Question bank IMSO Science

22nd International Mathematics and Science Olympiad (IMSO)
Group and Individual Experiment Test · Kedah, Malaysia · 07 October 2025

Instructions:


1\. Do not turnover this page until you are told to do so.

2\. Write your ID Number and Seat Number on each space provided in the answer sheet.

3\. Write your answer only on the separate answer sheet. There are 6 pages in the answer sheet.

4\. Follow all the instructions carefully.

5\. There are two experiments in this test. Make sure to answer BOTH papers to get full points.

6\. For the group experiment: ONLY the procedure of the experiment is done by group. The paper must be answered individually.

7\. Complete all the sections in English. There are Section I, II and III for the Group Experiment and Section I, II, and III for the individual experiment.

8\. The marks awarded for each section or question is shown in brackets, [ ].

9\. There are 6 printed pages in this booklet, excluding this cover page.

10\. You have 120 minutes to complete this test.

Editorial scoring note: The source does not print a total score. Only three group data tables show [1 mark] each. This study package assigns 20 editorial points to each experiment (40 editorial points overall); these are not official totals. Printed marks are retained below. Both experiments share the printed 120 minutes; the individual activity additionally has a printed 45-minute limit. No candidate information or measured results is supplied.

INDIVIDUAL EXPERIMENT · Why do Ships Float?

Objectives


1\. To demonstrate that average density (mass ÷ volume) determines flotation, not just the material’s density.

2\. To compare the flotation behavior of two equal-mass clay models

3\. To apply Archimedes’ Principle to explain why large ships float even though they are made of heavy materials like steel.

Materials

A. modelling clay
B. 250mL beaker
C. 500mL water

Procedure

NOTE: You are given forty-five (45) minutes to accomplish this experiment, after this you will be directed to work on your group experiment.


1\. Make two (2) equal mass models from clay.
a. Model A should be a compact clay ball or block.
b. Model B should shape the same mass of clay into a boat-like hull. Ensure there are no holes.

2\. Fill the beaker with water until the 150 mL line. Submerge each model fully (without touching sides). Record displaced volume by subtracting initial level from final level.

3\. Place Model A and B gently into a beaker of water.

4\. Observe which model floats or sinks.

5\. Do 3 trials each for Model A and B.

6\. Compute for the Average Density.

Average Density = Mass ÷ Displaced Volume.

Section I. Data Table

Table 1. ________________________________________

| Trial for Model A | Mass (g) | Displaced volume (cm³) | Average density (g/cm³) |
| --- | --- | --- | --- |
| 1 | 20.0 | | |
| 2 | 20.0 | | |
| 3 | 20.0 | | |

Table 2. ________________________________________

| Trial for Model B | Mass (g) | Displaced volume (cm³) | Average density (g/cm³) |
| --- | --- | --- | --- |
| 1 | 20.0 | | |
| 2 | 20.0 | | |
| 3 | 20.0 | | |

Table 3. ________________________________________

| Model | Observation after submerging the model |
| --- | --- |
| A | |
| B | |

Section II. Graph

Plot a graph comparing the average densities of Model A and Model B. Then, Draw a horizontal line at 1 g/cm³ (density of water) to show which objects float (below line) and sink (above line).



Section III. Guide Questions


1\. A steel block sinks in water, but a steel ship with the same mass of steel floats. Explain why.

2\. Define average density and explain its relation to flotation.

3\. In this experiment, why did the hollow model float while the solid model sank? Use Archimedes’ Principle.

4\. Identify two possible sources of error and suggest one improvement.

5\. A loaded ship sinks deeper into water compared to when it is empty. Why does this happen, and when will it eventually sink?

6\. Using your graph, predict whether a new clay model with average density 0.9 g/cm³ will float or sink. Explain.

THIS IS NOT YET THE END OF YOUR EXPERIMENT TEST. TURN TO PAGE 4 FOR THE GROUP EXPERIMENT.

22nd International Mathematics and Science Olympiad (IMSO)
Group and Individual Experiment Test · Kedah, Malaysia · 07 October 2025

Instructions:


1\. Do not turnover this page until you are told to do so.

2\. Write your ID Number and Seat Number on each space provided in the answer sheet.

3\. Write your answer only on the separate answer sheet. There are 6 pages in the answer sheet.

4\. Follow all the instructions carefully.

5\. There are two experiments in this test. Make sure to answer BOTH papers to get full points.

6\. For the group experiment: ONLY the procedure of the experiment is done by group. The paper must be answered individually.

7\. Complete all the sections in English. There are Section I, II and III for the Group Experiment and Section I, II, and III for the individual experiment.

8\. The marks awarded for each section or question is shown in brackets, [ ].

9\. There are 6 printed pages in this booklet, excluding this cover page.

10\. You have 120 minutes to complete this test.

Editorial scoring note: The source does not print a total score. Only three group data tables show [1 mark] each. This study package assigns 20 editorial points to each experiment (40 editorial points overall); these are not official totals. Printed marks are retained below. Both experiments share the printed 120 minutes; the individual activity additionally has a printed 45-minute limit. No candidate information or measured results is supplied.

GROUP EXPERIMENT · How Enzymes Make Reactions Faster

Objective

This experiment aims to test how different amounts of yeast affect the speed of balloon inflation when hydrogen peroxide breaks down and to connect this reaction to real-life applications.

Materials

A. A cup of 360mL of 3% hydrogen peroxide
B. A packet of active dry yeast
C. Warm water
D. Three identical clear plastic bottles
E. Three balloons
F. 10 mL graduated cylinder
G. ruler (in cm), stopwatch, marker, small cups

Procedure

By Group:

Note 1: The warm water will be distributed to your group by the invigilators.


1\. Using the bottles you used in the first experiment, label the bottles as A, B, and C. Then, pour 120 mL of hydrogen peroxide into each bottle.

2\. Label the small cups as A, B, and C. In the three small cups, prepare the yeast mixtures. Stir each cup 5–10 seconds.

| Cup | Content of the cup |
| --- | --- |
| A | 10 mL warm water |
| B | ¼ tsp yeast + 10 mL warm water |
| C | 1 tsp yeast + 10 mL warm water |


3\. Quickly pour the content of cup A into bottle A, immediately stretch the balloon over the mouth of the bottle and start the stopwatch. Record height at 0, 1, 2, 3, 4, 5, 6 min. Record everything on the data sheet.

Note 2: Measure balloon height from the bottle mouth to the highest point of the balloon (cm).


4\. Repeat for Cup B and C.

Individually:


5\. Draw a line graph of your result.

6\. Compute for the initial rate for each condition using the first two minutes.

Initial rate = (height at 2 min − height at 0 min) ÷ 2

Section I. Data Table

Table 1. ________________________________________

| Time (min) | Bottle A (cm) | Bottle B (cm) | Bottle C (cm) |
| --- | --- | --- | --- |
| 0 | | | |
| 1 | | | |
| 2 | | | |
| 3 | | | |
| 4 | | | |
| 5 | | | |
| 6 | | | |

[1 mark]

Table 2. ________________________________________

| Time (min) | Observation after 5 minutes |
| --- | --- |
| A | |
| B | |
| C | |

[1 mark]

Table 3. ________________________________________

| Time (min) | Height at 2 min | Height at 0 min | Initial Rate |
| --- | --- | --- | --- |
| A | | | |
| B | | | |
| C | | | |

[1 mark]

Section II. Graph

Graph your results on the answer sheet.



Section III. Guide Questions


1\. Which bottle acted as the control?

2\. Using the initial rate, which balloon inflated fastest?

3\. Which reached the highest final height at 6 min?

4\. By what percent did the fastest initial rate exceed the Control? Assume that the initial rate of the control is 0.7.

5\. Based on this experiment and your knowledge of biological catalysts, provide a detailed scientific explanation for your observations during the experiment.

6\. Identify two (2) possible sources of error for this experiment.

7\. Why do our bodies need the enzyme catalase, and what might happen if we did not have it?

8\. When doctors use hydrogen peroxide to clean small wounds, why do bubbles appear?

9\. Yeast is also used in bread-making. How is the gas released in bread different from the gas produced in this experiment?

--- END OF EXPERIMENT TEST ---

Original source text (the exact panel preserves diagram labels, tables and choices):

The spotted lanternfly (SLF) is an invasive species native to Asia that has become
a threatening pest in the United States. The SLF harms plants by using its piercing
mouthpart to suck sap from stems and branches, which weakens the plants and
can lead to their death. A major problem is that the SLF has no natural predators
in the U.S. and secretes a sticky substance that attracts other insects and causes
mold growth on plants. The SLF's preferred host is the invasive Tree of Heaven.
Both the SLF and the Tree of Heaven are invasive species that were separately
introduced to the United States. This relationship, is an example of what kind of
ecological interaction?





Source: https://k-5impactnewsg4-5.mheducation.com/2025/03/17/
spotted-lanternfly-natures-most-wanted/

A. Commensalism, because one species benefits while the other is unaffected.
B. Symbiosis, because the two species live closely together.
C. Parasitism, because the SLF benefits at the expense of its host.
D. Mutualism, because both organisms benefit from the relationship.

Original source text (the exact panel preserves diagram labels, tables and choices):

The diagram shows a person’s body temperature over a period of time. During
which period would the blood vessels supplying blood to the skin become dilated
to cool down the body?

Original source text (the exact panel preserves diagram labels, tables and choices):

Tardigrades are microscopic invertebrates with a real-life superpower. The
tardigrade's ability to survive extreme temperatures, from freezing cold to boiling
hot, is primarily due to a state of dormancy called "cryptobiosis". In this state, the
tardigrade expels nearly all the water from its body. What is the main scientific
reason that removing water is a crucial step for surviving freezing temperatures?





Source: https://k-5impactnewsg4-5.mheducation.com/2025/02/14/
tardigrades-the-tiny-invertebrates-with-a-real-life-superpower/

A. The tardigrade's body can produce a special antifreeze protein that works best
in a water-free environment.
B. Removing water lowers the tardigrade's core temperature, which helps it to
endure the cold.
C. Water is a good conductor of heat, so its absence insulates the tardigrade from
the cold.
D. The removal of water prevents the formation of sharp ice crystals, which would
otherwise rupture and destroy the tardigrade's cell membranes.

Original source text (the exact panel preserves diagram labels, tables and choices):

Leech therapy is a traditional treatment that uses live medicinal leeches to treat
diseases. The leeches’ saliva contains anticoagulants, anti-inflammatories, and
anaesthetic substances. By sucking blood, the leeches inject this saliva into the
patient’s body, which may improve blood flow, reduce pain and inflammation, and
promote healing. It is used for conditions such as arthritis, varicose veins,
cardiovascular diseases, and skin disorders.

Why does bleeding often continue for some time after the leech is removed?
A. Leeches secrete a specific toxin that reduces the blood’s ability to clot.
B. Leech saliva contains an anticoagulant substance called hirudin, which
prevents blood clotting.
C. Leeches rupture blood vessels, and the body does not have enough time to
repair them.
D. Leeches introduce bacteria into the body that disrupt the blood clotting process.

Original source text (the exact panel preserves diagram labels, tables and choices):

Kwashiorkor is a disease caused by nutrient deficiency. Symptoms include swelling
in the abdomen and legs, changes in skin and hair, poor growth, and muscle
weakness. It can be treated by eating foods such as meat, dairy, or soy.

A deficiency of which MAJOR nutrient leads to kwashiorkor?
A. Protein
B. Carbohydrate
C. Vitamin
D. Minerals

Original source text (the exact panel preserves diagram labels, tables and choices):

While helping her mother stitch clothes, Aisha accidentally pricks her finger with a
pin. Immediately, without thinking, her hand jerks back. This quick, automatic
response is called a reflex action. This helps protect the body from harm by
allowing it to respond to danger without waiting for the brain to process the
information. Curious, she looks at a diagram showing this simple reflex arc with
three neurons labelled X, Y, and Z.





Which sequence shows the CORRECT pathway of the nerve impulse during
this reflex action?

A. Neuron Z → Neuron Y → spinal cord → Neuron X
B. Neuron X → spinal cord → Neuron Z → Neuron Y
C. Neuron X → spinal cord → Neuron Y → Neuron Z
D. Spinal cord → Neuron Y → Neuron X → Neuron Z

Original source text (the exact panel preserves diagram labels, tables and choices):

Earl set up an experiment in a dark room as shown in Fig. 1. He then changed the
variable X and counted the number of bubbles in the tube. He kept the other
variables constant. His results are shown in Fig. 2.





Which of the following could be variable X?

A. Number of bubbles C. Amount of water
B. Distance of torch and the beaker D. Type of water plant

Original source text (the exact panel preserves diagram labels, tables and choices):

Jennifer performed an experiment to test the ability of different heavy metals to
inhibit normal enzyme activity in the liver. She placed 5 g of the liver in each of the
5 test tubes. In 4 of the tubes, she also placed equal amounts of heavy metal. She
then added 6 mL of hydrogen peroxide to all five tubes. She used the resulting
bubble column as an indicator of enzyme activity in the liver and recorded the data
in the table below:





Based on Jennifer’s data, which of the 4 heavy metals inhibited enzyme activity
the LEAST?

A. Zn
B. Mg
C. Hg
D. Pb

Original source text (the exact panel preserves diagram labels, tables and choices):

In a pond, life is interconnected through a food chain. Algae, small green
organisms, are primary producers, creating their own food using sunlight. They
serve as the main food source for consumers like aquatic insects and small fish.
These insects and small fish, in turn, become food for larger predators such as
frogs.

Consider a scenario where environmental pollution causes a significant decline in
the algae population. This change directly impacts the availability of food for the
insects and small fish, potentially affecting their numbers. Based on these
observations, what is the MOST likely result of the algae disappearing?

A. All animals in the pond will grow faster due to less competition.
B. Small fish and insects may decrease because their main food source is gone.
C. Frogs will have more food since algae are not blocking the water.
D. Insects will start making their own food and become producers.

Original source text (the exact panel preserves diagram labels, tables and choices):

Biology students carried out an experiment to determine if a certain fertilizer
increased the height of plants. The students selected 4 types of plants and
planted 10 seeds of each type. Five seeds of each type were treated with
fertilizer and 5 seeds of each type were not treated with fertilizer. All other
conditions were identical. The students recorded the plant height after 120 days,
as shown in the table.

Plant Height (cm)

Eggplant Tomato Radish Pepper


fertilized unfertilized fertilized unfertilized fertilized unfertilized fertilized unfertilized

150 145 150 140 15 10 75 70

145 150 145 130 20 15 80 80

155 150 155 135 25 20 75 70

160 155 155 145 20 15 75 65

140 140 160 120 20 20 75 70


Which plant type showed the LEAST change in average height between the fertilized
and unfertilized groups?

A. Eggplant B. Tomato C. Radish D. Pepper

Original source text (the exact panel preserves diagram labels, tables and choices):

The table below compares the body temperatures of several animals in the cold
and warm seasons.

Body Temperature

Animal Cold Season (°C) Warm Season (°C)

Lizard 10 30

Sparrow 40 42

Frog 5 25

Dog 38 39

Bat (hibernating) 8 38

Turtle 5 28


Based on the table above, which group of animals are poikilothermic (cold-
blooded), and which animals show heterothermy?


POIKILOTHERMIC HETEROTHERMIC


A Lizard, Frog, Turtle Bat


B Lizard, Dog, Turtle Sparrow


C Frog, Dog, Sparrow Bat


D Lizard, Frog, Turtle Sparrow, Dog

Original source text (the exact panel preserves diagram labels, tables and choices):

Tonsillitis is inflammation of the tonsils, which are two oval-shaped pads of tissue
located at the back of the throat, one on each side. The condition primarily affects
children and teenagers. Tonsillitis can be caused by either a virus or a bacterium.





Source: https://www.mayoclinic.org/diseases-conditions/tonsillitis/symptoms-causes/syc-20378479#

Which of the following is a key difference in how a doctor would treat viral versus
bacterial tonsillitis?

A. A doctor would prescribe antibiotics for viral tonsillitis because the medication will
directly kill the virus, whereas for bacterial tonsillitis, the body's immune system is
left to fight the infection naturally
B. A doctor would prescribe antibiotics for bacterial tonsillitis because these
medications are designed to destroy bacteria or stop them from reproducing.
Viruses, however, do not have the same cellular structures as bacteria, so
antibiotics are ineffective against them.
C. A doctor would recommend rest and fluids for both viral and bacterial tonsillitis, but
would only prescribe antibiotics if the symptoms of bacterial tonsillitis last for more
than two weeks, as this is when the infection becomes serious.
D. A doctor would use antivirals for both because they are effective against all types
of germs, but would only use antibiotics as a last resort if the patient's symptoms
worsened and a secondary bacterial infection developed.

Original source text (the exact panel preserves diagram labels, tables and choices):

Look at the following circuit diagrams. Assume that all lamps are identical.





Component X is a very good conductor, while Component Y is an insulator.
Which lamps are on and which are off in Setup 1 and Setup 2?

Set Up 1 Set Up 2

Bulb 1 Bulb 2 Bulb 3 Bulb 4 Bulb1 Bulb 2 Bulb 3 Bulb 4

A on off off off on off off on

B on off off on on on on on

C on off off off on on on on

D on off off on on off off on

Original source text (the exact panel preserves diagram labels, tables and choices):

Alex and Bella are playing their guitars together. Alex plays a note with a
frequency of 528 Hz, while Bella plays a note with a frequency of 396 Hz. Bella's
guitar sounds noticeably louder than Alex's. The speed of sound in air is 330 m/s.

Based on this information, which statement is INCORRECT?

A. The pitch of the note played by Alex is higher than that played by Bella.
B. The amplitude of the sound wave from Bella's guitar is greater than that from
Alex's guitar.
C. The period of the sound wave from Alex's guitar is shorter than that from
Bella's guitar.
D. If this experiment were repeated on the Moon, the difference in loudness
would be even more pronounced.

Original source text (the exact panel preserves diagram labels, tables and choices):

Several common optical phenomena are listed below:
i. A rainbow after rain
ii. A straw appearing bent in a glass of water
iii. The bottom of a clear lake appearing shallower than it really is.
iv. The Sun appearing slightly above the horizon when it has already set

Which statement BEST describes the role of refraction in these cases?

A. Refraction is the only mechanism in all four phenomena.
B. Refraction is irrelevant for (i), but explains (ii), (iii), and (iv).
C. Refraction is important only for (i) and (ii), while (iii) and (iv) are caused by
reflection and scattering.
D. Refraction alone explains (ii), (iii), and (iv), but (i) requires both refraction and
internal reflection.

Original source text (the exact panel preserves diagram labels, tables and choices):

Azzam did an experiment to find the relationship between the diameter of a
wire and the maximum current it can safely carry. He recorded the maximum
current for different wire diameters as shown in the table below:

Maximum current
Wire diameter (mm)
(A)
0.50 2
0.75 7
1.00 12
1.25 17
1.50 22
1.75 27


Based on this information, (assume the relationship between diameter and
maximum current is linear.) if a wire of the same type with a diameter of 1.40 mm
is connected to an electronic device with a voltage source of 220 V, calculate the
resistance of the wire.

A. 10 Ω
B. 11 Ω
C. 12 Ω
D. 20 Ω

Original source text (the exact panel preserves diagram labels, tables and choices):

An oscilloscope is an electronic instrument that visually displays time-varying
electrical signals as waveforms on a screen. When a light sensor is connected
to the oscilloscope and exposed to monochromatic light, it converts the light into
an electrical signal. The oscilloscope then displays the corresponding frequency
of that light on the screen. Four of such observations are given below.





If you have to guess the color of the lights in order, which of the following options
is the BEST assumption?
A. (i) Violet (ii) Red (iii) Blue (iv) Yellow
B. (i) Yellow (ii) Violet (iii) Red (iv) Blue
C. (i) Blue (ii) Yellow (iii) Violet (iv) Red
D. (i) Red (ii) Blue (iii) Yellow (iv) Violet

Original source text (the exact panel preserves diagram labels, tables and choices):

Study the circuit below. The batteries and bulbs are working properly.





Which of the following correctly states the number of the bulb(s) that would be
lit when bulbs are blown?

Bulbs that are blown Number of bulb(s) still lit

A B4 and B5 1

B B3 and B6 0

C B2 and B4 2

D B5 and B6 4