning a controlled experiment

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The questions in this exercise illustrate the issues faced when designing experiments that will give you results that are clear. They will help you think through which conditions need to be controlled in a given situation so that a fair test can be carried out. They do not show all possible situations but will give an idea of the range of investigations you may encounter.

a Sudso is a washing powder which has been designed to work best at 30 °C. ‘Mr Jones’ has always done her

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washing at 50 °C and thinks that that temperature will work better.

Fo ro u res tstan ult din sa g t

30 °

C!

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88

lts at resu nding a t s t u For o

!

30 °C

Devise an experiment to discover which temperature is best for the washing powder Sudso.

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