document resume author seager, doug: and others ...ages and seim: ling children in fifth through...

DOCUMENT RESUME

ED 196 656 SE 033 093

AUTHOR Seager, Doug: And OthersTITLE Teacher's Guide for Heating and Cooling. Elementary

Science Study.INSTITUTION Elementary Science Study, Newton, Mass.SPONS AGENCY National Science Foundation, Washington, D.C.TEMPT NO ISBN-07-017709-0PUB DATE 71NOTE 65p.: Photographs may not reproduce well.

EDFS PRICEDESCRIPTORS

ABSTRACT

ME01/PC03 Plus Postage.Elementary Education: *Elementary School Science:*Heat: Instructional Materials; Junior High SchoolStudents; *Science Activities; Science CourseImprovement Projects; Science Curriculum: ScienceEducation: Secondary Education: Secondary SchoolScience; Temperature

This teacher's guide suggests activities that provideopportunities for children in grades 5 through 8 to explore, bydirect exFeriment, the ways in which various materials behave whenthey are heated and cooled. Included within this guide areexplanations for a set of Problem Cards which suggest experiments forstudents to try individually. (CS)

************************************************************************ Reproductions supplied by EDRS are the best that can be made ** from the original document. ************************************************************************

NOV 2 2191

Teacher's Guide for

Heating and Cooling

Elementary Science Study

U S OEPARTMENT OF HEALTH.EDUCATION & WELFARENATIONAL INSTITUTE OF

EDUCATION

THIS DOCUMENT HAS BEEN REPRO.DUCED EXACTLY AS RECEIVED FROMTHE PERSON OR ORGANIZATION ORIGIN-ATING IT POINTS OF VIEW OR OPINIONSSTATED DO NOT NECESSARILY REPRE-SENT OFFICIAL NATIONAL INSTITUTE OFEDUCATION POSITION OR POLICY

"PERMISSION TO REPRODUCE THISMATERIAL HAS BEEN GRANTED BY

Mary L. r-tesof 441e, JUSF

TO THE EDUCATIONAL RESOURCESINFORMATION CENTER (ERIC)."

WEBSTER DIVISION, McGRAW-HILL BOOK COMPANYNew York St. Louis San Francisco Dallas London Sydney Toronto

2

The Heating and Cooling UnitTeacher's Guide for Heating and CoolingProblem Cards for Heating and CoolingKit for Heating and Cooling

Related UnitsGases and "Airs"Ice Cubes

Copyright © 1971, 1968 by Education Development Center, Inc. All Rights Reserved. Printedin the United States of America. No part of this publication may be reproduced, stored in aretrieval system, or transmitted, in any form or by any means, electronic, mechanical, photo-copying, recording, or otherwise, without the prior written permission of the publisher.

Except for the rights to material reserved by others, the publisher andthe copyright owner hereby grant permission to domestic persons of theUnited States and Canada for use of this work without charge in theEnglish language in the United States and Canada after January 1, 1976,provided that publications incorporating materials covered by these copy-rights contain the original copyright notice and a statement that the publi-cation is not endorsed by the original copyright owner. For conditions ofuse and permission to use materials contained herein for foreign publica-tion in other than the English language, apply to the copyright owner.ISBN 07-017709-0

ii

Preface

The Elementary Science Study is one of many curriculum developmentprograms in the fields of science, social studies, and mathematics underpreparation at Education Development Center, Inc. EDC (a private non-profit organization, incorporating the institute for Educational innovationand Educational Services Incorporated) began in 1958 to develop newideas and methods for improving the content and process of education.

ESS has been supported primarily by grants from the National ScienceFoundation. Development of materials for teaching science from kinder-garten through eighth grade started on a small scale in 1960. The work ofthe project has since involved more than a hundred educators in the con-ception and design of its units of study. Among the staff have been scien-tists, engineers, .mathematicians, and teachers experienced in workingwith students of all ages, from kindergarten through college.

Equipment, films, and printed materials are produced with the help ofstaff specialists, as well as of the film and photography studios, the designlaboratory, and the production shops of EDC. At every stage of develop-ment, ideas and materials are taken into actual classrooms, where childrenhelp shape the form and content of each unit before it is released to schoolseverywhere.

4

Acknowledgments

Many people have helped in the development of HEATING AND COOLING.Paul S. Lords originated the unit and developed the activities and equip-ment with the help of H. Paul Jolly. After much classroom teaching, theyprepared a trial teaching edition.

Revisions in the Teacher's Guide and Problem Cards were made inresponse to recommendations made by teachers in trial classes acrossthe country. Norma Arnow prepared the commercial edition with tech-nical guidance from Joe Griffith.

Adeline Naiman edited the manuscript and refined it to its present form.Nancy Weston handled its design and production.

Joan Hamblin and Major Morris took the photographs which appearthroughout the manuscript. The cover photograph is by George Cope.

Doug Seager

iv

Table of Contents

Introduction

Ages and Scheduling 2Starting the Unit 2Problem Cards 2

Materials 4

Supplied in Kit 4You Will Need to Provide 4A Note on the Materials 4Flames, Candles, and Alcohol Lamps 5Safety Precautions 6

Warming Up 8

"Hot Rods" 13Sheets 23

Cooling Off

Spoon Races 32Screens 33

Expansion 39

Children's Own Questions 45

6

Introduction

Everything NH a temperature. Fewthings stay at the same temperature,and we may be aware of the changes asthey happen around US, some quickly,some almost imperceptibly. Childrentouch the stinny side of a brick buildingand it feels warm; where the wall Isshaded, the building feels cool, As thesun moves clown in the sky, the wholebuilding feels cooler. We expect somethings to feel warmer than other things:The surface of the chalkboard feelsmuch cooler than its wooden frame;the metal legs of the desk feel coolerthan the wooden top; a pair of scissorsfeels cooler than a pencil. Some thingschange their shape or condition whenthey are heated or cooled. In thekitchen, children notice that ice cubesstart to melt as soon as they are takenfrom the freezer and that butter getssoft on a warm day and melts whenheated. (The appearance of a cookingpot does not change noticeably nomatter how hot it gets.) In summer,highway tar becomes soft and sticky,streams dry up, and sandy beaches mayget too hot to walk on comfortably.In winter, moist hands freeze fast tooutside doorknobs, automobile enginesare hard to start, and the furnace goesoff and on frequently (as a strip of metalinside its thermostat is heated or cooledthroughout the day). All these areevents with which children may al-ready be familiar.

The equipment for i NATI MI AND Cool,-has been selected to help children

experience the ways In which variousmaterials behave when they are heatedand cooled, The Kit contains metalwires, rods, screens, and sheets, Copperand aluminum wires of various diam-eters are supplied, as well as screeningof aluminum and copper and sheets ofaluminum, lead, and copper. There areeight different kinds of rods, so thatchildren can explore a variety of mate-rials (copper, aluminum, brass, andglass), rods of different diameters, andhollow as well as solid rods.The children soon see that materialsconduct heat at different rates. They runheat "races" to see which material getshot or cools off the fastest. Some of thematerials take a long time to cool down;others cool very quickly, and the exper-imenters begin to see what kinds ofthings can be done to keep a substancefrom losing heat.In the course of these comparisons, thechildren improve their technique andoften find they must repeat some exper-iments to confirm their initial results.A set of Problem Cards* for students con-tains suggestions for experiments totry. (See page 2 for ways to use theProblem Cards.)'Problem Cards for Heating and Cooling, availablefrom Webster Division, McGraw-Hill Book Com-pany, Manchester Road, Manchester, Missouri63011.

1

Ages and Seim: ling

Children in fifth through eighth gradeshave worked with this unit successfully,

The time you will need to teach it willdepend considerably on the kinds andnumbers of problems your studentsfind interesting. Most teachers allow 45minutes to an hour for each session,HEATING AND COOLING will take a mini-mum of 20 class periods, though theunit can easily go on for several months,especially when students wish to set upcarefully controlled experiments andtest many different variables.

Starting the Unit

HEATING AND COOLING has been taughtin several different ways, depending onthe preferences of the teacher. Youshould choose whatever method youfind most comfortable. Some teachersbegin with a brief class discussion:

What things are hot?

What things are cool?

What things feel hot or cool to thetouch?

Can two things have the same temper-ature, yet one feel colder than theother?

How do we make things hotter? . . .cooler?

2

The children's klitiOlifitiion will give youan idea of how much experience theyhave had in heating things and work-ing with fire, Many children are usedto lighting matches, working aroundstoves, and building campfires, Othersmay find this a new experience, andthey are likely to be excited at first lustby striking matches and watching theflames of the candles. Allow some timefor these children to get used to work-ing with fire. Discuss safety regula-tions you feel must be mentioned. (Seepage 6.)

Many children pursue their own inves-tigations right from the start. Oneteacher commented, "Some childrenhave an amazing reservoir of ideas,while others prefer to stick to thecards."

Problem CardsThe 22 Problem Cards are based on thekinds of experiments that children usu-ally try on their ow.i. The cards alsosuggest activities that may not haveoccurred to children. Most children usethe cards after they have done quite abit of their own experimenting. TheProblem Cards may also serve as a start-ing point for those who Hot used toworking independently. cry few chil-dren choose to complete all the cards,

9

Materials

The 111,1teritilii 4011411110d in 1110 1\11,4

41041-IA10d below, ffiltItilifik) for It)kir a class of 3(), it is sug-

gested that three Nils bo ordered,

Siippliod in Kit

I HI 5 solid 01111111110M rods, I" diameter

I I.11 5 solid aluminum rods, h" tilainotor112.1 2 solid aluminum rods, I" diameter

I HI 5 hollow aluminum tubes,diameter

1171 5 hollow brass tubes, I" diameternd 5 solid brass rods, I" diameter

1181 5 solid copper rods, I" diameter!NI 5 Pyrex glass rods, I" diameter1231 50 aluminum sheets, 4" X 4"1221 50 lead sheets, 4" x 4"

1211 30 copper sheets, 4" x 4"

I 91 20 copper screens, 4" x 4",20 openings per square inch

1101 20 copper screens, 4" x 4",10 openings per square inch

181 5 aluminum screens, 4" x 4",20 openings per square inch

151 25' copper wire, #18 gauge

[61 25' copper wire, #22 gauge

*Available from Webster Division, McGraw-HillBook Company, Manchester Road, Manchester,Missouri 63011.

lY4

It)' alinllinum 1Y11.0; gmlAit

'JO I pia \Oro ctitto

111 100 Conillos

I 1 1 5 cardboard trays, 14" x ts"

III 1 10 !,41111110Y110 1Vt141d4111 ilothespin

171 I box 011111111MM foil

I package stool wool (torcleaning soot from rods andsheets) (Not shown in rig,)

I expansion frame1,"1Thu cardboard trays aro used to

protect desk tops from melted wax,spilled water, and hot objects, Ilwclothespins make good tongs for hold-ing hot objects,

You Will Neod to Provideshoe boxes

fire extinguisherbuckets or cans for water

"junk box" itemswooden safety matches (enough small

boxes so that each child can have abox to strike on)

scissors for cutting sheets and screens

A Note on the MaterialsMost teachers find it helpful to haveeach child bring a shoe box in whichto store his own equipment. Empty

ky,Ing)ttoutole

her

theFor

the

rips!ss-inghey

5

Safety PrecautionsChildren quickly learn to be careful andat ease around open candle flames.Only a few minor finger burns haveoccurred in trial classes. Still, it is wiseto take simple precautions.Children should tie back long hair andloose clothing so that they will not fallinto the flame. They should work on thetrays, whether they use their desks orthe floor as work surfaces. They shouldplace the candles so that no one has toreach across a flame for materials.

6

Only wooden safety matches the kindsold in packets of small individualboxesshould be used. Then each stu-dent can have a box on which to strikematches at his desk. Book matches arenot recommended.Some schools require children to wearsafety goggles when working aroundopen flames. All classrooms shouldhave a fire extinguisher available, andthe children ought to learn how touse it.

13

Warming Up

After the children have spent enoughtime lighting candles to be comfortablewith them, you can suggest other activ-ities. The following is a record of thefirst day's discussion in one trial class-room.

The children began with candles and1-inch aluminum rods. After a prelimi-nary conversation about heat and coldand some talk about safety, the teacherasked:

What do you think will happen if youhold one of the rods in a flame?

"It will melt.""The heat will attract to it.""It would turn black.""If you held it a long time, the heat

would travel down the rod.""It will swell.""It might shrink.""The bottom will get hot, and it will

travel up.""Hollow rods might bend and close

at the end.""Rods may stay the same and not do

anything."All right, try it. Be sure to work on the

trays.

"I heated it at one end, and it traveledall the way to the other end."

8

How hot did it get?"Just warm. I could still hold it.""When I hold it straight up and down

in the flame with a clothespin, itgets hot at the top because heattravels up."

Would it get as hot if you held the rodsideways and heated it that way?

"I don't know. I don't think so. I'lltry it."

What do you think will happen to therod if you leave it in the flame a longtime?

Some children expected the rod to melt;a few expected it to shrink. One boycompared his rod with the clothespinholding it:

"I'm trying to see which keeps theheat in longer. The wood is justwarm, and the steel is hot. Themetal keeps the heat in longer."

One child had a rod that was sooty atone end. He held the ends and heatedthe center.

"The black end is hotterI triedthem both with my finger."

What would make the ends different?"Maybe I used different fingers and

one is more sensitive. Maybe the

15

black does something to one end.Maybe the candle isn't in themiddle."

How do you tell when an object is'hot?What does "hot" mean to you?

"When you touch it, your fingerssting. You can imagine that thetemperature is very high."

"You could almost burn yourself."Did it get too hot for all of you at the

same time?

r

.%' ir.. .. . ..,"

"

... t,

"No. Some people can stand moreheat than others."

"I was cooking something in theoven, and I couldn't open the doorit was so hot. My mother had todo it."

"People have different feelings, andsome can hold the hot bar longerthan others. When you try not tothink of how hot your hands are,you can hold it longer."

1 6

How long can you hold one end of a rodwhile you heat the other end?

"I dropped it in a minute.""1 held on for 4 minutes and 20

seconds."Can you hold some rods in the flame

longer than others if you use justyour fingers? Which things heat upthe fastest? . . . the slowest?

One child heated a thick, hollow alumi-num tube and a thin, solid aluminumrod. He dropped one when it got toohot.

"The solid rod heats up faster be-cause the air in the hole doesn'theat easily."

The fact that he was comparing rods ofdifferent diameters, as well as com-paring a solid rod with a hollow tube,did not occur to him at this point. A boysaid to him:

"You should have the same size rods,or you can't tell whether it's the airin the center of the rod or the metalthat makes the difference."

Children are usually slow to see thatthey must consider only one differenceat a time. It may help to suggest thatthey try different materials from the

10

basic equipment and from the "junkbox."

Can you think of a better test for "hot"than fingers?

"I made a rod of aluminum foil andput matches on top of it and waitedfor them to light."

"Use a thermometer. Leave it on therod."

Such a small part of the thermometertouches the rod that very little heat willbe transmitted. If the children put theirthermometers directly in the flame, theinstruments will break.

Several children suggested holding acandle against the rod until it melted.

One boy devised his own methodfor timing the heat flow down a. rod.He inserted candles in a pegboardholder at intervals along the rod (seephotograph).

"Timber! I have felled a mighty oak!The first candle took 5 minutes.Now the second one's beginning tomelt faster . . .. The brass rod took3 minutes to melt the first candle.It conducts heat faster than copper.Now I'm going to try the glass rod."

1 7

i

`k.

...''''''''':..%14.;

.1.1-11111.111C26.

t

12

'ti

Some children noticed a liquid on themetal being heated.

"It's bubbling at the end. The metalis melting!"

"Mine has grease!""It's gotten hot and also wet!"

It took them several days to discoverthat this liquid was wax and not meltedaluminum rod.

Three girls dripped small drops of waxin a straight line from one end to theother of an aluminum and a glass rod.Then they lit a flame under the centerof each rod, to find out which wouldheat up faster and whether heat wouldtravel in both directions. Their resultsshowed that wax drops were a helpfulway of measuring temperature, and themethod was soon adopted by the rest ofthe class.

Eventually, in every trial class, childrenthought of using wax as a "thermom-eter." (The melting point of wax isbetween 126°F and 133 °F just a littlebit too hot to touch.) This is a more con-sistent test of temperature than finger-tips, although some children may stillprefer other indicators. Several childrenhave used tiny drops of water as indi-cators, watching them evaporate as theheat moved along the rod.

19

"Hot Rods"

." .orgrrpp:p

Heat races come up naturallyclassrooms. They focus attenticway in which hollow tubesrods of different materials andsizes conduct heat.

Heating and Cooling Problem Card 1

Heat an aluminum rod and a copper rod. Which one wins?Try the same thing with a glass rod and any metal rod.

Copyright v 1971, I. by Education Development Center, Inc All Right% Reserved

Although most children in trial classesused solid rods for the Problem Card 1comparison, some compared hollowtubes. One boy found that a hollowbrass tube got hot faster than a hollowaluminum tube.

"Copper rod gets the hottest, thenaluminum, and then glass. .I thinkthat the heaviest rod gets hottestfastest, because the glass rod takesthe longest and is the lightest andthe copper is the heaviest and tookthe shortest time."

14

Many children brought in other kindsof metal to test. One boy used pieces ofwater pipe of different lengths. Othersused odds and ends of metal fromaround the house, such as old faucetsand fixtures.

"This (copper) should do it becausecopper carries heat better thanaluminum."

"I had five candles together. Theglass didn't break."

"I'm going to try it again after therods cool down to see if it happensthe same way again."

Throughout their investigations, chil-dren find that their results vary whenthey repeat experiments. Often they getdifferent results from those which theirfriends get.In one class, students gathered at theend of the third session and made twolistsone of observations on which allagreed, the other of experiments to tryover again either because there wereseveral dissenting results or becausethe findings didn't make sense in thelight of subsequent work.

21


Heat the end of a thick aluminum rod and the end of a thinaluminum rod. Which rod heats up faster?

Copyro;h1 1. 1471. Ivan by iducdtion Development Center. Inc All Rtghts Reserved

16

23

Regarding Problem Card 2, a boy said:"These rods are the same. They're

both aluminum, and they're bothsolid. They're just different sizes."

What do you think will happen whenyou heat them?

"I think the thin one will win therace."

Later he said:"It's incredible, but the thin one

never heated up. After 5 minutes,the thick rod was very hot, butafter 12 minutes, the thin rodwasn't really hot. It doesn't makesense that it should take that long.I think I'll do it over."

Another boy said:"If rods are the same length, the

thicker rod will take longer to heatbecause of the extra amount ofmaterial in it."

His partner argued that this wasn'ttrue, that the thinner rod had morecooling surface.Another group of children decided towork together at the same candle, sothat the race would be "fair."

When asked to predict whether wax atthe send of a solid rod or a hollow tubewould melt first, most children said,"Hollow."One boy claimed that the solid brassrod and the hollow brass tube would"carry the same amount of heat" fromone end to the other (that is, would heatin the same time). When this failed tohappen, he undertook to repeat theProblem Card 3 experiment. The teacherasked if the rod and the tube were atthe same temperature to begin with.This time the boy dunked both the rodand the tube in a bucket of water tomake sure that they were cool to beginwith.

"I put wax drops on both when theywere cool then I put them on thefire. The hollow tube was faster."


Heat a solid aluminum rod and a hollow aluminum tube (samediameter) at the end. Which one heats up faster?

Copyright i) 1971. 1968 by Education Development Cenmr. Inc. All Rights Reserved

24

17


If you hold the middle of a rod over the flame, will one endheat up before the other?

Copyright 1971. 191. by Education Development Center. Inc All Rights Reserved

18

"If you heat the rod in the middle,both ends get hot at the same time,and this is faster than heating atone end."

"This is like two cars trying to go amile. If they start at the middle anddrive toward the ends, they willcover the distance fastest."

Several students in trial classes becameconvinced that heat flows faster in onedirection along a rod than the other.

"Heat goes both ways, but one wayfaster."

They had to try the Problem Card 4experiment many times before theynoticed that sometimes they had theflame off center, put different sizes ofwax droplets on the ends of the rod, orleft the candle in a draft so that theflame was blown in one direction morethan in the other.

245

b or 7 minutes

15M1nOte5"It seems to go faster at first. Then itslows down."

Children often predict that it will talc(twice as long for the wax at the far endto melt. When their results don't ! rthis out, they blame their techn:Only after many repetitions, dorealize that heat doesn't travel atsame rate all of the time.

"Maybe the heat isn't going throughthe rod. Maybe the rod's beingheated from the outside in."


If you hold one end of a rod over the flame, will a drop of waxat the other end take twice as long to melt as a drop of wax inthe middle?

Copyright it) 1971. 1969 by Education Development Center, Inc All Rights Reserved


If you heat a horizontal rod and a vertical rod, which heatsfaster?

Copyright ip 1971. 19611 by Education Development Center. Inc. MI Rights Reserved

26

19


Can you prevent a drop of wax from melting at one end of analuminum rod when the rod is being heated at the other end?

14,1 1`... Do.clopmcnt Cenicr. Inc All Riht% kr,ened

aluminumrod

After tiley feel confident that theyknow something about the flow of heatthrough various materials, children en-joy "negative" heat races. They try Kitmaterials, "junk box" itemsanythingand everything. . . lead:

"We tried pouring lead in the hol-low tube and putting lead sheetsaround it, because lead is the bestinsulator we found so far. But itdidn't help much."

. . . clothespins:

"It took more than 30 minutes to melt.I ran out of time."

11111111111Mik

I /cmci le

20

clothespins/

. . . ice:

wax

Al

Ice cubenot tozelln9 rod

"Thi.; worked for a while."

matchbox

"The heat traveled through therod faster than the cold traveledthrough the aluminum sheet."

. . . water:

H2O

brass

Mhesive tape.. . but the adhesive melted, so we

tried a milk carton."

-bray"In a hot-rod race, the brass took 11minutes, 36 seconds. With this waterway, it's been cool for 35 minutes."

. .. rods:

Wax

many other-rods

"... but the wax melted anyway."

2

Two boys reported:"With copper coils heat went

through just as fast.""With copper coils, lead sheet, and

aluminum sheetjust as fast.""Small copper mesh stopped it

some.""Big copper mesh better.""Aluminum mesh it got hot, but the

mesh was loose."Most of the successful experimenterscooled the rods with water or usedsome combination of wires and screensthat interrupted the heat at many pointsof con tact.

29

Sheets

Use of metal sheets allows students toobserve the patterns made when heatspreads out (rather than when it travelsin a line as it does along the rod). Chil-dren cut the sheet metal into differentshapes in an attempt to conduct heatfaster from one point to another. Theyrace shapes with one another.

Vb. eAfrZ=-"*--

4'41,

1,4

N


Where can you hold a 4" by 4'fingers the longest when yousheet?Can you find a way to showthis experiment?

sheet of aluminum with yourare heating one corner of the

what path the heat follows in

COMTIKhi I 1471, 14n. by Educ.ttIon Del.elorrnent Center, Inc All Flight+ liewned

r.

--".....".

"1 took a flat piece of aluminum andput drops of wax on three cornersand in the middle. And then I puta candle under the end without anywax. First, the wax melted on bothcorners nearest the flame. Thenthe wax on the opposite cornermelted."

Children who have worked only withrods and tubes may hold the othercorners, expecting them to heat upmore slowly because "heat travels ina straight line and doesn't spread out."

at

24

31

Many children notice changes in theappearance of the metal as it becomesvery hot, and they can "follow" thepath that the heat takes across thealuminum sheet. Some children maytry to figure out the path that heattakes along a sheet by dripping waxover the surfaces of the metal and thenwatching the order in which the drop-lets melt. Other children may wet thesheet or rub the side of a candle allover it before they heat it to see wherethe water evaporates or the film of waxmelts.

One boy heated metal sheets he hadwrinkled.

"When it's wrinkled, the heat getsunderneath the folds and heats itfaster."


Where can you hold a 4" by 4" sheet of aluminum with yourfingers the longest when you are heating the middle of oneedge?Can you find a way to show what path the heat follows in thisexperiment?

CorynRht 1,071, Itttet by Education Development Center. In MI Right. Re.erved


Is there any difference in the way heat passes through a 4"by 4" sheet of aluminum and the way it passes through a4" by 4" sheet of another metal?Does it matter where you heat the different sheets?

Copyrtght I 1471. 14N4 by Education Develop bent Center. Inc All Right. Re.ervd

3225

Heating and Cooling

I II

ft- 4. 4,

Problem Card 11

Prediction Winner

For each pair of shapes cut from aluminum sheets, which shapewill conduct heat faster from point x to point y?

C4.Pvnithi is I471. Inn by Etturanon Development Center. In All Right. Revenred

It is difficult for the children to cutthe aluminum shapes without wastingsheets. If you wish to conserve sup-plies, you may cut these shapes beforeclass, using ordinary scissors.Unless students have placed the heatsource at y instead of at x or have heldthe metal pieces at different angles tothe flame (allowing more or less of theflame to pass along the bottom of themetal), all should find the same shapeswinning. Their predictions will varywidely, however.A boy cut the following shape:

26

4"When I heat it at x or at y, the wax

melts at the other end. But when Iheat it at A or B, the heat never getsto the other side."

The teacher asked if he had an explana-tion for this.

"I think that when I heat it at A or B,the heat can spread out after it'sgone just a little way."

Another boy predicted:"I think the dumbbell (%1

will win because the heat can justgo straight down it. With the other

one 14p the heat will goand fill up both sides before itgoes to the end."

After they have experimented for a bitwith the shapes cut by the teacher,some of the children may find it fun todesign and cut out shapes on their own.Trays from frozen TV dinners are goodto use if supplies are running Iow.

33

One boy started with this shape:Then he cut the arms off

and said it heated faster.

He went on to cut notches in the strip

MC:1 and found that heat traveled

across tt.e strip s faster."There's just as much heat, but

there's less place for the heat togo."


What flat shape can you cut from a sheet of aluminum thatwill allow the fastest heat transfer from one point to another4" away?

CopynKhi i) 147I. NM by Edocabon Deyylopinbnl Crnler. In All Flights Reserved

3427

Cooling Off

When children see a flame go out,especially when it has been coveredby something, they are likely to remarkthat the flame was "smothered," Oftenthey are right, but there are other waysto put out a fire besides keeping airaway from the flame.

To produce the heat and light we call"fire," there must indeed be air. Theremust also be fuel. Finally, there must be

40,

28

a temperature high enough (kindlingtemperature) to start a chemical re-action between the fuel and the air.

The removal of any one of the, threenecessities fuel, air, or high tempera-turecan cause a fire to go out.

The next set of problems deals withputting out a flame by removing heatto lower the temperature of the flame,

35

"Yes! After one hour, I did it, with acopper coil."

Children often start fanning the flamewith their wires to no avail. Eventu-ally they either wad up the wire ormake a coil of it to place around theflame.

One boy made a tightly wound candlesnuffer out of wire. It worked. Thechildren decided that it kept the airaway from the flame, so that the candlecouldn't burn. The teacher asked if thesnuffer would still work if the loopswere separated. The child reported:

"Hey! The loose coil put the flameout just as well, even though theair can get through. But the coilwon't work if it's wide open."

Floating and Cooling Problem Card 13

Without blowing on the flame or touching the wick, can youput out the flame by using a single piece of copper wire?

CorvtIghl 1. 1471, VIM Ilv litimation Ovelopment l enlel. In All RIA111.141..etved

3629

After several children were able tomake the flame go out with a wire, theteacher asked:

How many times in a row can you putout the flame in this way?

This led to a new difficulty. After thewire had been used several times, thechildren found it harder to put outthe flame. After much discussion andexperimenting, they decided that thecoil of wire gradually heated up tothe point at which it was too hot tocool down the flame. After more exper-

30

imentation, they reached a number ofconclusions:

"To put out the flame, the coil mustbe cool."

"I guess when the wire's cool, all theheat goes out of the flame into themetal."

"The metal takes the heat. The moremetal there is around the flame,the more heat it takes, so the flamegets too cool to burn. But when thewire is hot, it can't take any moreheat, so the flame stays on."

37

"I had two wiresone thick, theother thin, The thick one put it outfaster."

"The thick one puts it out faster,Each time I put the coil over theflame, it just goes out."

"[Jut if you coil the thin wire tightly,it's as fast as a loose coil of thickwire,"

After much experimenting, childrenare ready to talk about the conditionsthat allow heat to be carried away.

"We predicted that the thick wirewould put out the flame first, Thisproved true. So we tried to find thebest shape for putting it out. Aloosely wound cone works best."

thin-bc1 keS

Ions

Ilvating and Cooling Problvni Card 14

Is there any difference in the ability of a rapper wire and analuminum wire to put out a flame without touching the wick?Is there any difference in the ability of a thick copper wire anda thin copper wire to put out a flame without touching the wick?

Iry Ithication IhAelltrolvol Collo. Inc All INIA% 141,erved

-thick -thin-takes ireularregular

331

Spoon Ri

The idea tand that itareas to cinside maiway in ont

tUallanullIELT,

32

heat goes into materialshe transferred from hotareas, and even storedIs, came up in a specialis,

A girl put water in a plastic spoon andheld it over the flame to see if it wouldboil. The water did not boil, but thespoon melted. The girl tried this a sec-ond time and timed the experiment, Ittook 49 seconds for the spoon to startmelting.The teacher asked:

What would happen if the spoon wereempty?

The girl held the same kind of plasticspoon in the flame. In 14 seconds theempty spoon started to melt.*

The teacher asked:

Why did it take longer with the water?"Because the heat had to go into the

water and the spoon, so the spoondidn't get hot right away."

Would anything else work, besideswater?

The girl filled a plastic spoon withmelted wax, let it cool, and then put itin the flame. It took 35 seconds for thespoon to melt.

If your students do this kind of experiment, theyshould hold the spoon over a tray to catch anyhot drops of plastic. Warn them to avoid inhalingany fumes if the plastic burns.

39

Screens

When children start to compare metalsheets and screens, there may be somediscussion about whether air and metalconduct heat equally. Since the screensconsist mainly of air spaces, they willconduct heat differently than the solidsheets will. Children should be encour-

.r;f:

41, itilitat**/..01111*-

aged to test their hypotheses by bring-ing in screens of different mesh sizes.They can also snip wires within thescreen to make larger openings withthe same thickness of wire. (The sheetsand the screens can be cut with ordi-nary scissors.)

40


How will the heat travel when you heat a 4" by 4" piece ofscreen at one corner?

Cop Yrn,ht 1471.1 by hilllA111111 Development creme, I or Aft Rights Reserved

"It goes around on the outside. It willget hot at the far corner before itgets hot in the middle."

"It goes in a zigzag. It goes downthe edges and then in toward themiddle."

34

One boy decided to see if the heatwould go along a diagonal strip ofscreening. He cut two pieces thatlooked like the following drawings.He said that the heat didn't go downeither one very well.The children find that when they ruba candle across the screen they can seethe pattern that the heat makes.

Mu a..sinlmwwsSommoU.

a malustlisIII

p1111111111111C11111111111111111111111111111111111.....iw...111111111111111111IN11111111111

41

Most children were surprised to dis-cover that they could hold their fingersover a piece of screen that was beingheated and not feel much heat.

"Maybe all the heat goes into thescreen. When I hold a candle overthe screen it doesn't melt."

Someone said he was able to hold afinger over the screen for 2 minutes.

How many layers of screening did youuse?

"Two."

Ronald cut up a screen and found thatthe flame went through the little piecesevery time he held them in the fire witha clothespin. Quite by happenstance,he cut one piece on the bias and dis-covered that pulling at the edges of thescreen opened and closed the mesh.The flame shot up through the openmesh at once. When he tried the closedmesh, the flame took longer to comethrough.

"The holes are smaller.""When it's closed there's much more

metal near the flame. I think theextra metal takes the heat awaybetter."

Next Ronald tried putting a very smallpiece of screen in the flame. The flamewent through immediately, and soonthe screen crumpled and broke in half.


Does a screen prevent the flame from going through? Does itprevent heat from going through?

CoPYright IMM by Education Development Center. Inc. All Rights Reserved

Children begin to notice that a coolscreen prevents the heat from goingthrough longer than a hot screen does.

"When the screen is hot, the flame isbigger on top, but it's not as hot ontop as when the screen isn't there."

"Maybe if it got the screen hotall around, the flame would gothrough fast."

One girl held a piece of hot screen andthen a piece of cold screen in the candleflame.

4235

"I'm trying to see if the flame will gothrough both. The first two timesthe flame did not go through eitherone at all."

Two boys made a setup as illustratedand waited until the match ignited.Then they repeated the experiment.

"It goes through faster the secondtime because the screen's hotter."

o . g . ..". "' , NA api ma an .tsuressmArer- 'I'MoossaaNalax....4Iimororor 10;92 /11/111 A NUSe...co4v.t vei I'WM=11/, 'At 4* q V,4 pimaseamv Ai A #, IN ill Inuma

4241/7" 11pf v ver.O. 4'ON tv.4 r464 .°rd 0 j N,e4.4.4 P-

or14wAVAPA*.

36

look,t almosk( smothers the

-clame,but -Eheoutjsn't

t

43

"I made a screen cage and put somematches on the top and leaned othermatches against the sides. The one ontop lit first. The side matches took along time."

An unlit match head in an open flameusually catches fire immediately, sincethe temperature, is high enough. Inorder to hold a match in a flame with-out its catching fire, you must keep theheat of the flame from reaching thehead.

"I prevented the match from burstinginto flame for about 15 seconds bywrapping the wire around thematch head."

"You can do it by putting fourscreens on top of the flame. Thematch just smoked, but it didn'tlight."


Can you hold the head of an unlit match in the tip of a flameand prevent it from bursting into flame for 15 seconds? . .. 30seconds?Try this again, using any wires and screens you wish.

Copyright a_) Iv1l, loft by Education Development Center. inc. All Rights Reserved

37

Several children in trial classes held thematch head inside a wire coil in themiddle of the flame. It took severalseconds to light this way. Others triedplacing their matches on top of a pieceof screen and holding the screen in theflame.

One boy placed the match head be-tween two layers of screening and heldthe "sandwich" in the flame. After 25seconds the match head caught fire,and the boy noticed that the candleflame went down but did not go out.

Another boy rolled a match inside apiece of copper screen. He held this inthe flame for 40 seconds before thematch head burst into flame.

A girl put a match on top of fourscreens. It took 40 seconds for thematch head to light.

Soon a contest developed to see whocould hold a match head in the flame,without the match catching fire, for thelongest time. Children wrote theirtimes on a chart drawn on the chalk-board. The times ranged from 25 to250 seconds.

One girl managed to double her timeby folding two layers of screening in

s half and in half again and placing thematch on top of the screening.

45

Expansion

Some changes that occur when an ob-ject is heated are so slight that theycannot be seen. Rods and wires expandin diameter as well as in length whenheated, and they return to their originalsize when cooled. An expansion frameis included in the HEATING AND COOL-ING Kit for students who wish to in-vestigate the amount and the rate ofchange in the length of different rods.

The expansion in diameter is too smallfor children to measure with any accu-racy. Children find it hard to see thesmall changes in the length of a rod,much less to compare the change in tworods of different metals or diameters.The expansion frame is designed to

"magnify" the effect. As a rod expands,the pointer is pushed up by a corre-spondingly larger amount. Two rodscan be compared at a time. These maybe of different materials (aluminum,copper, brass, glass) or they may be ofdifferent diameters (the aiumir.um rodsare supplied in three diameters).

Students should have time to examinethe expansion frame thoroughly, to in-sert a rod, and to move the rod back andforth so that they may see the relation-ship between the movement of the rodand the motion of the pointer. Whenthey begin to heat the rods, they willneed to use partly burned candles or totrim new ones to fit in the frame.

39


When you put a rod in the expansion frame, does it matterwhere you put the flame?Will one of the pointers shown rise higher than the others?

Copy, Ight 1471. N.: by him Atton Development Center. Inc All 141glds Reserved

40

"When the candle is in the middle,the heat travels in both directionsat once, so the ends get hotterfaster and the rod expands more ina shorter time."

If the heat has to travel the length of therod instead of just half the length, willanything happen to the heat?

"Maybe the rod would cool becausesome of the heat can escape, as ithas to go a longer distance."

Most children feel that the rods expandonly at the ends. In fact, expansionoccurs all along the rods, with thehottest part of the rods expanding themost. This is hard to determine whenusing simple equipment.It is important that children have achance to work on as many differentproblems as possible, using their ownequipment and making their ownobservations.In the Problem Card 18 experiment, chil-dren are surprised to see that the flameposition does not affect either theamount or the speed of expansion.

47

Children try many ways to make thepointer move faster using more can-dles or different heat sources or placingthe flame at different locations underthe rod. They also try blowing, fanning,and rubbing with ice cubes as coolingmethods.


Put a rod in the expansion frame and heat it. What happensto the pointer?Put a rod in the expansion frame and cool it with ice or snow.What happens to the pointer?

Copyright r< 1971. Poet by ttttt Development Center. Inc All Rights Reserved

48

41


Which will produce a greater cl\ange in the pointerheatinga thick aluminum rod or a thin one?

COpylIght lv7I. pt ul by &l, ,loon Development Center. Inc All Roghts Reserved.


Which of the 1/4" rods will produce the greatest change in the

pointer when heated aluminum, copper, brass, or glass?

Copyright 14,8 by Education Development Center. Inc All Right Reserved

42

To keep a record of the movement ofthe pointer, children tape a sheet oflined paper on the cylinder and place itnear the end of the pointer. Then theychoose an interval-15 seconds, 30 sec-onds, or 1 minute after which to markthe position of the pointer with a dot.After each selected interval, they turnthe cylinder one space and markanother dot. The result is a simplegraph of the motions of the pointerduring heating as well as duringcooling.You may want to place several of thechildren's graphs on the wall or showthem on an overhead projector to serveas the basis for a discussion. The irreg-ular pattern formed by the dots onmany of the graphs will be obvious.Why do the dots occur irregularly? Whydo students using the same kind of rodget different graphs?

"Different people kept records.""Some people used different time

intervals for marking.""The dots weren't placed carefully.""The flames all flickered differently."

49


How many inches does the pointer rise in 1 minute as youheat a rod?How many inches in 2 minutes? . . . in 3 minutes?How many inches does the pointer fall in 1 minute whenyou stop heating a rod?How many inches in 2 minutes? . . . in 3 minutes?

Copvight 6 i47i, P.h. by Educdtion Development Center, Inc All Rights Ity,ervecl.

Gt 50

.S

nioY` Int;t'fitoe

;AI 4'171 :

Iry

Children's Own Questions

Wherever HEATING AND COOLING hasbeen taught, children have become in-terested in projects that were notthought of when the unit was beingdeveloped. For some of these projects,the materials in the Kit were used; forothers, items were scrounged from theclassroom or brought from home.

The following ideas and questions werethought up by teachers and children intrial classrooms. They give some idea ofthe range of investigations that canarise from the materials and proceduresof HEATING AND COOLING when a childstarts on a project of his own or when ateacher poses a question to a group ofchildren.

Can you make popcorn, 'using thecandle flame?

"I can get a piece of popcorn to popwithout burning if I wrap a coil ofwire around it."

What makes the best popping panmetal screens or metal sheets? Whichmetal?

How about an aluminum foil bag?

Which is better, a closed popper oran open one?

Does it make a difference if you add oilbefore heating the corn? If you addwater?

Does the corn weigh the same after it'spopped?

Some children were amazed at theweight loss. When they used a coveredcontainer, they noticed droplets on thelid.

"Wax?""No, water!"

A great many uses were found for bal-loons in trial classrooms.

What happens if you put a balloon onthe end of a hollow aluminum rod?

Wrap a balloon around the middle of ahollow aluminum rod with a rubberband, and see if heat will pass throughthe hollow tube.

Some children made their own "bal-loons" from foil or paper bags. Veryelaborate arrangements were designed.

5245

Will hot air make a bag rise?

1. "The balloon got larger and thenpopped."2. "The same thing happened."3. "Same arrangement as #2 but bal-loon was not blown up all the way. Itrocked back and forth and looked as ifit started to rise, then popped."

46

"Will heat make a balloon rise?"

First attempt, no motion.

53

Ca pin

aluminumfoil

clothespin

11/Pin

I 2-11

illl

mirrorSecond attempt, no result.

candle candle

I4espinThe bag went up in flames. "It wastoo close to the flame. I need a biggeraluminum cone."

54 47

4-7

re

-Pr,-;76; -

SC:i'Lt4

48

A"-

;,, if4,

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55

4_1 A

Some of the things that the childrenheated were:

. . . buttons:"Does the weight change while

they're burning?"

. . . sinkers:"It's lead. Tomorrow we'll try to melt

the stuff that dropped off it.""It gets shiny after it hardens in the

pool of wax. It's hard to bend now,but before it was very soft."

. . . iron filings:"I tried to make a 'sparkler' with can-

dle wax sprinkled with iron filingson a copper sheet .. . no luck. Thebest results came by blowing thefilings from a sheet of metal ontoa flame."

. . . magnets:"In 2 minutes, it lost its magnetic

power. After 5 minutes 50 seconds,it came apart."

. . . quartz:

Quartz wax

4_ dOtheSpiNS

"Can you melt wax on a rock?"

56

enough

Children asked many kinds ofquestions:

"Can you take the temperature of arod with a thermometer?"

"How can you make a hotter flame,using candles?"

57

One boy made a "blowtorch," usingcandles, aluminum foil, and an aquar-ium air pump. Then he put foil over the

id!A;+

4-

blowtorch to see if the flame would geteven hotter in that it had to go througha smaller hole.

IM:1.

5S

"Will heat travel through wire to arod and melt a wax drop?"

Does wire expand?"I heated a coil of copper wire. It

expands and unbends. I think ifI heated aluminum wire, it wouldspread out more, because in theexpansion frames aluminum ex-pands more than copper."

"Will heat travel through a rod andthrough a wire to light a match?"

6053

Can you get a candle to relight, afteryou've blown it out?

"If you blow out a candle and holdthe lighted match in the smoke abovethe candle, the flame travels down thesmoke, and the candle lights again.Will it work through a long tube?"

1:9h-gt(*))SITO

-tube,

burned -ou-Ecandie

"Trying to light the smoke, it sparkedalmost every time," said Chris.

6?

Smoke --*

"If you hold the edge of the screen ina flame, the flame seems to be goingthrough the screen, and then the toppart of the flame appears to becomedetached, float in air, and disappearinto smoke."

56

Can you keep a flame going in a closedcontainer?

One boy who tried to do this by pump-ing oxygen into the container said thathe failed because he couldn't keep theoxygen coming fast enough.

Does heating things change theirweight? Does cooling them changetheir weight?

"Does a steel ball weigh more whenhot or cold?"

stm_( balls witkwive a-Racheckto nick in theend of thebalance

holdingIce ov) 3,

S mall-tray

1. Balanced2. Hold ice against itno change inweight3. Heat ball with candleno changein weight

What happens when you heat alumi-num foil on a balance?

aluminunl-Fo.1

CO( ridevOS-tobalance unevenbeam Ipefore,

"Heat makes the balance beam rockback and forth."

64

57

Can you make new candles out of left-over wax?

Some children get involved in candlemaking, and they try molding candlesas well as dipping them. One boy madea candle at home. It was huge, made ofa pound of paraffin and five stringwicks. It produced quite a blaze,

"Can you get heat to go down a reallylong rod?"

paipMaiMPIrs,,

.Sr

58

These boys found a piece of pipe at thedump. They heated it for half an hourand were surprised that the heat wentonly a little way down it.

"*.e.11111

65

document resume author seager, doug: and others ...ages and seim: ling children in fifth through...

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