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Sydney, Melbourne, Brisbane, Perth andassociated companies around the world

Kerry WhalleyCarol Neville

Geoff PhillipsFaye Jeffery

Karin Johnstone

Peter RobersonGreg Rickard

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 companies throughout the world.

Copyright Pearson Education Australia 2005First published 2005

All rights reserved. Except under the conditions described in the Copyright Act 1968 of Australia and subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owner.

Designed by Polar DesignEdited by Writers ReignIllustrated by Wendy Gorton and Bruce RankinPrepress work by The Type FactorySet 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.

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5 Electricity 1255.1 Static electricity 1265.2 Moving electricity 1335.3 Using electricity 141Science focus: Solar challenge 147Chapter review 150

6 Ecology 1526.1 Ecosystems 1536.2 Physical attributes of an ecosystem 1596.3 Food chains and food webs:

interactions of life 1656.4 Effects of human civilisation on

the ecosystem 171Science focus: The right balance

a human problem 179Chapter review 184

7 Plant systems 1857.1 Plant transport systems 1867.2 Photosynthesis and respiration 1917.3 Leaves 201Chapter review 206

8 Astronomy 2088.1 Space rocks 2098.2 The night sky 2148.3 The Milky Way and other galaxies 2208.4 Satellites and remote sensing 225Chapter review 231

9 Team research project 2329.1 Teamwork and topics 2339.2 Planning your investigation 2379.3 Testing and evaluation 243Chapter review 247

Index 249

Acknowledgements ivIntroduction vCurriculum grids viiiVerbs 1

1 Science skills 21.1 What, why and how? 31.2 Scientific research 7Science focus: Scientific method: the path to

greater understanding 121.3 Better measurements 151.4 Scientific conventions 22Chapter review 28

2 Atoms 292.1 Elements, compounds and mixtures 302.2 Physical and chemical change 382.3 Inside atoms 46Science focus: Atomic models 50Chapter review 53

3 Microbes 553.1 What is a microbe? 563.2 Reproduction in microbes 643.3 Friend or foe? 70Chapter review 76

4 Body systems 784.1 Food 794.2 Digestion 894.3 Blood and circulation 984.4 Excretion: getting rid of wastes 1084.5 Respiratory systems 111Science focus: Spare parts 118Chapter review 122

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We would like to thank the following for permission to reproduce photographs, texts and illustrations.

Andromeda Oxford Limited: Based on original artwork from Ecology & Environment: The Cycles of Life by Sally Morgan, Oxford University Press NY Andromeda Oxford Limited 1995, figure 6.3.4.

Anglo-Australian Observatory / David Malin Images: 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: Andrew Henley, figure 6.4.6.

Australian Associated Press: figure 2.1.3.

Australian Picture Library: figures 1.3.14, 3.1.6, SF 6.1a, SF 6.1b, SF 6.3, 7.0.1, 7.2.7, 7.3.4; Hulton-Deutsch Collection/Corbis, figure 1.1.1a; Hermann/Starke, figure 2.2.2; Digital Art, figure 3.1.14; Lester V. Bergman/Corbis, figures 3.2.5b, 4.3.11; Lester Lefkowitz, figure 4.0.1; 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 Asset Library, figure SF 4.3.

Coo-ee Picture Library: figure 6.1.4.

CSIRO Publishing: figure 6.1.7, 8.2.8; CSIRO Human Nutrition and The Cancer Council South Australia Reproduced from 12345+ Food and Nutrition Plan (K Baghurst et al., 1990) by permission of CSIRO Australia and The Cancer Council South Australia, figure 4.1.4.

Dorling Kindersley: figures 2.1.2c, 5.0.1; Max Alexander, figure 2.1.2a; Erik Svensson & Jeppe Wikstrom, figure 2.1.2b; Steve Gorton, 4.3.1; Andy Crawford, figure 4.4.1; Based on original artwork from Nature Encyclopedia by David Burnie, Jonathan Elphic 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 from Anatomica: The Complete Reference Guide to the Human 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, 8.3.6, 8.3.7, 8.4.0, 8.4.6, 8.4.7, 8.4.10, 8.4.11; Glen Research Center, figure 8.4.2.

The National Library of Australia: figure SF 6.5; John Allcot, figure SF 6.4.

Oxford University Press: copyright from The Young Oxford Book of Ecology by Michael Scott (OUP, 1996), reprinted by permission of Oxford University Press, figure 6.4.2.

Pearson Education Australia: Anna Small, figures 2.2.1, 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 Abery, figures 3.1.10c, 3.3.1; Kim Nolan, figure 3.3.8; Tricia Confoy, figure 2.2.3.

Photolibrary: figures 1.1.1b, 1.1.1c, 2.0.1, 2.1.2d, 2.1.6, 2.3.3, 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, 8.2.4, 8.2.6, 8.3.3, 8.4.5, 8.4.9, 9.2.2; Graham J. Hills, figure 2.1.8; Dr Tony Brain & David Parker, figure 3.1.1; Samuel Ashfield, figure 3.1.2; Jackie Lewin, EM Unit, Royal Free Hospital, figure 3.1.8; Susumu Nishinaga, figure 3.1.10d; Sinclair Stammers, figure 3.1.11; Astrid & Hanns-Frieder Michler, figure 3.1.12a; Laguna Design, figure 3.1.12b; David Scharf, figure 3.2.1b; Claude Nuridsany & 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 Medical Imaging Limited, figure 4.4.2; Alred Pasieka, figure 4.5.2; Klaus Guldbrandsen, figure SF 4.2; James King-Holmes, figure SF 4.4; Volker Steger, figure 6.3.5; Sheila Terry, 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 from The Joy of Chemistry, 1st Edition 1976, reprinted with 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, SF 5.6c.

Every effort has been made to trace and acknowledge copyright. However, should any infringement have occurred, the publishers tender their apologies and invite the copyright owners to contact them.

vCoursebookThe coursebook consists of nine chapters with the following features.

Chapter opening pages include: the key

prescribed focus area for the chapter

outcomes presented in a way that students can easily understand

pre quiz questions to stimulate interest and test prior knowledge.

Chapter units open with a context to encourage students to make meaning of science in terms of their everyday experiences. The units also reinforce contextual learning by presenting theory, photos, illustrations and science focus segments in a format that is easy to read and follow.

Each PFA has one Science Focus special 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 Focus series has been written for the NSW Science syllabus, stages 4 and 5. It includes material that addresses the learning outcomes in the domains of knowledge, understanding and skills. Each chapter addresses 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 Focus 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 questions that build confidence, leading to think, analyse and skills questions that require further thought and application. Questions incorporate the syllabus verbs 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 activities suitable 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.

Online review questionsAuto-correcting chapter review questions can be used as a diagnostic tool or for revision at school or home, and include: multiple choice labelling matching fill in the blanks.

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Companion WebsiteThe 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 availablethese 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 knowledge in

a stimulating, visual way drag-and-drop activities to improve basic

understandings in a fun way interactives to enhance the learning of content in

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 the practical work. Cross-references to practical activities within the units signal suggested points for practical work. Some practical activities are design-your-own (DYO) tasks.

Chapter review questions follow the last unit in each chapter. These cover all chapter outcomes in a variety of question styles to provide opportunities for all students to consolidate new knowledge and skills.

The use of the Aboriginal flag in the coursebook denotes material that is included to cover Aboriginal perspectives in science.

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Homework BookThe Homework Book provides a structured program to complement the coursebook. These homework activities: cover various skills

required in the syllabus offer consolidation of key

content and interesting extension activities

provide revision activities for each chapter, including the construction of a glossary

cater for a multiple intelligences approach through varied activities

have Worksheet icons in the coursebook to denote when a homework activity is available.

Teacher resource centreA wealth of teacher support material is provided and is password-protected. It includes: a chapter test for each chapter, in MS Word to

allow editing by the teacher coursebook answers Homework Book answers teaching programs

Teacher resource packMaterial 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 Book answers.

Worksheet 1.5 Sci-skills crossword

Worksheet 4.3 The heart

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A fully mapped and detailed correlation of the stage 4 curriculum outcomes is available in the Science Focus 2 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

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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 4 5 6 7 8 9Atoms1Science skills 3Microbes Body systems Electricity Ecology Plant systems Astronomy Team research project

Extrapolate infer from what is knownIdentify recognise and nameInvestigate plan, inquire into and draw conclusionsJustify support an argument or conclusionList write down phrases only, without further

explanationModify change in form or amount in some wayOutline sketch in general terms; indicate the main

features ofPredict suggest what may happen based on available

informationPresent provide information for considerationPropose put forward (eg a point of view, idea, argument,

suggestion) for consideration or actionRecall present remembered ideas, facts or

experiencesRecord store information and observations for laterRecount retell a series of eventsResearch investigate through literature or practical

investigationState provide information without further explanationSummarise express concisely the relevant details

VerbsScience Focus 2 uses the following verbs in the student activities.

Account account for: state reasons for; report on give an account of: narrate a series of events or transactions

Analyse identify components and the relationships among them; draw out and relate implications

Apply use, utilise, employ in a particular situationAssess make a judgement of value, quality, outcomes,

results or sizeCalculate determine from given facts, figures or informationClarify make clear or plainClassify arrange or include in classes/categoriesCompare show how things are similar or differentConstruct make; build; put together items or argumentsContrast show how things are different or oppositeDeduce draw conclusionsDefine state meaning and identify essential qualitiesDemonstrate show by exampleDescribe provide characteristics and featuresDiscuss identify issues and provide points for and/or

againstDistinguish recognise or note/indicate as being distinct or

different from; note differences betweenEvaluate make a judgement based on criteria; determine

the value ofExamine inquire intoExplain relate cause and effect; make the relationships

between things evident; provide the why and/or how

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By the end of this chapter you should be able to:

ask questions that can be tested or investigated

plan investigations, identifying what type of information or data needs to be collected and why

identify variables that need to be controlled

identify dependent and independent variables in experiments

plan a procedure for performing a fair test

perform experiments and record observations and measurements accurately

organise data in various forms, including tables and graphs

identify relationships, patterns and contradictions in information and data

analyse results

comment on the accuracy and meaning of 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 work

is accurate?

6 How do scientists communicate their ideas to each other?

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11Science skillsScience skillsKey focus area:The nature and practice of science>>>

Asking questionsScientists ask What, why and how? about the natural world. What protects some people from catching chicken pox? Why is the sky blue, not green? How do birds know the direction in which they should migrate? Why did 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 have no idea how these work, but someone invented them and others improved them so that they became small, cheap and reliable enough to have in homes, schools, factories, farms and businesses.

Scientists ask What, why and how? when they want to invent something new or improve current technology. What causes poor reception on your TV? Why does your computer crash? How can 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 textbooks or the Internet. Other answers can be found out only by doing first-hand investigations or experiments. This is the job of a scientist.

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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.

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Fig 1.1.1 You may have heard about Einstein, and Newton, but what did a Howard Florey, b Marie Curie and c Charles Darwin do? Which of them was Australian?

Poisoned!Sir Isaac Newton (16421727)

developed many laws in science and mathematics, but spent much of his time with

the ancient art of alchemy. He was trying to change common metals into pure gold! Other

scientists often found Newton extremely childish and difficult

to work with and it is now thought that the fumes from

his alchemy experiments were slowly poisoning him. In the

laboratory scientists must take care with the chemicals they use, particularly fumes. What rules about chemicals should you obey in the laboratory?

Newer but not betterThe scientists of the electronics industry usually aim to develop

parts that are smaller, faster and more powerful. There is,

however, a growing demand for the large and clumsy valves of

old. Top recording studios often use them since it is thought that sound quality is better than with modern electronic components. The radiation from X-rays can

knock out modern electronics, so medical laboratories use valves to keep equipment running. Fighter aircraft often use valves to avoid being knocked out of the air by radiation from a possible nuclear

explosion in war.

a b c

8 Record the measurement shown on each of the micrometer scales illustrated at right.

9 Draw the shaft and barrel of a micrometer showing a measurement of 12.87 mm.

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What, why and how?What, why and how?

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1 List three things about the natural world that confuse you.

2 Construct a what, why and how? question about each of the things that confuses you.

3 Describe how you would go about finding an answer to each of your questions.

4 Contrast the methods you listed in question 3 with the methods used by workers who arent scientists.

Think 5 Construct a two- or three-frame cartoon that explains

how to use a micrometer. Hint: Check Prac 1 on page 5.

6 State whether 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 Construct a diagram of a micrometer and label the

parts.

[ Extension ]Investigate

1 There are many other instruments that can measure small quantities very accurately. Research information on:a other devices that are used to measure thicknesses

and distances accuratelyb how the worlds most accurate clock worksc how very small quantities of chemical pollutants are

measuredd how small signals from space are amplified so that

they can be measured.

2 Research a vernier caliper to find out what it measures and how its scale works. Include a diagram and description in your response.

3 Some scientific discoveries, such as the discovery of penicillin, are made by accident. a Research the 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 outlining your discovery.

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A sheeps burpWhen a sheep farts or burps, it releases

methane, a greenhouse gas that contributes to global warming. Each sheep releases

about 25 litres of methane each day! CSIRO scientists designed the device shown in

Figure 1.1.2. to measure the amount of gas emitted without harming the sheep. This device is the result of scientists asking:

What is the problem? Why is it occurring? How are we going to solve it?

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A useful tool: the micrometerAim To use a device that can accurately measure the thickness of objects to within a fraction of a millimetre

EquipmentMicrometer, various common school items

shaft readsbetween26 and 27

barrelreads32

10 15 20 25

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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 textbook and 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 micrometer.

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 Compare and contrast the use of a micrometer with the use of a ruler for the measurements in the experiment.

2 Propose a 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

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Does nature follow rules?Aim To investigate how a tree grows and see if it follows any rules of nature

Equipment1 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 you should make them 8 to 10 cm apart.

Prac 2 Unit 1.1

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markings

twig micrometer

Fig 1.1.6 Checking if there is a growth rule

4 Construct a 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 from the rest, then calculate the average diameter for each marking.

Questions

1 Identify which set of measurements, Distance along the branch or Diameter of the branch, is the controlled measurement.

2 Plot the controlled measurements on the horizontal axis 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 Construct a line graph to show your results.

What, why and how?What, why and how?

4 Assess whether 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 twig used in the experiment and propose a reason for them being outfor example, there may be a split, knot or side branch at that spot.

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

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give 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, persistence 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 the questions 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 inferences about what they observed.

Carl and his friends thought about it carefully. They came up 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 off

at night (all his mates complained about that too!).

Fig 1.2.1Observation: grass goes yellow-white in colour when it is covered.

Ancient observations

In the year 5 BC Chinese astronomers noted that

there was a star burning with unusual brightness for 70 days. What they

saw was probably the exploding star or

supernova Aquilae. Many believe that 5 BC was

also the year of the birth of Jesus Christ. Was the

star that led the three wise men to Bethlehem actually the supernova

seen in China?

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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 variable) What is going to be kept the same? (the controlled

variables) What is going to be measured or

recorded? (the dependent variable)The results obtained depend upon what

we change. Therefore what we measure or record is called the dependent variable.

Carl grew four identical patches of grass. The same type and amount of grass was in each patchthe controlled variables. In each experiment he was careful to change only one variable 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 be right or wrong.

Carls conclusion was that the grass died because of a lack of sunlight. His hypothesis seemed to be correct.

Prac 2p. 11

Scientific research Scientific research

Did scientists create AIDS?

A virus called SIV has always infected the monkeys of Africa, but they never became ill from it. Most scientists believe SIV

sprang from monkey to human from a scratch or from eating

infected monkey meat. The SIV then mutated to become HIV, the

virus that causes AIDS. Some think, however, that infected monkey kidneys were used

in the development of a polio vaccine called CHAT. Polio was

devastating the world in the 1950s and the experimental CHAT vaccine was given to

thousands of people in Africa between 1957 and 1960. The

first outbreaks of AIDS were in the same region that the vaccine was given, the first death being in 1959. Did the CHAT vaccine

cause the AIDS outbreak? Did scientists take enough care in their research? As scientists

we have a responsibility to take extreme care in everything

we do.

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1 Define the following terms:a observations d hypothesisb qualitative e variablec inference f controlled variable.

2 State whether 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 List the three questions regarding well-designed experiments that need to be addressed.

4 Explain why 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 Summarise your observations.b Describe inferences you can make from the

observations.c Predict what 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 Identify the variables in the race.

Fig 1.2.3Controlling variables in an experiment

1.21.2

Fig 1.2.4

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Worksheet 1.1 Carls new experiments

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[ Practical activities ]

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Happy birthday to you!Aim To observe and interpret what happens when a candle is burnt in a sealed space

Equipment68 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 spreadsheet

with 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 1 Unit 1.2

[ Extension ]Investigate

Choose one of the occupations listed below. Research what areas of science a person would need to know to work effectively and safely in that occupation. Present your findings as a pamphlet to be displayed in the careers information centre in your school.

Architect Laser eye surgeon Chemist Optometrist Firefighter Car mechanic

b Assess whether it was a fair race.c Describe ways of making it a fair race.

Analyse 7 Referring to Carls experiments on factors that affect the

growth of grass:a identify the two variables tested by Carlb list other variables that could affect the growth of the

grass under the tentc outline previous knowledge used by Carl.

8 Referring to Carls research:a propose a heading for the research projectb construct an introductory sentence explaining why

the research was being performedc propose aims for the research and the two

experimentsd 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.

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Aircraft refueller Structural engineer Nurse Racing car driver Pilot Physiotherapist

Create10 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, describe it and have a partner deduce what it is.

a a food d an animal or insectb a tool of some sort e a sport.c a piece of furniture

Scientific research Scientific research

elastic band

water

pan

matches

glass

plasticinecandles

REDHEADS

elastic bands

Fig 1.2.5Which variable caused

more water to rise?1.2

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Questions

1 From the list below, identify the 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 Identify the chosen variable and the controlled variable in this experiment.

3 Propose reasons for the rise in water level in the jar.

4 Identify any trend evident from the graph which shows a relationship between the variables you plotted.

Why do cooks add salt to water?Aim To investigate why cooks usually add salt to water when cooking vegetables, pasta or rice

Equipment3 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 2 Unit 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? Justify your answer.

1.21.2 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, deduce why cooks add salt to water.

3 Extension: Construct a 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 mL beaker

60 mLwater

no saltthen2 g saltthen4 g salt

Fig 1.2.6Why do cooks add salt?

Flameout!When candles burn, wax

melts and some of it vaporises into a gas. The flame you see is actually burning wax vapour. If

you blow the candle out, a trail of smoke will rise from the wick. This too is wax vapour but it is

unburnt. Can you relight a candle by setting fire to its smoke? Try lighting a candle, then blowing

it out. Slowly lower a lit match down the smoke

trail. The flame will jump down the smoke to relight the candle. Test how far it can jump.

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 towards true understandingFigure 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 climbAs 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 answer to 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 stepDesigning the right experiment that will be a valid test of the hypothesis is a very important skill for a scientist. The experiment can be considered the most important component of the scientific method because a well-designed experiment produces and confirms results and knowledge that scientists can trust to be accurate. It provides supportive evidence.

If the experiment produces results that disagree with the hypothesis, this results in a downward path 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 idea becomes a theory. A theory is an explanation of an idea that is supported by a large amount of evidence and testing.

A theory can lead to the development of a model. 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 like 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 technology that usually improves our lives.

Science focus: Scientific method: the path to

greater understanding

Prescribed focus area: The nature and practice of science

13

Law

Technology released to

benefit humans

Designand

engineering

Applicationsto servehumans

RESEARCHincluding

mathematicalpredictions fromtheory or model

New orcontradictorypredictions

Modifiedor new

hypothesis

Confirmationby many

experiments

Hypothesissupported byexperiments

Hypothesisnot supportedby experiments

Newhypothesis

Ideahypothesis

Problem,question,

observation

TheoryModel

Design experimentaltest for hypothesis

or prediction

New orunexpected

observations

New level ofunderstanding

Greaterknowledge

Model or theory foundto apply and hold true

in many areas ofscientific study

Experiment

Fig SF 1.1A mountain of research: the scientific method

14

[ Student activities ] 1 a Investigate further the meanings of the following

terms: hypothesis, experiment, theory, law, model.b Construct a table to summarise your findings,

including a definition and example of each term. 2 When discussing the scientific method, many scientists

claim There is no such thing as a scientific fact!.a Justify this 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, propose possible reasons why Newtons Gravitation Theory:i is no longer used by scientists doing

research into gravityii is still taught in Science classes in

schools.b List the possible reasons you have proposed and

share your findings with the other groups.c Write a paragraph to present your own view and

explain why you have made your choice.

4 a Investigate at least three scientific laws.b State the law in the scientific language used in your

source (be sure to include your reference).c In your own words construct a simple description

to allow you to clearly explain each law to your classmates.

d Choose one of the laws you have found and construct a 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 laws and 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 upwardThe 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 way co

ntex

t

Mistakes and errorsMistakes are 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.

Errors are 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 eye in line with the measurement.

CORRECTREADINGM,

READINGTOOHIGH

ALWAYSMEASURETHELEVELATTHEBOTTOMOFTHECURVEMENISCUS

READINGTOOLOW

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 errorsMeasurements often fall between the markings of a measuring device. Some estimation is required for 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 errorsSometimes 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 timeA stopwatch normally reads to one-hundredth of a second

100 milliseconds away from death

Detailed studies by Saab have shown that a head-on collision of a car with a solid wall

takes less than 100 milliseconds, or 0.1 s. How does this compare with your reaction time?

If less, then the car accident is over before

you can react to it! There is no chance of getting

ready or bracing to avoid injurya good case for

wearing seatbelts.

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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 average or mean can be obtained.

To find an average:1 add all the measurements together to get a total2 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 best to average the other four results; that is, add the four 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 cmNotice 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 little guesswork.

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 different measurements.

Prac 2p. 20

27 1C

0

5

10

15

25

30

35

C

Fig 1.3.5

Better measurements Better measurements

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[ Questions ]

6 From the following, identify the measurements that could be taken accurately:a the number of kangaroos in Australiab the number of kangaroos in the zooc the length of the science laboratory at schoold the number of cloudy days in the next monthe the number of students who buy chips at the

school canteen.

7 Classify the 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 Calculate the average of these values to obtain the

most accurate measurement. a 39 mm, 38 mm, 40 mm, 41 mm, 40 mmb 25.3C, 26.8C, 27.5Cc 45 mL, 47 mL, 46 mL, 58 mL (be careful here!)

9 For each example in Figure 1.3.6, describe the 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 give or take 0.2 centimetres, or 8.3 0.2 cm.

Prac 3p. 20

1.31.3

Checkpoint1 Compare an error with a mistake.2 Explain why it is difficult to avoid errors.3 Outline four different types of errors.4 Why do scientists use different procedures to avoid or

minimise errors? Justify your answer.

Think 5 State whether 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.

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Worksheet 1.2 Extreme units

18

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10 a Define .b Record the following measurements with a error.

12

34

1020

3040

5060

7080

9010

011

012

013

014

015

016

017

018

019

020

0

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 beakerb 100 mL measuring cylinderc school electronic balance.

2 Police often give accurate estimates of crowd numbers at sporting events.a Explain how you could determine the number of

people in the photo in Figure 1.3.8 without counting each person.

b Use your method to estimate the number of people in Figure 1.3.8.

3 Use your method to estimate numbers in the following examples:a the number of grains of sand that would fit in a

shoebox filled with sandb the number of leaves on a treec the number of words and individual letters printed in

this chapter.

4 Use the diagram in Figure 1.3.9 to explain the difference between accuracy and precision.

5 a Research and summarise what is meant by the frequency of a pendulum.

b Propose a way of measuring the frequency of a pendulum.

c Design an experiment to investigate your method of measurement.

Action 6 Examine each of the following instruments to find the

smallest markings or divisions on them: a digital stopwatchb normal rulerc tape measured thermometere kitchen scale.

DYO

Better measurementsBetter measurements

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How quickly can you react?Aim To find your reaction time

EquipmentRuler (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 1 Unit 1.3

Fig 1.3.10Measuring reaction time

1.31.3

good accuracypoor precision

good precisionpoor accuracy

good accuracygood precision

bad news

ruler

have your fingers level with zero the ruler

has dropped 22 cm

>>

Experiment Distance ruler dropped Average ruler drop Average reaction time (cm) (cm) (s)

No distractions

No warnings

With countdown

With distractions

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 Identify the degree of accuracy of a normal stopwatch. 2 Contrast the reaction time with the accuracy of a

stopwatch.

3 Identify factors that affected the reaction time in this experiment.

4 Outline factors that affect your reaction time in everyday life.

Repeated measurementsAim To examine why taking a number of measurements is important

EquipmentMeasuring 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 to the floor.

2 Calculate the average for each measurement.

3 Record this average with a error.

Introduction to the pendulumA pendulum is a mass (called a bob) attached to a rod, chain or rope, which swings back and forth repeatedly.

The period of 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 3 Unit 1.3

Fig 1.3.11 Pendulums are everywhere!

Better measurementsBetter measurements

Prac 2 Unit 1.3

Chaos at play!Have you ever noticed that professional tennis players are always on their toes when they are about to receive a serve?

The unstable nature of their footing seems to quicken their response, making them more

likely to return the ball. Accurate measurements of heartbeats show

that they are roughly the same, but are all slightly different. The slightly unstable

beat helps keep our heart on its toes. It can then respond to any sudden need for increased blood supply when we exercise.

This is the scientific theory called chaos at work.

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Fig 1.3.14A practical pendulum

1 period

stringretort stand

boss head and clamp

bob

Fig 1.3.12 Is the mass an important variable?

Aim To investigate the effect of changing the mass of the bob on a pendulum

EquipmentMaterials 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

Perio

d (s

)

Mass (g)0

Fig 1.3.13Use these axis markings

1.31.3

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 Describe variables that you controlled in this experiment. 2 Identify the dependent and independent variables. 3 Describe how you made sure the angle was always

the same.

4 Explain why ten periods were measured rather than just one.

5 Identify other variables that could affect the period. (Think about the bob and the string itself.)

22

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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.

cont

ext

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 or materials used your methodexplanation of what was done in the

experiment, including the quantities used. A diagram can be useful here too

your results and observationscomplete list of measurements and observations that were taken, preferably displayed in a table

a discussion or analysis, 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 a bibliography.

Organising resultsData is the word used for a lot of measurements or observations. Data is usually placed in a table (tabulated), sometimes as a computer spreadsheet or database. This makes any patterns that may exist more obvious. Headings and units should be at the top of each column.

Drawing line graphsPatterns become even more obvious when data is plotted 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 labels and units on the axes regular markings for the scale along the axes all your points clearly marked on the graph

itself.The independent variable is placed on the

the horizontal axis. The independent variable is 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 variable is 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 up the points in a dot-to-dot manner suggests that there is no error. It is more sensible to draw a straight line or smooth curve approximately through the centre of

Prac 1p. 26

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Graphs showing common relationships

As x gets bigger, y gets bigger but then levels out.

As x gets bigger y gets much bigger(y more than doubles if x doubles).

Could be described as a linear relationship(y doubles if x doubles).

y

x

y

x

y

x

Fig 1.4.3

A line of best fit is not dot-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

Leng

th o

f mou

se (m

m)

Days after birth

independent variableyou choose how big

dependent variablechanges naturally

line of best fit

Length of baby mouse as it grows

Fig 1.4.1 your points: this is called the line of best fit or curve of best fit. Patterns and results can then be predicted. You can predict extra results by continuing the shape 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 temperature after 15 minutes would be 22C.

Describing patternsGraphs of straight lines or smooth curves indicate that there is a pattern, rule or relationship between the variables that you tested. Some ways of describing 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

Tem

pera

ture

(C)

Time (minutes)

curve of best fit

extrapolation (logical extension of graph)

The cooling curve of water

Fig 1.4.2 Line graphs can be used to predict missing values. For example, the temperature was 32C at 8 minutes, and took 41/2 minutes to reach 48C. What do you predict the temperature to be at 15 minutes?

Prac 2p. 26

Prac 3p. 27

Using and converting metric unitsScientific 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 be sensibly 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),

1.41.4

The size of a smellA smell might be invisible but is

actually particles of the material

that made the smell, dissolving in the thin layer of mucus in

the nose. A frightening thought

considering what we smell each

day! A typical smell has a mass

of only 760 ng or 760 billionths

of a gram. This is about 1/5 the

mass of the smallest insect (the

parasite wasp) but 10 000 times

heavier than the lightest virus. This means that we cannot

possibly smell a virus like the common cold.

Worksheet 1.3 Graphing skills

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[ Questions ]

10 Metric prefixes are not usually used for time. State the following metric time units in seconds (s): a 1 kilosecond or 1 ksb 1 centiminute or 1 cminc 1 kiloday or 1 kdd 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 Define the following terms:

a convention d relationshipb hypothesis e bibliography.c line of best fit

2 Describe the type of information found in the discussion section of an experiment.

3 List all the details that must be included on a graph. 4 Propose the correct axis for the independent variable

on a graph.

5 Explain the usefulness of the metric system in science. 6 Describe how a line of best fit is obtained when

drawing a graph.

7 Propose two places where diagrams would be useful in an experimental report.

8 Explain why scientists use line graphs more often than pie charts and bar graphs.

Think 9 Modify the following values to make the conversions

shown: a 5 ML into litresb 375 mL into litresc 500 000 mm into metresd 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

Tim

e to

dro

p (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

Mas

s (k

g)

Time (min)

60

50

40

30

20

10

0

Fig 1.4.5

c Construct a correct version of the graph.

0 1 2 3 4 5 6 7 8 9 10

Tem

pera

ture

Seconds

100

90

80

70

60

50

21.3

15.5

9.1

7.8

3.2

0

Fig 1.4.6

[ Extension ]Investigate

1 Research and present information about the following features of the metric system. Include a bibliography in the information presented.a Outline where, when and why the metric system

was developed.b Describe how the length of a metre was originally

determined.c Use an example to explain what a measurement

standard is.

2 Carry out research to identify the metric units used for the following measurements:a air pressureb forcec energyd electrical currente electrical voltage.

3 Describe where the following units are used:a megatonne (Mt)b decibel (dB)c gigabyte (Gb).

13 a Identify five mistakes in the plotting of the graph in Figure 1.4.6.

b Decide whether the independent variable is plotted on the correct axis. Justify your answer.

a Propose an aim for Sams experiment.b Construct a table of results for the experiment.c Use the graph to identify the drop time for the feather

and stone from these heights:i 1.5 mii 2.5 miii 3500 mm.

d Extrapolate the height that the feather and the stone were dropped from, given the following times.i 0.5 sii 1.2 siii 1.9 s.

e Extrapolate the graph to find the values of the following measurements:i time taken to drop the feather 5 mii time taken to drop the stone 5 miii the position of the feather after 2.5 s.

f Draw conclusions from the experiment.

Skills 12 a Examine Figure 1.4.5 and assess whether all the data

for the points plotted is reliable. b Copy the graph onto graph paper and construct a line

of best fit.c Propose a title for the graph.

1.41.4

26

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[ Practical activities ]1.4

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How does length affect a pendulum?Aim To investigate if the length of a pendulum affects its period

EquipmentMaterials 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 a straight 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 Discuss any precautions taken in the experiment to reduce errors.

2 Identify the controlled variables.3 Identify the independent and dependent variables.4 Use the shape of the curve obtained in the graph

to outline any relationship evident between the dependent and independent variables.

5 Draw conclusions from the data obtained.Pe

riod

(s)

Length

Fig 1.4.7 Plotting period against square root length

Prac 2 Unit 1.4

Does the angle matter?Aim To investigate the effect of angle on the period of a pendulum

EquipmentMaterials 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 Outline how you controlled variables that you did not want to test.

2 Does the shape of the graph support your hypothesis? Justify your answer.

3 Propose further questions that arise from this experiment.

Scientific conventionsScientific conventions

Foucaults pendulumA pendulum looks as if it

never changes direction. This is because most pendulums are short and all pendulums

eventually stop due to air resistance. As a pendulum

moves back and forth, the Earth is slowly spinning underneath. If the pendulum kept going we

would see it slowly change direction. After 24 hours it would return to its original

orientation. A pendulum that does this is called Foucaults

pendulum.

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Prac 3 Unit 1.4

Complex pendulumsAim To investigate different pendulums

EquipmentMaterials 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

bridgependulum

chainpendulum

doublependulum

Fig 1.4.8Other pendulums to try

Prac 4 Unit 1.4

3 Describe the shape of all graphs you plotted. 4 From the shape of the graphs describe any patterns in

the relationships between variables.

5 Use the information obtained from graphs to draw conclusions for both experiments.

Drop timeAim To investigate the variables in the drop time of a parachute.

EquipmentLightweight 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 Identify the variables that may be important in this experiment.

2 Explain why you chose the variables you tested and not others.

Fig 1.4.9 Testing parachutes

1.41.4

light materials,eg paper, plastic

sticky tape reinforcing

mass

stopwatch

chute

2 m or more

28

>>>

Chapter review

[ Summary questions ] 1 Contrast the work of scientists with that of other workers. 2 Identify two examples of each of the following types of

observations:a qualitativeb quantitativec visuald made with the sense

of touch only

3 Contrast each of the following terms:a an experiment and researchb a qualitative and a quantitative observationc an aim and a hypothesisd an error and a mistake.

4 Draw diagrams to explain the following types of errors:a parallax errors b reading errors.

5 Use an example to contrast a dependent with an independent variable.

6 Use an example to explain how human reflex can add errors to an experiment.

7 In order, list the features normally included in an experimental report.

[ Thinking questions ] 8 Sarah wrote the length of an insect as 2.1 0.1 cm.

State the biggest and the smallest length of the insect.

9 Record the 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 Calculate the average value for the following measurements.a 87 mL, 90 mL, 86 mL and 93 mLb 115 g, 123 g and 125 g.

11 Propose a 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. Calculate the 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

Soun

d in

tens

ity

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 identify the independent variableb identify the variable that changed naturallyc identify what is missing from the axesd construct a table of results for the experimente construct a line or curve of best fit through the dataf predict the sound intensities for the following distances:

i 1.5 mii 2.8 m

g predict the distances for the following sound intensities:i 45ii 32

Australia we eat 13 500 kJ. Many claim that Australians eat more than the recommended allowance. Justify this statement.

14 Recommend appropriate metric units for the following measurements:a the length of a sugar antb the amount of water in Botany Bayc 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 increase in 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.

iii 350 cmiv 6000 mm

v 0 m.

iii 20iv 55.

Worksheet 1.5 Sci skills crossword

Worksheet 1.6 Sci-words

>>>

By the end of this chapter you should be able to:

distinguish between an element, a compound and a mixture

distinguish between an atom, a molecule and a lattice

recall the symbols of some elements

write the formulae for some simple compounds

identify whether a change in a substance is due to a physical or a chemical change

write simple word equations to describe a 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 for ferret, ferocious or iron?

2 Which do you think is the symbol for chlorine? C, Ca, Cl or Co?

3 Are you making a new substance when you add water to cordial?

4 List what is produced when paper is burnt.

5 Why are vegetables stored in the refrigerator?

6 Which do you think will relieve a headache more quickly: a whole aspirin tablet or the same tablet crushed?

7 You can easily see an atom with an ordinary microscope. True or false?

Outcom

es 4.1, 4.2, 4.7.4, 4.7.5

, 4.7.6, 5

.7.1, 5.7.2, 5

.7.3

Pre quiz

22 AtomsAtomsKey focus areas:The nature and practice of scienceThe history of science>>>>>>

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>>>UNITUNIT

2.12.1In 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 and every substance that we see, breathe, drink and use. They even make up our bodies.

cont

ext

ElementsAn element is 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 in detail 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 water vapour, carbon and other substances. The water vapour bubbles through the carbon to produce an impressive black cone of charcoal.

Warning: This demonstration must be done in a fume cupboard, as the fumes produced may trigger respiratory problems. Safety goggles must be worn.

sugar

sulfuric acid

beaker

Fig 2.1.1 Concentrated acid may be used to break down sugar into carbon and other substances.

Prac 1p.36

These have never been found in nature but were created by scientists in the laboratory. Many of the synthetic elements are unstable and exist for only a few seconds after being created. Some elements are listed in Figure 2.1.2.

The most abundant elements

The most abundant element on Earth is

oxygen, which constitutes about 47 per cent of the

Earth. Next is silicon (28 per cent of the Earth),

followed by aluminium (8 per cent) then iron

(5 per cent).

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The Hindenburg explodes. Fig 2.1.3

Some elements and their symbolsFig 2.1.2

Element Symbol Element Symbol

Aluminium Al Lead Pb

Americium Am Magnesium Mg

Barium Ba Mercury Hg

Boron B Neon Ne

Calcium Ca Nickel Ni

Carbon C Oxygen O

Chlorine Cl Platinum Pt

Chromium Cr Plutonium Pu

Copper Cu Potassium K

Einsteinium Es Radium Ra

Europium Eu Sodium Na

Fluorine F Silver Ag

Gold Au Sulfur S

Helium He Tin Sn

Hydrogen H Titanium Ti

Iodine I Tungsten W

Iron Fe Uranium U

Krypton Kr Zinc Zn

Each element has a unique symbol made up of one or two letters. Carbon has the symbol C. Because carbon uses the single letter C, chlorine is given a different symbol, Cl. Cobalt has the symbol Co. The first letter of a symbol is always a capital, while the second is always in lower case. But what about copper? C and Co have been used already! Many elements get their

symbols from Latin or Greek words. Coppers symbol, Cu, is taken from the Latin word for coppercuprium. The names of some elements are not at all obvious initiallysodium has the symbol Na, from the Latin word natrium. Potassiums symbol, K, comes from the Latin word kalium, while golds symbol, Au, comes from the Latin word for the metal, aurum. Worksheet 2.1 The elements

2.12.1Phosphorus

discovered in P!In medieval times, people called

alchemists worked on potions and spells. They attempted to

find the legendary philosophers stone that would turn base

metals such as lead into gold. A German alchemist, Henry Brand, was working on an

elixir of life potion when he extracted from urine an element

that glowed in the dark! He had accidentally discovered

phosphorus (nowadays given the symbol P).

The HindenburgThe Hindenburg airship (or Zeppelin) was filled with the element hydrogen, and exploded in 1937 with the loss of 35 lives. Hydrogen reacts with

oxygen in the air. It burns explosively, producing lots of energy and water.

32

>>>Metal and non-metal elementsOf the 106 known elements, 84 are metals and 22 are non-metals.

All metallic elements are solids at room temperature except for mercury, which is a liquid. The properties of metallic elements make them very useful to humans. For example, aluminium is used to form cooking utensils, copper for electrical wires and plumbing pipes, while mercury is used in thermometers.

Elements

Metallic elements Non-metallic elements

Solid Liquid Solid Liquid Gas (Iron, Magnesium) (Mercury) (Carbon) (Bromine) (Oxygen)

Fig 2.1.4Metals and non-metals are classified according to their properties.

Many useful products are made of metals.Fig 2.1.5

Non-metallic elements can exist as solids, liquids or gases. They are also very useful to humans. Nitrogen gas is used for making fertilisers, carbon (diamond) for jewellery and cutting tools, and carbon (graphite) for bicycle frames and as a lubricant.

Sulfur displays all the typical properties of a non-metal. It is used for making sulfuric acid and fertilisers, it has antibacterial and antifungal properties and its compounds are used to preserve food.

The different properties of metals and non-metals

Fig 2.1.6 The sulfur shown is a typical example of a non-metal.

Metals Properties Non-metals

solid physical state solid liquid (except mercury) or gas

shiny appearance dull

high melting point low

high density low

malleable malleability brittle (ability to be shaped) (easily broken)

ductile ductility (ability to be no stretched into wires)

good conductivity poor

AtomsImagine you wish to share a thin sheet of gold equally among your class. You begin t