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>>>
Sydney, Melbourne, Brisbane, Perth andassociated companies around the world
Kerry Whalle
Carol Nevill
Geoff Phillip
Faye Jeffer
Karin Johnston
Peter Roberso
Greg Rickar
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Pearson Education AustraliaA division of Pearson Australia Group Pty LtdLevel 9, 5 Queens RoadMelbourne 3004 Australiawww.pearsoned.com.au/schools
Offices in Sydney, Brisbane and Perth, and associated companiesthroughout the world.
Copyright Pearson Education Australia 2005First published 2005
All rights reserved. Except under the conditions described in theCopyright Act 1968 of Australia and subsequent amendments, nopart of this publication may be reproduced, stored in a retrievalsystem or transmitted in any form or by any means, electronic,mechanical, photocopying, recording or otherwise, without theprior permission of the copyright owner.
Designed by Polar DesignEdited by Writers ReignIllustrated by Wendy Gorton and Bruce RankinPrepress work by The Type Factory
Set in Melior 10 ptProduced by Pearson Education AustraliaPrinted in Hong Kong
National Library of AustraliaCataloguing-in-Publication data:
Science Focus 2.
Includes index.For secondary school students.
ISBN 0 1236 0445 1.
1. Science - Textbooks. I. Whalley, Kerry.
500
ii
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UNIT
UN
IT
UN
IT
UNIT
UNIT
5 Electricity
5.1 Static electricity
5.2 Moving electricity
5.3 Using electricity Science focus:Solar challenge
Chapter review
6 Ecology
6.1 Ecosystems
6.2 Physical attributes of an ecosystem
6.3 Food chains and food webs:
interactions of life
6.4 Effects of human civilisation on
the ecosystem
Science focus:The right balance
a human problem Chapter review
7 Plant systems
7.1 Plant transport systems
7.2 Photosynthesis and respiration
7.3 Leaves
Chapter review
8 Astronomy
8.1 Space rocks
8.2 The night sky
8.3 The Milky Way and other galaxies
8.4 Satellites and remote sensing
Chapter review
9 Team research project
9.1 Teamwork and topics
9.2 Planning your investigation
9.3 Testing and evaluation
Chapter review
Index
Acknowledgements iv
Introduction v
Curriculum grids viii
Verbs 1
1 Science skills 2
1.1 What, why and how? 3
1.2 Scientific research 7
Science focus:Scientific method: the path to
greater understanding 12
1.3 Better measurements 15
1.4 Scientific conventions 22
Chapter review 28
2 Atoms 29
2.1 Elements, compounds and mixtures 30
2.2 Physical and chemical change 38
2.3 Inside atoms 46
Science focus:Atomic models 50
Chapter review 53
3 Microbes 55
3.1 What is a microbe? 56
3.2 Reproduction in microbes 64
3.3 Friend or foe? 70
Chapter review 76
4Body systems
78
4.1 Food 79
4.2 Digestion 89
4.3 Blood and circulation 98
4.4 Excretion: getting rid of wastes 108
4.5 Respiratory systems 111
Science focus:Spare parts 118
Chapter review 122
UNIT
UNIT
UNIT
UNIT
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iv
We would like to thank the following for permission toreproduce photographs, texts and illustrations.
Andromeda Oxford Limited: Based on originalartwork from Ecology & Environment: The Cyclesof Lifeby Sally Morgan, Oxford University Press NYAndromeda Oxford Limited 1995, figure 6.3.4.
Anglo-Australian Observatory / David MalinImages: figures 8.2.2, 8.3.1.
ANT Photo Library: B.G. Thomson, figure 6.1.5;M.J. Tyler, figure 6.4.7.
Auscape International Photo Library: AndrewHenley, figure 6.4.6.
Australian Associated Press: figure 2.1.3.
Australian Picture Library:figures 1.3.14, 3.1.6, SF6.1a, SF 6.1b, SF 6.3, 7.0.1, 7.2.7, 7.3.4; Hulton-DeutschCollection/Corbis, figure 1.1.1a; Hermann/Starke, figure2.2.2; Digital Art, figure 3.1.14; Lester V. Bergman/Corbis, figures 3.2.5b, 4.3.11; Lester Lefkowitz, figure4.0.1; Paul A. Souders, figure 5.1.7; John Carnemolla,figure 6.1.8; Galen Rowell, figure 6.2.5; Jonathan Blair,figure 6.2.7; Michael & Patricia Fogden, figure 6.3.9.
Dr Charles Vacanti: provided by Pearson AssetLibrary, figure SF 4.3.
Coo-ee Picture Library: figure 6.1.4.
CSIRO Publishing:figure 6.1.7, 8.2.8; CSIRO HumanNutrition and The Cancer Council South AustraliaReproduced from 12345+ Food and Nutrition Plan (KBaghurst et al., 1990) by permission of CSIRO Australiaand The Cancer Council South Australia, figure 4.1.4.
Dorling Kindersley: figures 2.1.2c, 5.0.1; MaxAlexander, figure 2.1.2a; Erik Svensson & JeppeWikstrom, figure 2.1.2b; Steve Gorton, 4.3.1; AndyCrawford, figure 4.4.1; Based on original artwork fromNature Encyclopediaby David Burnie, JonathanElphic et al, figure 6.1.2.
Fundamental Photographs: NYC Richard Menga,
figure 2.2.4.Getty: figure 6.1.3.
Global Publishing: Based on original artwork fromAnatomica: The Complete Reference Guide to theHuman Body, figure SF 4.5.
HarperCollins Publishers Ltd:figure 1.3.11.
Dr Ian Jamie:figure 1.1.2.
Kerry Whalley: figures 9.1.3, 9.2.1, 9.2.4, 9.3.1a, 9.3.1b, 9.4.1.
NASA: figures SF 5.3c, 8.0.1, 8.1.1, 8.3.4, 8.3.5, 8.3.68.3.7, 8.4.0, 8.4.6, 8.4.7, 8.4.10, 8.4.11; Glen ResearchCenter, figure 8.4.2.
The National Library of Australia: figure SF 6.5; JoAllcot, figure SF 6.4.
Oxford University Press: copyright from The YouOxford Book of Ecologyby Michael Scott (OUP, 199reprinted by permission of Oxford University Press,figure 6.4.2.
Pearson Education Australia: Anna Small, figures2.2.1, SF 5.3a; Elizabeth Anglin, figures 1.1.4, 2.1.5,2.1.11c, 3.1.3, 3.1.9, 3.1.15, 3.3.2, 3.3.3, 3.3.6, 4.1.1,4.1.2, 4.1.3, 4.3.22, SF 5.1, SF 5.3d, 8.1.3; Karly Aberyfigures 3.1.10c, 3.3.1; Kim Nolan, figure 3.3.8; TriciaConfoy, figure 2.2.3.
Photolibrary:figures 1.1.1b, 1.1.1c, 2.0.1, 2.1.2d, 2.12.3.3, 3.0.1, 3.1.4, 3.2.8, 3.3.9a, 3.3.9b, 3.3.9c, 4.3.4,4.3.6, 4.3.19, 4.4.4, 5.2.9, 6.1.6, 6.2.1, 6.2.4, 6.3.10,7.1.7, 7.2.1, 7.2.2, 7.3.2, 8.1.2, 8.1.4, 8.1.5, 8.1.7, 8.2.48.2.6, 8.3.3, 8.4.5, 8.4.9, 9.2.2; Graham J. Hills, figure2.1.8; Dr Tony Brain & David Parker, figure 3.1.1;Samuel Ashfield, figure 3.1.2; Jackie Lewin, EM UnitRoyal Free Hospital, figure 3.1.8; Susumu Nishinaga,figure 3.1.10d; Sinclair Stammers, figure 3.1.11; Astri& Hanns-Frieder Michler, figure 3.1.12a; Laguna Desifigure 3.1.12b; David Scharf, figure 3.2.1b; ClaudeNuridsany & Marie Perennou, figure 3.2.4; Jean-Loup
Charmet, figure 3.3.5; John Heseltine, figure 3.3.7;National Cancer Institute, figure 4.3.2; Du Cane MediImaging Limited, figure 4.4.2; Alred Pasieka, figure4.5.2; Klaus Guldbrandsen, figure SF 4.2; James KingHolmes, figure SF 4.4; Volker Steger, figure 6.3.5; SheTerry, figure 6.3.8; Dr Jeremy Burgess, figures 7.1.3,7.2.4; St Marys Hospital Medical School, figure 9.3.2
Skymaps.com: figure 8.2.7.
Thomson Learning:Based on original artwork fromThe Joy of Chemistry, 1st Edition 1976, reprintedwith permission of Brooks/Cole, an imprint of the
Wadsworth Group, a division of Thomson Learning,figure 1.3.9.
World Solar Challenge: figures SF 5.6a, SF 5.6b, SF5.6c.
Every effort has been made to trace and acknowledgecopyright. However, should any infringement haveoccurred, the publishers tender their apologies andinvite the copyright owners to contact them.
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Coursebook
The coursebook consists of nine chapters with the
following features.
Chapter opening pages include:
the key
prescribed
focus areafor
the chapter
outcomes
presented in
a way that
students
can easily
understand
pre quiz
questions
to stimulate
interest and test
prior knowledge.
Chapter unitsopen with a context to encourage
students to make meaning of science in terms oftheir everyday experiences. The units also reinforce
contextual learning by presenting theory, photos,
illustrationsand science focus segments in a format
that is easy to read and follow.
Each PFAhas one Science Focusspecial
feature which uses a contextual approach to focus
specifically on the outcomes of that PFA. Student
activities on these pages allow further investigation
and exploration of the material covered.
The Science Focusseries has been written for the NSW Science syllabus, stages 4 and 5. It includes material th
addresses the learning outcomes in the domains of knowledge, understanding and skills. Each chapter address
at least one prescribed focus area in detail. The content is presented through many varied contexts to engage
students in seeing the relationship between science and their everyday lives. By learning from the Science Foc
series students will become confident, creative, responsible and scientifically literate members of society.
Each unit ends with a set of questions. These
begin with straightforward checkpoint questionsthat build confidence, leading to think, analyse
and skills questions that require further thought an
application. Questions incorporate the syllabus ver
so that students can begin to practise answering
questions as required in examinations in later years
The extension questions
can be set for further
exploration and assignment
work and include a variety
of structured tasks including
research, creative writing
and Internet activitiessuitable for all students.
Extension questions cater
for a range of learning
styles using the multiple
intelligences approach, and
may be used for extending
more able students.
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Online review questions
Auto-correcting chapter review questions can be
used as a diagnostic tool or for revision at schoo
or home, and include:
multiple choice
labelling
matching fill in the blanks.
vi
Companion Website
The Companion Website contains
a wealth of support material for
students and teachers, which has been written to
enhance the content covered in the coursebook.
Destinations
A list of reviewed websites is available
these relate directly to chapter content
for students to access.
Technology activities
These are activities that apply and review
concepts covered in the chapters. They are
designed for students to work independently, and
include:
animations to develop key skills and knowledgea stimulating, visual way
drag-and-drop activitiesto improve basic
understandings in a fun way
interactives to enhance the learning of content i
an interactive way.
Key numeracy and literacy tasks are
indicated with icons.Practical activities
follow the questions.These are placed at the
end of the unit to
allow teachers
to choose when
and how to best
incorporate thepractical work.
Cross-referencesto practical
activities within
the units signalsuggested points
for practical work. Some
practical activities are design-your-own (DYO) tasks.
Chapter review
questionsfollowthe last unit in
each chapter. Thesecover all chapter
outcomes in a
variety of questionstyles to provide
opportunities for
all students toconsolidate new
knowledge andskills.
The use of the Aboriginal flag in the coursebook
denotes material that is included to cover Aboriginal
perspectives in science.
DYO
Prac 1Unit 1.2
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Homework Book
The Homework Book provides a structured program
to complement the coursebook. These homework
activities:
cover various skills
required in the syllabus
offer consolidationof keycontent and interesting
extension activities
provide revisionactivities
for each chapter,
including the construction
of a glossary
cater for a multiple
intelligencesapproach
through varied activities
have Worksheet icons in the coursebook to
denote when a homework activity is available.
Teacher resource centre
A wealth of teacher support material is provided an
is password-protected. It includes:
a chapter testfor each chapter, in MS Word to
allow editing by the teacher
coursebookanswers
Homework Bookanswers teaching programs
Teacher resource pack
Material in the teacher resource pack consists of a
printout and electronic copy on CD. It includes:
curriculum correlation grids mapped in detail to
the NSW syllabus
chapter-based teaching programs contextual teaching programs
coursebook answers
chapter tests in MS Word
Homework Bookanswers.
Worksheet 1.5 Sci-skills crossword
Worksheet 4.3 The heart
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viii
A fully mapped and detaile
correlation of the stage 4
curriculum outcomes is
available in the Science Fo
Teacher Resource.
Note: indicates the Key Prescribed Focus Area covered in each chapter.Chapters may also include information on other Prescribed Focus Areas.
Science Focus 2 Stage 4 Syllabus Correlation
chapter
outco
mes4.1
4.2 4.3 4.4
4.5
4.6
4.7
4.8 4.9 4.10
4.11
4.12
4.13
4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24 4.25 4.26 4.27
2 456789Atoms1Science
skills 3MicrobesBody
systemsElectricity Ecology
Plant
systemsAstronomy
Tea
resea
proj
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Extrapolate infer from what is known
Identify recognise and name
Investigate plan, inquire into and draw conclusions
Justify support an argument or conclusion
List write down phrases only, without furtheexplanation
Modify change in form or amount in some way
Outline sketch in general terms; indicate the mafeatures of
Predict suggest what may happen based on avainformation
Present provide information for consideration
Propose put forward (eg a point of view, idea, arsuggestion) for consideration or action
Recall present remembered ideas, facts orexperiences
Record store information and observations for l
Recount retell a series of events
Research investigate through literature or practicainvestigation
State provide information without further expSummarise express concisely the relevant details
Verbs
Science Focus 2uses the following verbs in thestudent activities.
Account account for: state reasons for; report ongive an account of: narrate a series of eventsor transactions
Analyse identify components and the relationships amongthem; draw out and relate implications
Apply use, utilise, employ in a particular situation
Assess make a judgement of value, quality, outcomes,results or size
Calculate determine from given facts, figures or information
Clarify make clear or plain
Classify arrange or include in classes/categories
Compare show how things are similar or different
Construct make; build; put together items or arguments
Contrast show how things are different or opposite
Deduce draw conclusions
Define state meaning and identify essential qualities
Demonstrate show by example
Describe provide characteristics and features
Discuss identify issues and provide points for and/oragainst
Distinguish recognise or note/indicate as being distinct ordifferent from; note differences between
Evaluate make a judgement based on criteria; determinethe value of
Examine inquire into
Explain relate cause and effect; make the relationshipsbetween things evident; provide the whyand/or how
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>>>
By the end of this chapter you should beable to:
ask questions that can be tested orinvestigated
plan investigations, identifying what
type of information or data needs to becollected and why
identify variables that need to becontrolled
identify dependent and independentvariables in experiments
plan a procedure for performing a fairtest
perform experiments and recordobservations and measurementsaccurately
organise data in various forms, includingtables and graphs
identify relationships, patterns andcontradictions in information and data
analyse results
comment on the accuracy and meaningof observations and results.
1 What is a scientist?
2 Name as many different areas of work
done by scientists as you can.3 How do scientists go about their work?
4 What is a variable?
5 How do scientists ensure that their workis accurate?
6 How do scientists communicate theirideas to each other?
Outc
omes
4.2,
4.1
3,
4.1
4,
4.1
5,4.1
7,
4.1
8,
4.1
9
Prequ
iz
11
Science skillsScience skillsKey focus area:
The nature and practice of science>>>
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Asking questionsScientists ask What, why
and how? about the naturalworld. Whatprotects some
people from catching chicken
pox? Whyis the sky blue, not
green? Howdo birds know the
direction in which they should
migrate? Whydid the chicken
cross the road? They also ask
How does this information
connect with the information
we already know?.
We live in a technological world where we use
machines and equipment every day. Most of us hav
no idea how these work, but someone invented them
and others improved them so that they became sma
cheap and reliable enough to have in homes, school
factories, farms and businesses.
Scientists ask What, why
and how? when they want
to invent something new or
improve current technology.
Whatcauses poor receptionon your TV? Whydoes your
computer crash? Howcan
we make an alarm that alerts
a surgeon that a patient
is waking up during an
operation?
The answers to these
questions can sometimes be
found in written resources
such as textbooksor the
Internet. Other answers can
be found out only by doingfirst-hand investigationsor
experiments. This is the job
of a scientist.
UNITUNIT
1.11.1The world often seems to be a very confusing
place: there seem to be so many mysterious
things going on around us. Albert Einstein
said that the job of scientists was to
coordinate our experiences of the world and
try to fit them into some logical system.context
Prac 2p. 6
Prac 1p. 5
Fig 1.1.1 You may have heard about Einstein, and Newton, but what did aHoward Florey, bMarie Curie and cCharles Darwin do?Which of them was Australian?
Poisoned!
SirIsaacNewton(16421727)
developedmanylawsin
scienceandmathematics, but
spentmuchofhistimewith
theancientart of alchemy.He
wastryingtochangecommon
metalsintopuregold!Other
scientistsoftenfoundNewton
extremelychildishanddifficult
toworkwithanditisnow
thoughtthatthefumesfrom
hisalchemyexperimentswere
slowlypoisoninghim.Inthe
laboratoryscientistsmusttake
carewiththechemicalsthey
use,particularlyfumes.What
rulesaboutchemicalsshould
youobeyinthelaboratory?
NewerbutnotThescientistsof thee
industryusuallyaimtpartsthataresmalleandmorepowerful. Thowever,agrowingdethelargeandclumsyold.ToprecordingstudusethemsinceitisthosoundqualityisbettermodernelectroniccomTheradiationfromX-
knockoutmodernelectmedicallaboratoriesusekeepequipment runningaircraft often
usevalvesbeingknockedoutoftradiationfromapossibl
explosioninwar
a b c
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8 Recordthe
measurement shown
on each of the
micrometer scales
illustrated
at right.
9 Draw the shaftand barrel of a
micrometer showing
a measurement of
12.87 mm.
Fig 1.1.2
4
What, why and how?What, why and how?
1.1
UNIT
[ Questions ]Checkpoint
1 Listthree things about the natural world that confuse
you.
2 Constructa what, why and how? question about each
of the things that confuses you.
3 Describehow you would go about finding an answer to
each of your questions.
4 Contrastthe methods you listed in question 3 with the
methods used by workers who arent scientists.
Think
5 Constructa two- or three-frame cartoon that explains
how to use a micrometer. Hint: Check Prac 1 on page 5.
6 Statewhether the following statements are true or false.
a Scientists carry out experiments on what confuses
them about the world.
b A micrometer is used to measure thick objects.
c The barrel of a micrometer usually has markings from
0 to 100. Hint: Check Prac 1 on page 5.
d The measurements that you control should always go
on the vertical axis of a graph.
e Points on a graph should be joined up dot-to-dot.
Skills
7 Constructa diagram of a micrometer and label the
parts.
[ Extension ]Investigate
1 There are many other instruments that can measure
small quantities very accurately. Researchinformatioon:
a other devices that are used to measure thicknesse
and distances accurately
b how the worlds most accurate clock works
c how very small quantities of chemical pollutants a
measured
d how small signals from space are amplified so th
they can be measured.
2 Researcha vernier caliper to find out what it measur
and how its scale works. Include a diagram and
description in your response.
3 Some scientific discoveries, such as the discovery ofpenicillin, are made by accident.
a Researchthe discovery of penicillin and describe
who discovered it, when and how; what it is used
for and its importance to society.
b Imagine that you are the person who
discovered penicillin. Write a letter to the
Royal Society of Medicine outliningyour discover
Fig 1.1.3
5 10
55
50
45
40
10 15
80
75
70
65
30 35
25
20
15
a
b
c
AsheepsburpWhenasheepfartsor burps,it releasesmethane,agreenhousegasthatcontributestoglobalwarming. Eachsheepreleases
about 25litresofmethaneeachday!CSIROscientistsdesignedthedeviceshowninFigure1.1.2.tomeasuretheamount of gasemittedwithoutharmingthesheep.Thisdeviceistheresult of scientistsasking:
Whatistheproblem?Whyisitoccurring?Howarewegoingtosolveit?
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[ Practical activities ]1.1
UNIT
A useful tool:the micrometer
AimTo use a device that can accurately measurethe thickness of objects to within a fraction of
a millimetre
Equipment
Micrometer, various common school items
shaft readsbetween26 and 27
barrelreads32
10 15 20 25
40
35
30
25
Fig 1.1.5This micrometer reads 26.32 mm.
Creative writing
The big flash!
A massive and blinding white light blasts planet Earth.
You get up and go to school the next day, but something
odd happens in Science. The pages in your textbookand workbook are all blank. Your Science teacher just
mumbles, not knowing what to say. That night there are
news reports of scientists going to their laboratories
having no idea why they are there. It seems that all the
scientific knowledge of the world has been erased and
needs to be learnt again. In a piece of writing explain what
troubles humans will get into in the next week without any
idea of science, its inventions or how the world works.Write it as either:
an essay
a series of newspaper front pages
a timeline starting from the big flash.
barrel(usually numbered from 0 to 100). Read the
millimetre measurement off the shaft of the micromete
3 Along the shaft is a line. Read off the barrel
measurement where it meets the barrel (it will be a
number between 0 and 100).
4 Use a micrometer to measure the:
thickness of your little finger
thickness of this textbook
thickness of five sheets of paper
diameter of the ball of a ballpoint pen
thickness of a pencil thickness of a coin.
Questions
1 Compareand contrastthe use of a micrometer with t
use of a ruler for the measurements in the experiment.
2 Proposea method in which a normal ruler could be
used for the measurements in the experiment.
Fig 1.1.4 A micrometer
Method
1 To take a measurement, place the object in the opening
of the micrometer and screw down the barrel until the
knob starts to slip. Do not overtighten; you dont want to
squash the object.
2 There are two measurement scalesone on the shaft(in
millimetres just like a ruler) and another on the rotating
Prac 1Unit 1.1
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>>>
6
Does nature follow
rules?
Aim To investigate how a tree grows and see if it
follows any rules of natureEquipment
1 m ruler/tape measure, micrometer, permanent marker or
chalk
Method
1 Collect a branch or long twig from a tree, preferably an
old twig from the ground. The branch needs to be 80 cm
to 1 m long and no more than 2 cm thick at its base. It
should not be broken off before its small end.
2 Strip the branch of any side twigs and leaves.
3 Make ten regularly spaced markings with the permanent
marker or chalk along the length of the branch. The
spacing must be the same for each marking, so youshould make them 8 to 10 cm apart.
Prac 2Unit 1.1
8 to 10 cmregular spacing
markings
twig micrometer
Fig 1.1.6 Checking if there is a growth rule
4 Constructa table or
spreadsheet like that
shown opposite.
You need 11 lines.
Distance of marking Diameter or thickness Average diameter or(cm) (mm) thickness (mm)
5 Use the micrometer to measure the thickness of the
branch at each marking.
6 Have all partners in your group measure the diameters
at each marking too. 7 Cross out any measurements that are very different fro
the rest, then calculate the average diameter for each
marking.
Questions
1 Identifywhich set of measurements, Distance along
the branch or Diameter of the branch, is the controlle
measurement.
2 Plot the controlled measurements on the horizontal axi
on a sheet of graph paper. Markings along each axis
should be equal and evenly spaced. Each axis should
have a label and correct units.
3 Constructa line graph to show your results.
What, why and how?What, why and how?
4 Assesswhether there is a pattern to
nature by examining whether the graph
obtained approximates
a smooth curve or a straight line.
5 Are there some points on the graph that
are out of pattern? If so, examine the tw
used in the experiment and proposea
reason for them being outfor examp
there may be a split, knot or side branch
at that spot.
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Scientists generally do not perform just one
experiment: they usually carry out many
experiments, all of them investigating the
one topic. These experiments are often done
by a team of people all collecting different
pieces of information to help solve a puzzle.
This is called scientific research. Research can
take a long time as experiments do not always
context
UNITUNIT
1.21.2give the desired results the first time. It can take
many years just to make a simple discovery. Many
discoveries occur by chance, as a scientist notices
something unusual and tries to work out what it was
Scientific research requires great patience, persisten
and creativity.
The research journeyResearch normally starts with observations made in
everyday life or maybe by accident. An observation
is a fact and can be either qualitative(described
and written down in words only) or quantitative
(measured and stated as numbers).
There is no guesswork in observations. You use
your fives senses to observe and
record observations accurately.
You should check your
observations a number of times
to be sure you have not made
any errors. The recording and
reporting of your results will
allow other scientists to repeat
your research.
Observations lead to
questions about what was
observed.
Look at the following
problem that confronted a
Year 8 student during the
last school holidays. His
observations led to thequestions what, why and
how?.
Carl and his friends went camping for a week over the school
holidays. When they collapsed the tent to go home Carl found
that the grass under the floor of the tent had gone a yellow-
white colour and was dying. Carl wondered what had caused
the apparent death of the grass.
When scientists are confronted with a problem
they make logical explanations or inferencesabout
what they observed.
Carl and his friends thought about it carefully. They came u
with a list of factors that may have affected the grass in the
week it was covered by the tent.
It was trampled badly in the week.
It didnt like the black colour of the plastic tent floor.
It received no water.
It didnt receive any sunlight.
It didnt like the smell of his socks when he took them o
at night (all his mates complained about that too!).
Observation: grass goes yellow-white in colourwhen it is covered.
Ancientobservations
Intheyear5BCChineseastronomersnotedthattherewasastarburningwithunusual brightnessfor70days.Whattheysawwasprobablytheexplodingstaror
supernovaAquilae.Manybelievethat 5BCwasalsotheyearofthebirthofJesusChrist.WasthestarthatledthethreewisementoBethlehem
actuallythesupernovaseeninChina?
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8
>>>
Scientists also try to fit the new observation with
what they know already about similar situations.
Carl knew from his science classes that plants need sunlight
and carbon dioxide gas from the air to make energy and stay
alive. A lack of carbon dioxide was another possible factor.
These factors are known as variables.
Some of Carls variables were downright silly. After
thinking more scientifically about it, Carl decided
that the most important factors were the lack of
sunlight and water. But which one of these was
more important?
Scientists then make a hypothesis, a prediction
or educated guess about what they might find
in an experiment or what might have caused the
observations. A hypothesis is something that can be
tested by an experiment.
Carl thought that the lack of sunlight was probably the most
likely reason the grass was dying. This was his hypothesis.
Scientists then develop questions regarding the
problem. These questions can become the aim for
experiments.
Carl planned two experiments.
In the first he tried to find out if a lack of water would
cause the grass to die in a week.
In the second he asked, Does a lack of sunlight kill grass
in one week?.
These were the aims of his experiments.
Good scientists run fair tests. They carefully plan
their experiments so that only one variable will be
Fig 1.2.2Factors that might have affected the grass
Prac 1p. 10
tested at a time. Otherwise they would not be able
to work out which variable caused the effect. The
variable that is changed in an experiment is also
known as the independent variable.
Scientists ask four questions when they are
planning an experiment. What is being tested? (the aim)
What is being changed? (the independent variab
What is going to be kept the same? (the controlle
variables)
What is going to be measured or
recorded? (the dependent variable)
The results obtained dependupon what
we change. Therefore what we measure or
record is called the dependent variable.
Carl grew four identical patches of grass. The same type a
amount of grass was in each patchthe controlled variableIn each experiment he was careful to change only one varia
at a time, keeping everything else the same.
Experiment 1: Carl watered
two pieces the same. One
patch was left in the sun (this
one is called the control)
and the other was covered by
black plastic.
Experiment 2: The other two
patches were placed side
by side in the sun. One was
watered regularly (the control)
while the other was kept dry.
Carl found that a lack of
water made the grass go brown,
not yellow.
The lack of sunlight caused
the grass to first go yellow, with
some blades then turning white.
These were his observations.
From observations and
measurements, a conclusion
can be made that should
prove the hypothesis to beright or wrong.
Carls conclusion was that the
grass died because of a lack
of sunlight. His hypothesis
seemed to be correct.
Pracp. 1
Scientific researchScientific research
DidscientistscreaAIDS?
AviruscalledSIVhasalwinfectedthemonkeysofAfbuttheynever becameillfit.Most scientistsbelieve
sprangfrommonkeytohufromascratchorfromeatinfectedmonkeymeat.ThethenmutatedtobecomeHIVvirusthatcausesAIDS. Sothink,however, thatinfectemonkeykidneyswereuseinthedevelopmentofapovaccinecalledCHAT. Poliowdevastatingtheworldinth1950sandtheexperimentaCHATvaccinewasgiventthousandsof peopleinAfribetween1957and1960.Thfirst outbreaksofAIDSwere
thesameregionthatthevaccwasgiven, thefirstdeathbeiin1959. DidtheCHATvaccicausetheAIDSoutbreak?
Didscientiststakeenoughcaintheir research?Asscientiswehavearesponsibilityto
takeextremecareineverythinwedo.
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1.2
UNIT [
Questions]Checkpoint
1 Definethe following terms:
a observations d hypothesis
b qualitative e variable
c inference f controlled variable.
2 Statewhether the following statements are true
or false.
a Research is a number of experiments run on the
same topic.
b Observations involve guesswork.
c A hypothesis can be tested with an experiment.d A variable is the same as an inference.
e The grass is yellow is a qualitative observation.
f The grass grew
5 mm in a day
is a qualitative
observation.
g Controlled
variables are
variables that are
not changed in an
experiment.
3 Listthe three
questions regarding
well-designed
experiments
that need to be
addressed.
4 Explainwhy only
one variable should
be tested at a time.
Think
5 You arrive home after a large storm and notice that the
television set isnt working. There is a puddle of water
on top of it and another underneath it.
a Summariseyour observations.
b Describeinferences you can make from the
observations.
c Predictwhat may happen to the television set and
the house.
6 Fi and Cathy were in an egg-and-spoon race (see
Figure 1.2.4).a Identifythe variables in the race.
Fig 1.2.3Controlling variables in an experiment
Fig 1.2.4
>>
Worksheet 1.1 Carls new experiments
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10
>>>
[ Practical activities ]
UNIT
Happy birthday to you!
AimTo observe and interpret what happenswhen a candle is burnt in a sealed space
Equipment
68 birthday candles and matches, plasticine or
Blu-tack, 2 elastic bands, a shallow pan, 1 gas jar
or tall narrow drinking glass
Method
1 Construct a two-column results table or spreadsheetwith the headings Number of candles and Rise in
height (mm).
2 Make a small mound of plasticine or Blu-tack in the
centre of the pan and then fill the pan with water.
3 Stick one candle in the plasticine. Place the gas jar or
glass over the candle.
4 Place one elastic band around the glass at the level of
the water.
Prac 1Unit 1.2
[ Extension ]Investigate
Choose one of the occupations listed below. Research
what areas of science a person would need to know towork effectively and safely in that occupation. Present
your findings as a pamphlet to be displayed in the career
information centre in your school.
Architect
Laser eye surgeon
Chemist
Optometrist
Firefighter
Car mechanic
b Assesswhether it was a fair race.
c Describeways of making it a fair race.
Analyse
7 Referring to Carls experiments on factors that affect the
growth of grass:
a identifythe two variables tested by Carl
b listother variables that could affect the growth of the
grass under the tent
c outlineprevious knowledge used by Carl.
8 Referring to Carls research:
a proposea heading for the research project
b constructan introductory sentence explaining why
the research was being performed
c proposeaims for the research and the two
experiments
d draw conclusions from the two experiments and from
the research project.
Investigate
9 Carl wondered whether the grass under the
tent would die or whether it would recover.
Design a controlled experiment to test a
hypothesis he could make about this extra
question.
DYO
Aircraft refueller
Structural engineer
Nurse
Racing car driver
Pilot
Physiotherapist
Create
10 Im red with a cream-coloured interior. I grow on a tree
and can be eaten. What am I? Select an item from the
categories listed below, describeit and have a partnededuce what it is.
a a food d an animal or insect
b a tool of some sort e a sport.
c a piece of furniture
Scientific researchScientific research
elasticband
water
pan
matches
g
plasticinecandles
REDHEADS
elastic bands
Fig 1.Which variable caused
more water to rise?1.2
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Questions
1 From the list below, identifythe
variable which probably had the
most effect on the change in water
level: the volume or depth of water
in the tray, the height and diameter
of the gas jar, the number or colour
of the candles, the amount of
plasticine or Blu-tack.
2 Identifythe chosen variable and
the controlled variable in this
experiment.
3 Proposereasons for the rise in
water level in the jar.
4 Identifyany trend evident from the
graph which shows a relationship
between the variables you plotted.
Why do cooks add salt
to water?
AimTo investigate why cooks usually add salt towater when cooking vegetables, pasta or rice
Equipment
3 x 100 mL beakers, 100 mL measuring cylinder, Bunsen
burner, bench mat, retort stand, bossheads and clamps,
gauze mat, thermometer, timer, table salt, beam balance or
electronic scale
Method
1 Set up the Bunsen burner with a beaker containing
60 mL of water.
2 Heat the water and record the temperature every
30 seconds until the water boils.
3 Add 2 g of salt to another 60 mL of water and repeat
the experiment with the same Bunsen flame.
4 Repeat with 4 g of salt.
5 Record your results in a table or spreadsheet like this:
Prac 2Unit 1.2
Time (s) Temperature (C)
No salt 2 g salt 4 g salt
0
30
60
Questions
1 Were the observations made qualitative or quantitative?
Justifyyour answer.
5 Remove the jar, light the candle and quickly place the jar
over the candle.
6 Allow the candle to burn until it goes out. Wait a short
while and observe what happens to the water level.
7 Place the other elastic band over the glass at the new
water level. 8 Measure the change in water level and record the
measurements in the table.
9 Repeat the experiment with two, then three, five and
seven candles.
10 Plot a line graph showing what happened to the height
the water rose as more candles were added.
11 Use the graph to predict the water rise for four, six and
eight candles.
12 Run the experiment again for four, six and eight candles
to check your predictions.
2 Based on your observations, deducewhy cooks add
salt to water.
3 Extension: Constructa line graph for the temperatures
recorded without any salt. On the same graph plot
heating curves for the beaker with 2 g and 4 g of salt
added.
thermometer
retort stand
100 mLbeaker
60 mLwater
no saltthen2 g saltthen
4 g salt
Fig 1.2.6Why do cooks add salt?
FlameouWhencandlesbumeltsandsom
vaporisesintoag
flameyouseeisburningwaxvapyoublowthecanatrail of smokewfromthewick.Thiswaxvapour buunburnt.Canyouacandlebysettingitssmoke?Tryligacandle,thenbloit out.Slowlylowmatchdownthestrail.Theflame
jumpdownthesmrelightthecandle
howfaritcanju
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12
Why use the scientific
method?
Humans have always asked questions and sought to
understand the observations they make. This desire
to understand the world around them led the Ancient
Greeks to develop the term scientia(to know) and to
make the first steps towards a study of what we now
call science.Initially people gained an understanding by
simply thinking about a problem and coming up with
an explanation! Over time, however, they began to
want deeper understandings and began to conduct
experiments. Through the work of Galileo and
Newton, the scientific method was formalised and
became the accepted technique for testing and proving
ideas in science. Experiments became so important
because they provided evidence to support the
answers to questions.
Climbing the mountain towardstrue understanding
Figure SF 1.1 indicates how the scientific method
has steadily led to humans gaining an increased
understanding. The quest for knowledge can be
viewed as similar to climbing a mountain.
Starting the climb
As shown in the diagram, at the beginning of the
path up the mountain the scientist asks questions in
an attempt to explain observations or problems. The
scientist comes up with an idea as a possible answerto the question, usually supported by observations
and current knowledge. This idea becomes known as
a hypothesis. Experiments must then be designed to
allow the hypothesis to be tested.
The first and most important
step
Designing the right experiment that will be a valid
test of the hypothesis is a very important skill for a
scientist. The experimentcan be considered the mos
important component of the scientific method becau
a well-designed experiment produces and confirms
results and knowledge that scientists can trust to beaccurate. It provides supportive evidence.
If the experiment produces results that disagree
with the hypothesis, this results in a downward pat
and the scientist must develop a new hypothesis. If
the experiments produce results that agree with the
hypothesis, further experiments are conducted to
continue to test whether the hypothesis is true.
Going up!
If, after many experiments have been conducted
and all have shown the hypothesis to be correct, the
scientist climbs further up the mountain, and the idbecomes a theory. A theory is an explanation of an
idea that is supported by a large amount of evidenc
and testing.
A theory can lead to the development of a mode
Models provide scientists and others with a clearer
way to describe or explain their understanding. A
model might not match exactly what is really going
on, but it can be used to help us understand and
predict what will happen in other situations, just lik
a model of a planned aircraft helps engineers better
understand the real thing.
As models develop and research continues,
the new scientific understandings lead to another
path resulting in technologythat usually improves
our lives.
Science focus:
Scientific method: the path to
greater understanding
Prescribed focus area: The nature and practiceof science
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Law
Technology
released to
benefit humans
Design
and
engineering
Applications
to serve
humans
RESEARCHincluding
mathematical
predictions from
theory or model
New or
contradictory
predictions
Modified
or new
hypothesis
Confirmation
by many
experiments
Hypothesis
supported by
experiments
Hypothesis
not supported
by experiments
New
hypothesis
Idea
hypothesis
Problem,
question,
observation
TheoryModel
Design experimental
test for hypothesis
or prediction
New or
unexpected
observations
New level of
understanding
Greater
knowledge
Model or theory found
to apply and hold true
in many areas of
scientific study
Experiment
Fig SF 1.1A mountain of research: the scientific method
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14
[ Student activities ] 1 a Investigatefurther the meanings of the following
terms: hypothesis, experiment, theory, law, model
b Construct a table to summariseyour findings,
including a definition and example of each term.
2 When discussing the scientific method, many scientis
claim There is no such thing as a scientific fact!.
a Justifythis statement by writing a paragraph to
clarify your ideas.
b Organise a class debate about this topic.
3 The Gravitation Theory developed by Isaac Newton
in the 17th century is still discussed in science
classrooms. Yet, for scientists working in modern
research, Newtons theory has been replaced.
a Based on your understanding of scientific method
proposepossible reasons why Newtons
Gravitation Theory:i is no longer used by scientists doing
research into gravity
ii is still taught in Science classes in
schools.
b Listthe possible reasons you have proposed and
share your findings with the other groups.
c Write a paragraph to presentyour own view and
explainwhy you have made your choice.
4 a Investigateat least three scientific laws.
b Statethe law in the scientific language used in yo
source (be sure to include your reference).
c In your own words constructa simple descriptioto allow you to clearly explain each law to your
classmates.
d Choose one of the laws you have found and
constructa model to help you explain the law
to others.
Sometimes scientists develop a theory that is found
to apply in many areas of scientific research, and is
always proven true in every experiment. These very
significant and important pieces of knowledge and
understanding become known as lawsand provide a
solid base for scientists doing their work.
Slipping down Sometimes, just when scientists think that they have
a full understanding of an idea, the experimentsor
sometimes mathematical predictionsshow that the
theory is not really the whole story, or in some cases,
is completely wrong. This leads to a very steep slide
back down the mountain to the development of a
new hypothesis. This new hypothesis must then go
through scientific method again before it is accepted
as a replacement for old theories.
Onward and upward
The scientific method has its ups and downs, but has
been a powerful tool in increasing our understanding
of the world around us. The strength of this method
is based on the evidence gained from experiments.
The scientific method has allowed us to gain a greater
understanding, which has led to developments that
have improved our quality of life. With continued
research and experiment the quest to reach the top
of the mountain continues.
Fig SF 1.2A scientist in the lab
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1.31.3UNITUNIT
Accurate measurements are often impossible
to make. Estimates are often the best we
can do. If you wanted to know the amount
of water in Sydney Harbour you would need
to estimate it since there is no accurate waycontext
Mistakes and errorsMistakesare things that could have been avoided if
you took a little more care. They can include:
careless reading of a measurement incorrect recording of a measurement
spillage of material
use of the wrong piece of equipment.
Errorsare things that are unavoidable. They are
usually small and are not your fault. Errors will
always happen and it doesnt matter how careful you
are. Nothing is exact. Even accurate measurements
are in fact estimates, all because of errors.
Common errors are:
parallax error
Your eye can never be exactly over the marking of
a measuring device. Everyone looks at markings
at slightly different angles so everyone will take
slightly different readings.
Reduce parallax errors by keeping your eyein line with the measurement.
Fig 1.3.1
of measuring it. The number of people in a shopping
mall would constantly change as people left and
new people arrived. An exact count would be near
impossible.
reading errors
Measurements often fall between the markings o
measuring device. Some estimation is required f
you to take your measurement.
0 cm 1 2 3 4 5 6 7
Fig 1.3.2Not quite 6 cm long, but is it 5.7, 5.8 or
5.9 cm?
instrument errors
Sometimes the instrument
you are using is faulty and
will never give the correct
reading. Some instruments
give correct readings only
at certain temperatures and
will give small errors if used
at any other temperature. A
metal ruler expands when
hot, causing the markings to
move further apart. This makes
measurements taken on a hot
day slightly smaller than those
made on a cold day.
human reaction time
A stopwatch normally reads
to one-hundredth of a second
100millisecon
awayfromdea
Detailedstudies
Saabhaveshown
ahead-oncollisio
acarwithasolid
takeslessthan1
milliseconds, or 0Howdoesthiscom
withyour reaction
Ifless,thenthe
accidentisoverb
youcanreacttoit!
isnochanceofg
ready orbracingto
injuryagoodca
wearingseatbe
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16
>>>
0 cm 1 2 3 4 5 6 7
0 cm 1 2 3 4 5 6 7
metal rulers contract on cold days
metal rulers expand when hot
Fig 1.3.3 Same match, different days, different
measurements
(0.01 s). Humans are not as accurate as this: we
simply cant react quickly enough. Measurements
of time will vary among people because
we all have different reaction times. Data
loggers have faster reaction time than
humans and are more accurate, but there
are still errors involved.
Repeated measurementsBecause errors always exist, people can measure the
same thing differently. So who has taken the correct
measurement? They all have! Unless someone made
a silly mistake there is no wrong answer. Repeating
measurements is a good way to improving accuracy.
Once a collection of different measurements is taken,
an averageor meancan be obtained.
To find an average:
1 add all the measurements together to get a total
2 divide this total by the number of measurements
taken.
Various members of a group measured the length of
a mouses tail and each got different results: Anna 8.1 cm
Lee 8.4 cm
Millai 8.5 cm
Nicole 8.2 cm
Steve 12.9 cm.
Steves result is too far away from the rest of the
results. It looks like he made a mistake so his result
should be ignored.
Prac 1p. 19
To obtain the most accurate measurement it is beto average the other four results; that is, add the fou
results:
8.1 + 8.4 + 8.2 + 8.5 = 33.2
and divide the total by the number of readings:
33.2 4 = 8.3 cm
Notice that no one in the group actually
took a measurement that was the same as
the average.
A little give and takeIt is often useful to
write measurements
with an estimation
of how big the error
might be. We allow a
little give and take
by showing the error
as (standing for
plus or minus). The
exact measurement
shown in Figure
1.3.5 needs a littleguesswork.
Although it looks
as if it should be
about 27C it could
be a little higher or
lower, perhaps as
much as 1C. The
measurement could
Fig 1.3.4Everyone will get slightly differentmeasurements.
Prap. 2
27 1C
0
5
10
15
25
30
35
C
Fig 1.3.5
Better measurementsBetter measurements
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1.3
UNIT
[ Questions ]
6 From the following, identifythe measurements that
could be taken accurately:
a the number of kangaroos in Australia
b the number of kangaroos in the zoo
c the length of the science laboratory at school
d the number of cloudy days in the next monthe the number of students who buy chips at the
school canteen.
7 Classifythe following as either mistakes or errors.
a Mia poured water from a measuring cylinder but
could not get every drop out.
b Kim spilt some of the chemicals he was to use in
an experiment.
c Johnno didnt bother cleaning the dirt off the beam
balance he used.
d Sara found it difficult to decide on measurements
that fell between the markings on a tape measure.
e Michas electronic scale was reading 0.1 g when
empty and he didnt zero it.
Skills
8 Calculatethe average of these values to obtain the
most accurate measurement.
a 39 mm, 38 mm, 40 mm, 41 mm, 40 mm
b 25.3C, 26.8C, 27.5C
c 45 mL, 47 mL, 46 mL, 58 mL (be careful here!)
9 For each example in Figure 1.3.6, describethe type
of error made.
Fig 1.3.6
be written as 27C give or take 1C. Scientists write
this as 27 1C.
The mouse-tail measured earlier averaged
8.3 centimetres even though no one actually
measured it as that. The mouse-tail could be
said to be between 8.1 and 8.5 centimetres.
This could be written as 8.3 centimetres giveor take 0.2 centimetres, or 8.3 0.2 cm.Prac 3p. 20
Checkpoint
1 Comparean error with a mistake.
2 Explainwhy it is difficult to avoid errors.
3 Outlinefour different types of errors.
4 Why do scientists use different procedures to avoid or
minimise errors? Justifyyour answer.
Think
5 Statewhether the following statements are true
or false.
a All measurements are exact.
b An average can also be called the mode.
c A mistake is an error.
d A measurement of 56 2C actually goes from
58C to 56C.
e Human reactions are always fast and accurate.
>>
Worksheet 1.2 Extreme units
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18
>>>
10 a Define.
b Recordthe following measurements with a error.
1
2
3
4
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
mm
0
20
40
60
80100 120 140
160
180
200
220
240km/h
a
c
b
Fig 1.3.7
Fig 1.3.8
[ Extension ]Investigate
1 Conduct research to find the correct operating
temperatures for the following apparatus:
a 250 mL beaker
b 100 mL measuring cylinder
c school electronic balance.
2 Police often give accurate estimates of crowd numbers
at sporting events.
a Explainhow you could determine the number of
people in the photo in Figure 1.3.8 without counting
each person.
b Use your method to estimatethe number of people
in Figure 1.3.8.
3 Use your method to estimatenumbers in the following
examples:
a the number of grains of sand that would fit in a
shoebox filled with sand
b the number of leaves on a tree
c the number of words and individual letters printed in
this chapter.
4 Use the diagram in Figure 1.3.9 to explainthe
difference between accuracy and precision.
5 a Researchand summarisewhat is meant by
the frequency of a pendulum.
b Proposea way of measuring the frequency
of a pendulum.
c Design an experiment to investigateyour
method of measurement.
Action 6 Examineeach of the following instruments to find the
smallest markings or divisions on them:
a digital stopwatch
b normal ruler
c tape measure
d thermometer
e kitchen scale.
DYO
Better measurementsBetter measurements
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[ Practical activities ]1.3
UNIT
How quickly can
you react?
AimTo find your reaction time
Equipment
Ruler (for most people a 30 cm ruler
will do), access to a calculator
Method 1 Hold a metre ruler vertically, with the zero
level with the top of your partners hand.
2 Without warning, let go of the ruler.
Your partner must catch it as quickly as
possible.
3 Note the reading of the ruler (in centimetres)
level with the top of your partners open hand.
4 Have two trial runs and then record the next
three runs.
Fig 1.3.9
Prac 1Unit 1.3
Fig 1.3.10Measuring reaction time
good accuracypoor precision
good precisionpoor accuracy
good accuracygood precision
bad news
ruler
have yourfingerslevel withzero the ruler
hasdropped22 cm
>>
Experiment Distance ruler dropped Average ruler drop Average reaction time
(cm) (cm) (s)
No distractions
No warnings
With countdown
With distractions
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20
>>>
5 Calculate the reaction time by dividing the average ruler
drop by 490. Now square root ( ) your answer. The
final answer is the time in seconds that your partner
took to react.
6 Repeat the experiment, but this time count down(54321) before dropping the ruler.
7 Try again, but this time get another student to distract
your partner, by talking to them, tickling them, etc.
Questions
1 Identifythe degree of accuracy of a normal stopwatch
2 Contrastthe reaction time with the accuracy of a
stopwatch. 3 Identifyfactors that affected the reaction time in this
experiment.
4 Outlinefactors that affect your reaction time in everyd
life.
Repeated measurements
AimTo examine why taking a number ofmeasurements is important
Equipment
Measuring tape, thermometer, stopwatch
Method
1 Measure each of the following as carefully as you can.
Have each member of your group do the same:
the length of the laboratory
the temperature of tap water
the number of heartbeats in a minute.
the time it takes for a pen to drop 2 m to the floor.
the time it takes
for a flat piece
of A4 paper to
flutter from a
height of 2 m tothe floor.
2 Calculate the
average for each
measurement.
3 Record this average
with a error.
Introduction to the
pendulumA pendulumis a mass (called a bob) attached to
a rod, chain or rope, which swings back and forth
repeatedly.
The periodof a pendulum is the time it takes to
complete one entire swing, back and forth.
A grandfather clock has a pendulum that keeps the clock
on time. Many machines have arms and parts that also act
like pendulums. Their timing is important and scientists must
know what affects the period so that these machines and
devices stay accurate.
Important variables that could logically affect the period
are: the length of the string
the mass of the bob (sometimes incorrectly called its
weight)
the angle of the bob from vertical at the start.
In this experiment you will see if the mass has any effect
on period.
Prac 3Unit 1.3
Fig 1.3.11 Pendulums are everywhere!
Better measurementsBetter measurements
Prac 2Unit 1.3
Chaosatplay!Haveyouevernoticedthatprofesstennisplayersarealwaysontheirwhentheyareabouttoreceivease
Theunstablenatureoftheirfootingsequickentheir response, makingthem
likelytoreturntheball.Accuratemeasurementsofheartbeatsthattheyareroughlythesame,butallslightlydifferent.Theslightlyunsbeathelpskeepourheartonitstoe
It canthenrespondtoanysuddenneeincreasedbloodsupplywhenweexerThisisthescientifictheorycalled
chaosatwork.
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Fig 1.3.14A practical pendulum
1 period
stringretort stand
boss headand clamp
bob
Fig 1.3.12 Is the mass an important variable?
AimTo investigate the effect of changing the mass of thebob on a pendulum
Equipment
Materials to construct a pendulum, stopwatch or appropriate
data-logging equipment, clock or watch, protractor (optional)
6 Plot a graph of period versus mass, with mass on the
horizontal axis.
Mass Time for Average time for Period 10 swings (s) 10 swings (s) (s)
Mass 1
Mass 2
Period(s)
Mass (g)0
Fig 1.3.13Use these axis markings
Method
1 Before you start you need to decide:
what masses should be used (50 g masses, paper
clips, metal washers?)
what length your pendulum is to be what angle your pendulum needs to be swung from
each time and a method of making sure it is always
the same.
2 Construct a results table or spreadsheet like the following:
3 Tie one mass on the end of the pendulum, measure the
length of the pendulum and hold the mass out to the
angle you have decided on.
4 Let go and time ten complete swings.
5 Put your results in the table, add another mass and
repeat. Keep adding until you have tested five different
masses.
7 Draw a line or curve of best fit for the points.
Questions
1 Describevariables that you controlled in this experime
2 Identifythe dependent and independent variables.
3 Describehow you made sure the angle was always
the same.
4 Explainwhy ten periods were measured rather than
just one.
5 Identifyother variables that could affect the period.
(Think about the bob and the string itself.)
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1.41.4Scientists follow conventions or rules
when they present their data, graphs and
reports. This is so that other scientists know
exactly what was observed, and how the
information was interpreted. It also allows
them to repeat the experiment if necessary.
As a scientist you should follow these
conventions too.
context
What do you write in a report?When you write a report you need to include the
following:
a heading, the date of the experimental work and a
list of partners who assisted you
your aimstatement of what you intended to do or
find out
a hypothesis(optional)prediction or educated
guess about what you thought might be found
out
a list of equipment ormaterialsused
your methodexplanation of what was done in theexperiment, including the quantities used.
A diagram can be useful here too
your results andobservationscomplete list of
measurements and observations that were taken,
preferably displayed in a table
a discussion oranalysis, in which you discuss
what you think your results show. This also
includes what you have found about the
experiment from secondary sources. It could
include graphs, ideas for further experiments, a
description of problems encountered and what
was done to overcome them
a conclusionsummary of what was found out in
the experiment. It must be short and must relate to
the aim.
A report sometimes ends with a list of all resources
used in gathering information about the experiment.
This is called abibliography.
Organising results
Data is the word used for a lot of measurements
or observations. Data is usually placed in a table
(tabulated), sometimes as a computer spreadsheet o
database. This makes any patterns that may exist m
obvious. Headings and units should be at the top of
each column.
Drawing line graphs
Patterns become even more obvious when data isplotted as a line graph. Line graphs can be used to
predict patterns and measurements that were never
actually taken in the experiment. Pie charts, bar
graphs and histograms are useful but cannot be used
to predict missing measurements.
When drawing a line graph you must always
include:
a heading, explaining what the graph is about
ruled vertical and horizontal axes
labelsand unitson the axes
regular markings for the scale along the axes
all your points clearly marked on the graphitself.
The independent variable is placed on the
the horizontal axis. The independent variableis
the variable you have chosen to change in your
experiment. You decide how large it should be and
how much it should change by. The number of
days after birth is the independent variable in
Figure 1.4.1.
The dependent variableis placed on
the vertical axis. This is the variable that
depends upon the independent variable and
is measured throughout the experiment.
In Figure 1.4.1, the length of the mouse is
the dependent variable.
All experiments include errors, and connecting u
the points in a dot-to-dot manner suggests that there
is noerror. It is more sensible to draw a straight lin
or smooth curveapproximately through the centre
Pracp. 2
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Graphs showing common relationships
As xgets biggygets bigger bthen levels out
As xgets biggerygets much bigger(ymore than doublesif xdoubles).
Could be describedas a linear relationship(ydoubles if xdoubles).
y
x
y
x
y
Fig
A line of best fit is notdot-to-dot
0 1 2 3 4 5 6 7 8 9 10
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Lengthofmouse(mm)
Daysafter birth
independent variableyou choose how big
dependentvariable
changesnaturally
line of best fit
Length of baby mouse as it grows
Fig 1.4.1your points: this is called the line of best fitor curv
of best fit. Patterns and results can then be predicte
You can predict extra results by continuing the shap
of the line or curve. This is called
extrapolation. In Figure 1.4.2 the
curve has been extrapolated to allow
us to predict that the temperatureafter 15 minutes would be 22C.
Describing patterns
Graphs of straight lines or smooth curves indicate
that there is a pattern, rule or relationship between
the variables that you tested. Some ways of describi
these rules are shown in Figure 1.4.3.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
100
90
80
70
60
50
40
30
20
10
0
Temperature(C)
Time (minutes)
curve of best fit
extrapolation (logicalextension of graph)
The cooling curve of water
Fig 1.4.2 Line graphs can be used to predict missingvalues. For example, the temperature was 32Cat 8 minutes, and took 41/2minutes to reach48C. What do you predict the temperature tobe at 15 minutes?
Prac 2p. 26 Pracp. 2
Using and converting metric units
Scientific measurements are
based on the metric system.
Length is measured in metres
(m), mass in grams (g) and
volume in litres (L). Other units,
such as newtons (N) for weight
and force, and joules (J) for
energy, depend on these units.
Sometimes measurements
are too big or too small to besensibly measured with these
units. Other units have been
developed from them using a
series of prefixes. The prefixes
you have probably already met
are centi, milli and kilo in units
such as centimetre or cm (100
are required to make up a metre),
Thesizeofa
Asmellmightbeinvi
actuallyparticlesoft
thatmadethesmell,
inthethinlayerof
thenose.Afrighteni
consideringwhatweday!Atypicalsmell
of only760ngor76
ofagram.Thisisa
massofthesmalles
parasitewasp)but1
heavierthanthelig
Thismeansthatw
possiblysmellavi
commonc
Worksheet 1.3 Graphing skills
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1.4
UNIT
[ Questions ]
10 Metric prefixes are not usually used for time. Stateth
following metric time units in seconds (s):
a 1 kilosecond or 1 ks
b 1 centiminute or 1 cmin
c 1 kiloday or 1 kd
d 1 megasecond or 1 Ms.
Analyse
11 Sam measured the times it took for a feather and a
stone to fall from different heights so that she could
compare them. She obtained the graph shown in
Figure 1.4.4.
Checkpoint
1 Definethe following terms:
a convention d relationship
b hypothesis e bibliography.
c line of best fit
2 Describethe type of information found in the discussion
section of an experiment.
3 Listall the details that must be included on a graph.
4 Proposethe correct axis for the independent variable
on a graph.
5 Explainthe usefulness of the metric system in science.
6 Describehow a line of best fit is obtained when
drawing a graph.
7 Proposetwo places where diagrams would be useful in
an experimental report.
8 Explainwhy scientists use line graphs more often than
pie charts and bar graphs.
Think
9 Modifythe following values to make the conversions
shown:
a 5 ML into litres
b 375 mL into litres
c 500 000 mm into metres
d 6 000 000 000 nm into metres.
millilitre or mL (one thousand make up one litre) and
kilogram or kg (equal to a thousand grams).
You have probably never heard of the
other prefixes, although all of them
are used for very small or very large
quantities.
Prefix symbol Name of prefix Size Decimal notation Example
G Giga one billion 1 000 000 000 GL
M Mega one million 1 000 000 ML
d deci one-tenth 1/10 = 0.1 dL micro one-millionth 1/1 000 000 = 0.000 001 m
n nano one-billionth 1/1 000 000 000 = 0.000 000 001 nm
Prac 4p. 27
0 1 2 3 4 5
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
Timetodrop(s)
Height of drop (m)
stone
feather
Drop times
Fig 1.4.4Sams graph
Scientific conventionsScientific conventions
Worksheet 1.4 Body mass index
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0 1 2 3 4 5 6 7 8 9 10
Mass(kg)
Time (min)
60
50
40
30
20
10
0
Fig 1.4.5
c Constructa correct version of the graph.
0 1 2 3 4 5 6 7 8 9 10
Temperature
Seconds
100
90
80
70
60
50
21.3
15.5
9.1
7.8
3.20
Fig 1.4.6
[ Extension ]Investigate
1 Researchand presentinformation about the followin
features of the metric system. Include a bibliography the information presented.
a Outlinewhere, when and why the metric system
was developed.
b Describehow the length of a metre was originally
determined.
c Use an example to explainwhat a measurement
standard is.
2 Carry out research to identifythe metric units used fo
the following measurements:
a air pressure
b force
c energy
d electrical current
e electrical voltage.
3 Describewhere the following units are used:
a megatonne (Mt)
b decibel (dB)
c gigabyte (Gb).
13 a Identifyfive mistakes in the plotting of the graph in
Figure 1.4.6.
b Decide whether the independent variable is plotted on
the correct axis. Justifyyour answer.
a Proposean aim for Sams experiment.
b Constructa table of results for the experiment.
c Use the graph to identifythe drop time for the feather
and stone from these heights:
i 1.5 m
ii 2.5 m
iii3500 mm.
d Extrapolatethe height that the feather and the stone
were dropped from, given the following times.
i 0.5 s
ii 1.2 s
iii1.9 s.
e Extrapolatethe graph to find the values of the
following measurements:
i time taken to drop the feather 5 m
ii time taken to drop the stone 5 m
iiithe position of the feather after 2.5 s.
f Draw conclusions from the experiment.
Skills
12 a ExamineFigure 1.4.5 and assesswhether all the data
for the points plotted is reliable.
b Copy the graph onto graph paper and constructa line
of best fit.
c Proposea title for the graph.
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[ Practical activities ]1.4
UN
IT
Prac 1Unit 1.4
How does length affect a pendulum?
AimTo investigate if the length of a pendulumaffects its period
Equipment
Materials to construct a pendulum, stopwatch or appropriate
data-logging equipment, clock or watch, protractor (optional)
Method
1 You need to keep constant the mass and the angle from
which the pendulum is swung. Decide what values you
will use.
2 Decide on the lengths that you will test. At least five
different lengths should be tested.
3 You need to repeat measurements for the time taken for
ten complete swings. Decide how many times you will
repeat each experiment.
4 Construct a table or spreadsheet for the measurements
you take.
5 Perform the experiment, recording the time taken.
6 Calculate the average time for ten swings and for one
swing (the period).
7 Plot a graph of period versus length.
Extension
One aim of a scientist when analysing results is to try and
get a straight line when plotting graphs. If you didnt get astraight line then try this.
8 Make another
column in your
table. Use a
calculator to take
the square root
( ) of the lengths
you used and enter
these into the new
column.
9 Plot a new graph
of period versus
square root length.
Questions
1 Discussany precautions taken in the experiment to
reduce errors.
2 Identifythe controlled variables.
3 Identifythe independent and dependent variables.
4 Use the shape of the curve obtained in the graph
to outlineany relationship evident between the
dependent and independent variables.
5 Draw conclusions from the data obtained.
Period(s)
Length
Fig 1.4.7 Plotting period
against squareroot length
Prac 2Unit 1.4
Does the angle matter?
AimTo investigate the effect of angle on theperiod of a pendulum
Equipment
Materials to construct a pendulum, stopwatch or appropriate
data-logging equipment, protractor
Method 1 Bigger angles could mean longer periods, shorter periods
or no change in period. Construct your hypothesis about
the effect of angle on period.
2 Design an experiment to test your hypothesis.
3 Construct a graph showing the relationship between
period and angle of pendulum swing.
Questions
1 Outlinehow you controlled
variables that you did not
want to test.
2 Does the shape of the graph
support your hypothesis?
Justifyyour answer.
3 Proposefurther questions
that arise from this
experiment.
Scientific conventionsScientific conventions
FoucaultspenduApendulumlooksas
neverchangesdirectionisbecausemostpenduareshortandall pendueventuallystopduetoresistance.Asapendu
movesbackandforth, thisslowlyspinningunderIfthependulumkeptgoiwouldseeit slowlychadirection.After24houwouldreturntoitsorigorientation.ApendulumdoesthisiscalledFouca
pendulum.
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Prac 3Unit 1.4
Complex pendulums
AimTo investigate different pendulums
Equipment
Materials to construct a pendulum, stopwatch
Method 1 Construct one of the pendulums shown.
2 Identify two variables that you think could
affect the period.
3 Design two experiments that test those
variables.
4 Report on your findings, including a graph for
each experiment.
DYO
bridge
pendulum
chain
pendulum
double
pendulum
Fig 1.4.8Other pendulums to try
Prac 4Unit 1.4
3 Describethe shape of all graphs you plotted.
4 From the shape of the graphs describeany patterns in
the relationships between variables.
5 Use the information obtained from graphs to draw
conclusions for both experiments.
Drop time
AimTo investigate the variables in the droptime of a parachute.
Equipment
Lightweight materials (such as tissue paper, plastic sheet
(garbage bags), newspaper), fine cotton, hole punch, sticky
tape, small masses (plasticine or paper clips are ideal),
electronic balance, stopwatch
Method
1 Brainstorm a list of variables that could affect the drop
time of a parachute.
2 Select the two variables that your group
thinks will have the most effect. 3 Design two experiments that will test your
two variables. Remember to keep everything
else the same.
4 When constructing your chutes, reinforce the
string holes with patches of sticky tape.
5 Drop your chutes from a height of at least
2 m.
6 Make repeated measurements of the time the
chutes take to hit the ground, recording the
measurements in a table or spreadsheet.
7 Write a report of your research, including a
line graph for each experiment.
Questions
1 Identifythe variables that may be important
in this experiment.
2 Explainwhy you chose the variables you
tested and not others.
Fig 1.4.9 Testing parachutes
light materials,eg paper, plastic
sticky tapereinforcing
mass
stopwatch
chute
2 mor more
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Chapter review
[ Summary questions ] 1 Contrastthe work of scientists with that of other workers.
2 Identifytwo examples of each of the following types of
observations:
a qualitative
b quantitative
c visual
d made with the sense
of touch only
3 Contrasteach of the following terms:
a an experiment and research
b a qualitative and a quantitative observation
c an aim and a hypothesis
d an error and a mistake.
4 Draw diagrams to explainthe following types of errors:
a parallax errors b reading errors.
5 Use an example to contrasta dependent with an
independent variable.
6 Use an example to explainhow human reflex can add
errors to an experiment.
7 In order, listthe features normally included in an
experimental report.
[ Thinking questions ] 8 Sarah wrote the length of an insect as 2.1 0.1 cm.
Statethe biggest and the smallest length of the insect.
9 Recordthe following measurements correctly showing
the errors.
a The time a stone took to drop to the ground was
measured by Kim as 2.5 seconds, give or take half a
second.
b Jess measured the temperature that salt water boiled
at as somewhere between 102C and 108C.
10 Calculatethe average value for the following
measurements.
a 87 mL, 90 mL, 86 mL and 93 mL
b 115 g, 123 g and 125 g.
11 Proposea reason for all scientists using the same units
for their measurements.
12 One of the most powerful cars built in Australia was the
285 kW HSV Clubsports R8. Calculatethe cars power
in watts.
13 The World Health Organization recommends that people
should eat 10.9 MJ of food each day. On average in
0 1 2 3 4 5
Soundintensity
Distance (m)
70
60
50
40
30
20
10
0
Fig 1.5.1
16 Copy Figure 1.5.1 into your workbook and:
a identifythe independent variable
b identifythe variable that changed naturally
c identifywhat is missing from the axes
d constructa table of results for the experiment
e constructa line or curve of best fit through the data
f predictthe sound intensities for the following distani 1.5 m
ii 2.8 m
g predictthe distances for the following sound intensi
i 45
ii 32
Australia we eat 13 500 kJ. Many claim that Australian
eat more than the recommended allowance. Justifyth
statement.
14 Recommendappropriate metric units for the following
measurements:
a the length of a sugar ant
b the amount of water in Botany Bay
c the distance from here to the next galaxy.
15 Design a controlled experiment that would test the
hypothesis that adding salt to water causes an increas
the boiling point of water.
[ Interpreting questions ]
e made with the sense
of hearing only
f made with the sense
of taste or smell only.
iii350 cm
iv6000 mm
v 0 m.
iii20
iv 55.
Worksheet 1.5 Sci skills crossword
Worksheet 1.6 Sci-words
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By the end of this chapter you should beable to:
distinguish between an element, acompound and a mixture
distinguish between an atom, a moleculeand a lattice
recall the symbols of some elements
write the formulae for some simplecompounds
identify whether a change in a substanceis due to a physical or a chemical change
write simple word equations to describea chemical change
classify chemical reactions into one of
four types identify ways in which chemical reactions
can be sped up.
1 Do you think the symbol Fe stands forferret, ferocious or iron?
2 Which do you think is the symbol forchlorine? C, Ca, Cl or Co?
3 Are you making a new substance whenyou add water to cordial?
4 List what is produced when paper isburnt.
5 Why are vegetables stored in therefrigerator?
6 Which do you think will relieve aheadache more quickly: a whole aspirintablet or the same tablet crushed?
7 You can easily see an atom with anordinary microscope. True or false?
22
AtomsAtomsKey focus areas:
The nature and practice of scienceThe history of science
>>>
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2.12.1
In the fourth century BC, Greek philosophers
thought that everything was made from
four basic ingredients: earth, air, fire and
water. We now know that all matter is made
from basic ingredients. These are not the
ingredients of the ancients, however, but
elementsaround one hundred of them. These
elements make up the planets and the stars andevery substance that we see, breathe, drink and
use. They even make up our bodies.
context
ElementsAn elementis an absolutely pure substance that
cannot be broken down into other substances. If you
were asked to name some pure substances, you might
mention substances such as plastic, paper, air and
sugarhowever, none of these are elements! The
reasonthey can all be broken down into simpler
substances. There are several possible ways to break
down a substance, such as burning or using acids or
other chemicals. When plastic, wood or paper are
burnt, they break down to reveal the carbon within
them. Carbon is an element, as it cannot be broken
down any further.
Some other elements are
aluminium, copper, oxygen,
sodium and chlorine.
The periodic table
(to be studied indetail next year) is a
complete list of all
the known elements.
There are 92 naturally
occurring elements, most of
which were discovered in
the last 400 years, and over
20 synthetic elements.
Teacher demonstration
Your teacher may conduct a demonstration in a fume
cupboard, showing how sugar may be broken down by
concentrated sulfuric acid. The acid breaks the sugar
down into
Recommended