IJSO 2007 THEORY Problems Final

8/10/2019 IJSO 2007 THEORY Problems Final

1/14

Read carefully the following instructions:

1. The time available is 3 hours.

2. The total number of the problems is 3. Check that you have a complete

set of the test problems and the answer sheets.

3. Use only the pen provided.

4. Write down your name code country and si!nature in the first pa!e of

your answer sheet. Write down your name and code in the other pa!es

of your answer sheet.

". #ead carefully each problem and write the correct answer in the

answer sheet.

$. %ll competitors are not allowed to brin! any stationary and tools

provided from outside. %fter completin! your answers all of the

&uestion and answer sheets should be put neatly on your desk.

'. (oint rules) %ccordin! with each &uestion markin!.

T*i

4thINTERNATIONAL JUNIOR SCIENCE OLYMPIADTHEORETICAL COMPETITION

December 6, 2007


2/14

EXAMINATION RULES

1. %ll competitors must be present at the front of e+amination room ten minutes before

the e+amination starts.

2. ,o competitors are allowed to brin! any tools e+cept his-her personal medicine or

any personal medical e&uipment.

3. ach competitor has to sit accordin! to his or her desi!nated desk.

4. /efore the e+amination starts each competitor has to check the stationary and any

tools 0pen ruler calculator provided by the or!anier.

". ach competitor has to check the &uestion and answer sheets. #aise your hand if

you find any missin! sheets. tart after the bell.

$. urin! the e+amination competitors are not allowed to leave the e+amination room

e+cept for emer!ency case and for that the e+amination supervisor will accompany

them.

'. The competitors are not allowed to bother other competitor and disturb the

e+amination. 5n case any assistance is needed a competitor may raise his-her hand

and the nearest supervisor will come to help.

6. There will be no &uestion or discussion about the e+amination problems. The

competitor must stay at their desk until the time allocated for the e+amination is

over althou!h he-she has finished the e+amination earlier or does not want to

continue workin!.

7. %t the end of the e+amination time there will be a si!nal 0the rin!in! of a bell. 8ou

are not allowed to write anythin! on the answer sheet after the allocated time is

over. %ll competitors must leave the room &uietly. The &uestion and answer sheets

must be put neatly on your desk.

T*ii

4thINTERNATIONAL JUNIOR SCIENCE OLYMPIADTHEORETICAL COMPETITION

December 6, 2007


3/14

ro!le" I #orces in #luid

When an ob9ect moves throu!h a fluid in addition to the buoyant force it also e+periences a force

due to the resistance of the fluid. This force is known as the dra! force F. 5t is known that for ob9ects

movin! with low velocities Fis proportional to the velocity v of the ob9ectrelative to the fluid and

the linear sieR of the ob9ect 0if the ob9ect is a sphereRis the radius of the sphere. Therefore we can

writeF: CvR where Cis a constant that depends on properties of fluids and the !eometry of the

ob9ect. Usin! this fact and assumin! the velocities involved in below are low answer the followin!

&uestions.

I$% &%'( )oint*

What is the unit of C; 0in terms of 5 units) k! s m.

I$+ &%', )oints*

1=*$ m falls in air at 2=?C. The

numerical value of Cfor this particle in the air at 2=?C is 3.4>1= *40in 5 units. The density of the

particle is 2.=>1=3k!@m*3. uppose that the particle can move indefinitely without bein! blocked

by the surface of the earth. The fallin! particle will soon move with a fi+ed velocity known as the

terminal speed. 5f the acceleration due to !ravitygis fi+ed at the value 7.6 m@s *2and the density of the

air is 1.2 k!@m*3 find the terminal speed of the dust particle.

I$- &%'( )oint*

%s shown schematically in 1=3k!@m*3in the water with density 1.=>1=3k!@m*3. uppose that the centripetal acceleration can

be considered as a constant and is 1="timesg.


4/14

T*iv


5/14

I$. &+', )oints*

1=*2'k!. Aere we assume that the protein molecule can be re!arded as a sphere

with radiusR: 2.">1=*$m and the numerical value of Cfor this protein in water is 4.=>1= *"0in 5

units. 0"int) Consider the centripetal force is actin! as a stron! !ravitational force.

I$,

5n different pA environment each protein may carry different net char!e. This is demonstrated in


6/14

T*vi

,et char!e of a protein=

nvironmental pA

5soelectric point


7/14

ro!le" II 0he"istry of0ar!on dio2ide

Carbon dio+ide 0CD2 is involved in several important biolo!ical and environmental processes.

CD2is used in photosynthesis to make !lucose 0C$A12D$ and D20!. The ener!y re&uired to produce 1

mol of !lucose is 26== kE. 5t is estimated that the net avera!e amount of CD 2fi+ed by photosynthesis

on the landmass of the arth is 3'= ! per s&uare meter per year. %ll carbon atoms produced are

converted into !lucose. CD2is also the final o+idation product of all carbon*based fuelsF its increase in

the atmosphere is causin! !lobal warmin!. The metabolism of !lucose yields CD 20gand A2D0las the

final products. Aeat released in the process is converted to useful work with about '=G efficiency. The

e+cess CD2produced by the metabolic processes in a human body is e+haled. The e+pired air normally

contains 3=.= mmA! 05 unit) 1 atm : '$= mm A!1 mm A! : 133.3 (a of CD2at 3'C. % simple

test for CD2 in the breath is carried out by blowin! the e+pired air into a limewater 0a saturated

solution of Ca0DA20s to turn it milky. % very useful property of CD2 is its ability to react with

potassium supero+ide 0HD20s to !enerate D20! which can be used in o+y!en masks. /ased on the

above information answer the followin! &uestions. 0molar mass 0!Imol *1) A : 1 C : 12 D : 1$F !as

constant # : 6.314 EImol*1IH*10or =.=62 BIatmImol*1IH*1F !ravitational acceleration ! : 7.6 mIs *2

II$% &('3 )oint*

Write down the balanced chemical e&uation for the photosynthesis of !lucose from CD2and A2D.

II$+ &+'+ )oints*

The sun supplies about 1.= kE of ener!y per second per s&uare meter of land on the arthJs surface.

What percenta!e of this ener!y is used to produce !lucose;

II$- &%'3 )oints*

Calculate the mass of !lucose metabolied by a $= k! person in climbin! a mountain with an

elevation !ain of 1=== m. %ssume that the ener!y consumed in the climbin! is five times of the

mechanical ener!y re&uired for liftin! a $= k! ob9ect by 1=== m and the ener!y is supplied solely from

the metabolism of !lucose.

II$. &('4 )oint*

Write down the balanced chemical e&uation for the reaction of HD20sand CD20!to form H2CD30sand

D20!.

T*vii

Theoretical Competition, 4thIJSO, Taipei, Taiwan, December 6, 2!


8/14

II$, &%'3 )oints*


9/14

ro!le" III

III$% lant hysiology

% student added 2= cm3of " mK HACD3solution and " drops of universal pA indicator into a

2"= cm3conical flask 0


10/14

III$%$A

Ae placed the flask 3= cm from a $= W tun!sten lamp and turned on the lamp for 3 hours. urin!the 3 hours he found the pA value of the solution in the flask a . The reason is that the leaves

lar!ely carried out the process of b which consumed c and caused the concentration of ions of

d and e in the solution to have f .

III$%$/

Ae turned off the lamp and left the flask in the dark for 3 hours. urin! the 3 hours he found the

pA value of the solution in the flask a . The reason is that the leaves underwent the process of b

which released c and caused the concentration of ions of d and e in the solution to have f .

III$%$0

Ae chan!ed the solution of HACD3to 2= cm3of "mK ,aDA replaced the leaves with fresh ones

resealed the flask and then turned on the lamp for 3 hours. urin! the 3 hours he found that first the

process of aMM in leaves decreased and then the process of b in leaves decreased.

T*+

Theoretical Competition, 4thIJSO, Taipei, Taiwan, December 6, 2!


11/14

III$+ 6o"eostasis of !lood sugar

The term homeostasis refers to the maintenance of the human body at relatively constant

conditions. %n e+ample of homeostasis is the concentration of the blood su!ar 0mainly the blood

!lucose which is re!ulated within a narrow ran!e by hormones. Kr. Chen took the blood su!ar test

by followin! the procedures) Ae first had thesupper with his re!ular hospital meal at $)== pm and

fasted and rela+ed afterwards till the ne+t breakfast at 6)== am 5mmediately after his supper blood

samples for su!ar concentration tests were taken and e+amined at every hour for 6 hours. The results

are shown in


12/14

e. blood su!ar e+creted into urine

III$+$A &('- )oint*

Which one of the statements in Table 555*3 e+plains why the blood su!ar concentration of Kr.

Chen increased durin! the phase 1 after the supper;

III$+$/

III$+$/$a0('- )oint*

Which statement in Table 555*3 e+plains the decreasin! trend in Kr. ChenJs blood su!ar

concentration durin! the phase 2;

III$+$/$!0('- )oint*

Which one of the hormones in Table 555*2 controls this phenomenon shown in phase 2;

III$+$00('- )oint*

Which one of the followin! fi!ures would best capture the chan!e of blood su!ar concentration in

Kr. ChenJs body durin! the $ hours after phase 3 i.e. the period durin! 6N14 hours after supper;0The followin! fi!ures have the same scales as that in


13/14

III$+$7

III$+$7$a 0('- )oint*Which one of the hormones in Table 555*2 is the most possible candidate to re!ulate the blood

su!ar concentration of Kr. Chen after phase 3 0as described in &uestion 555*2*C;

III$+$7$!0('- )oint*

Which one of the statements in Table 555*3 is related to blood su!ar concentration present after

phase 3 0as described in &uestion 555*2*C;

III$+$E 0('4 )oint*

Kr. Wan! is a mild diabetic patient. Ae also has his suppers with the hospital re!ular meal at $)==

pm and fasts afterwards for blood test. (lease predict the chan!e of blood su!ar concentration of Kr.

Wan! durin! 6 hours period after supper.


14/14

III$-ests in the rice field

Documents

IJSO 2007 THEORY Problems Final