ijso question paper 2007 (experimental)

8/13/2019 IJSO Question Paper 2007 (Experimental)

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4thInternational Junior

Science Olympiad

Practical Examination

December 08, 2007


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Important emar!"

1. While you are in the laboratory, you should wear safety spectacles at all times.

2. Eating of any kind of food is strictly prohibited in the laboratory. If necessary you may ask

Lab Assistant and take a snack break nearby the laboratory.

. !he safety showers are located inside the bathroom on both side of the stage.

". #articipants are e$pected to work safely, to beha%e socially and to keep e&uipment and work

en%ironment clean. When carrying out discussions with your teammates, keep your %oice

low.

'. (o not lea%e the e$amination laboratory until you ha%e permission to do so. Ask LabAssistant if you need to use the bathroom.

#$ %or! may only be&in 'hen the "tart "i&nal i" &i(en$

). *ou ha%e 4$) hour" +including e$tra min reading time- to complete the e$perimental task,

and record your results on the answer sheets. !here will be a prewarning minutes before

the end of your time. *ou must stop your work immediately after the stop command is gi%en.

A delay in doing this by ' minutes will lead to /ero points for the task.

0. e sure that your team has a complete set of the e$perimental e$amination + copies- and the

answer sheets +" copies-. Only one copy *li&ht yello' paper+ o the an"'er "heet" "hould

be "ubmitted or mar!in&$

-$ ."e only the pen and calculator pro(ided$

1. !eam code and student codes must be written on e%ery page of the final answer sheets. Each

team member mu"t "i&n on the ront pa&e o the inal an"'er "heet"$

11. All results must be written in the designated bo$es on the answer sheets. (ata written

elsewhere will not be graded.

12. After completing the task, put all the e&uipments back to its original place and discard all

solutions in the beaker labeled Waste3.

1. /ter the "top command i" &i(en, put O1 the inal an"'er "heet" *one copy+ on top o

the en(elope on the de"!$ %ait or the 1ab /""i"tant to chec! and collect it$ ou can

ta!e the other paper" 'ith you$

2


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/$ Introduction

Energy is essential in our e%eryday life. Electricity is one of the forms of energy that is

easily obtained in modern society. !o produce and con%ert electricity efficiently is one of the

most important issues in the 21stcentury. In this task, you will construct a chemical battery, find

out how electrolytes affect the current, and assess how well +or poorly- natural products conduct

electricity. Electricity can be utili/ed to promote light, heat, and chemical reactions. *ou will

connect commercial batteries to a system to initiate electrolysis and initiate a chemical process.

4eat is an unwanted byproduct upon the con%ersion of electricity to light. *ou will determine

the temperature of an incandescent lamp.

3$ Obecti(e" *5hey are not nece""arily to be "ol(ed in "e6uence$+

I. !o study the characteristics of a fruit battery and to determine the factors that influence the

efficiency of the fruit battery.

II. !o obser%e the starch particles in potato and to determine how chemical reagents affect them.

III. !o assess the relationship between the concentration of an electrolyte and the conducti%ity of

an electrolysis cell. !o determine the concentration of an electrolyte solution from the

concentrationconducti%ity relationship and by acidbase titration.

I5. !o in%estigate the thermal and energy transfer properties of the tungsten filament in an

incandescent lamp.


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$ /pparatu" and aterial"

Part I9 :ruit 3attery

aterial" ;uantity aterial" ;uantity

Lime 6 #etridish 7ultimeter +in common

basket-1 8uler +in common

basket-

1

9onnecting wire 6 :cissor 1

7etal plate 1 set +A, , 9, (- inder clips 6

LE( de%ice 1 ;nife +


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/pparatu" ;uantity /pparatu" ;uantity

7ultimeter +in common basket- 1 urette holder and rack 1

9onnecting wire " urette ' mL 1

attery set +5, for this #artonly- 1


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Part I=9 Ener&y 5ran"er /""ociated 'ith an Incande"cent 1amp9

/pparatu" ;uantity Photo >

attery set +65, for this #art only- 1 #hoto I51

Light ulb 1 #hoto I528esistors D #hoto I5

9onnecting wire 6 #hoto I5"

!hermometer +fi$ed on the partition. 8eadonly, dont touch-

1 #hoto I5'

7ultimeter +in common basket- 2

#hoto I51. attery setF !he %oltage is 6 5. !here are two leads, positi%e and negati%e,

colored red and black, respecti%ely. !he battery set will

be represented by the circuit symbol .

#hoto I52. Incandescent light bulb set. !his light bulb set has two

leads for connection. !he light bulb set will be represented by the circuit

symbol .

#hoto I5. 8esistors. Each is labeled with power

rating +1W-, 8esistance +G ),and !ype +H-.!he

resistorwill be represented by the circuit symbol

.

6


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#hoto I5". 9onnecting wires. !wo types of

wires are pro%idedF alligator alligator and

alligatorbanana.

#hoto I5'. !hermometerF !he thermometer shows 9elsius reading. If


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%ire connection and dial "ettin& or u"in& ultimeter

ea"ure =olta&e9

ea"ure current9 !here are three ranges setting for measuring current. In #art I and III you

will use mA and A ranges. !he wire connection is the same for both mA and A range

measurements, but the dial should turn to the appropriate place.

0


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In #art I5, you ha%e to use 2 A setting for measuring current. Incorrect dial "ettin& and

'irin& o multimeter 'ill cau"e dama&e" and no point" 'ill be &i(en$

ea"ure e"i"tance9 hmmeter can only be used in the open circuit condition.

D


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D$ Experiment" and ;ue"tion"

Part I9 :ruit 3attery

atteries contain two electrodes which typically consist of different kinds of metals, and are

filled with electrolyte to produce electricity from the chemical reactions between the electrodes

and the electrolyte. Instead of chemical batteries, fruits can also be utili/ed to generate

electricity.


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2. Kse metal as the positi%e electrode +- and metal A, 9 and ( as the negati%e electrode +-

in different setups, measure the %oltage generated by these fruit batteries. Wire connections

are shown in


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;ue"tion I?29 (etermine how different %ariables affect the fruit battery

Procedure"9

1. Kse metal as the positi%e electrode +- and metal 9 as the negati%e electrode +- to

assemble the fruit battery.

2. 8ead Juestion I2a and I2b before proceeding with the e$periment.

. (esign your own e$periment to answer the &uestion I2a and I2b.

."e ABto repre"ent increa"e, AC to repre"ent decrea"e, and A or no chan&e *le"" than

20F+ in an"'erin& ;ue"tion" I?2?a and I?2?b$

I?2?a. (ecrease the contact area +at least times- between the metals and the fruit and obser%e

the %oltage +5- and current +A- generated by this battery.

I?2?b$ Increase the thickness of the lime slice +at least times- and obser%e the %oltage +5- and

current +A- generated by this battery.

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;ue"tion I?G$ ased on the characteristics of fruit battery, design the simplest de%ice to light up

the LE( de%ice and answer the following &uestionsF

Hint"9 A lightemitting diode +LE(- is a semiconductorde%ice that emits narrowspectrum

lightwhen it is dri%en electricallybiasedin the forward direction of thepn unction. !his effect

is called electroluminescence. 9urrent flows easily from the pside +- to the nside +- of LE(,

but not in the reverse direction. The electroluminescence will not occur otherwise.

%rite do'n your 1ED de(ice number on your an"'er "heet

Set up your o'n experiment" to "ol(e the ollo'in& problem"

I?G?a$ If a single positi%e and negati%e electrodes is used to create the battery unit, how manyunits are re&uired +the minimum number- to light up the LE( de%iceM

I?G?b$ Identify the metals chosen for the positi%e and negati%e electrodes.

I?G?c$ What is the color of the LE( luminescenceM +Abbre%iationF red +8-, green +B-, blue +-,

white +W--

%hen the 1ED lumine"ce", rai"e your hand to inorm the 1ab /""i"tant, 'ho 'ill conirm

your an"'er and "i&n o on your an"'er "heet$

1
http://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Voltage_biashttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Electroluminescencehttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Voltage_biashttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Electroluminescence


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Part II9 Starch


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."in& a bri&ht ield micro"cope

7ount the specimen on the stage

!urn on the light, optimi/e the lighting

Adust the iris diaphragm.

!hink about what you are looking for


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;ue"tion II?@9 !o obser%e the structure of starch granules in potato

Procedure"9

1. Kse the knife to cut the potato and scrapesome potato uice +e$tract- on the slide.

2. Add one drop of 1> iodine solution on the potato uice. 7i$ them well to stain starch

granules as shown in


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II?2?a$After adding the reagent A, the potato starch granules were

+A- unchanged +- swollen only +9- swollen to lyse +(- shrinked

II?2?b$After adding the reagent , the potato starch granules were


II?2?c$Afteradding the reagent 9, the potato granules were


10


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Part III9 onducti(ity o an Electrolyte Solution

7etals are good conductors. :ome compounds are also good conductors while dissol%ed in

water, such as sulfuric acid, sodium hydro$ide, and nitric acid. We name this type of molecules

electrolytes3. A&ueous solution of sucrose or alcohol do not conduct electricity, therefore, they

are not electrolytes. It is clear that the physical properties of the molecules determine the

conducti%ity of their a&ueous solutions. In this e$periment we shall determine the effect of

concentration on the conducti%ities of a gi%en electrolyte. !he conducti%ity of a solution is

proportion to the current at constant %oltage. In this e$periment we measure the current to

denote the conducti%ity.

!here are three parts in this e$periment. In III1, sodium hydro$ide solutions were utili/ed

to test the effect of concentration on the conducti%ity of these solutions. *ou need to plot the

results and figure out the relationship between conducti%ity and the concentration of theelectrolyte. In III2, a sodium hydro$ide solution of unknown concentration will be gi%en, and

you ha%e to measure the conducti%ity and figure out the concentration by interpolating from the

data in the correct figure you plotted in III1. In III, the con%entional titration method will be

used to determine the concentration of the same unknown sodium hydro$ide solution.

;ue"tion III?@9 5he relation"hip bet'een "odium hydroxide "olution concentration and

conducti(ity

Procedure"9 ecord all your data on the an"'er "heet"

1. Kse the .' mol?L1@a4+a&-solution pro%ided and the graduated cylinder to prepare '.

mL of each of .', .2', .12, and .6 mol?L1of @a4+a&-solutions. !ransfer the solutions

into 1 mL beakers for later use.

2.


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. 7easure out '. mL of .6 mol?L1@a4+a&-solutions and pour into the plastic bo$. !he

solution should not reach the alligator clamps. 7ake sure all connections are correct then

switch the battery bo$ to the on3 position and start counting time. 8ecord the current

reading at seconds after switch on.

III?@?a9 8ecord your data in the appropriate place.

". 8epeat step with other @a4+a&-solutions and record the data.

III?@?b9 #lot +a- concentration +in molL-1- %.s. s&uare root of current +in mA -,

+b- s&uare root of concentration +in 1Lmol - %.s. current +in mA-, and

+c- s&uare root of concentration +in 1Lmol - %.s. current s&uare +in +mA-2- on

graph papers in the answer sheets.

III?@?c9 Which of the plots in III?@?bis the best appro$imation of a straight lineM

;ue"tion III?29 Determine the concentration o a aOH*a6+"olution by u"in& conducti(ity

mea"urement"

Procedure"9

1. 7easure out '. mL of @a4+a&-solution with unknown concentration, and pour into plastic

bo$.

2. #erform the measuring procedures.

III?2?a98ecord the current measured.

III?2?b9 Kse the graph you decided to be the best straight line in III?@?b to determine the

concentration of the @a4+a&-solution by using interpolation.

2


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. After completed all the current measurements, rinse the #t electrodes and put them back in

their bag. 8eturn it to the #art III basket.

;ue"tion III?G9 Determine the concentration o a aOH*a6+"olution by u"in& acid?ba"e

titration

Procedure"9

1. !ake ' mL of .2' mol?L

1

49l solution into a test tube. Add a few drops of the indicator andkeep it for titration endpoint comparison.

2. !ake ' mL of .' mol?L1@a4 solution into a test tube. Add a few drops of the indicatorand keep it for titration endpoint comparison.

. #our 49l solution into the burette.

". 7easure 2. mL of the unknown concentration of @a4 solution into a 12' mL Erlenmeyerflask and add a few drops of indicator.

'. Kse 49l solution to titrate.

III?G?a9 ecord the (olume u"ed$

6. 8epeat steps " and ' as many times as necessary, and calculate the a%erage %olume.

III?G?b9 9alculate the concentration of the gi%en @a4+a&-solution.

21


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Part I=9 Ener&y 5ran"er /""ociated 'ith Incande"cent 1amp

!he conducti%ity +or resistance- of a material will not only %ary with the carrier

concentration but also %ary with temperature. 7aterials with properties such as %olume, color,

resistance that %ary with temperature may be used as temperature indicator. !he temperature

scales are different in %arious professional communities. !he most commonly used temperature

scales are 9elsius and ;el%in as listed in !able I51.

!able I51F !wo commonly used temperature scales.

@ame :ymbol Knit 8elationship

9elsius 9

! 9CC

TT =

;el%in ! ; 2)+= CTT

22


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;el%in is commonly used in scientific data recording and analysis.


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I=?@$ 8ead the room temperature from the thermometer. 8ecord your data in 9elsius. What is

the room temperature in ;el%inM

I=?2$ Kse the multimeter to measure the room temperature resistance of the tungsten filament

in the light bulb.

!he circuit symbol used in this part is gi%en in the !able I52

!able I52F 9ircuit symbols.

(e%ice Light bulb attery 8esistor Amperemeter

5olt

meter

:ymbol

9onnect the battery bo$ +6 5-, the light bulb, and the largest resistor as illustrated in the circuit

diagram of


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I=?G$ *ou may change the resistor to %ary the %oltage and current of the light bulb. A data

point without a resistor +/ero resistance- should be recorded. At least 1 data points are

re&uired. Write the data set +I, V- in the answer sheet. a!e "ure you record and

calculate e(ery data to t'o di&it" ater the decimal point$

I=?4$


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!he tungsten filament can transfer its energy to the en%ironment through three channels.

!hey are conduction, con%ection, and radiation. !he powers of energy transfer are the

conduction power, CDP , con%ection power, CVP , and radiation power, RDP , respecti%ely.

!wo of the energy transfer channels, the conduction and con%ection, are mediated through

matters, and their total power is proportional to the temperature difference, -+ eTTT = ,

between the filament temperature +T - and en%ironment temperature + eT -. While the energy

transfer %ia radiation can propagate through %acuum without any medium. !he energy radiation

rate is proportional to the power law T of the filament temperature +T -, and is larger than 1.

!herefore, the total power transfer from the hot filament to the en%ironment may be modeled as

TTPtot

+= . Where and are positi%e constants.

I=?8$ Analy/e your data, and determine the %alue of . (raw necessary cur%es in the plot, and

write down the answers and formulae used in the corresponding blanks.

ijso question paper 2007 (experimental)

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