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Contents
Acknowledgementsviii
Introductionx
1 Characteristics and classification of living organisms
Characteristics of living organisms
Concept and use of a classification system
Features of organisms
Dichotomous keys
2 Organisation of the organism
Cell structure and organisation
Levels of organisation Size of specimens 3 Movement in and out of cells
1
1
2
6
21
23
25
27
30
33
Diffusion36
Osmosis38
Active transport
42
4 Biological molecules
Biological molecules
5Enzymes
45
47
52
Enzymes52
6 Plant nutrition
57
Photosynthesis60
Leaf structure
62
66
Mineral requirements
7 Human nutrition
70
Diet72
Alimentary canal
74
Mechanical and physical digestion
77
Chemical digestion
80
Absorption82
8 Transport in plants
85
Transport in plants
86
Water uptake
87
Transpiration90
Translocation92
v
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9 Transport in animals
95
Circulatory system
95
Heart100
Blood and lymphatic vessels
101
Blood103
10 Diseases and immunity
105
Pathogens and transmission
Defences against diseases
110
113
11 Gas exchange in humans
Gas exchange in humans
12Respiration
118
118
130
Respiration132
Aerobic respiration
140
Anaerobic respiration
146
13 Excretion in humans
151
Excretion153
14 Co-ordination and response
162
Nervous system in humans
166
Sense organs
170
173
Hormones in humans
Homeostasis176
180
Tropic responses
15Drugs
183
Drugs185
Medicinal drugs
190
194
Misused drugs
16Reproduction
Asexual reproduction
Sexual reproduction
Sexual reproduction in plants
Sexual reproduction in humans
Sex hormones in humans
Methods of birth control in humans
Sexually transmitted infections (STIs)
17Inheritance
199
202
207
213
216
220
223
225
232
Inheritance240
Chromosomes, genes and proteins
243
Mitosis246
Meiosis250
Monohybrid inheritance
259
vi
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18 Variation and selection
270
Variation275
Adaptive features
285
Selection290
19 Organisms and their environment
Energy flow
Food chains and food webs
Nutrient cycles
Population size
20 Biotechnology and genetic engineering
300
304
309
315
320
330
Biotechnology and genetic engineering
334
Biotechnology338
Genetic engineering
342
21 Human influences on ecosystems
351
Food supply
353
Habitat destruction
359
Pollution344
Conservation350
Index361
vii
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1
Characteristics and classification of
living organisms
Characteristics of living organisms
Listing and describing the characteristics of living organisms
The basic features of plants and animals
The main features of groups in the animal kingdom
Concept and use of a classification system
How organisms are classified, using common features
Defining species
Using the binomial system of naming species
Dichotomous keys
Use of keys based on easily identifiable features
Construction of dichotomous keys
Features of organisms
Identifying the main features of cells
●● Characteristics of living
organisms
Key definitions
Movement is an action by an organism causing a change of
position or place (see Chapter 14).
Respiration describes the chemical reactions in cells that
break down nutrient molecules and release energy (see
Chapter 12).
Sensitivity is the ability to detect and respond to changes in
the environment (see Chapter 14).
Growth is a permanent increase in size (see Chapter 16).
Reproduction is the processes that make more of the
same kind of organism (see Chapter 16). Single-celled
organisms and bacteria may simply keep dividing into two.
Multicellular plants and animals may reproduce sexually or
asexually.
Excretion is the removal from organisms of toxic materials and
substances in excess of requirements (see Chapter 13).
Nutrition is the taking in of materials for energy, growth and
development (see Chapters 6 and 7).
All living organisms, whether they are singlecelled or multicellular, plants or animals, show
the characteristics included in the definitions
above: movement, respiration, sensitivity, growth,
reproduction, excretion and nutrition.
One way of remembering this list of the
characteristics of living things is by using the
mnemonic MRS GREN. The letters stand for the
first letters of the characteristics.
Mnemonics work by helping to make the material
you are learning more meaningful. They give a
structure which is easier to recall later. This structure
may be a word, or a name (such as MRS GREN) or a
phrase. For example, ‘Richard of York gave battle in
vain’ is a popular way of remembering the colours of
the rainbow in the correct sequence.
The five-kingdom classification scheme
The main features of groups in the plant kingdom
The main features of viruses
Key definitions
If you are studying the extended syllabus you need to learn more
detailed definitions of some of the characteristics of living things.
Movement is an action by an organism or part of an organism
causing a change of position or place.
Most single-celled creatures and animals move about as a
whole. Fungi and plants may make movements with parts
of their bodies (see Chapter 14).
Respiration describes the chemical reactions in cells that
break down nutrient molecules and release energy for
metabolism. Most organisms need oxygen for this (see
Chapter 12).
Sensitivity is the ability to detect or sense stimuli in the
internal or external environment and to make appropriate
responses (see Chapter 14).
Growth is a permanent increase in size and dry mass by an
increase in cell number or cell size or both (see Chapter 16).
Even bacteria and single-celled creatures show an increase
in size. Multicellular organisms increase the numbers
of cells in their bodies, become more complicated and
change their shape as well as increasing in size (see ‘Sexual
reproduction in humans’ in Chapter 16).
Excretion is the removal from organisms of the waste products
of metabolism (chemical reactions in cells including
respiration), toxic materials and substances in excess of
requirements (see Chapter 13).
Respiration and other chemical changes in the cells
produce waste products such as carbon dioxide. Living
organisms expel these substances from their bodies in
various ways (see Chapter 13).
Nutrition is the taking in of materials for energy, growth and
development. Plants require light, carbon dioxide, water
and ions. Animals need organic compounds and ions and
usually need water (see Chapters 6 and 7).
Organisms can take in the materials they need as solid
food, as animals do, or they can digest them first and
then absorb them, like fungi do, or they can build them
up for themselves, like plants do. Animals, using readymade organic molecules as their food source, are called
heterotrophs and form the consumer levels of food chains.
Photosynthetic plants are called autotrophs and are usually
the first organisms in food chains (see Chapters 6 and 19).
1
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Concept and use of a classification system
The use of DNA has revolutionised the process
of classification. Eukaryotic organisms contain
chromosomes made up of strings of genes. The
chemical which forms these genes is called DNA
(which is short for deoxyribonucleic acid). The
DNA is made up of a sequence of bases, coding for
amino acids and, therefore, proteins (see Chapters 4
and 17). Each species has a distinct number of
chromosomes and a unique sequence of bases in
its DNA, making it identifiable and distinguishable
from other species. This helps particularly when
different species are very similar morphologically (in
appearance) and anatomically (in internal structure).
The process of biological classification called
cladistics involves organisms being grouped together
according to whether or not they have one or more
shared unique characteristics derived from the
group’s last common ancestor, which are not present
in more distant ancestors. Organisms which share a
more recent ancestor (and are, therefore, more closely
Orang-utan
48 chromosomes
Gorilla
48 chromosomes
related) have DNA base sequences that are more
similar than those that share only a distant ancestor.
Human and primate evolution is a good example
of how DNA has been used to clarify a process of
evolution. Traditional classification of primates (into
monkeys, apes and humans) was based on their
anatomy, particularly their bones and teeth. This put
humans on a separate branch, while grouping the
other apes together into one family called Pongidae.
However, genetic evidence using DNA provides
a different insight – humans are more closely
related to chimpanzees (1.2% difference in the
genome – the complete set of genetic material of
the organism) and gorillas (1.6% different) than to
orang-utans (3.1% different). Also, chimpanzees are
closer to humans than to gorillas (see Figure 1.6).
Bonobos and chimps are found in Zaire and were
only identified as different species in 1929. The two
species share the same percentage difference in the
genome from humans.
Chimpanzee
48 chromosomes
Bonobo
48 chromosomes
Human
46 chromosomes
0
1
2
common
ancestor,
now extinct
time/millions of years ago
3
4
5
6
common ancestor,
now extinct
7
8
9
common ancestor,
now extinct
10
11
12
13
common ancestor,
now extinct
14
15
Figure 1.6 Classification of primates, based on DNA evidence
5
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Features of organisms
The animal kingdom
Animals are multicellular organisms whose cells have
no cell walls or chloroplasts. Most animals ingest
solid food and digest it internally.
Animal kingdom
(Only 8 groups out of 23 are listed here.)
*
Coelenterates (sea anemones, jellyfish)
Flatworms
Nematode worms
Annelids (segmented worms)
Arthropods
CLASS
Crustacea (crabs, shrimps, water fleas)
Insects
Arachnids (spiders and mites)
Myriapods (centipedes and millipedes)
Molluscs (snails, slugs, mussels, octopuses)
Echinoderms (starfish, sea urchins)
Vertebrates
CLASS
Fish
Amphibia (frogs, toads, newts)
Reptiles (lizards, snakes, turtles)
Birds
Mammals
(Only 4 subgroups out of about 26 are listed.)
Insectivores
Carnivores
Rodents
Primates
*All the organisms which do not have a vertebral column are often referred to as
­invertebrates. Invertebrates are not a natural group, but the term is convenient to use.
Arthropods
The arthropods include the crustacea, insects,
centipedes and spiders (see Figure 1.8 on page 10).
The name arthropod means ‘jointed limbs’, and this is
a feature common to them all. They also have a hard,
firm external skeleton, called a cuticle, which encloses
their bodies. Their bodies are segmented and,
between the segments, there are flexible joints which
permit movement. In most arthropods, the segments
are grouped together to form distinct regions, the
head, thorax and abdomen. Table 1.1 outlines the key
features of the four classes of arthropod.
Crustacea
Marine crustacea are crabs, prawns, lobsters, shrimps
and barnacles. Freshwater crustacea are water fleas,
Cyclops, the freshwater shrimp (Gammarus) and the
water louse (Asellus). Woodlice are land-dwelling
crustacea. Some of these crustacea are illustrated in
Figure 1.8 on page 10.
Like all arthropods, crustacea have an
exoskeleton and jointed legs. They also have two
pairs of antennae which are sensitive to touch
and to chemicals, and they have compound eyes.
Compound eyes are made up of tens or hundreds
of separate lenses with light-sensitive cells beneath.
They are able to form a crude image and are very
sensitive to movement.
Typically, crustacea have a pair of jointed limbs
on each segment of the body, but those on the
head segments are modified to form antennae
or specialised mouth parts for feeding (see
Figure 1.12).
second antenna
segmented
abdomen
thorax
compound
eye
first antenna
claw
walking legs
Figure 1.12 External features of a crustacean (lobster × 0.2)
Insects
The insects form a very large class of arthropods.
Bees, butterflies, mosquitoes, houseflies, earwigs,
greenfly and beetles are just a few of the subgroups in
this class.
Insects have segmented bodies with a firm
exoskeleton, three pairs of jointed legs, compound
eyes and, typically, two pairs of wings. The segments
are grouped into distinct head, thorax and abdomen
regions (see Figure 1.13).
11
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1
Characteristics and classification of living organisms
compound eye
thorax
are used in reproduction; the chelicerae are used
to pierce their prey and paralyse it with a poison
secreted by a gland at the base. There are usually
several pairs of simple eyes.
1 pair antennae
head
pedipalp
wing
abdomen
(segmented)
3 pairs of legs
position
of
chelicerae
cephalothorax
poison sac
chelicera (poison fang)
held on underside
of cephalothorax
Figure 1.13 External features of an insect (greenbottle, × 5). Flies,
midges and mosquitoes have only one pair of wings.
Insects differ from crustacea in having wings, only
one pair of antennae and only three pairs of legs.
There are no limbs on the abdominal segments.
The insects have very successfully colonised the
land. One reason for their success is the relative
impermeability of their cuticles, which prevents
desiccation even in very hot, dry climates.
Arachnids
These are the spiders, scorpions, mites and ticks.
Their bodies are divided into two regions, the
cephalothorax and the abdomen (see Figure 1.14).
They have four pairs of limbs on the cephalothorax,
two pedipalps and two chelicerae. The pedipalps
abdomen
Figure 1.14 External features of an arachnid (× 2.5)
Myriapods
These are millipedes and centipedes. They have a head
and a segmented body which is not obviously divided
into thorax and abdomen. There is a pair of legs on
each body segment but in the millipede the abdominal
segments are fused in pairs and it looks as if it has two
pairs of legs per segment (see Figure 1.15).
As the myriapod grows, additional segments are
formed. The myriapods have one pair of antennae
and simple eyes. Centipedes are carnivorous;
millipedes feed on vegetable matter.
up to 70 abdominal
segments fused in pairs
}
thorax (4 segments)
2 pairs of legs on each
paired abdominal segment
1 pair of legs on
each thoracic
segment
antenna
simple eye
head
Figure 1.15 External features of a myriapod (× 2.5)
Table 1.1 Key features of the four classes of arthropods
Insects
e.g. dragonfly, wasp
• three pairs of legs
Arachnids
e.g. spider, mite
• four pairs of legs
• body divided into head, thorax • body divided into
and abdomen
cephalothorax and abdomen
• one pair of antennae
• one pair of compound eyes
• several pairs of simple eyes
• usually have two pairs of
• chelicerae for biting and
wings
poisoning prey
Crustacea
e.g. crab, woodlouse
• five or more pairs of legs
• body divided into
cephalothorax and abdomen
• two pairs of antennae
• one pair of compound eyes
• exoskeleton often calcified to
form a carapace (hard)
Myriapods
e.g. centipede, millipede
• ten or more pairs of legs
(usually one pair per segment)
• body not obviously divided
into thorax and abdomen
• one pair of antennae
• simple eyes
12
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Contents
Acknowledgementsix
Preface to the reader
xi
Chapter 1 The particulate nature of matter
1
Solids, liquids and gases
2
The kinetic theory of matter
2
Changes of state
4
6
Diffusion – evidence for moving particles
Checklist8
Additional questions
9
Chapter 2 Elements, compounds and experimental techniques
10
Elements10
Compounds13
Mixtures16
Separating mixtures
17
25
Accuracy in experimental work in the laboratory
Gels, sols, foams and emulsions
26
Mixtures for strength
28
Checklist29
Additional questions
31
Chapter 3 Atomic structure and bonding
33
Inside atoms
33
The arrangement of electrons in atoms
37
38
Ionic bonding
Covalent bonding
45
54
Glasses and ceramics
Metallic bonding
55
Checklist56
58
Additional questions
Chapter 4 Stoichiometry – chemical calculations
59
Relative atomic mass
59
Reacting masses
59
Calculating moles
61
Calculating formulae
64
Moles and chemical equations
66
Checklist69
Additional questions
71
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Chapter 5 Electricity and chemistry
72
Electrolysis of lead(ii) bromide
73
Electrolysis of aluminium oxide
74
Electrolysis of aqueous solutions
77
80
Electrolysis of concentrated hydrochloric acid
80
Electrolysis of copper(ii) sulfate solution
Electrolysis guidelines
83
Electroplating83
Checklist85
Additional questions
86
Chapter 6 Chemical energetics
88
Substances from oil
88
Fossil fuels
90
What is a fuel? 92
93
Alternative sources of energy
Chemical energy
95
Changes of state
97
Cells and batteries
98
Checklist100
Additional questions
101
Chapter 7 Chemical reactions
104
Factors that affect the rate of a reaction
105
Enzymes111
Checklist114
Additional questions
115
Chapter 8 Acids, bases and salts
117
Acids and alkalis
117
Formation of salts
122
127
Crystal hydrates
Solubility of salts in water
129
Titration129
Checklist132
Additional questions
133
Chapter 9 The Periodic Table
135
Development of the Periodic Table
135
Electronic structure and the Periodic Table
138
Group I – the alkali metals
138
Group II – the alkaline earth metals
140
Group VII – the halogens
141
Group 0 – the noble gases
143
Transition elements
144
The position of hydrogen
146
Checklist146
Additional questions
147
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Chapter 10Metals
149
Metal reactions
150
Decomposition of metal nitrates, carbonates, oxides and hydroxides
152
Reactivity of metals and their uses
153
155
Identifying metal ions
Discovery of metals and their extraction
157
Metal waste
161
Rusting of iron
161
Alloys165
Checklist168
Additional questions
169
Chapter 11 Air and water
171
The air
171
How do we get the useful gases we need from the air? 174
Ammonia – an important nitrogen-containing chemical
176
180
Artificial fertilisers
Atmospheric pollution
182
Water184
The water cycle
186
187
Hardness in water
Water pollution and treatment
190
Checklist193
Additional questions
194
Chapter 12Sulfur
197
Sulfur – the element
197
Sulfur dioxide
198
199
Sulfuric acid
Checklist203
204
Additional questions
Chapter 13 Inorganic carbon chemistry
206
Limestone206
Carbonates211
Carbon dioxide
212
Checklist215
Additional questions
216
Chapter 14 Organic chemistry 1
218
Alkanes218
The chemical behaviour of alkanes
220
Alkenes222
The chemical behaviour of alkenes
224
226
A special addition reaction of alkene molecules
Checklist230
Additional questions
231
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Chapter 15 Organic chemistry 2
233
Alcohols (R—OH) 233
Biotechnology236
Carboxylic acids
237
239
Soaps and detergents
Condensation polymers
241
Some biopolymers
242
Pharmaceuticals246
Checklist247
Additional questions
249
Chapter 16 Experimental chemistry
Objectives for experimental skills and investigations
Suggestions for practical work and assessment
Notes on qualitative analysis
Revision and exam-style questions
251
251
251
261
264
Alternative to practical paper
264
Theory275
The Periodic Table of the elements
294
Index295
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Preface to the reader
This textbook has been written to help you in your
study of chemistry to Cambridge IGCSE. The
different chapters in this book are split up into
short topics. At the end of many of these topics are
questions to test whether you have understood what
you have read. At the end of each chapter there are
larger study questions. Try to answer as many of
the questions as you can as you come across them
because asking and answering questions is at the
heart of your study of chemistry.
Some questions selected from the Cambridge
IGCSE examination papers are included at the end
of the book. In many cases they are designed to test
your ability to apply your chemical knowledge. The
questions may provide certain facts and ask you to
make an interpretation of them. In such cases, the
factual information may not be covered in the text.
To help draw attention to the more important
words, scientific terms are printed in bold the first
time they are used. There are also checklists at the
end of each chapter summarising the important
points covered.
As you read through the book, you will notice
three sorts of shaded area in the text.
You will see from the box at the foot of this page
that the book is divided into four different areas
of chemistry: Starter, Physical, Inorganic and organic
chemistry. We feel, however, that some topics lead
naturally on to other topics not in the same area. So
you can, of course, read and study the chapters in
your own preferred order and the colour coding will
help you with this.
The accompanying Revision CD-ROM provides
invaluable exam preparation and practice. We want to
test your knowledge with interactive multiple choice,
mix and match, and true or false questions that cover
both the Core and Extended curriculum. These are
organised by syllabus topic.
Together, the textbook and CD-ROM will
provide you with the information you need for the
Cambridge IGCSE syllabus. We hope you enjoy
using them.
Bryan Earl and Doug Wilford
Material highlighted in green is for the Cambridge
IGCSE Extended curriculum.
Areas highlighted in yellow contain material that
is not part of the Cambridge IGCSE syllabus. It is
extension work and will not be examined.
Questions are highlighted by a box like this.
We use different colours to define different areas of chemistry:
‘starter’ chapters – basic principles
physical chemistry
inorganic chemistry
organic chemistry and the living world.
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11 Air and water
●● Water pollution and
treatment
An adequate supply of water is essential to the health
and well-being of the world’s population. Across the
planet, biological and chemical pollutants are affecting
the quality of our water. An adequate supply of fresh
drinking water is needed for everyone on the planet.
Lack of availability of fresh water leads to waterborne
diseases, such as cholera and typhoid, and to diarrhoea,
which is one of the biggest killers across the world.
Agriculture needs a water supply in order to
irrigate crops, especially in areas of the world with
hot climates. The production of more and more
crops for the ever-increasing population is essential.
Water is very good at dissolving substances. Thus,
it is very unusual to find really pure water on this
planet. As water falls through the atmosphere, on to
and then through the surface of the Earth, it dissolves
a tremendous variety of substances. Chemical
fertilisers washed off surrounding land will add
nitrate ions (NO3−) and phosphate ions (PO43−) to
the water, owing to the use of artificial fertilisers such
as ammonium nitrate and ammonium phosphate.
The nitrates encourage the growth of algae which
eventually die and decay, removing oxygen from the
water. It may also contain human waste as well as
insoluble impurities such as grit and bacteria, and
oil and lead ‘dust’ (to a decreasing extent) from the
exhaust fumes of lorries and cars (Figure 11.37).
Figure 11.37 A badly polluted river.
All these artificial, as well as natural, impurities must
be removed from the water before it can be used.
Recent regulations in many countries have imposed
strict guidelines on the amounts of various substances
allowed in drinking water.
Figure 11.38 This lake is used as a source of drinking water.
A lot of drinking water is obtained from lakes and rivers
where the pollution levels are low (Figure 11.38).
Undesirable materials removed from water include:
colloidal clay (clay particles in the water)
●● bacteria
●● chemicals which cause the water to be coloured
and foul tasting
●● acids, which are neutralised.
●●
Making water fit to drink
The treatment needed to make water fit to drink
depends on the source of the water. Some sources,
for example mountain streams, may be almost
pure and boiling may be enough to kill any microorganisms present. However, others, such as slowflowing rivers, may be contaminated. The object of
treating contaminated water is to remove all microorganisms that may cause disease.
The process of water treatment involves both
filtration and chlorination and is summarised in
Figure 11.39.
1Impure water is passed through screens to filter out
floating debris.
2 Aluminium sulfate is added to coagulate small
particles of clay so that they form larger clumps,
which settle more rapidly.
3 Filtration through coarse sand traps larger, insoluble
particles. The sand also contains specially grown
microbes which remove some of the bacteria.
4 A sedimentation tank has chemicals known as
flocculants, for example aluminium sulfate, added
to it to make the smaller particles (which remain in
the water as colloidal clay) stick together and sink
to the bottom of the tank.
5These particles are removed by further filtration
through fine sand. Sometimes a carbon slurry is
used to remove unwanted tastes and odours, and a
lime slurry is used to adjust the acidity.
190
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Water pollution and treatment
1
water passed through screen
covered
storage
tank
2
aluminium sulfate added
water
in
pump
sulfur
dioxide
added
screen
3
coarse
sand filter
4
sedimentation
tank
5
fine sand
filter
6
chlorine added
pump
sodium
hydroxide
added
to
homes
and
factories
Figure 11.39 The processes involved in water treatment.
6 Finally, a little chlorine gas is added, which
sterilises the water and kills any remaining bacteria.
Excess chlorine can be removed by the addition
of sulfur dioxide gas. The addition of chlorine gas
makes the water more acidic and so appropriate
amounts of sodium hydroxide solution are added.
Fluoride is sometimes added to water if there
is insufficient occurring naturally, as it helps to
prevent tooth decay.
Sewage treatment
After we have used water, it must be treated again
before it can be returned to rivers, lakes and seas.
This multi-stage process known as sewage treatment
is shown in Figure 11.41.
sewage
1
screens
2
settlement tank
The ‘iron problem’
If the acidity level of the treated water is not
controlled, problems occur due to the precipitation
of iron(iii) hydroxide. These include:
vegetables turning brown
tea having an inky appearance and a bitter taste
●● clothes showing rusty stains after washing
(Figure 11.40).
●●
●●
5
sludge
(for either dumping
or conversion to fertiliser)
and methane gas
3
trickling filter
gravel
4
treated water is chlorinated
and returned to the river
Figure 11.41 The processes involved in sewage treatment.
Used water, sewage, contains waste products such
as human waste and washing-up debris as well as
everything else that we put down a drain or sink.
The processes that are involved in its treatment are
as follows.
Figure 11.40 The rusty stains on this pillowcase are due to iron (III)
compounds in the water.
1 Large screens remove large pieces of rubbish.
2 Sand and grit are separated in large sedimentation
tanks. The process is speeded up by adding
aluminium sulfate, which helps the solids to
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Contents
Prefacevii
Physics and technology
viii
Scientific enquiry
x
Section 1 General physics
Measurements and motion
1Measurements
2 Speed, velocity and acceleration
3 Graphs of equations
4 Falling bodies
5Density
Forces and momentum
6 Weight and stretching
7 Adding forces
8 Force and acceleration
9 Circular motion
10 Moments and levers
11 Centres of mass
12Momentum
Energy, work, power and pressure
13 Energy transfer
14 Kinetic and potential energy
15 Energy sources
16 Pressure and liquid pressure
2
9
13
17
21
24
27
30
35
39
43
47
50
56
60
66
Section 2 Thermal physics
Simple kinetic molecular model of matter
17Molecules
18 The gas laws
Thermal properties and temperature
19 Expansion of solids, liquids and gases
20Thermometers
21 Specific heat capacity
22 Specific latent heat
Thermal processes
23 Conduction and convection
24Radiation
72
76
81
85
88
91
97
102
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Section 3 Properties of waves
General wave properties
25 Mechanical waves
Light
26 Light rays
27 Reflection of light
28 Plane mirrors
29 Refraction of light
30 Total internal reflection
31Lenses
32 Electromagnetic radiation
Sound
33 Sound waves
106
113
116
119
122
126
129
135
140
Section 4 Electricity and magnetism
Simple phenomena of magnetism
34 Magnetic fields
Electrical quantities and circuits
35 Static electricity
36 Electric current
37 Potential difference
38Resistance
39Capacitors
40 Electric power
41 Electronic systems
42 Digital electronics
Electromagnetic effects
43Generators
44Transformers
45Electromagnets
46 Electric motors
47 Electric meters
48Electrons
146
150
157
162
167
174
177
185
193
199
204
209
215
219
222
Section 5 Atomic physics
49Radioactivity
50 Atomic structure
Revision questions
Cambridge IGCSE exam questions
Mathematics for physics
Further experimental investigations
Practical test questions
Alternative to practical test questions
230
238
245
251
279
282
283
291
Answers299
Index307
Photo acknowledgements
312
vi
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12
●
●
●
●
Momentum
Conservation of momentum
Explosions
Rockets and jets
Force and momentum
●
Momentum is a useful quantity to consider when
bodies are involved in collisions and explosions. It
is defined as the mass of the body multiplied by
its velocity and is measured in kilogram metre per
second (kg m/s) or newton second (N s).
momentum = mass × velocity
A 2 kg mass moving at 10 m/s has momentum
20 kg m/s, the same as the momentum of a 5 kg mass
moving at 4 m/s.
Repeat the experiment with another trolley stacked on top
of the one to be pushed so that two are moving before the
collision and three after.
Copy and complete the tables of results.
Before collision (m2 at rest)
Mass
m1
(no. of trolleys)
Velocity
v/m/s
Momentum
m1v
1
2
After collision (m1 and m2 together)
Practical work
Mass
m1 + m2
(no. of trolleys)
Collisions and momentum
photogate 2
sloping
runway
Velocity
v1/m/s
Momentum
(m1 + m2)v1
2
Figure 12.1 shows an arrangement which can be used to find
the velocity of a trolley before and after a collision. If a trolley
of length l takes time t to pass through a photogate, its velocity
= distance/time = l/t. Two photogates are needed, placed each
side of the collision point, to find the velocities before and after
the collision. Set them up so that they will record the time taken
for the passage of a trolley.
trolley with
‘interrupt card’
photogate 1
Sport: impulse and collision time
Practical work: Collisions and momentum
●
to timer
Figure 12.1
Do the results suggest any connection between the momentum
before the collision and after it in each case?
● Conservation of
momentum
When two or more bodies act on one another, as in a
collision, the total momentum of the bodies remains constant,
provided no external forces act (e.g. friction).
This statement is called the principle of
conservation of momentum. Experiments like
those in the Practical Work Section show that it is
true for all types of collisions.
As an example, suppose a truck of mass 60 kg
moving with velocity 3 m/s collides and couples
with a stationary truck of mass 30 kg (Figure 12.2a).
The two move off together with the same velocity v
which we can find as follows (Figure 12.2b).
Total momentum before is
(60 kg × 3 m/s) + (30 kg × 0 m/s) = 180 kg m/s
▲
▲
A tickertape timer or motion sensor, placed at the top end of the
runway, could be used instead of the photogates if preferred.
Attach a strip of Velcro to each trolley so that they ‘stick’ to each
other on collision and compensate the runway for friction (see
Chapter 17). Place one trolley at rest halfway down the runway and
another at the top; give the top trolley a push. It will move forwards
with uniform velocity and should hit the second trolley so that they
travel on as one. Using the times recorded by the photogate timer,
calculate the velocity of the moving trolley before the collision and
the common velocity of both trolleys after the collision.
3
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12 MOMENTUM
Total momentum after is
(60 kg + 30 kg) × v = 90 kg × v
Since momentum is not lost
90 kg × v = 180 kg m/s or v = 2 m/s
3m /s
60 kg
v
at rest
30 kg
a Before
60 kg
air
balloon
30 kg
b After
Figure 12.2
● Explosions
Momentum, like velocity, is a vector since it has both
magnitude and direction. Vectors cannot be added
by ordinary addition unless they act in the same
direction. If they act in exactly opposite directions,
such as east and west, the smaller subtracts from the
greater, or if the same they cancel out.
Momentum is conserved in an explosion such as
occurs when a rifle is fired. Before firing, the total
momentum is zero since both rifle and bullet are
at rest. During the firing the rifle and bullet receive
equal but opposite amounts of momentum so
that the total momentum after firing is zero. For
example, if a rifle fires a bullet of mass 0.01 kg with
a velocity of 300 m/s,
forward momentum of bullet = 0.01 kg × 300 m/s
= 3 kg m/s
∴
by burning fuel and leaves the exhaust with large
momentum. The rocket or jet engine itself acquires
an equal forward momentum. Space rockets carry
their own oxygen supply; jet engines use the
surrounding air.
backward momentum of rifle = 3 kg m/s
If the rifle has mass m, it recoils (kicks back) with a
velocity v such that
mv = 3 kg m/s
Taking m = 6 kg gives v = 3/6 m/s = 0.5 m/s.
● Rockets and jets
If you release an inflated balloon with its neck open,
it flies off in the opposite direction to that of the
escaping air. In Figure 12.3 the air has momentum
to the left and the balloon moves to the right with
equal momentum.
This is the principle of rockets and jet engines. In
both, a high-velocity stream of hot gas is produced
Figure 12.3 A deflating balloon demonstrates the principle of a rocket
or a jet engine.
● Force and momentum
If a steady force F acting on a body of mass m
increases its velocity from u to v in time t, the
acceleration a is given by
a = (v − u)/t
(from v = u + at)
Substituting for a in F = ma,
F =
m (v − u ) mv − mu
=
t
t
Therefore
force =
change of momentum = rate of change of
time
momentum
This is another version of Newton’s second law. For
some problems it is more useful than F = ma.
We also have
Ft = mv − mu
where mv is the final momentum, mu the initial
momentum and Ft is called the impulse.
● Sport: impulse and
collision time
The good cricketer or tennis player ‘follows
through’ with the bat or racket when striking
the ball (Figure 12.4a). The force applied then
acts for a longer time, the impulse is greater and
so also is the gain of momentum (and velocity)
of the ball.
When we want to stop a moving ball such as
a cricket ball, however, its momentum has to be
48
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Sport: impulse and collision time
reduced to zero. An impulse is then required in
the form of an opposing force acting for a certain
time. While any number of combinations of force
and time will give a particular impulse, the ‘sting’
can be removed from the catch by drawing back the
hands as the ball is caught (Figure 12.4b). A smaller
average force is then applied for a longer time.
Figure 12.5 Sand reduces the athlete’s momentum more gently.
Questions
Figure 12.4a Batsman ‘following through’ after hitting the ball
Figure 12.4b Cricketer drawing back the hands to catch the ball
The use of sand gives a softer landing for longjumpers (Figure 12.5), as a smaller stopping force
is applied over a longer time. In a car crash the
car’s momentum is reduced to zero in a very short
time. If the time of impact can be extended by
using crumple zones (see Figure 14.6, p. 58) and
extensible seat belts, the average force needed to
stop the car is reduced so the injury to passengers
should also be less.
1 What is the momentum in kg m/s of a 10 kg truck travelling at
a 5 m/s,
b 20 cm/s,
c 36 km/h?
2 A ball X of mass 1 kg travelling at 2 m/s has a head-on
collision with an identical ball Y at rest. X stops and Y
moves off. What is Y’s velocity?
3 A boy with mass 50 kg running at 5 m/s jumps on to a 20 kg
trolley travelling in the same direction at 1.5 m/s. What is
their common velocity?
4 A girl of mass 50 kg jumps out of a rowing boat of mass
300 kg on to the bank, with a horizontal velocity of 3 m/s.
With what velocity does the boat begin to move backwards?
5 A truck of mass 500 kg moving at 4 m/s collides with
another truck of mass 1500 kg moving in the same
direction at 2 m/s. What is their common velocity just after
the collision if they move off together?
6 The velocity of a body of mass 10 kg increases from 4 m/s to
8 m/s when a force acts on it for 2 s.
a What is the momentum before the force acts?
b What is the momentum after the force acts?
c What is the momentum gain per second?
d What is the value of the force?
7 A rocket of mass 10 000 kg uses 5.0 kg of fuel and oxygen
to produce exhaust gases ejected at 5000 m/s. Calculate the
increase in its velocity.
Checklist
After studying this chapter you should be able to
• define momentum,
• describe experiments to demonstrate the principle of
conservation of momentum,
• state and use the principle of conservation of momentum
to solve problems,
• understand the action of rocket and jet engines,
• state the relationship between force and rate of change
of momentum and use it to solve problems,
• use the definition of impulse to explain how the time of
impact affects the force acting in a collision.
49
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Ultrasonics
tuning fork (sine wave)
piano
transmitter
receiver
violin
Figure 33.8 Notes of the same frequency (pitch) but different quality
ultrasonic
waves
●● Ultrasonics
Sound waves with frequencies above 20 kHz
are called ultrasonic waves; their frequency is
too high to be detected by the human ear but
they can be detected electronically and displayed
on a CRO.
a) Quartz crystal oscillators
Ultrasonic waves are produced by a quartz crystal
which is made to vibrate electrically at the required
frequency; they are emitted in a narrow beam in the
direction in which the crystal oscillates. An ultrasonic
receiver also consists of a quartz crystal but it
works in reverse, i.e. when it is set into vibration
by ultrasonic waves it generates an electrical signal
which is then amplified. The same quartz crystal can
act as both a transmitter and a receiver.
Figure 33.9 A ship using sonar
In medical ultrasound imaging, used in antenatal
clinics to monitor the health and sometimes to
determine the sex of an unborn baby, an ultrasonic
transmitter/receiver is scanned over the mother’s
abdomen and a detailed image of the fetus is built
up (Figure 33.10). Reflection of the ultrasonic
pulses occurs from boundaries of soft tissue, in
addition to bone, so images can be obtained of
internal organs that cannot be seen by using X-rays.
Less detail of bone structure is seen than with
X-rays, as the wavelength of ultrasonic waves is
larger, typically about 1 mm, but ultrasound has no
harmful effects on human tissue.
b) Ultrasonic echo techniques
Ultrasonic waves are partially or totally reflected
from surfaces at which the density of the medium
changes; this property is exploited in techniques such
as the non-destructive testing of materials, sonar
and medical ultrasound imaging. A bat emitting
ultrasonic waves can judge the distance of an object
from the time taken by the reflected wave or ‘echo’
to return.
Ships with sonar can determine the depth of a
shoal of fish or the sea bed (Figure 33.9), in the
same way; motion sensors (Chapter 2) also work on
this principle.
Figure 33.10 Checking the development of a fetus using ultrasound
imaging
▲
▲
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33 sound Waves
c) Other uses
Ultrasound can also be used in ultrasonic drills
to cut holes of any shape or size in hard materials
such as glass and steel. Jewellery, or more mundane
objects such as street lamp covers, can be cleaned
by immersion in a tank of solvent which has an
ultrasonic vibrator in the base.
l● Seismic waves
Earthquakes produce both longitudinal waves
(P-waves) and transverse waves (S-waves) that are
known as seismic waves. These travel through the
Earth at speeds of up to 13 000 m/s.
When seismic waves pass under buildings, severe
structural damage may occur. If the earthquake occurs
under the sea, the seismic energy can be transmitted to
the water and produce tsunami waves that may travel
for very large distances across the ocean. As a tsunami
wave approaches shallow coastal waters, it slows down
(see Chapter 25) and its amplitude increases, which
can lead to massive coastal destruction. This happened
in Sri Lanka (see Figure 33.11) and Thailand after
the great 2004 Sumatra–Andaman earthquake. The
time of arrival of a tsunami wave can be predicted if its
speed of travel and the distance from the epicentre of
the earthquake are known; it took about 2 hours for
tsunami waves to cross the ocean to Sri Lanka from
Indonesia. A similar time was needed for the tsunami
waves to travel the shorter distance to Thailand. This
was because the route was through shallower water and
the waves travelled more slowly. If an early-warning
system had been in place, many lives could have been
saved.
Questions
1 If 5 seconds elapse between a lightning flash and the
clap of thunder, how far away is the storm? (Speed of
sound = 330 m/s.)
2 a A girl stands 160 m away from a high wall and claps
her hands at a steady rate so that each clap coincides
with the echo of the one before. If her clapping rate is
60 per minute, what value does this give for the speed
of sound?
b If she moves 40 m closer to the wall she finds the
clapping rate has to be 80 per minute. What value do
these measurements give for the speed of sound?
c If she moves again and finds the clapping rate becomes
30 per minute, how far is she from the wall if the speed
of sound is the value you found in a?
3 a What properties of sound suggest it is a wave motion?
b How does a progressive transverse wave differ from a
longitudinal one? Which type of wave is a sound wave?
4 a Draw the waveform of
(i) a loud, low-pitched note, and
(ii) a soft, high-pitched note.
b If the speed of sound is 340 m/s what is the wavelength
of a note of frequency
(i) 340 Hz,
(ii) 170 Hz?
Checklist
After studying this chapter you should be able to
• recall that sound is produced by vibrations,
• describe an experiment to show that sound is not
transmitted through a vacuum,
• describe how sound travels in a medium as progressive
longitudinal waves,
• recall the limits of audibility (i.e. the range of frequencies)
for the normal human ear,
• explain echoes and reverberation,
• describe an experiment to measure the speed of sound
in air,
• solve problems using the speed of sound, e.g. distance of
thundercloud,
• state the order of magnitude of the speed of sound in air,
liquid and solids,
• relate the loudness and pitch of sound waves to amplitude
and frequency.
Figure 33.11 This satellite image shows the tsunami that hit the southwestern coast of Sri Lanka on 26 December 2004 as it pulled back out to
sea, having caused utter devastation in coastal areas.
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Cambridge IGCSE exam questions
1 General physics
block
Measurements and motion
1a (i)The two diagrams show the dimensions of
a rectangular block being measured using
a ruler. They are not shown full size.
Use the scales shown to find the length
and the width of the block, giving your
answers in cm.
[1]
40
50
60
grams
70
Find the density of this block.
[4]
[Total: 8]
140 150 160 170 180 190 200 210 220 230 240 250
millimetres
40
50
60
70
80
90 250
90 100 110 120 130 140 150 160
30
80
20
70
10
60
140
50
140 210 220 230 240 250 260 270 280 290 300 250
millimetres
(ii) When the block was made, it was cut from
a piece of metal 2.0 cm thick.
Calculate the volume of the block.
[2]
b Another block has a volume of 20 cm3.
The diagram shows the reading when the
block is placed on a balance.
(Cambridge IGCSE Physics 0625 Paper 21 Q1
November 2010)
2 An engineering machine has a piston which is
going up and down approximately 75 times per
minute.
Describe carefully how a stopwatch may be used
to find accurately the time for one up-and-down
cycle of the piston.
[4]
[Total: 4]
(Cambridge IGCSE Physics 0625 Paper 31 Q1 June 2009)
3 Imagine that you live beside a busy road. One of
your neighbours thinks that many of the vehicles
are travelling faster than the speed limit for the
road.
You decide to check this by measuring the speeds
of some of the vehicles.
a Which two quantities will you need to
measure in order to find the speed of a vehicle,
and which instruments would you use to
measure them?
Quantity measured
Instrument used
[4]
b State the equation you would use to calculate
the speed of the vehicle. If you use symbols,
state what your symbols mean.
[1]
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Title
Author
ISBN
Publication Date
Price
Student’s Book 3rd edition plus CD-ROM
D. G. Mackean and
Dave Hayward
9781444176469
September 2014
£20.99
Laboratory Practical Book
Mike Cole
9781444191615
November 2014
£6.99
Teacher’s CD-ROM
D. G. Mackean and
Dave Hayward
9781444196306
December 2014
£65.00
Workbook
Dave Hayward
9781471807268
November 2014
£6.00
Student’s Book 3rd edition plus CD-ROM
Bryan Earl and
L. D. R. Wiford
9781444176445
July 2014
Laboratory Practical Book
Tim Greenway
9781444192209
November 2014
£6.99
Teacher’s CD-ROM
Bryan Earl and Doug Wilford
9781444196290
December 2014
£65.00
Workbook
Bryan Earl and Doug Wilford
9781471807251
November 2014
£6.00
Student’s Book 3rd edition plus CD-ROM
Heather Kennett
and Tom Duncan
9781444176421
June 2014
Laboratory Practical Book
Heather Kennett
9781444192193
November 2014
£6.99
Teacher’s CD-ROM
Heather Kennett
and Tom Duncan
9781444196283
December 2014
£65.00
Workbook
Heather Kennett
9781471807244
November 2014
£6.00
BIOLOGY
CHEMISTRY
£20.99
PHYSICS
£20.99
Also Revision Guides coming soon for first examination 2016.
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