Science Skills Guideashaw43.weebly.com/uploads/9/4/4/5/9445145/bc8text_bm_skills.pdf · 474 MHR •...

474 MHR • Science Skills Guide

Science Skills GuideScienceSkill Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475

Safety Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475WHMIS Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475

ScienceSkill Scientific Inquiry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476Making Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476Stating an Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477Making a Prediction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477Identifying Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477Designing a Fair Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478Forming a Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479A Process for Scientific Inquiry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479

ScienceSkill Technological Problem Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480Identifying the Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480Identifying Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480Planning and Constructing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481Evaluating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481A Process for Technological Problem Solving . . . . . . . . . . . . . . . . . . . 481

ScienceSkill Societal Decision Making . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482Identifying the Issue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482Gathering Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482Making a Decision. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483A Process for Societal Decision Making . . . . . . . . . . . . . . . . . . . . . . . 484

ScienceSkill Organizing and Communicating Scientific Results with Graphs . . . . . . . 485Drawing a Line Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485Constructing a Bar Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486Constructing a Circle Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487Graphing on a Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489

ScienceSkill Scientific Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490Making a Scientific Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490Drawing to Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491

ScienceSkill Estimating and Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492Estimating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492Measuring Length and Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493Measuring Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493Measuring Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495Measuring Angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496Measuring Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497

ScienceSkill Using Models in Science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498

ScienceSkill Using a Microscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 499Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500

ScienceSkill Using Your Textbook as a Study Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . 501Using Your Textbook to Read for Information . . . . . . . . . . . . . . . . . . . 501Using Your Textbook Visuals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 501Using the Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 501Using the Review Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502Using Graphic Organizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502

ScienceSkill Units of Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503The Metric System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 505SI Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506

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Science Skill 1 • MHR 475

Safety SymbolsThe following safety symbols are used in BCScience 8 to alert you to possible dangers. Besure you understand each symbol used in anactivity or investigation before you begin.

Disposal AlertThis symbol appears when care must be takento dispose of materials properly.

Thermal SafetyThis symbol appears as a reminder to use caution when handling hot objects.

Sharp Object SafetyThis symbol appears when a danger of cuts or punctures caused by the use of sharpobjects exists.

Electrical SafetyThis symbol appears when care should betaken when using electrical equipment.

Skin Protection SafetyThis symbol appears when use of causticchemicals might irritate the skin or when contact with micro-organisms might transmit infection.

Clothing Protection SafetyA lab apron should be worn when this symbol appears.

Fire SafetyThis symbol appears when care should be taken around open flames.

Eye SafetyThis symbol appears when a danger to theeyes exists. Safety goggles should be wornwhen this symbol appears.

Safety

WHMIS SymbolsLook carefully at the WHMIS (WorkplaceHazardous Materials Information System)safety symbols shown here. The WHMISsymbols are used throughout Canada toidentify dangerous materials used in allworkplaces, including schools.

Make certain you understand what thesesymbols mean. When you see these symbols oncontainers in your classroom, at home, or in aworkplace, use safety precautions.

Compressed Gas Flammable andCombustible Material

Oxidizing Material Corrosive Material

Poisonous and InfectiousMaterial Causing Immediate

and Serious Toxic Effects

Poisonous and InfectiousMaterial Causing Other

Toxic Effects

Biohazardous InfectiousMaterial

Dangerously ReactiveMaterial

Instant Practice—Safety Symbols

Find four of the BC Science 8 safety symbolsin activities or investigations in thistextbook. Record the page number and thetitle of the investigation or activity in whichyou found the symbol. What are the possibledangers in the activity or investigation youhave identified that relate to each symbol?

Instant Practice—WHMIS

Find any two WHMIS symbols oncontainers in your school, or ask yourparent or guardian to look for WHMISsymbols in a workplace. Record the nameof the substance on which the symbols areused, and where you or your parent orguardian saw the containers stored. Whatdangers are associated with the substance ineach container?

Science Skill 1

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476 MHR • Science Skill 2

Scientific InquiryThe rain has stopped and the Sun is out. You notice that a puddle has disappeared from thesidewalk. What happened to that puddle of water that was here a while ago? You could probablyquickly answer that question, but how would you prove your answer? You would need to makeobservations and record data.

Making ObservationsFirst, you might observe what happens to some other puddles. You would watch them closelyuntil they disappeared and record what you observed.

One observation you might make is, “The puddle is almost all gone.” If you did, you wouldbe making a qualitative observation, an observation in which numbers are not used. A little later,you might also say, “It took five hours for the puddle to disappear completely.” You have made aquantitative observation, an observation that uses numbers.

(a) Food colouring madethe water blue.Adding 3 mL of foodcolouring turned 250 mL of water blue.

(b) The water becamewarmer.The water’s temperatureincreased by 5°C.

(c) We needed just over a dozen floor tiles forour model room.We needed 14 floor tilesfor our model room.

(d) The liquid boiled in 5 min.The liquid took onlya few minutes to boil.

(e) The mass of this solid is5 g more than that one.This solid is heavierthan that one.

(f) He drinks eight glassesof water each day.He drinks 2 L of watereach day.

Instant Practice—Making Qualitative and Quantitative Observations

In your notebook, copy the observations below. Beside each, write “Qual” if you think it is aqualitative observation and “Quan” if you think it is a quantitative observation.

Science Skill 2

Beginning your observations of water puddles Concluding your observations of water puddles

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You probably already know that evaporationis the reason that the puddles are disappearing,but there are still lots of questions you can askabout evaporation. Although the two puddleswere the same size, one evaporated much more quickly than the other one did. Yourquantitative observations tell you that oneevaporated in 4 h, whereas the other one took 5 h. Your qualitative observations tell you thatthe one that evaporated more quickly was in theSun. The one that evaporated more slowly wasin the shade. You make the same observationsabout another pair of puddles. You now have aquestion to ask: Does water always evaporatemore quickly in the Sun than in the shade?

Stating an HypothesisNow you are ready to make an hypothesis, astatement about an idea that you can test, basedon your observations. Your test will involvecomparing two things to find the relationshipbetween them. You know that the Sun is asource of thermal energy, so you might use thatknowledge to make this hypothesis: Evaporationfrom natural pools of water is faster for pools insunlight than for pools in shade.

Making a PredictionAs you prepare to make your observations, youcan make a prediction, a forecast about whatyou expect to observe. In this case, you mightpredict that pools A, B, and C will dry upmore quickly than pools X, Y, and Z.

Identifying Variables“But wait a minute,” you think, as you lookagain at your recorded observations. “Therewas a strong breeze blowing today. What effectmight that have had?” The breeze is one factorthat could affect evaporation. The Sun isanother factor that could affect evaporation.Scientists think about every possible factor thatcould affect tests they conduct. These factorsare called variables. It is always important totest only one variable at a time.

You need to control your variables. Thismeans that you change only one at a time. Thevariable that you change is called themanipulated variable. In this case, themanipulated variable is the condition underwhich you observe the puddle (one variablewould be adding thermal energy; anotherwould be moving air across it).

According to your hypothesis, addingthermal energy will change the time it takes forthe puddle to evaporate. The time in this case iscalled the responding variable.

Often, experiments have a control. This isa test that you carry out with no variables, sothat you can observe whether yourmanipulated variable does indeed cause achange. Look at the illustration below to seesome examples of variables.

(a) Find the best filter for muddy water

(b) Find the best plant food for plant-growth

( ) D h f id i ff d i i ?

control(no manipulated

variable)

responding variable

(clarity of water)

manipulatedvariable(filter)

control(no manipulated

variable)

responding variable(growth)

manipulatedvariable

(plant food) plantfood B

plantfood A

two layers ofcheesecloth

four layers ofcheesecloth

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Designing a Fair TestIf you consider more than one variable in atest, you are not conducting a fair test (onethat is valid and unbiased), and your resultswill not tell you anything useful. You will notknow whether the breeze or the Sun made thewater evaporate.

As you have been reading, a question may haveoccurred to you: How is it possible to do a fairtest on puddles? How can you be sure thatthey are the same size? In situations such asthis one, scientists often use models. A modelcan be a mental picture, a diagram, a workingmodel, or even a mathematical expression. Tomake sure your test is fair, you can preparemodel “puddles” that you know are all exactlythe same. Science Skill 8 gives you moreinformation on using models.

Instant Practice—Doing a Fair Test

1. With a partner, examine the followingillustration. In your notebook, write theletters of the “puddles” you would notuse to set up a fair test. Explain why youwould not use them.

2. Now, you can carry out yourexperiment. How many times will youdo it in order to be sure that you havetruly tested your hypothesis?

3. What kinds of errors can creep into atest such as the one described above?Use your sense of humour, and workwith a partner to draw some sketchesthat illustrate some errors. (Make surethey are errors that could actuallyoccur!)

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Forming a ConclusionMany investigations are much more complexthan the one described here, and there aremany more possibilities for error. That is whyit is so important to keep careful qualitativeand quantitative observations.

After you have collected all your data, youare ready to analyze it and draw a conclusion.A conclusion is a statement that indicateswhether your results support or do not supportyour hypothesis. If you had hypothesized thatthe addition of thermal energy would have noeffect on the evaporation of water, your resultswould not support your hypothesis. Anhypothesis gives you a place to start and helpsyou design your experiment. If your results donot support your hypothesis, you use what youhave learned in the experiment to come upwith a new hypothesis to test.

Scientists often set up experiments withoutknowing what will happen. Sometimes theydeliberately set out to prove that somethingwill not happen.

Eventually, when a hypothesis has been thoroughly tested and nearly all scientists agree that the results support thehypothesis, it becomes a theory.


A Process for Scientific InquiryOne model of the scientific inquiry process isshown in the concept map below.

repeat several times

revise prediction or hypothesis

prediction or hypothesis supported

prediction or hypothesis not supported

observations and curiosity stimulate questions

identify the problem

gather information

form an hypothesis or make a prediction

perform an experiment/ investigation

analyze data

draw conclusions

communicate results

The Scientific Inquiry Process

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“Technology”—what does that word make youthink of? Do you think of complicatedelectronic equipment? Do you think of thelatest-model cars? Do you think of spaceexploration? Well, all of those have to do withtechnology, but think about this: Have youever used a pencil to flip something out of atight spot where your fingers could not reach?Have you ever used a stone to hammer basesor goal posts into the ground?

These, too, are examples of technology.Technology is the use of scientific knowledge,as well as everyday experience, to solve practicalproblems. You may not know why your pencilworks as a lever or the physics behind levers, butyour everyday experiences tell you how to use alever successfully. Often, science has a part intechnology, but not always.

Identifying the ProblemWhen you used that pencil to move the smallitem you could not reach, you did so becauseyou needed to move that item. In other words,you had identified a problem that needed to besolved. Clearly identifying a problem is a goodfirst step in finding a solution. In the case of thelever, the solution was right before your eyes, butfinding a solution is not always quite so simple.

Your school is soon to close for a 16-daywinter holiday. Your science class has a hamsterwhose life stages the class observes. Student volunteers will take the hamster home and carefor it over the holiday. However, there is athree-day period when no one will be availableto feed the hamster. Leaving extra food in thecage is not an option because the hamster willeat it all at once. What kinds of devices couldyou invent to solve this problem?

First, you need to identify the exact natureof the problem you have to solve. You couldstate it as follows:

The hamster must receive food and wateron a regular basis so that it remains healthyover a certain period and has noopportunity to overeat.

Identifying CriteriaNow, how will you be able to assess how wellyour device works? You cannot invent a devicesuccessfully unless you know what criteria(standards) it must meet.

In this case, you could use the following asyour criteria:1. Device must feed and water the hamster.2. Hamster must be thriving at the end of the

three-day period.3. Hamster must not appear to be “overstuffed.”

How could you come up with such adevice? On your own, you might not. If youwork with a team, however, each of you willhave useful ideas to contribute.

Technological Problem Solving

Science Skill 3


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Planning and ConstructingYou will probably come up with somethinggreat. Like all other scientists, though, you willwant to make use of information and devicesthat others have developed. Do some researchand share your findings with your group. Canyou modify someone else’s idea? With yourgroup, brainstorm some possible designs. Howwould they work? What materials would theyrequire? How difficult would they be to build?How many parts are there that could stopworking during the three-day period? Make aclear, labelled drawing of each design, with anexplanation of how it would work.

Examine all of your suggested designscarefully. Which do you think would work best?Why? Be prepared to share your choice and yourreasons with your group. Listen carefully to whatothers have to say. Do you still feel yours is thebest choice, or do you want to change yourmind? When the group votes on the design thatwill be built, be prepared to co-operate fully,even if the group’s choice is not your choice.

Get your teacher’s approval of the drawingof the design your group wants to build. Thengather your materials and build a prototype (amodel) of your design. Experiment with yourdesign to answer some questions you might haveabout it. For example, should the food and waterbe provided at the same time? Until you try itout, you may be unsure if it is possible (or even agood idea) for your invention to deliver both atthe same time. Keep careful, objective records ofeach of your tests and of any changes you maketo your design.

You might find, too, that your inventionalways seems to fail in a particular way. Perhapsit always leaks at a certain point where twoparts are joined. Perhaps the food and waterare not kept separate. Perhaps you notice amore efficient way to design your device asyou watch it operate. Make any adjustmentsand test them so that your device works in thebest and most efficient way possible.

EvaluatingWhen you are satisfied with your device, youcan demonstrate it and observe thoseconstructed by other groups. Evaluate eachdesign in terms of how well it meets the designcriteria. Think about the ideas other groupsused and why they work better than (or not aswell as) yours. What would you do differentlyif you were to redesign this device?

A Process for Technological Problem SolvingThe problem-solving model you have just usedis shown here.

Identify the problem.

Decide on design criteria. .

Solving a Technological Problem

The design criteria were not

satisfactory.

Patent the product or technique for possible

mass production.

Use the productor technique.

Plan and construct:• Make a sketch.

• Draw a complete plan.• Build a model.

Evaluate the plan.

The product or techniqueis an excellent solution

to the problem.

Revisethe designcriteria.

The plan had obviousflaws.

Revise the plan.


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Suppose you are part of an enthusiastic mixedhockey team that practises at an arenabelonging to a town a few kilometres away.The town council is in the middle of budgetdiscussions, and one of the items underdiscussion is the salting of roads. The council isprepared to expand the salting program so thatroads in your area will be salted in winter. Youand your teammates are delighted. This willmake your trip to the arena easier—and alwayspossible. There are days now when you justcannot get there because the roads are too icy.

Identifying the IssueSoon after hearing the news about the road-salting, you go to your friend’s house. You findyour friend sitting in front of the computer, composing a letter to the town council. In it,your friend is asking that the salting program notbe expanded to your area. You cannot believeyour eyes, but as you begin discussing the letter,you start to see your friend’s point of view.

“What do you mean, damage theenvironment?” you ask. “Surely it is importantto make our roads safer.”

Gathering Information“It is,” answers your friend, “but is there someway we can make the roads safer without doingso much harm to the plants at roadsides and tothe drinking water in springs and wells? I wasgoing to check the Internet to find informationabout these questions I have written down.”

“Whew,” you say. “There is an awful lot tothink about here. Let us see what we can findout from the Internet.”

“Well, we found a lot of information, but Iam still not completely convinced that salting theroads could cause a problem with our water,”you say. “What sorts of things do we need tofind out in order to answer that question?”

“We could do an investigation,” yourfriend suggests. “Then I could use the resultsin my letter to the town council.”

Societal Decision Making

Science Skill 4

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“I guess road salt does get into the watersystem,” you admit after completing yourinvestigation. “But we added quite a lot of salt.I wonder if any salt stays in the soil—maybewe could add less salt so that much less wouldget into the water, and our roads would still besafe for driving.

Let us do some more research in thelibrary and on the Internet, and see if we canfind out how salt leaches through soil. Maybewe can also see what alternatives there are. Wecould look for something about using less salton the roads—or even no salt.”

When you have all of the data that yourscientific studies can provide, your decision willstill involve some very human and personalelements. People have strong feelings aboutthe social and environmental issues that affectthem. Something that seems obvious to youmight not be so obvious to another person.Even your scientific data might not change thatperson’s mind. If you are going to encourage agroup to make what you consider a good

decision, you have to find ways to persuade thegroup to think as you do.

After all the data are in, and after all thepersuading is done, it is time to take someaction. The seemingly small actions done byyou and your friends can have a snowballeffect. You are very keen to show your sense ofresponsibility and community spirit by gettingyour ideas across to town council when one ofyour friends makes you stop and think. “I havenoticed you putting a lot of salt out on yoursidewalk,” says your friend. “You could use abit of time and muscle power to chip away theice, but that is not the choice you make.” Yourealize your friend is right—it is not up to thetown council or any other group to actresponsibly; it is up to you and your friends.How easy is it for you to give up anundemanding way of doing a task in order tomake an environmentally responsible decision?

Making a DecisionIssues rarely have easy answers. Those who areaffected have differing, valid points of view. Itis easier for you to act as an individual, but ifyou can persuade a group to act, you will havegreater influence. In the issue discussed here,you might write a letter to town council. As acompromise, you might suggest a combinationof salt and sand on the roads. Your scientificstudy can provide you with appropriatestatistics. As a group, you could attend a town


Title:Investigation STS 1 Effect of Road Salt on Water SystemsQuestion:Does the addition of salt to soil affect thesurrounding water?Manipulated Variable:– saltResponding Variable:– amount of salt in waterHypothesis:– Water near soils that contain salt will also contain salt.Prediction:– If we add salt to soil, any water that drains through

that soil will contain salt.Procedure1.

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council meeting or sign a petition to makeyour views known.

Over time, you can assess the effects ofyour actions: Are there fewer accidents on thesalted/sanded roads? Does less salt end up inthe water than when more salt alone is used?

A Process for Societal DecisionMakingAs you reached your decision, you wentthrough various stages. Now you can thinkabout how well each stage worked and howwell you feel you completed each stage. If youlook back over these pages, you will see thatwe have indeed developed a process that canbe used for decision making.

Examine the flowchart below. You can seethat you used every step in this process. Aswith science inquiry and technological problemsolving, having a process to use helps you tofocus your thinking and stay on track.

A Process for Societal Decision Making

Identify the Issue

Gather Relevant Information

Identify All the Alternatives

Weigh Each Alternative by Clarifying its Consequences

Make a Decision

Evaluate the Decision

The decision is the best alternative basedon risks/benefits and,

thus, probable consequences.

Erro

rs o

f jud

gmen

t may

hav

e be

en m

ade

at a

ny

of th

ese

step

s in

the

deci

sion

-mak

ing

proc

ess.

One or more of the stepsin the decision-making

process were faulty. No action should be taken

and the process should be repeated to ensure

that the faulty steps are eliminated and replaced by

improved thinking.

Take Action/Communicate the Decision

Instant Practice—Making SocietalDecisions

1. Describe two ways in which each of the following technological developmentshas affected society positively:(a) dam building(b) production of supertankers(c) mass production of the automobile(d) mass production of computers(e) harnessing nuclear reactions

2. Now describe two ways in which each ofthe above technologies has affected ormight affect society negatively.

3. How would you evaluate whether eachof the technologies in question 1 is“good” or “bad” for society?

4. For each of the technologies in question1, record ideas you have on the kinds of scientific knowledge that were necessaryfor its development.

5. An issue has two or more possiblesolutions, and a decision must be madein favour of one solution over theothers. In weighing the advantages anddisadvantages of the solutions, is itimportant to take into account:(a) Who benefits from the solution?(b) Who is affected by the costs or

disadvantages?(c) Who proposes a solution? Why or why not?

6. As a class, discuss the possible shortageof fresh water. Identify possible solutionsand consider the benefits and risks ofeach solution. Do the solutions involvethe use of technology? Do we haveenough scientific knowledge to assessthe risks attached to each solution? Isthere a simple answer? Is there asolution that does not interfere with the environment at all? If so, is it arealistic solution?

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Science Skill 5

In your investigations, you will collectinformation, often in numerical form. Toanalyze and report the information, you willneed a clear, concise way to organize andcommunicate the data.

A graph is the most visual way to presentdata. A graph can help you to see patterns andrelationships among the data. The type ofgraph you choose depends on the type of datayou have and how you want to present it. Youwill be using line graphs, bar graphs, and circlegraphs (pie charts).

Drawing a Line GraphA line graph is used to show the relationshipbetween two variables. The following examplewill demonstrate how to draw a line graphfrom a data table.

Example

Suppose you have conducted a survey to findout how many students in your school arerecycling drink containers. Out of 65 studentsthat you surveyed, 28 are recycling. To findout if more recycling bins would encouragestudents to recycle cans and bottles, you placetemporary recycling bins at three otherlocations in the school. Assume that, in afollow-up survey, you obtained the datashown Table 1. Compare the steps in theprocedure with the graph on the next page tolearn how to make a line graph to display yourfindings.

1. With a ruler, draw an x-axis and a y-axison a piece of graph paper. (The horizontalline is the x-axis, and the vertical line isthe y-axis.)

2. To label the axes, write “Number ofrecycling bins” along the x-axis and“Number of students using recyclingbins” along the y-axis.

3. Now you have to decide what scale touse. You are working with two numbers(number of students, and number ofbins). You need to show how manystudents use the existing bin, and howmany would recycle if there were asecond, a third, and a fourth bin. Thescale on the x-axis will go from 0 to 4.There are 65 students, so you might wantto use intervals of 5 for the y-axis. Thatmeans that every space on your y-axisrepresents 5 students. Make a mark atmajor intervals on your scale, as shown inthe graph on the next page.

4. On the x-axis, you want to make sure youwill be able to read your graph when it iscomplete, so make sure your intervals arelarge enough.

5. To plot your graph, gently move a pencilup the y-axis until you reach a point just below 30 (you are representing 28 students). Now move along the line onthe graph paper until you reach thevertical line that represents the firstrecycling bin. Place a dot at this point (1 bin, 28 students). Repeat this processuntil you have plotted all of the data forthe four bins. Now, draw a line from onedot to the next.

Organizing and Communicating Scientific Results with Graphs

Number of students using recycling binsNumber of bins

1

2

3

4

Table 1 Students Using Recycling Bins

28

36

48

62

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6. If it is possible, draw a line that connectsall of the points on your graph. Thismight not be possible. Scientificinvestigations often involve quantities thatchange smoothly. On a graph, this meansthat you should draw a smooth curve (orstraight line) that has the general shapeoutlined by the points. This is called aline of best fit. Such a best fit line oftenpasses through many of the points, butsometimes it goes between them. Think ofthe dots on your graph as clues aboutwhere the perfect smooth curve (orstraight line) should go. A line of best fitshows the trend of the data. It can beextended beyond the first and last pointsto indicate what might happen.

7. Give your graph a title. Based on thesedata, what is the relationship between thenumber of students using recycling binsand the number of recycling bins?

Constructing a Bar GraphBar graphs help you to compare a numericalquantity with some other category, at a glance.The second category may or may not be anumerical quantity. It could be places, items,organisms, or groups, for example.

Example

To learn how to make a bar graph to displaythe data in Table 3, examine thecorresponding graph in the column next to thetable as you read the steps below. The datashow the number of days of fog recordedduring one year, at one weather station in eachof the provinces and territories.

0 1 Number of

recycling bins

Num

ber

of s

tude

nts

usin

g re

cycl

ing

bins

Graph of Student Use ofRecycling Bins

2 3 4

10

20

30

40

50

60

70

Instant Practice—Drawing a LineGraph

Make a line graph using the following dataon the development of a fetus. The firstcolumn represents the time sinceconception, in months. Plot these valuesalong the x-axis. The second column is theaverage length of a fetus at that stage ofdevelopment. Plot these values along the y-axis. Be sure to include units. Give yourgraph a title.

Average length (cm)

Time since conception (months)

1

2

3

4

5

6

7

8

9

Table 2 Development of a Fetus

0.6

3.0

7.5

18.0

27.0

31.0

37.0

43.0

50.0

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1. Draw your x-axis and y-axis on a sheet ofgraph paper. Label the x-axis with thenames of the provinces and territories andthe y-axis with the average number of daysof fog.

2. Look at the data carefully in order to selectan appropriate scale. Write the scale of youry-axis on the lines.

3. Decide on a width for the bars that will belarge enough to make the graph easy toread. Leave the same amount of spacebetween each bar.

4. Using Newfoundland and 206 as the firstpair of data, move along the x-axis thewidth of your first bar, then go up the y-axis to 206. Use a pencil and ruler todraw in the first bar lightly. Repeat thisprocess for the other pairs of data.

5. When you have drawn all of the bars, youmight want to colour them so that eachone stands out. If you have no colours, youcould use cross-hatching, dots, or diagonallines to distinguish one bar from another.If you are comparing two or moremanipulated variables that you have plottedon the x-axis, you will need to make alegend or key to explain the meaning ofthe colours. Write a title for your graph.

Constructing a Circle GraphA circle graph (sometimes called a pie chart)uses a circle divided into sections (pieces ofpie) to show the data. Each section representsa percent of the whole. All sections togetherrepresent all (100%) of the data.

Number of days of fog Province

Newfoundland

Prince Edward Island

New Brunswick

Nova Scotia

Québec

Ontario

Manitoba

Saskatchewan

Alberta

British Columbia

Yukon Territory

Northwest Territories

Table 3 Average Number of Days of Fog per Year in Canadian Provinces and Territories (prior to April 1, 1999)

206

47

106

127

85

76

48

37

39

226

61

196

NewfoundlandPrince Edward IslandNew BrunswickNova ScotiaQuébecOntario

ManitobaSaskatchewanAlbertaBritish ColumbiaYukon TerritoryNorthwest Territories

50

100

150

200

250

Average Number of Days of Fog per Year in Canadian Provinces and Territories before April 1, 1999

Aver

age

Num

ber

of D

ays

of F

og

Instant Practice—Drawing a Bar Graph

Construct a bar graph to display the data in Table 4 showing the average heart rates of adult animals in severaldifferent species.

Heart rate (beats per min)

Species

codfish (in water at 18˚C)

iguana (in hot sun)

duck (resting)

dog (resting)

human (resting)

elephant (resting)

white rat (resting)

Table 4 Heart Rate and Species

30

90

240

100

70

30

350

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Example

To learn how to make a circle graph from thedata in Table 5, study the corresponding circlegraph on the right as you read the followingsteps.

1. Use a mathematical compass to make alarge circle on a piece of paper. Make a dotin the centre of the circle.

2. Determine the percent of the total numberof species that each type of bird representsby using the following formula.

Percent of total �

For example, the percent of all species of birds that are ducks is:

Percent that �

are ducks

3. To determine the degrees in the “piece ofpie” that represents each type of bird, usethe following formula.

Degrees in �

“piece of pie”

Round your answer to the nearest whole number. For example, the “piece of pie” for ducks is:

Degrees for ducks �

4. Draw a straight line from the centre to theedge of the circle. Use your protractor tomeasure 32° from this line. Make a mark,then use your mark to draw a second line32° from the first line.

5. Repeat steps 2 to 4 for the remaining types of birds.

Type of bird

Number of species

Degrees in “piece of pie”

Percent of total

ducks

birds of prey

shorebirds

owls

perching birds

other

36

19

71

14

180

80

9.0

4.8

17.7

3.5

45.0

20.0

32

17

64

13

162

72

Table 5 Birds Breeding in Canada

Species of Birds Breeding in Canada

owlsshorebirds birds of prey

ducks

other

perching birds

Instant Practice—Drawing a Circle Graph

Make a circle graph using the following dataon the elements in Earth’s crust. Noticethat the data are given in percent.

Element

Percent of Earth’s crust (%)

aluminum

calcium

iron

magnesium

oxygen

potassium

silicon

sodium

other

8.0

2.4

6.0

4.0

46.0

2.3

28.0

2.1

1.0

Table 6 Percent of Elements in Earth’s Crust

Number of species within the typeTotal number of species � 100%

� 100% � 9.0%36 species of ducks

400 species

� 360°Percent for a type of bird

100%

� 360° � 32.4° or 32°9.0%100%

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Graphing on a ComputerComputers are a great tool for graphpreparation for the following reasons:1. Data need only be entered once. As many

graphs as you need can then be preparedwithout any more data entry.

2. Once the data are entered, you can use thecomputer to manipulate them. You canchange the scale, zoom in on importantparts of the graph, graph different parts ofthe data in different ways, and so on—allwithout doing any calculations!

3. Computers prepare graphs far more quicklythan people working carefully.

4. Computers can be hooked up to sensors(thermometers, timers, and such) so youdo not need to read instruments and enterdata by hand, with all the resultingpossibilities for error. The computer candisplay the readings on a graph as data arecollected (in “real” time) so you canquickly get a picture of how yourexperiment is going.

5. Errors can be corrected much more easilywhen working with a computer. Justchange the incorrect number and printagain. Imagine the time and effort involvedif you had to redo your graph by hand.

6. Computer graphs can be easily insertedinto written lab reports, magazine articles,or Internet pages. It is possible to scanhand-drawn graphs into a computer, but itisn’t easy to do it well, and the resultingfiles are very large.

7. Once data have been entered into acomputer, the computer can determine aline of best fit and a mathematical equationthat describes the line. This helps scientiststo discover patterns in their data and makepredictions to test their inferences in a veryprecise manner.

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Have you ever used a drawing to explainsomething that was too difficult to explain inwords? A clear drawing can often assist orreplace words in a scientific explanation.In science, drawings are especially importantwhen you are trying to explain difficultconcepts or describe something that contains alot of detail. It is important to make scientificdrawings clear, neat, and accurate.

Examine the drawing shown below. It istaken from a Grade 8 student’s lab report onan experiment to test the expansion of air in aballoon. The student’s verbal description ofresults included an explanation of how theparticle model can explain what happens to theballoon when the bottle is placed in hot waterand in cold water. As you can see, the cleardiagrams of the results can support or evenreplace many words of explanation. While yourdrawing itself is important, it is also importantto label it clearly. If you are comparing andcontrasting two objects, label each object anduse labels to indicate the point of comparisonsbetween them.

Making a Scientific DrawingFollow these steps to make a good scientificdrawing.1. Use unlined paper and a sharp pencil with

an eraser.2. Give yourself plenty of space on the paper.

You need to make sure that your drawing willbe large enough to show all necessary details.You also need to allow space for labels. Labelsidentify parts of the object you are drawing.Place all of your labels to the right of yourdrawing, unless there are so many labelsthat your drawing looks cluttered.

3. Carefully study the object that you will bedrawing. Make sure you know what youneed to include.

4. Draw only what you see, and keep yourdrawing simple. Do not try to indicate partsof the object that are not visible from theangle you observed. If you think it isimportant to show another part of the object,do a second drawing, and indicate the anglefrom which each drawing is viewed.

5. Shading or colouring is not usually used in scientific drawings. If you want to indicatea darker area, you can use stippling (a seriesof dots). You can use double lines toindicate thick parts of the object.

Scientific Drawing

Science Skill 6

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6. If you do use colour, try to be as accurateas you can and choose colours that are asclose as possible to the colours in theobject you are observing.

7. Label your drawing carefully andcompletely, using lower-case (small) letters.Pretend you know nothing about theobject you have just observed, and thinkabout what you would need to know if youwere looking at it for the first time.Remember to place all your labels to theright of the drawing, if possible. Use aruler to draw a horizontal line from thelabel to the part you are identifying. Makesure that none of your label lines cross.

8. Give your drawing a title. Note: Thedrawing of a human skin cell shown here isfrom a Grade 8 student’s notebook. Thisstudent used stippling to show darkerareas, horizontal label lines for the cellparts viewed, and a title—all elements of anexcellent final drawing.

The stippling on this drawing of a human skin cell showsthat some areas are darker than others.

Drawing to ScaleIn Unit 1, you will be making drawings ofobjects that have been magnified using amicroscope. When you draw objects seenthrough a microscope, the size of yourdrawing is important. Your drawing should bein proportion to the size of the object as theobject appears when viewed through the

microscope. This type of drawing is called ascale drawing. A scale drawing allows you tocompare the sizes of different objects and toestimate the actual size of the object beingviewed. Here are some steps to follow whenmaking scale drawings.1. Use a mathematical compass to draw an

accurate circle in your notebook. The sizeof the circle does not matter. The circlerepresents the microscope’s field of view.

2. Imagine the circle is divided into fourequal sections (see the diagram below).Use a pencil and a ruler to draw thesesections in your circle, as shown here.

3. Using low or medium power, locate anobject under the microscope. Imagine thatthe field of view is also divided into fourequal sections.

4. Observe how much of the field of view istaken up by the object. Also note thelocation of the object in the field of view.

5. Draw the object in the circle. Position theobject in about the same part of the circleas it appears in the field of view. Also, drawthe object so that it takes up about thesame amount of space within the circle as ittakes up in the field of view, as shown inthe diagram.

drawing made to scale (100x)

field of view under the microscope (100x) divided into four equal sections

=

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EstimatingHow long will it take you to read this page?How heavy is this textbook? What is the heightof your desk? You could probably answer all ofthese questions fairly quickly by estimating —making an informed judgement about ameasurement. You recognize that the estimategives you an idea of the measure but anestimate is not totally accurate.

Scientists often make estimates, as well,when exact numbers are not essential. You willfind it useful to be able to estimate asaccurately as possible, too. For example,suppose you wanted to know how many antslive in a local park. Counting every ant wouldbe very time-consuming—and the ants wouldbe most unlikely to stay in one spot for yourconvenience! What you can do is count thenumber of ants in a typical square-metre area.Multiply the number of ants by the number ofsquare metres in the total area you areinvestigating. This will give you an estimate ofthe total population of ants in that area.

Estimating and Measuring

Science Skill 7

Instant Practice—Estimating

1. A blue whale has a mass of about 140 000 kg. Students in your class have anaverage mass of about 60 kg. Estimate thenumber of students it would take to equalthe whale in mass. Calculate the exactnumber to see how close your estimate was.

2. The arctic tern is a bird that nests in theCanadian Arctic and migrates 17 500 kmto the Antarctic to spend the winter. Itmakes the trip in about 16 weeks.Estimate how far the tern flies in oneweek. Calculate the exact distance to seehow close your estimate was.

3. A 1 L (1000 mL) jar is filled withpopcorn kernels. How can you make agood estimate of the number ofpopcorn kernels in the jar?(a) Decide how you can use a 100 mL

container and a small number ofpopcorn kernels to estimate thenumber in the 1 L jar.

(b) Carry out your plan.(c) Compare your results with those of

two or three classmates.(d) About how many popcorn kernels

will a 1 L jar hold?

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Measuring Length and AreaYou can use a metre stick or a ruler to measureshort distances. These are usually marked off incentimetres and/or millimetres. Use a ruler tomeasure the length in millimetres betweenpoints A and F, C and E, F and B, and A andD. Convert your measurements to centimetresand then to metres.

To calculate an area, you can use lengthmeasurements. For example, for a square or arectangle, you can find the area by multiplyingthe length by the width.

Area of square is 4 cm � 4 cm = 16 cm2.

Area of rectangle is 18 mm � 12 mm � 216 mm2.

Make sure you always use the same units—if you mix up centimetres and millimetres,your calculations will be wrong. Remember toask yourself if your answer is reasonable (youcould make an estimate to consider this).

Measuring VolumeThe volume of an object is the amount of spacethat the object occupies. There are several waysof measuring volume, depending on the kindof object you want to measure. A cubic metreis the space occupied by a 1 m � 1 m � 1 mcube. This unit of volume is used to measurelarge quantities, such as the volume ofconcrete in a building. In this course, you aremore likely to use cubic centimetres (cm3) orcubic millimetres (mm3) to record the volumeof an object. You can calculate the volume of acube by multiplying its sides. For example, volume � 1 cm � 1 cm � 1 cm � 1 cm3.

You can calculate the volume of a rectangularsolid if you know its length, width, and height.

volume � length � width � height

If all the sides are measured in millimetres(mm), the volume will be in cubic millimetres(mm3). If all the sides are measured incentimetres (cm), the volume will be in cubiccentimetres (cm3). The units for measuring thevolume of a solid are called cubic units.

A

C E

B

D

F

4 cm

4 cm

18 mm

12 mm

Instant Practice—Measuring Lengthand Area

Imagine you are in charge of tiling the floor of your classroom. How many 10 cm � 10 cm tiles would you need tocover it? (a) First, decide what unit would be most

practical for the floor area—mm2, cm2,or m2.

(b) Measure the length and width of yourclassroom.

(c) Calculate the floor area in the unit youhave selected.

(d) Calculate how many tiles you wouldneed to fill one unit of area.

(e) Multiply that number by the number ofthese units in the floor area.

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The units used to measure the volume of liquids are called capacity units. The basicunit of volume for liquids is the litre (L). Inthis course, you also measure volume usingmillilitres (mL). Recall that 1 L � 1000 mL.You have probably seen capacity in litres andmillilitres printed on juice, milk, and soft drinkcontainers.

Cubic units and capacity units areinterchangeable, for example:

1 cm3 � 1 mL1 dm3 � 1 L1 m3 � 1 kLAs you can see in Diagram A, the volume

of a regularly shaped solid object can be measured directly.

Measuring the volume of a regularly shaped solid

Similarly, the volume of a liquid can bemeasured directly, as shown in Diagram B.Make sure you measure to the bottom of themeniscus, the slight curve where the liquidtouches the sides of the container. To measureaccurately, make sure your eye is at the samelevel as the bottom of the meniscus.

Measuring the volume of a liquid

The volume of an irregularly shaped solidobject, however, must be measured indirectly.This is done by determining the volume of aliquid it will displace, as shown below.

Record the volume of the liquid.

Carefully lower the object intothe cylinder containing theliquid. Record the volume again.

The volume of the object isequal to the difference betweenthe two volumes. The equationbelow the photograph showsyou how to calculate this.

3

2

1

Measuring the volume of an irregularly shaped solid

volume of object � volume of water with object � original volume of water� 85 mL � 60 mL� 25 mL

1 2 3

4 cm

4 cm

4 cm

6 cm

5 cm

3 cm

4 cm × 4 cm × 4 cm = 64 cm3 5 cm × 6 cm × 3 cm = 90 cm3

graduated cylinder

line where liquid touches glass

meniscus

liquid

too high

too low

read here

60

50

40

30

90

80

70

100

A

B

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a medium-sized dog10 kg

a sliceof toast25 g

a postagestamp20 mg

a grape 600 mg

a very small car1000 kg

Measuring MassIs your backpack heavier than your friend’s backpack? It can be difficult to check by holding a backpack in each hand. At suchtimes, you need a way to measure massaccurately. The mass of an object is themeasure of the amount of material that makes up the object. Mass is measured in milligrams, grams, kilograms, and tonnes. You need a balance for measuring mass. A

triple beam balance is one commonly used type.Following are the steps involved in

measuring the mass of a solid object.1. Set the balance to zero. Do this by sliding all

three riders back to their zero points. Usingthe adjusting screw, make sure the pointerswings an equal amount above and belowthe zero point at the far end of the balance.

2. Place the object on the pan. Observe what happens to the pointer.

3. Slide the largest rider along until thepointer is just below zero. Then move itback one notch.

4. Repeat with the middle rider and then withthe smallest rider. Adjust the last rider untilthe pointer swings equally above and belowzero again.

5. Add the readings on the three scales to find the mass.

Instant Practice—Measuring Volume

1. Imagine you are cooking potatoes fordinner. You decide to measure thevolume of a potato so that you canfigure out how much water to use.

What You Needwater500 mL beakerlarge potatowax pencilgraduated cylinder

(a) Add water to the beaker (your“saucepan”). How much do youthink you can add and still leaveroom for the potatoes?

(b) Carefully add the potato. What is itsvolume? (If your beaker does nothave millilitre markings, use a waxpencil to mark the water levelsbefore and after the potato is added.Pour out the water and use agraduated cylinder to measure andrecord the number of millilitresbetween the two wax pencil marks.)

(c) Could you add a second potato of the same size without spilling water, or would you need to pour off someof the water?

2. Now that you know the volume of apotato in millilitres, what is its volumein cubic centimetres?

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How can you find the mass of a certainquantity of a substance, such as table salt, thatyou have added to a beaker? First, find themass of the beaker. Next, pour the salt into thebeaker and find the mass of the beaker and salttogether. To find the mass of the salt, simplysubtract the beaker’s mass from the combinedmass of the beaker and salt.

The mass of the table salt and beaker together is 230 g.Therefore, the mass of the salt is 70 g.

The mass of the beaker is 160 g.

Measuring AnglesIn Unit 2, Optics, you need to be able tomeasure angles using a protractor. Protractorsusually have an inner scale and an outer scale.The scale you use depends on how you placethe protractor on an angle (symbol ��). Lookat the following examples to learn how to usea protractor.

Example 1

What is the measure of �XYZ?

SolutionPlace the centre of the protractor on point Y.YX crosses 0° on the outer scale. YZ crosses 70°on the outer scale. So �XYZ is equal to 70°.

Example 2

Draw �ABC � 155°.

SolutionFirst, draw a straight line, AB. Place the centreof the protractor on B and line up AB with 0°on the inner scale. Mark C at 155° on theinner scale. Join BC. The angle you havedrawn, �ABC, is equal to 155°.

XY

Z

Instant Practice—Measuring Mass

1. Which takes more “muscle” to carry:your favourite paperback book or yourfavourite portable electronic game? Findout by using a balance to compare theirmasses.

2. Write the steps you would take to findthe mass of the contents of a containerof juice.

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Measuring Temperature Temperature is a measure of the thermalenergy of the particles of a substance. In thevery simplest terms, you can think oftemperature as a measure of how hot or howcold something is. The temperature of amaterial is measured with a thermometer.

For most scientific work, temperature is measured on the Celsius scale. On this scale,the freezing point of water is zero degrees(0°C), and the boiling point of water is 100 degrees (100°C). Between these points,the scale is divided into 100 equal divisions.Each division represents one degree Celsius.On the Celsius scale, average human bodytemperature is 37°C, and a typical roomtemperature may be between 20°C and 25°C.

The SI unit of temperature is the Kelvin(K). Zero on the Kelvin scale (0 K) is thecoldest possible temperature. This temperature

is also known as absolute zero. It is equivalentto �273°C, which is 273 degrees below thefreezing point of water. Notice that degreesymbols are not used with the Kelvin scale.

Most laboratory thermometers are markedonly with the Celsius scale. Because thedivisions on the two scales are the same size,the Kelvin temperature can be found byadding 273 to the Celsius reading. Thus, onthe Kelvin scale, water freezes at 273 K andboils at 373 K.

Tips for Using a Thermometer

When using a thermometer to measure thetemperature of a substance, here are threeimportant tips to remember:• Handle the thermometer extremely

carefully. It is made of glass and can breakeasily.

• Do not use the thermometer as a stirringrod.

• Do not let the bulb of the thermometertouch the walls of the container.


010

0

Instant Practice—Measuring Angles

1. State the measure of each of the followingangles using the following diagram.(a) �DAE (d) �HAG (g) �EAH(b) �DAG (e) �GAE (h) �EAF(c) �IAH (f) �DAH (i) �FAI

2. Use a protractor to draw angles with the following measures. Label each angle.(a) ABC 60° (c) XYZ 10° (e) HAL 45°(b) QRS 90° (d) JKL 32°

100 110 120130

140150

160170

180

8070

60

50

40

3020

100

100110

120

130

140

150

160

170

180

80 7060

50

4030

2010

0

90

AD

E

F G

H

I

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When you think of a model, you probablythink of a toy such as a model airplane. Is amodel airplane similar to a scientific model? Ifbuilding a model airplane helps you learnabout flight, then you can also say it is ascientific model.

In science, a model is anything that helpsyou better understand a scientific concept. Amodel can be a picture, a mental image, astructure, or even a mathematical formula.Sometimes, you need a model because theobjects you are studying are too small to seewith the unaided eye. You may have learnedabout the particle theory of matter, forexample, which is a model that suggests thatall matter is made of tiny, invisible particles.On the other hand, sometimes a model isuseful because some objects are extremelylarge—the planets in our solar system, forexample. In other cases, the object may behidden from view, like the interior of Earth orthe inside of a living organism. A mathematicalmodel shows you how to perform a calculation.

Scientists often use models to communicatetheir ideas to other scientists or to students.They also use models to test an idea and tofind out if an hypothesis is supported. Modelsassist scientists in planning new experiments inorder to learn more about the subject they arestudying. Sometimes, scientists discover somuch new information that they have tomodify their models. Examine the models inthe illustrations on this page. How can theyhelp you learn about science?

You can learn about day and night by using a globe and aflashlight to model Earth and the Sun.

Using Models in Science

Science Skill 8

The particles shown here are models representing theatoms and molecules of a gas.

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The light microscope is an optical instrumentthat greatly increases our powers ofobservation by magnifying objects that areusually too small to be seen with the unaidedeye. The microscope you will use is called acompound light microscope because it uses aseries of lenses (rather than only one as in amagnifying glass) and it uses light to view theobject.

A microscope is a delicate instrument, soproper procedure and care must be practised.This Science Skill reviews the skills that youwill need to use a microscope effectively.Before you use your microscope, you need toknow the parts of a microscope and theirfunctions.

Using a Microscope

B. TubeHolds the eyepiece and theobjective lenses at the properworking distance from eachother.

C. Revolving nosepieceRotating disk holds two ormore objective lenses. Turn itto change lenses. Each lensclicks into place.

D. Objective lensesMagnify the object. Each lenshas a different power ofmagnification, such as 4�,10�, 40�. (Your microscopemay instead have 10�, 40�,and 100� objective lenses.)For convenience, theobjective lenses are referredto as low, medium, and highpower. The magnifying poweris engraved on the side ofeach objective lens. Be sureyou can identify each lens.

E. ArmConnects the base and thetube. Use the arm forcarrying the microscope.

F. Coarse focus knobMoves the tube up and downto bring the object into focus.Use it only with the low-power objective lens.

G. Fine focus knobUse with medium- and high-power magnification to bringthe object into sharper focus.

H. StageSupports the microscopeslide. Stage clips hold theslide in position. An openingin the centre of the stageallows light from the lightsource to pass through theslide.

I. Condenser lensDirects light to the objectbeing viewed.

J. DiaphragmControls the amount of light reaching the object being viewed.

A. Eyepiece (or ocular lens)You look through this part. It has a lensthat magnifies the object, usually by 10 times (10�). The magnifying poweris engraved on the side of the eyepiece.

K. Light sourceShining a light through the object beingviewed makes it easier to see the details.Your microscope might have a mirrorinstead of a light. If it does, it must beadjusted to direct the light source throughthe lenses. CAUTION: Use an electric light,not sunlight, as the light source forfocussing your mirror.

A

B

C

D

E

F

G

H

I

K

J

Science Skill 9

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Instant Practice—Drawing

A scale drawing is a drawing in which youkeep constant the proportions of what yousee through the microscope. This isimportant because it allows you to comparethe sizes of different objects and helps youform an idea of the actual size of an object.Also, a scale drawing makes it easier toexplain what you see to someone else. Dothe following to make a scale drawing.1. Draw a circle (the size does not matter)

in your notebook. The circle representsthe microscope’s field of view.

2. Imagine that the circle is divided into fourequal sections (see the diagram below).Use a pencil and a ruler to draw thesesections in your circle, as shown below.

3. Using low or medium power, locate asample from the prepared slide thatinterests you. Imagine that the field of viewis also divided into four equal sections.

4. Note in what part of the field of viewthe object lies and how much of thefield of view the object occupies.

5. Draw the object in the circle. Position itso that it is in the same part of the circleas it appears in the field of view. Draw theobject to scale. This means that it shouldtake up the same proportion of space onthe circle as it does in the field of view.

6. Label your drawing.7. Estimate the size of the object in your

drawing.

TroubleshootingYou may encounter difficulties when usingyour microscope. The following list details themore common problems and how you can dealwith them.• You cannot see anything. Make sure the

microscope is plugged in and the light is on.If the microscope has no light, adjust yourmirror.

• Are you having trouble finding anything onthe slide? Be patient. Follow all of the stepsoutlined in this procedure from thebeginning and make sure the object beingviewed is in the middle of the stageopening. While watching from the side,lower the low-power objective as far as itwill go. Then look through the ocular lensand slowly raise the objective lens using thecoarse-adjustment knob.

• Are you having trouble focussing, or is theimage very faint? Try closing the diaphragmslightly. Some objects that you will examineare almost transparent. If there is too muchlight, a specimen may be difficult to see orwill appear “washed out.”

• Do you see lines and specks floating across theslide? These are probably structures in thefluid of your eyeball that you see when youmove your eyes. Do not worry; this isnormal.

• Do you see a double image? Check that theobjective lens is properly clicked into place.

• Do you close one eye while you look through themicroscope with the other eye? You might trykeeping both eyes open. This will helpprevent eye fatigue. It also lets you sketchan object while you are looking at it.

• Always place the part of the slide you areinterested in at the centre of the field ofview before changing to a higher-powerobjective lens. When you turn to mediumand high power, you otherwise may not seethe object you were viewing under lowpower.

drawing made to scale

microscope'sfield of view

=

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How can you use your textbook effectively tounderstand science concepts better? ThisScience Skill will give you strategies to helpyou better understand what you read. It willalso explain how to use textbook visuals anddescribe different types of graphic organizersthat can help you organize your information.

Using Your Textbook to Read forInformationReading a textbook is different from reading anovel or magazine. A textbook contains manydifferent terms and concepts that you mustunderstand and apply throughout each section.Here are several strategies to help you recordthe information.1. Before reading a section, scan the pages.

While you are scanning, look at thepictures and try to predict what you thinkthe section will be about. Try to figure outthe definitions for bolded words with thehelp of the Glossary or from the sentencethe bolded word is in.

2. A light brown shaded box at the beginningof each section summarizes the key ideascovered in the section. Read this summary.You may not completely understandeverything in the summary at first. Whenyou finish working through the section,reread this summary. If you still do notunderstand something in the summary, askyour teacher for help.

3. Rewrite the section headings andsubheadings as questions. Then look forthe answer to each question as your read.

4. When you finish reading the text under aheading or subheading, think about whatyou have just read. Then write brief notesthat explain the key ideas discussed there.Try to do this without looking at the text.After you make your notes, go back to thetext you have just read. Add or change

Using Your Textbook as a Study Toolanything you have just written to help youunderstand the text better.

5. As you read each section, you willencounter Reading Checks. You should beable to answer these questions. If youcannot answer them correctly, go back andreview the material you just read.

Using Your Textbook VisualsAs you read each page, look at anyphotographs, illustrations, or graphs thatappear on the page. Read the captions andlabels that accompany the photographs, as wellas the titles of graphs. Think about theinformation each visual provides, and notehow it helps you to understand the ideaspresented in the text. For example, look closelyat the illustration on this page. Whatinformation does it convey to you?

Water on Earth moves in an endless water cycle.

Using the GlossaryLook, as well, at any terms that are in bold(dark, heavy) type. These terms will provideimportant definitions that you will need inorder to understand and write about theinformation in each topic. Make sure that youunderstand these terms and how they are used.Each boldfaced term appears in the Glossary atthe back of this book.

Science Skill 10

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Using the Review QuestionsAt the end of every section, you will findreview questions under the heading CheckYour Understanding. At the end of everychapter, there are questions in the ChapterReview. If you are unable to answer thequestions at the end of the sections andchapters, reread the material to find theanswers. Ask your teacher to explain anythingyou still do not understand.

Using Graphic OrganizersA good way to organize information you arelearning is to use a graphic organizer. Onekind of graphic organizer you will find useful isa concept map.

Concept Map

A concept map is a diagram that representsvisually how ideas are related. Because theconcept map shows the relationships amongconcepts, it can clarify the meaning of theideas and terms and help you to understandwhat you are studying.

Study the construction of the concept mapbelow. Notice how some words are enclosedwhile others are written on connecting lines.The enclosed words are ideas or terms calledconcepts. The lines in the map show relatedconcepts, and the words written on themdescribe relationships between the concepts.

As you learn more about a topic, yourconcept map will grow and change. Conceptmaps are just another tool for you to use.There is no single “correct” concept map, onlythe connections that make sense to you. Makeyour map as neat and clear as possible andmake sure you have good reasons forsuggesting the connections between its parts.

When you have completed the concept map,you may have dozens of interesting ideas. Yourmap is a record of your thinking. Although itmay contain many of the same concepts as otherstudents’ maps, your ideas may be recorded andlinked differently. You can use your map forstudy and review. You can refer to it to help yourecall concepts and relationships. At a later date,you can use your map to see what you havelearned and how your ideas have changed.

silverand gold

appearance

valuevalue

two-dollarcoin

CANADIAN COINS

copper silver gold

appearance appearance appearance

value

one-dollarcoin

quarterdimenickelpenny

value value value

Instant Practice — Reading forInformation

1. Go to the unit your teacher tells youthat your class will be studying next.Scan the unit to predict the key ideasyou will be studying.

2. In the first section of the unit, usestrategies 1 and 2 on the previous pagebefore you read the section.

3. Read the first section of the unit usingstrategies 3 and 4 to make notes.

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Flowchart

A flowchart describes ideas in order. In sciencea flowchart can be used to describe a sequenceof events, the steps in a procedure, or thestages of a process. When making a flowchart,you must first find the one event that starts thesequence. This event is called the initiatingevent. You then find the next event andcontinue until you reach an outcome. Here is aflowchart showing how an animal fossil may beformed.

A cycle chart is a special type of flowchart.In a cycle chart, the series of events do notproduce a final outcome. This type of chart hasno beginning and no end.

To construct a cycle chart, you first decideon a starting point and then list eachimportant event in order. Since there is nooutcome and the last event relates back to thefirst event, the cycle repeats itself. Look at thecycle chart in the next column, which showschanges in the state of water.

Spider Map

A spider map is a concept map that you mayfind useful for brainstorming. You may, forexample, have a central idea and a jumble ofassociated concepts, but they may notnecessarily be related to each other. By placingthese associated ideas outside the mainconcept, you can begin to group these ideas sothat their relationships become easier tounderstand. Examine the following spider mapof the geological time scale to see how variousconcepts related to this time scale may begrouped to provide clearer understanding.

solid

gas

liquid liquidChanges inthe stateof water

An animal dies.

Scavengers consume most of the body.

Bacteria cause soft parts to decay.

A solution of water and quartz flows through the bones.

The water dissolves the calcium in the bones.

The quartz takes the place of the calcium.

A hard, rocklike fossil is formed.

few rocks

ice ages

Precambrian

MesozoicCe

nozo

ic

Paleo

zoicbacteria

age of mammals

1st time span

4th time span

AppalachianMountains

trilobites, brachiopods

Rocky Mountains

age of dinosaurs

2nd time span

3rd time span

GEOLOGICAL TIME SCALE

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Venn Diagram

Comparing and contrasting is another way tohelp solidify your learning. When youcompare, you look for similarities between twoconcepts or objects. When you contrast, youlook for differences. You can do this by listingways in which two things are similar and waysin which they are different. You can also use agraphic organizer called a Venn diagram to dothis, using two circles.

Example

Similarities DifferencesDifferences

Plants• make their

own food• remain in

one place

• living• made of cells

Animals• must find food• move from place to place

Instant Practice—Using GraphicOrganizers

1. Use the following words to produce aconcept map: music for listening, musicfor dancing, rap, classical, rhythm andblues, favourite CDs, rock, folk.

2. Make a Venn diagram to compare and contrast chocolate chip cookies with oatmeal cookies.

3. Produce a a flowchart that starts withthe buzzing of your clock radio andends with your sitting at your desk asschool begins.

4. Design a spider map to representdifferent means of transportation.

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Throughout history, people have developed systems of numbering and measurement. Intime, when different groups of people beganto communicate with each other, theydiscovered that their systems and units ofmeasurement were different. Groups withinsocieties created their own unique systems ofmeasurement.

Today, scientists around the world use themetric system of numbers and units. Themetric system is the official system ofmeasurement in Canada.

The Metric SystemThe metric system is based on multiples of 10. For example, the basic unit of length is themetre. All larger units of length are expressedin units based on metres multiplied by 10,100, 1000, or more. Smaller units of lengthare expressed in units based on metres dividedby 10, 100, 1000, or more.

Each multiple of 10 has its own prefix (aword joined to the beginning of anotherword). For example, kilo- means multiplied by1000. Thus, one kilometre is 1000 metres.

1 km � 1000 m

The prefix milli- means divided by 1000.Thus, one millimetre is one one-thousandth of a metre.

1 mm � m

In the metric system, the same prefixes areused for nearly all types of measure, such asmass, weight, area, and energy. A table of themost common metric prefixes is given at thetop of the next column.

Example 1

The distance from Halifax to Winnipeg is 3538 km Express this distance in metres.

Solution3538 km � ? m

1 km � 1000 m3538 km � 3538 � 1000 m

� 3 538 000 m

Example 2

There are 250 g of cereal in a package. Expressthis mass in kilograms.

Solution1000 g � 1 kg

250 g � 4 � 1000 g

g � 250 g

kg � 0.25 kg

The next table lists most of the frequently usedmetric quantities you will encounter in yourscience classes.

Units of Measurement

Science Skill 11

Symbol Prefixes Relationship to the base unit

giga-

mega-

kilo-

hecto-

deca-

–

deci-

centi-

milli-

micro-

nano-

Commonly Used Metric Prefixes

G

M

k

h

da

–

d

c

m

�

n

109

106

103

102

101

100

10–1

10–2

10–3

10–6

10–9

= 1 000 000 000

= 1 000 000

= 1 000

= 100

= 10

= 1

= 0.1

= 0.01

= 0.001

= 0.000 001

= 0.000 000 001

14

11000 1000

4

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SI UnitsIn science classes, you will often be instructedto report your measurements and answers in SIunits. The term SI is taken from the Frenchname Le Système international d’unités. In SI,the unit of mass is the kilogram, the unit oflength is the metre, the unit of time is thesecond, the unit of temperature is the Kelvin,and the unit of electric current is the ampere.Nearly all other units are defined ascombinations of these units.

Example 1

Convert 527 cm to SI units.

SolutionThe SI unit of length is the metre.1 m � 100 cm

Example 2

Convert 3.2 h to SI units.

SolutionThe SI unit of time is the second.1 min � 60 s; 1 h � 60 min

Frequently Used Scientific Quantities, Units, and Symbols

Unit Quantity Symbol

nanometre micrometre millimetre centimetre metre kilometre

length nm�mmmcmmkm

mass

gram kilogram tonne

g kg t

area square centimetre square metre hectare

cm2

m2 ha volume cubic centimetre

cubic metre millilitre litre

cm3 m3 mL L time second s

temperature degree Celsius

˚C

force newton N

electric current ampere A

quantity of electric charge

coulomb C

frequency hertz Hz

power watt W

energy joule kilojoule

J kJ

pressure pascal kilopascal

Pa kPa

Instant Practice—Using MetricMeasurements

1. A box is 35 cm wide. Express the width in metres.

2. You ride your bicycle 1.4 km to school. Express the distance in metres.

3. A teaspoon of water has a mass of 5.0 g. Express the mass in milligrams.

4. There are 600 mL of soft drink in abottle. Express the volume in litres.

5. A glass of water contains 32 µg of sulfur. Express the mass in grams.

6. A student added 0.0055 L of cleaningsolution to some water. Express thevolume in mL.

527 cm × 1 m100 cm = 5.27 m

3.2 h × 60 minh

× 60 s1 min = 11 520 s

Instant Practice – Converting to SI Units

Convert the following quantities to SI units.1. 52 km 5. 537 891 cm2. 43 min 6. 1.75 h3. 8.63 g 7. 16 Mg (megagrams)4. 45 973 mm 8. 100 km/h

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