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PIMSO 2023 - Science - Secondary 4 - National Round

Question 1

Which of the following omics describe the collective study and analysis of mRNAs from environmental samples?
  1. Epigenomics
  2. Epitranscriptomics
  3. Metabolomics
  4. Metagenomics
  5. Metatranscriptomics

Question 2

Alphafold is a revolutionary artificial intelligence program developed by Deepmind which can predict protein structure with high accuracy. Which type of protein structure does Alphafold predict?

Question illustration

Editorial scope: use the 2021 AlphaFold study cited in the source.

Image credit: Jumper J et al., Nature 596 (2021), 583–589, https://www.nature.com/articles/s41586-021-03819-2
  1. Primary structure
  2. Secondary structure
  3. Tertiary structure
  4. Quaternary structure
  5. Protein interactions

Question 3

What is the function of the following body tissue?

Question illustration

Image credit: http://blogs.berkshirecc.edu/bccoer/
  1. Transmission of electrical signals
  2. Provide lining to the organs and body cavities
  3. Provide structure and support for the body
  4. Facilitate wide range of movements
  5. Connect muscles to the bones

Question 4

Which of the following statements is NOT true regarding adaptive immune response?
  1. Antigen-presenting cell presents foreign antigen bound to MHCII and activates naïve CD4+ T cells.
  2. Naïve CD4+ T cells are activated to become helper cells.
  3. Naïve CD8+ T cells are activated to become natural killer cells.
  4. Helper T cells activate naïve B cells to become plasma cells.
  5. Plasma cells secrete antibodies into the bloodstream to bind to foreign bodies.

Question 5

Terminally differentiated cells, such as neurons and myocytes, are cells with specialized functions. These cells are no longer capable of cell division, and therefore arrested at which particular phase of the cell cycle?
  1. $G_0$
  2. $G_1$
  3. $G_2$
  4. S
  5. M

Question 6

Bats have played a significant role as natural reservoir for zoonotic viruses, some of which have caused major epidemics in the human population. Which of the following viruses does not utilize bats as its reservoir?

A. Ebola virus
B. Marburg virus
C. SARS-CoV-2
D. Zika virus
E. Influenza A virus

Editorial review: explain the scientific issue and assess whether the source supports a unique choice.

Question 7

After months of exposure in air, 1.9 g of nail made of steel rusted partially. The rusting process, forming a compound of iron and oxygen (which comes from air) stopped only once the whole surface of the nail was covered in rust, effectively protecting the iron under the surface from rusting. What can you say about the mass of this nail upon rusting?

Editorial assumption: all metal and corrosion products remain attached; evaluate the mass claim separately from the stated protective-layer mechanism.
  1. The insides were protected so the mass should still be 1.9 g because the rusting stops
  2. The mass should be less than 1.9 g because the insides were protected
  3. The mass should still be 1.9 g because of the law of conservation of mass
  4. The mass should be more than 1.9 g because of oxygen incorporates in the material
  5. Nothing meaningful could be said based on the information given

Question 8

You are helping your parents to cook sinigang, a popular Filipino dish composed of meat and vegetables in a clear sour broth:

They asked you to boil some water to make soup and notify them as soon as the water starts to boil at 100 °C. You told them that it started to boil after ten minutes, but they are not yet ready preparing the meat and vegetables. So to conserve energy, they asked you to lower the heat. You lowered the heat just enough so that some bubbles still appear to rise to the top of the water, although it is not boiling vigorously anymore. What is the temperature of the water at this point?

Question illustration

Editorial assumption: the bubbles represent continued boiling of pure water at unchanged pressure.

Image credit: Original source attribution: author name appears as ??? ???; Sinigang na Baboy, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=2935529
  1. 95 °C
  2. not exactly 95 °C but still below 100 °C
  3. 100 °C
  4. around 105 °C
  5. Cannot be determined from the given information

Question 9

Which of the following elements would you consider to be isoelectronic to oxygen (O)?
(Refer to the periodic table below.)

Question illustration

Image credit: Dmarcus100, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=53070632

A. Ge
B. As
C. Se
D. Br
E. Kr

Editorial review: explain the scientific issue and assess whether the source supports a unique choice.

Question 10

The Philosopher’s Stone have been the subject of many myths and legends. In the Harry Potter series, the Philosopher’s Stone was sought by Voldemort because it produces the Elixir of Life which could grant immortality. Historically, the field of alchemy, which arguably eventually led to the scientific study of chemistry, aimed to make this legendary stone since it is fabled to be able to transform base metals such as lead (Pb) to precious metals such as gold (Au). With modern theories of the atomic model, this is known to be impossible chemically but feasible by nuclear methods, i.e. by changing the nuclear components of Pb. What nuclear transformation would be necessary to change lead (Pb) to gold (Au)?
  1. removing three neutrons from Pb would lead to Au
  2. adding three neutrons to Pb would lead to Au
  3. adding three protons to Pb would lead to Au
  4. removing three protons from Pb would lead to Au
  5. None of the above

Question 11

Even if adobo has many varieties, one main component unites this popular Filipino dish: acidity. This flavour is usually due to vinegar that contains acetic acid. Acetic acid is a weak acid, with a so that only a small amount dissociates in water in an equilibrium reaction:
$\mathrm{CH_3COOH+H_2O \rightleftharpoons CH_3COO^-+H_3O^+}$
Identify all the bases in this reaction.

Editorial correction: read the repeated option formula CH₃OO⁻ as CH₃COO⁻, consistent with the printed reaction; the original choices remain visible. The source contains the incomplete phrase “with a so”.
  1. H₂O only
  2. CH₃OO⁻ only
  3. CH₃OO⁻ and H₃O⁺
  4. H₂O and CH₃OO⁻
  5. H₂O, CH₃OO⁻, and H₃O⁺

Question 12

The amount of helium in a balloon is difficult to determine because it is difficult to weigh. However, it is possible by knowing some quantities. A helium balloon was found to have a volume of 6.8 L at 30 °C and 1 atm. Determine the mass of helium inside the balloon.
Use R = 0.0821 L·atm/(mol·K), M = 4 g/mol for He

Question illustration

Image credit: AJ, Open Clip Art Library, CC0, https://commons.wikimedia.org/w/index.php?curid=6214800
  1. 11 g
  2. 2.8 g
  3. 0.27 g
  4. 1.1 g
  5. none of the above

Question 13

A ship leaves Manila bay at 6:00. Shown below is the distance travelled by the ship over time.

What was the highest acceleration the ship attained?

Question illustration

Editorial convention: use the quantity and unit printed on the graph axis, despite the inconsistent introductory prose.
  1. 10 km/h²
  2. 12 km/h²
  3. 30 km/h²
  4. 15 km/h²
  5. none of the above

Question 14

Which of the following colors in the visible spectrum has the lowest energy?

Editorial scope: compare the energy per photon.
  1. Violet
  2. Blue
  3. Green
  4. Yellow
  5. Red

Question 15

What would happen to the force between two charged objects when the distance between them doubles?

Editorial assumption: fixed point charges in the same medium.
  1. The force is divided by 4
  2. The force halves
  3. The force remains constant
  4. The force doubles
  5. The force quadruples (4x)

Question 16

What property of sound waves determine the loudness of sound?
  1. amplitude
  2. wavelength
  3. frequency
  4. phase
  5. none of the above

Question 17

Several phenomena/observations in the 19th to early-20th century could not be explained by classical Newtonian physics, demanding new physical theories which eventually led to the development of quantum mechanics. The following lists these phenomena EXCEPT ONE. Which of the following is NOT a phenomenon that contributed to the development of quantum mechanics?
  1. Discrete colors of line spectra of elemental gasses
  2. The photoelectric effect
  3. Ultraviolet catastrophe in blackbody radiation
  4. Particle-like properties of electrons
  5. Stable orbits of electrons

Question 18

Two resistors (R₁ = 6 Ω, R₂ = 2 Ω) are connected in series in an electrical circuit and an external voltage of 12 V is connected to them. Determine the power through the circuit.
  1. 8 W
  2. 18 W
  3. 24 W
  4. 72 W
  5. none of the above

Question 19

What is the composition of the atmospheric gasses, without the water vapor?
  1. 78% Nitrogen, 21% Oxygen, 0.93% Argon, 0.04% Carbon dioxide
  2. 78% Carbon dioxide, 21% Nitrogen, 0.93% Oxygen, 0.04% Argon
  3. 78% Argon, 21% Carbon dioxide, 0.93% Nitrogen, 0.04% Oxygen
  4. 78% Oxygen, 21% Carbon dioxide, 0.93% Nitrogen, 0.04% Argon
  5. 78% Carbon dioxide, 21% Oxygen, 0.93% Nitrogen, 0.04% Argon

Question 20

How do hailstones form?

Question illustration

Image credit: https://commons.wikimedia.org/
  1. When tiny ice crystals in the cloud clump together and solidify
  2. When big ice crystals in the cloud clump together and solidify
  3. When tiny raindrops are pushed back to the clouds and freeze
  4. When tiny raindrops freeze as they approach the ground
  5. When rain puddles in the ground freeze