science skills guide · a process for scientific inquiry one model of the scientific inquiry...

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460 MHR • Science Skills Guide Science Skills Guide Science Skill Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462 Safety Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462 WHMIS Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462 Science Skill Scientific Inquiry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463 Making Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463 Stating an Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464 Making a Prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464 Identifying Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464 Designing a Fair Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 Forming a Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466 A Process for Scientific Inquiry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466 Science Skill Technological Problem Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 Identifying the Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 Identifying Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 Planning and Constructing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468 Evaluating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468 A Process for Technological Problem Solving . . . . . . . . . . . . . . . . . . 468 Science Skill Societal Decision Making . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469 Identifying the Issue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469 Gathering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469 Identifying Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 Making a Decision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 Evaluating the Decision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 A Process for Societal Decision Making . . . . . . . . . . . . . . . . . . . . . . . 471 Science Skill Organizing and Communicating Scientific Results with Graphs . . . . . . . 472 Drawing a Line Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472 Constructing a Bar Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473 Constructing a Circle Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474 Graphing on a Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476 Science Skill Scientific Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477 Making a Scientific Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477 Drawing to Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 Science Skill Estimating and Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479 Estimating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479 Measuring Length and Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479 Measuring Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480 Measuring Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 Measuring Angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483 Measuring Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 7 6 5 4 3 2 1

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Page 1: Science Skills Guide · A Process for Scientific Inquiry One model of the scientific inquiry process is shown in the concept map below. Repeat several times. Revise prediction or

460 MHR • Science Skills Guide

Science Skills GuideScience Skill Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462

Safety Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462WHMIS Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462

Science Skill Scientific Inquiry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463Making Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463Stating an Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464Making a Prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464Identifying Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464Designing a Fair Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465Forming a Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466A Process for Scientific Inquiry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466

Science Skill Technological Problem Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467Identifying the Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467Identifying Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467Planning and Constructing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468Evaluating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468A Process for Technological Problem Solving . . . . . . . . . . . . . . . . . . 468

Science Skill Societal Decision Making . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469Identifying the Issue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469Gathering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469Identifying Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470Making a Decision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470Evaluating the Decision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470A Process for Societal Decision Making . . . . . . . . . . . . . . . . . . . . . . . 471

Science Skill Organizing and Communicating Scientific Results with Graphs . . . . . . . 472Drawing a Line Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472Constructing a Bar Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473Constructing a Circle Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474Graphing on a Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476

Science Skill Scientific Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477Making a Scientific Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477Drawing to Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478

Science Skill Estimating and Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479Estimating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479Measuring Length and Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479Measuring Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480Measuring Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482Measuring Angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483Measuring Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484

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Page 2: Science Skills Guide · A Process for Scientific Inquiry One model of the scientific inquiry process is shown in the concept map below. Repeat several times. Revise prediction or

Science Skills Guide • MHR 461

Science Skill Using Models in Science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485

Science Skill Using a Microscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487

Science Skill Using Chemistry Skills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488Periodic Table of the Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488Names, Formulas, and Charges of Some Common Ions . . . . . . . . . . 490Electron Arrangements of the First 20 Elements . . . . . . . . . . . . . . . . 490Folding a Round Filter Paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490

Science Skill Using Electric Circuit Symbols and Meters. . . . . . . . . . . . . . . . . . . . . . . . 491Circuit Diagram Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491Using Meters to Measure Voltage and Current . . . . . . . . . . . . . . . . . 491

Science Skill Using Your Textbook as a Study Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . 494Using Your Textbook to Read for Information . . . . . . . . . . . . . . . . . . . 494Using Your Textbook Visuals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494Using the Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494Using the Review Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495Using Graphic Organizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495

Science Skill Units of Measurement and Scientific Notation . . . . . . . . . . . . . . . . . . . . 498The Metric System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498SI Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 499Exponents of Scientific Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500

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Page 3: Science Skills Guide · A Process for Scientific Inquiry One model of the scientific inquiry process is shown in the concept map below. Repeat several times. Revise prediction or

462 MHR • Science Skill 1

Safety SymbolsThe following safety symbols are used in BCScience 9 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. Make certain youunderstand what these symbols mean. Whenyou see these symbols on containers, use safetyprecautions.

Compressed Gas

Flammable and Combustible Material

Oxidizing Material Corrosive Material

Poisonous and Infectious Material Causing Immediate

and Serious Toxic Effects

Poisonous and Infectious Material Causing Other

Toxic Effects

Biohazardous Infectious Material

Dangerously Reactive Material

Instant Practice—Safety Symbols

Describe the safety symbols you might see inthe following areas and why they would bethere:• technical arts room• home economics room• cafeteria• your kitchen• garage or storage shed

Instant Practice—WHMIS Symbols

Methyl alcohol is both flammable andpoisonous. 1. Draw the two symbols that are on its

label. 2. Describe (a) the risks illustrated by the

symbols, (b) precautions that youwould take when working with thematerial, (c) where you might store itso that it is safe, and (d) first aid oremergency treatment.

3. If you did not know the answer to (d),where would you find this information?

Science Skill 1

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Science Skill 2 • MHR 463

Scientific InquiryThe rain has stopped, and the Sun is out. Younotice that a puddle has disappeared from thesidewalk. What happened to that puddle ofwater? You could probably quickly answer thatquestion, but how would you prove youranswer? You would need to make observationsand record data.

Making ObservationsFirst, you might observe what happens tosome other puddles. You would watch themclosely until they disappeared and record whatyou observed.

One observation you might make is “Thepuddle is almost all gone.” That would be aqualitative observation, an observation inwhich numbers are not used. A little later, you

Science Skill 2

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

Instant Practice—Making Qualitativeand Quantitative Observations

Copy the observations below in yournotebook. Beside each write “Qual” if youthink it is a qualitative observation and“Quan” if you think it is a quantitativeobservation.1. (a) The bowling ball is heavier than the

basketball.(b) The red ball weighs 5 g more than

the blue ball.2. (a) The temperature increased by

several degrees. (b) The temperature increased by 2°C.

3. (a) The water was lukewarm.(b) The water was cooler than the oil.

4. (a) The colour changed from blue to green.

(b) The sound became louder as the vibrations increased.

5. (a) The second light bulb was the brightest.

(b) The 60 W bulb was brighter than the40 W bulb.

6. (a) The flight lasted nine minutes.(b) The flight lasted 2 h.

might also say, “It took five hours for thepuddle to disappear completely.” You havemade a quantitative observation, anobservation that uses numbers.

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 now have a question to ask:Does water always evaporate more quickly inthe Sun than in the shade?

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464 MHR • Science Skill 2

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 important to test onlyone variable at a time.

You need to control your variables. Thismeans that you change only one variable at atime. The variable 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 illustrations on the nextpage to see some examples of variables.

Instant Practice—Stating anHypothesis

Write an hypothesis for each of thefollowing situations. You may wish to usean “If…then…” format. For example: Iftemperature affects bacterial growth, thenbacterial culture plates at a highertemperature will have more bacterialcolonies than those at a lower temperature.1. The relationship between studying and

your score on quizzes2. The relationship between types of

atmospheric gases and global warming3. Do batteries last the same amount of

time in different devices?4. Does the colour of flowers influence

honeybee visitations?

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Science Skill 2 • MHR 465

(a) Find the best filter for muddy water.

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

control (no manipulated

variable)

responding variable

(clarity of water)

manipulated variable (filter)

control(no manipulated

variable)

responding variable(growth)

manipulatedvariable

(plant food) plantfood B

plantfood A

two layers of cheesecloth

four layers of cheesecloth

Instant Practice—IdentifyingVariables

For each of the following questions, stateyour control, your manipulated variable,and your responding variable.1. Does light travel the same way through

different substances?2. Does the addition of compost to soil

promote vegetable growth?3. How effective are various kinds of

mosquito repellent?

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 be useful. You will not know whetherthe breeze or the Sun made the waterevaporate.

As you have been reading, a question mayhave occurred to you: How is it possible to doa fair test on puddles? How can you be surethat they are the same size? In situations suchas this one, scientists often use models. Amodel can be a mental picture, a diagram, aworking model, or even a mathematicalexpression. To make sure your test is fair, youcan prepare model “puddles” that you knoware all exactly the same. Science Skill 8 givesyou more information on using models.

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466 MHR • Science Skill 2

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

Repeat several times.

Revise predictionor hypothesis.

prediction or hypothesissupported

prediction or hypothesisnot 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

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 completed all yourobservations, you are ready to analyze yourdata and draw a conclusion. A conclusion is astatement that indicates whether your resultssupport or do not support your hypothesis. Ifyou had hypothesized that the addition ofthermal energy would have no effect on theevaporation of water, your results would notsupport your hypothesis. An hypothesis givesyou a place to start and helps you design yourexperiment. If your results do not supportyour hypothesis, you use what you havelearned in the experiment to come up with anew hypothesis to test.

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

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

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Page 8: Science Skills Guide · A Process for Scientific Inquiry One model of the scientific inquiry process is shown in the concept map below. Repeat several times. Revise prediction or

Science Skill 3 • MHR 467

Science Skill 3

“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.

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.

Suppose school is soon to close for a 16-day winter holiday. Your science class has ahamster whose life stages the class observes.Student volunteers will take the hamster homeand care for it over the holiday. However,there is a three-day period when no one will beavailable to feed the hamster. Leaving extrafood in the cage is not an option because thehamster will eat it all at once. What kinds ofdevices could you 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 does not 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

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You might find, too, that your invention failsin a particular way. Perhaps it always leaks at acertain point where two parts are joined.Perhaps the food and water are not keptseparate. Perhaps you notice a more efficientway to design your device as you watch itoperate. Make any adjustments and test themso that your device works in the best and mostefficient way possible.

EvaluatingWhen you are satisfied with your device, youcan demonstrate it and observe devicesconstructed 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 your 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.

468 MHR • Science Skill 3

Planning and ConstructingYou will probably come up with good ideas.Like all other scientists, though, you will wantto make use of information and devices thatothers have developed. Do some research andshare your findings with your group. Can youmodify someone else’s idea? With your group,brainstorm some possible designs. How wouldthe designs 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.

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Suppose you are part of a hockey team thatpractises at an arena in a town a few kilometresaway. Every winter, there are days when youcannot get to the arena because the roads aretoo icy. The town council is in the middle ofbudget discussions, 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.

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 are surprised,but as you begin discussing the letter, you startto see your friend’s point of view.

“What do you mean, damage theenvironment?” you ask. “Isn’t it important tomake 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 research to find information aboutthese 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.”

After researching you say, “Well, we founda lot of information, but I am still notcompletely convinced that salting the roadscould cause a problem with our water. Whatsorts of things do we need to find out in orderto 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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470 MHR • Science Skill 4

Identifying Alternatives“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.”

Making a DecisionWhen 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 that

person’s mind. If you are going to encourage agroup to make what you consider a gooddecision, 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 only up tothe town council or any other group to actresponsibly; it is also up to you and yourfriends. How easy is it for you to give up aneasy way of doing a task in order to make anenvironmentally responsible decision?

Evaluating the DecisionIssues rarely have easy answers. People 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 E ect of Road Salt on Water SystemsQue stion:Doe s the addition of salt to soil a ect thesurrounding wa ter?Man ipulated Variable:– saltResponding V ariable:– amount of salt in waterHyp othesis:– W ater near soils that contain salt, will also con tain salt.Prediction:– If we add salt to soil, an y water that drains through

that soil will contain salt.Procedure1.

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Science Skill 4 • MHR 471

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.

Examine the flowchart below. You can seethat you used every step in this process. Aswith scientific inquiry and technologicalproblem solving, having a process to use helpsyou to focus your thinking and stay on track.

A Process for Societal Decision Making

Identify the issue.

Gather relevant information.

Identify all the alternatives.

Consider 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

gem

ent m

ay h

ave

been

mad

e at

any

of

thes

e st

eps

in th

e de

cisi

on-m

akin

g pr

oces

s.

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

We live in an energy-intensive society. Oneof the most common sources of the energywe use is fossil fuel. Complete the followingexercise in a group of four.1. Start by dividing your group into two

pairs. 2. One pair will brainstorm and record the

advantages of fossil fuel use and how it has affected members of our society in a positive way.

3. The second pair will brainstorm and record the disadvantages of fossil fuel use along with its negative impacts on society.

4. The pairs will then regroup, and both sides can present their findings. Record key points on a chart for comparison.

5. Determine which pair has the more convincing evidence for its view of the use of fossil fuels.

6. As a group, brainstorm alternative energy sources, including advantages and disadvantages of each. Determinethe best alternative, based on theinformation you have brainstormed in steps 2 and 3.

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472 MHR • Science Skill 5

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 a visual way to present data. A graph can help you to see patterns andrelationships among the data. The type ofgraph you choose depends on the type of data you have and how you want to present it.You can use 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 in Table 1. Compare the steps in theprocedure with the graph on the next page tolearn how to make a line graph to display yourfindings.

Procedure

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 of bins).You need to show how many students usethe existing bin and how many wouldrecycle if there were a second, a third, anda fourth bin. The scale on the x-axis willgo from 0 to 4. There are 65 students, soyou might want to use intervals of 5 forthe y-axis. That means that every space onyour y-axis represents 5 students. Use atick mark at major intervals on your scale,as shown in the graph on the next page.

4. You want to make sure you will be able toread your graph when it is complete, so make sure your intervals on the x-axis are large 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 thatdo not change smoothly. On a graph, thismeans that you should draw a smoothcurve (or straight line) that most closelyfits the general shape outlined by thepoints. This is called a line of best fit. Abest-fit line often passes through many ofthe points, but sometimes it goes betweenpoints. Think of the dots on your graph asclues about where the perfect smoothcurve (or straight line) should go. A lineof best fit shows the trend of the data. Itcan be extended beyond the first and lastpoints to 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 on the next page, examinethe graph in the column next to the table asyou read the steps that follow. The data showthe number of days of fog recorded during oneyear at one weather station in each of theprovinces and territories.

01Number of

Recycling Bins

Num

ber

of S

tude

nts

Usi

ng R

ecyc

ling

Bins

2 3 4

10

20

30

40

50

60

70

Instant Practice—Line Graphs

The level of ozone in the upper atmosphereis measured in Dobson units (all the ozonepresent in a column of air above a particularpoint). Using the information in the tablebelow, create a line graph showing whathappened to the amount of ozone overAntarctica during a period of 40 years.

Total Ozone (DU)

Year

1960

1965

1970

1975

1980

1985

1990

1995

2000

Table 2 Ozone Levels in Upper Atmosphere

300

280

280

275

225

200

160

110

105

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474 MHR • Science Skill 5

Procedure

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.

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.

6. 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 percentage of the whole. All sectionstogether represent all (100%) of the data.

Number of Days of FogProvince

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—Bar Graphs

Make a vertical bar graph using thefollowing table of each planet’sgravitational force in relation to Earth’sgravity.

Gravitational Pull (g)

Planet

Mercury

Venus

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

Table 4 Gravitational Pull of Planets

0.40

0.90

1.00

0.40

2.50

1.10

0.90

1.20

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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.

Procedure

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 sectionthat represents each type of bird, use thefollowing formula.

Degrees in �

“piece of pie”

Round your answer to the nearest whole number. For example, the section 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 BirdNumber

of SpeciesDegrees in

SectionPercent 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—Circle Graph

Use the following data on total energy (oil,gas, electricity, etc.) consumption for 2004to develop a circle graph to visualize energyconsumption in the world.

Consumption (quadrillion btu)

Area in the World

North America

Central and South America

Europe

Eurasia

Middle East

Africa

Eastern Asia and Oceania

Table 6 World Energy Consumption in 2004

120.62

22.54

85.65

45.18

21.14

13.71

137.61

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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476 MHR • Science Skill 5

Graphing on a ComputerComputers are a useful 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, etc.), so you do notneed to read instruments and enter data byhand, with all the resulting possibilities forerror. The computer can display thereadings on a graph as data are collected(in “real” time), so you can quickly get apicture of how your experiment is going.

5. Errors can be corrected much more easilywhen working with a computer. Justcorrect the error and print again.

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 itis not 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 line can helpyou to discover patterns in your data andmake predictions to test your inferences.

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Science Skill 6 • MHR 477

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 student’s lab report on anexperiment to test the expansion of air in aballoon. The student’s written 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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478 MHR • Science Skill 6

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.Think about what you would need toknow if you were looking at the object forthe first time. Remember to place all yourlabels to the right of the drawing, ifpossible. Use a ruler to draw a horizontalline from the label to the part you areidentifying. Make sure that none of yourlabel lines cross.

8. Give your drawing a title. The drawing of a human skin cell shown below is from astudent’s notebook. This student usedstippling to show darker areas, horizontallabel lines for the cell parts viewed, and atitle—all elements of an excellent finaldrawing.

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

Drawing to ScaleWhen you draw objects seen through amicroscope, the size of your drawing isimportant. Your drawing should be inproportion to the size of the object as theobject appears when viewed through themicroscope. This type of drawing is called ascale drawing. A scale drawing allows you tocompare the sizes of different objects and to

estimate the actual size of the object beingviewed. Here are some steps to follow whenmaking scale drawings of magnified objects.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. Note the locationof 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. Draw theobject so that it takes up about the sameamount of space within the circle as it takesup in the field of view, as shown in thediagram.

drawing made to scale (100x)

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

=

Instant Practice—Scale DrawingsDesign a scale drawing of your bedroom,using the shape of the floor rather than acircle like the example given above. Includescale drawings of the furniture in yourroom. When you are finished, label the fireescape routes.

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Science Skill 7 • MHR 479

Measuring Length and AreaYou can use a metre stick or a ruler to measureshort distances. These tools are usually markedin centimetres and/or millimetres. Use a rulerto measure 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).

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 by estimating—making aninformed judgement about a measurement. Anestimate gives you an idea of the measure butis not an exact measurement.

Scientists often make estimates when exactmeasurements are not essential. You will find ituseful to be able to estimate as accurately aspossible, too. For example, suppose youwanted to know how many ants live in a localpark. Counting every ant would be very time-consuming—and the ants would be mostunlikely 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

A

C E

B

D

F

4 cm

4 cm

18 mm

12 mm

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480 MHR • Science Skill 7

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 a cube bymultiplying 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.

Instant Practice—Estimating andMeasuring

Imagine that all rulers within the schoolhave vanished. The only measurement toolthat you now have is a toothpick. 1. Estimate the length and width of your

textbook in toothpick units. Compare your estimates with your partner’s estimates.

2. Measure the length and width of your textbook with your toothpick. How close was your estimate to the actual measurement?

3. Estimate the length and width of your desk in toothpick units. Compare your estimates with your partner’s estimates.

4. Measure the length and width of yourdesk with your toothpick. How closewas your estimate to the actualmeasurement?

5. If you had a much larger area tomeasure, such as the floor of yourclassroom, what could you use insteadof toothpicks to measure? (Be creative!)

6. What is your estimate of the number ofunits you chose in (question 5) for thewidth of your classroom?

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Science Skill 7 • MHR 481

The units used to measure the volume of liquids are called capacity units. The basic unitof volume for liquids is the litre (L). In thiscourse, 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 kL

The volume of a liquid can be measureddirectly, as shown in Diagram B. Make sureyou measure to the bottom of the meniscus,the slight curve where the liquid touches thesides of the container. To measure accurately,make sure your eye is at the same level as thebottom of the meniscus.

Measuring the volume of a liquid

The volume of an irregularly shaped solidobject, however, must be measured indirectlyas shown in Diagram C. This is done bydetermining the volume of a liquid it willdisplace.

1. Record the volume of the liquid.

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

3. The volume of the object isequal to the difference betweenthe two volumes of the liquid.The equation below thephotograph shows you how tocalculate this.

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

C

As 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

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482 MHR • Science Skill 7

Measuring MassIs your backpack heavier than your friend’s backpack? You can check by holding abackpack in each hand. The mass of an objectis the amount of matter in a substance orobject. Mass is measured in milligrams, grams,kilograms, and tonnes. You need a balance,such as a triple beam balance, for measuringmass.

Use the following steps to measure themass 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.

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 beaker is 160 g.

900

800

700

600

500

100

90

80

70

60

50

40

30

20

1010

15

20

25

2

2

Instant Practice—Measuring Volume

Determine the volumeof liquids present inthe followinggraduated cylinders.

C

A

B

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Science Skill 7 • MHR 483

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

Measuring AnglesYou can use a protractor to measure angles.Protractors usually have an inner scale and anouter scale. The scale you use depends on howyou place the protractor on an angle (symbol��). Look at the following examples to learnhow to use a 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

Determine the masses represented on thefollowing centigram balances.

0 100 200g

0 10 20 30 40 50 60 70 80 90 100g

0 1 2 3 4 5 6 7 8 9 10g

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.10g

0 100 200g

0 10 20 30 40 50 60 70 80 90 100g

0 1 2 3 4 5 6 7 8 9 10g

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.10g

0 100 200g

0 10 20 30 40 50 60 70 80 90 100g

0 1 2 3 4 5 6 7 8 9 10g

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.10g

A

B

C

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484 MHR • Science Skill 7

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 about 273 degrees belowthe freezing 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. This meansthat on the Kelvin scale, water freezes at 273 Kand boils 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) �DAF (d) �HAF (g) �EAG(b) �DAH (e) �GAD (h) �EAI(c) �IAG (f) �DAI (i) �FAG

2. Use a protractor to draw angles with the following measures. Label each angle.(a) ABC 50° (c) XYZ 5° (e) HAL 90°(b) QRS 85° (d) JKL 45°

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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Science Skill 8 • MHR 485

When you think of a model, you might thinkof a toy such as a model airplane. Is a modelairplane similar to a scientific model? Ifbuilding a model airplane helps you learnabout flight, then you could say it is a scientificmodel.

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 model of matter, forexample, which is a model that states that allmatter is made of tiny, invisible particles.Sometimes a model is useful because theobjects you are studying are extremely large—the planets in our solar system, for example. Inother cases, the object may be hidden fromview, like the interior of Earth or the inside ofa living organism. A mathematical model canshow 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, to findout if an hypothesis is supported, and to plannew experiments in order to learn more aboutthe subject they are studying. Sometimes,scientists discover so much new informationthat they have to modify their models.Examine the models in the illustrations on thispage. How can these models help you learnabout 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.

Instant Practice—Using Models

Models are used outside of the sciencelaboratory as well as inside of it. How doesusing models help each of the followingprofessions in their work?(a) architects(b) aviation engineers(c) theatre directors(d) geographers(e) landscape designers

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486 MHR • Science Skill 9

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, soyou must use proper procedure and care. ThisScience Skill reviews the skills that you willneed to use a microscope effectively. Beforeyou use your microscope, you need to knowthe parts of a microscope and their functions.

Using a Microscope

B. TubeThe tube holds the eyepieceand the objective lenses atthe proper working distancefrom each other.

C. Revolving nosepieceThis rotating disk holds twoor more objective lenses. Turnit to change lenses. Each lensclicks into place.

D. Objective lensesThe objective lenses magnifythe object. Each lens has adifferent power ofmagnification, such as 4�,10�, 40�. (Your microscopemay instead have 10�, 40�,and 100� objective lenses.)The objective lenses arereferred to as low, medium,and high power. Themagnifying power isengraved on the side of eachobjective lens. Be sure youcan identify each lens.

E. ArmThe arm connects the baseand the tube. Use the arm forcarrying the microscope.

F. Coarse focus knobThe coarse focus knob movesthe tube up and down tobring the object into focus.Use it only with the low-power objective lens.

G. Fine focus knobUse the fine focus knob withmedium- and high-powermagnification to bring theobject into sharper focus.

H. StageThe stage supports themicroscope slide. Stage clipshold the slide in position. Anopening in the centre of thestage allows light from thelight source to pass throughthe slide.

I. Condenser lensThe condenser lens directslight to the object beingviewed.

J. DiaphragmThe diaphragm controls the amount of light reaching the object being viewed.

A. Eyepiece (or ocular lens)You look through the eyepiece. It has alens that magnifies the object, usually by10 times (10�). The magnifying power isengraved on the side of the eyepiece.

K. Light sourceShining a light through the object beingviewed makes it easier to see the details.If your microscope has a mirror instead ofa light, adjust the mirror to direct lightthrough the lenses. CAUTION: Use anelectric light, not sunlight, as the lightsource for focussing your mirror.

A

B

C

D

E

F

G

H

I

K

J

Science Skill 9

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Science Skill 9 • MHR 487

Instant Practice—Applying Stains

A common problem when working withmicroscopic specimens is that it may bedifficult to observe structures clearly. Youcan use various stains to colour thestructures that you want to see. Commonstains used for biological specimens are:

• Iodine—for staining starch• Crystal violet—for staining bacterial

cell walls• Methylene blue—for observing nuclei

in cheek cells

Suppose you want to observe the stagesof mitosis in an onion root tip. 1. Slice off the root tips from a green

onion, or from a yellow onion that hasbeen allowed to grow in water for a fewdays.

2. Cut off the root tips and place them in asmall amount of 1 M HCl for a fewminutes to stop mitosis. Warning: HClis a strong acid. Follow safety rules forworking with acids.

3. Slice a very thin section of the onionroot tip and place it on a microscopeslide.

4. Add several drops of 1% toluidine blueto the root tip section. Leave the stainon for several minutes.

5. Blot off the extra stain with a papertowel. Add a few drops of water to thesection to remove extra stain. Blot off.Repeat, if necessary. There should notbe a lot of stain left on the section.

6. Add one drop of water. Place a coverslip, edge first, and lower it carefullyover your specimen.

7. If the section is too thick, carefully applygentle pressure to flatten the section.

8. Place the slide on your microscope, anduse the low power for your firstobservation.

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 isturned on. If the microscope has no light,adjust your mirror.

• Are you having trouble finding anything onthe slide? Be patient. Make sure the objectbeing viewed 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 are almosttransparent. If there is too much light, aspecimen may be difficult to see or willappear “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. Otherwise, when you turn tomedium and high power, you may not seethe object you were viewing under lowpower.

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488 MHR • Science Skill 10

Science Skill 10

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Science Skill 10 • MHR 489

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Names, Formulas and Charges ofSome Common Polyatomic Ions

FormulaName

acetate CH3COO�

ammonium NH4�

carbonate CO32�

chlorate ClO3�

chlorite ClO2�

chromate CrO42�

cyanide CN�

dichromate Cr2O72�

hydrogen carbonate HCO3�

hydrogen sulphate HSO4�

hydrogen sulphide HS�

hydrogen sulphite HSO3�

hydroxide OH�

hypochlorite ClO�

nitrate NO3�

nitrite NO2�

perchlorate ClO4�

permanganate MnO4�

phosphate PO43�

phosphite PO33�

sulphate SO42�

sulphite SO32�

IonAtom

Electron Arrangements of the First20 Elements

H

He

Li

Be

B

C

N

O

F

Ne

Na

Mg

Al

Si

P

S

Cl

Ar

K

Ca

1 p

2 p

3 p

4 p

5 p

6 p

7 p

8 p

9 p

10 p

11 p

12 p

13 p

14 p

15 p

16 p

17 p

18 p

19 p

20 p

1

2

2, 1

2, 2

2, 3

2, 4

2, 5

2, 6

2, 7

2, 8

2, 8, 1

2, 8, 2

2, 8, 3

2, 8, 4

2, 8, 5

2, 8, 6

2, 8, 7

2, 8, 8

2, 8, 8, 1

2, 8, 8, 2

H�

H�

He

Li�

Be2�

B3�

C4�

N3�

O2�

F�

Ne

Na�

Mg2�

Al3�

Si4�

P3�

S2�

Cl�

Ar

K�

Ca2�

1 p

1 p

3 p

4 p

5 p

6 p

7 p

8 p

9 p

11 p

12 p

13 p

14 p

15 p

16 p

17 p

19 p

20 p

0

2

2

2

2

2, 8

2, 8

2, 8

2, 8

2, 8

2, 8

2, 8

2, 8, 8

2, 8, 8

2, 8, 8

2, 8, 8

2, 8, 8

2, 8, 8

does not form an ion

does not form an ion

does not form an ion

490 MHR • Science Skill 10

1

1. Fold the round pieces of filter paper in half.

2. Crease the fold.

2

3. Fold the paper in half again and crease it to produce a quarter circle.

3

4. Separate one outer layer of paper from the other three.

4

5. Make the opening wider by squeezing slightly together at the creases.

5

6. Place the cone of filter paper into a funnel and slightly dampen it.

6

Folding a Round Filter Paper

Table 1 Common Polyatomic Ions Table 2 Electron Arrangements

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Science Skill 11 • MHR 491

Science Skill 11

Using Electric Circuit Symbols and Meters

Circuit Diagram Symbols

Using Meters to Measure Voltage and Current

Types of Meters

The meters you use in your classroom areeither analogue meters or digital meters.Analogue meters are meters that have a needle pointing to a dial. Digital metersdisplay measured values directly as numbers,similar to how a digital watch displays the timedirectly.

conducting wire

cell

voltmeter

battery

bulb

open switch

closed switch

resistor

ammeter

� �

� �

B. Analogue meters have aneedle pointing to differentscales.

The Terminals of a Meter

All meters have two terminals (connectingpoints) that you connect to the circuit. Thenegative terminal (�) is black. The positiveterminal (�) is red. In a circuit, conventionalcurrent is defined as flowing from positive tonegative. This means that current leaves thepositive side of the battery or power supplyand returns to the negative. In order not todamage the meter, you must take care toconnect the meters so that the positive (red)terminal of the meter is connected to thepositive side of the power source. That is, ifyou trace the current leaving the source itshould enter the meter through its positive(�) terminal. The negative (�) terminal of themeter is always connected to the negative sideof the source. The rule is “positive to positive,and negative to negative.”

Connecting an Ammeter

An ammeter is used to measure the electriccurrent in a circuit. Electric current is theamount of charge passing a given point persecond. To measure the current at a givenlocation in an electric circuit, the ammetermust be connected so that all the current isallowed to pass through the ammeter. To dothis, you must disconnect the circuit at thelocation where you wish to measure thecurrent. Then insert the ammeter so thatcurrent leaving the power source enters thepositive (red) terminal of the ammeter andleaves from the negative (black) terminal.

A. Digital metersdisplay the numericalvalues directly.

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492 MHR • Science Skill 11

To measure the current entering the light bulb, first disconnect thewire connected to the light bulb. Then insert the ammeter into thecircuit.

Connecting a VoltmeterA voltmeter is a device used to measureelectric potential difference, or voltage as it ismore commonly called. A voltage existsbetween two points in a circuit such as across abattery, light bulb, or resistor. Whenconnecting a voltmeter to a circuit, you do notneed to disconnect or open the circuit. Sincevoltage is measured between two points ofpotential difference in a circuit, you connectthe terminals of the voltmeter at these twopoints. Two wires from the terminals of thevoltmeter are connected to opposite sides ofthe component where you wish to measure thepotential difference. Again, as with theammeter, the positive terminal of the voltmeteris connected on the positive side of the powersource and the negative terminal of thevoltmeter is connected on the negative side ofthe source.

Connecting a Multimeter

Modern digital meters can also be multimeters.Multimeters can be used to measure voltage,current, and other electrical properties. Whenusing a multimeter, it is important that youposition the dial on the correct setting for yourapplication. As well, the connecting wires must beinserted into the correct meter terminals.

Reading a Meter

A digital meter is easy to read since the measuredvalue is displayed directly as numbers. In order toget the most accurate reading on a digital meter,the meter needs to be set to the appropriate scale.The dial on a digital meter has several settings.For example, if the dial is set on the 2 V range,the meter will measure voltages between zero and2 V. Moving the dial to the 200 V setting willallow the meter to measure between zero and 200 V, but with less accuracy. Therefore, whenusing meters, you must choose the best settingfor your measurement. The best approach is to setthe meter on the largest scale to obtain anapproximate value. Then lower the scale until youhave the highest possible reading without goingoff scale.

This approach is the same for analoguemeters. Some analogue meters have a dial, similarto a digital meter, that is used to change the scale.In other analogue meters, the scale is changed byhow the wires are connected to the terminals.Once the scale is selected, you then obtain yourreading from the most appropriate display on themeter.

++–– light bulb

source(battery)

connect additionalwire

disconnect

connect

switch 0

+–

ammeter

AA

++––

light bulb

source(battery)

switch

0

voltmeter

additionalwires

connect connect

Voltmeters are connected across a component in the circuit.

.41.0

2.2.5 1

0 0 0

.82.04

12.55

.61.53

D.C.VOLTS

5025

10

52.5

1

100

250500

1000

� �

A. This voltmeter has its dialset at 10 V. To determine themeasured potentialdifference, look for a numberat the top of the scale withthe same first digit as 10. Thetop scale has a maximumvalue of 1, so now the 1represents 10 V. To read thescale, multiply the numberthe needle is pointing to by10. The dial is reporting 7.2 V.

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Science Skill 11 • MHR 493

Instant Practice—Using CircuitSymbols and Electric Meters

1. Sketch the following circuit diagramsymbols:(a) battery(b) light bulb(c) resistor(d) open switch(e) ammeter(f) voltmeter

2. State the colour that is associated with:(a) the positive terminal of a meter(b) the negative terminal of a meter

3. When you connect a meter to a circuit, to which side of the power source should you always connect the positive terminal of the meter?

4. For which type of meter do you need todisconnect the circuit before connectingthe meter to the circuit?

5. A student wishes to use a meter tocollect the most accurate measurementwithout damaging the meter. Describethe correct approach for choosing theappropriate scale.

6. Determine the value of current orvoltage indicated by meters A to D inthe next column.

.41.0

2.2.5 1

0 0 0

.82.04

12.55

.61.53

D.C.VOLTS

5025

10

52.5

1

100

250500

1000

� �

.41.0

2.2.5 1

0 0 0

.82.04

12.55

.61.53

D.C.Amperes

500 mA 1 A

5 A

10 A

100 mA

10 mA

B. This ammeter has thepositive wire connected tothe 500 mA scale. The 5 onthe bottom scale is the firstdigit in 500 mA, so the 5now represents 500 mA. Theneedle is pointing to 4.7, sothe meter is reporting 470mA of current.

.41.0

2.2.5 1

0 0 0

.82.04

12.55

.61.53

D.C.VOLTS

5025

10

52.5

1

100

250500

1000

� �

.41.0

2.2.5 1

0 0 0

.82.04

12.55

.61.53

D.C.VOLTS

5025

10

52.5

1

100

250500

1000

� �

.41.0

2.2.5 1

0 0 0

.82.04

12.55

.61.53

D.C.Amperes

500 mA 1 A

5 A

10 A

100 mA

10 mA

A

B

C

D

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494 MHR • Science Skill 12

How can you use your textbook effectively tounderstand science concepts better? ThisScience Skill will give you strategies to help youbetter understand what you read. It will alsoexplain 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 you 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 GlossaryNotice the terms that are in bold (dark, heavy)type. These terms are important words thatyou will need in order to understand and writeabout the information in each topic. Make surethat you understand these terms and how theyare used. Each boldfaced term appears in theGlossary at the back of this book.

Science Skill 12

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Science Skill 12 • MHR 495

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. There isno single “correct” concept map, there areonly the connections that make sense to you.Make your map as neat and clear as possible.Make sure you have reasons for suggesting theconnections between the concepts.

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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496 MHR • Science Skill 12

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.

Cycle Chart

A cycle chart is a special type of flowchart. In acycle chart, the series of events do not producea final outcome. This type of chart has nobeginning 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 of the body to decay.

A solution of water and minerals flows through the bones.

The water dissolves the calcium in the bones.

The minerals take 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 information isanother way to help solidify your learning.When you compare, you look for similaritiesbetween two concepts or objects. When youcontrast, you look for differences. You can dothis by listing ways in which two things aresimilar and ways in which they are different.You can also use a graphic organizer called aVenn diagram to do this, 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—Graphic Organizers

1. Create a concept map with a sketch ofthe atom at the centre of the map.Include the following terms on the map:electrons, neutrons, protons, ions,nucleus, neutral, negative, and positive.Show how each term is connected tothe atom and to other terms. Continueadding terms, connections, and sketches.

2. Create a flowchart that takes youthrough all the steps involved incarrying out a scientific investigation.

3. Design a spider map with the centraltheme of space exploration.

4. Create a Venn diagram in which youcompare and contrast one of thefollowing pairs.(a) bats and birds(b) hurricanes and tornadoes(c) your two favourite science topics

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498 MHR • Science Skill 13

Throughout history, people have developed systems of numbering and measurement.When different groups of people began tocommunicate with each other, they discoveredthat their systems and units of measurementwere different. Some groups within societiescreated 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 multipliedby 1000. Thus, one kilometre is 1000 metres.

1 km � 1000 m

The prefix “milli-” means divided by 1000.Thus, one millimetre is 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 Penticton to Prince Rupertis 1431 km. Express this distance in metres.

Solution1431 km � ? m

1 km � 1000 m1431 km � 1431 � 1000 m

� 1 431 000 m

Example 2

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

Solution1 kg � 1000 g

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 and Scientific Notation

Science Skill 13

SymbolPrefixes 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

UnitQuantity Symbol

nanometremicrometremillimetrecentimetremetrekilometre

length nm�mmmcmmkm

mass

gramkilogramtonne

gkgt

area square centimetresquare metrehectare

cm2

m2

ha

volume cubic centimetrecubic metremillilitrelitre

cm3

m3

mLL

time second s

temperature degree Celsius ˚Cforce newton N

electric current ampere A

quantity of electric charge

coulomb C

frequencyelectrical resistance

hertzohm

Hz�

power watt W

energy joulekilojoule

JkJ

pressure pascalkilopascal

PakPa

Instant Practice—Using MetricMeasurements

1. A hummingbird has a mass of 3.5 g.Express its mass in mg.

2. For an experiment, you need to measure350 mL of dilute acetic acid. Express the volume in L.

3. A bald eagle has a wingspan up to 2.3 m. Express the length in cm.

4. The heaviest blue whale ever recordedwas a massive 190 tonnes. Express itsmass in grams.

5. A student added 0.0025 L of foodcolouring to water. Express the volumein 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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58 000 000.

Exponents of Scientific NotationAn exponent is the symbol or numberdenoting the power to which another numberor symbol is to be raised. The exponentshows the number of repeated multiplicationsof the base. In 102, the exponent is 2 and thebase is 10. The place table below shows thepowers of 10 as numbers in standard formand in exponential form.

Why use exponents? Consider this.Mercury is about 58 000 000 km from theSun. If a zero were accidentally added to thisnumber, the distance would appear to be 10times larger than it actually is. To avoidmistakes when writing many zeros, scientistsexpress very large and very small numbers inscientific notation.

Example 1

Mercury is about 58 000 000 km from theSun. Write 58 000 000 in scientific notation.

SolutionIn scientific notation, a number has the form x � 10n, where x is greater than or equal to 1but less than 10, and 10n is a power of 10.

The decimal point starts here.Move the decimal point 7 placesto the left.= 5.8 � 10 000 000= 5.8 � 107

When you move the decimal point to the left,the exponent of 10 is positive. The number ofplaces you move the decimal point is thenumber in the exponent.

Example 2

The electron in a hydrogen atom is, on the average, 0.000 000 000 053 m from thenucleus. Write 0.000 000 000 053 inscientific notation.

SolutionTo write the number in the form x � 10n,move the decimal point to the right untilthere is one, non-zero number to the left ofthe decimal point. The decimal point starts here.Move the decimal point 11 places to the right.

= 5.3 � 0.000 000 000 01= 5.3 � 10-11

When you move the decimal point to theright, the exponent of 10 is negative. Thenumber of places you move the decimal pointis the number in the exponent.

0.000 000 000 053

Instant Practice—Scientific Notation

1. Express each of the following in scientific notation.(a) The approximate number of stars in our

galaxy, the Milky Way: 400 000 000 000 stars

(b) The approximate distance of the Andromeda Galaxy from Earth:23 000 000 000 000 000 000 km

(c) The estimated distance across the universe: 800 000 000 000 000 000 000 000 km

(d) The approximate mass of a proton:0.000 000 000 000 000 000 000 0017 g

2. Change the following to standard form.(a) 9.8 � 105 m(b) 2.3 � 109 kg(c) 5.5 � 10–5 L(d) 6.5 � 10–10 s

Standard ExponentialForm Form

ten thousands 10 000 104

thousands 1000 103

hundreds 100 102

tens 10 101

ones 1 100

tenths 0.1 10–1

hundredths 0.01 10–2

thousandths 0.001 10–3

ten-thousandths 0.0001 10–4

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