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PIMSO 2025 - Science - Secondary 1 - National Round

Question 1

A mouse’s habitat is a grassland containing rocks, soil, and grass. The mouse lives in a burrow underground. Based on this information, which statement best describes how the mouse interacts with its environment?

Question illustration
  1. The mouse uses soil for food and shelter.
  2. The mouse gets energy from its predators.
  3. The mouse changes its environment to create food.
  4. The mouse gets energy and shelter from its environment.

Question 2

What is the role of alveoli in the transport of gases in the body?

Question illustration
  1. They serve as the linkage from the respiratory system and the circulatory system.
  2. They serve as the carrier of the deoxygenated blood.
  3. They serve as the carrier of the oxygenated blood.
  4. They serve as the linkage from the respiratory system and the digestive system.

Question 3

When a plant cell is placed in a hypotonic solution, __________.
  1. the cell membrane shrinks.
  2. the cytoplasm shrinks.
  3. the vacuole expands.
  4. the cell wall breaks.

Question 4

How do biodiversity and stability work together?
  1. Biodiversity has nothing to do with ecosystem stability.
  2. The higher the biodiversity, the greater the stability of the ecosystem.
  3. The higher the biodiversity, the less stable the ecosystem
  4. The lower the biodiversity the greater the stability of an ecosystem.

Question 5

Organisms that reproduce sexually exhibit zygotic, gametic, or sporic meiosis. One way to determine the type of life cycle an organism has is by_____
  1. observing embryonic development.
  2. comparing the diploid and haploid forms of the organism.
  3. determining when in the life cycle fertilization occurs.
  4. determining if gametes are multicellular or unicellular.

Question 6

Which of the following accurately describes the relationship between a dominant and a recessive allele?

Editorial convention: assume complete dominance.
  1. The dominant allele physically alters the recessive allele so that it cannot be expressed.
  2. The dominant allele blends with the recessive allele to produce an in between trait.
  3. The dominant allele is expressed however, the recessive allele is unaltered.
  4. The dominant allele is more common in the species population than the recessive.

Question 7

What do you call an atom that has more protons than electrons?
  1. A cation
  2. A molecule
  3. An anion
  4. An isotope

Question 8

A drop of food coloring spreading out in a cup of water is an example of which transport process?
  1. Diffusion
  2. Effusion
  3. Osmosis
  4. Vapor Pressure

Question 9

Which subatomic particle is the lightest?

Source table (mass in grams): electron $9.109\times10^{-28}$; proton $1.672\times10^{-24}$; neutron $1.675\times10^{-24}$.

Question illustration
  1. Electron
  2. Neutron
  3. Nucleus
  4. Proton

Question 10

Which subatomic particle/s make/s up most of the mass of the atom?

Source table (mass in grams): electron $9.109\times10^{-28}$; proton $1.672\times10^{-24}$; neutron $1.675\times10^{-24}$.

Question illustration
  1. Electrons
  2. Protons
  3. Neutrons and Electrons
  4. Neutrons and Protons

Question 11

The following species have the same electronic configuration. Which of them has the biggest radius? (Shown below is the Periodic Table for reference.)

Question illustration
  1. $\mathrm{O}^{2-}$
  2. $\mathrm{F}^{-}$
  3. $\mathrm{Ne}$
  4. $\mathrm{Na}^{+}$

Question 12

Given the electronic configuration of Sc ($1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,4s^2\,3d^1\,4s^2$), what are the possible charges of the Sc cation?

A. +1
B. +3
C. +1 and +2
D. +1, +2, and +3

Editorial review: explain the source ambiguity and the scientifically supported conclusions.

Question 13

The year 1905 was said to be Einstein´s Annus Mirabilis or ¨miracle year¨, when he published several papers that brought him to international fame. (One of the papers actually won him the Nobel Prize.) Which of the following is NOT a subject of one of his papers that year?
  1. Photoelectric effect
  2. Brownian motion
  3. Special relativity
  4. General relativity

Question 14

On July 26, 2021, the weightlifter Hidilyn Diaz won the first Olympic gold medal for the Philippines. This was after a 127 kg lift. In this category, she lifted the weight overhead, with her arms stretched, i.e. almost 2.0 m above ground. If she were to let this weight fall freely after the lift, by what speed would the weight hit the ground (in m/s)?
  1. 20
  2. 10
  3. 4.5
  4. 6.3

Question 15

Which of the following would increase the electrical resistance through a wire?
  1. Decreasing the length of the wire
  2. Decreasing the resistivity
  3. Decreasing the diameter of the wire
  4. All of the above

Question 16

Shown below is the graph of distance (y-axis) travelled by a particle over time (x- axis). The graph traced is a parabola, showing that the acceleration is constant. What is the acceleration of the particle?

Question illustration
  1. 1.25 $\mathrm{m/s^2}$
  2. 2.5 $\mathrm{m/s^2}$
  3. 5 $\mathrm{m/s^2}$
  4. 10 $\mathrm{m/s^2}$

Question 17

Which of the following properties of a wave is directly related to its energy?

Editorial convention: compare classical mechanical waves with frequency, medium and other conditions held fixed.
  1. Wavelength
  2. Frequency
  3. Speed
  4. Amplitude

Question 18

Which of the following would NOT cause an electron to accelerate?
  1. Placing it in a constant electric field
  2. Placing it in a gap with potential energy difference
  3. Placing a point charge of opposite charge near it
  4. Placing it in a magnetic field parallel to the direction of motion

Question 19

This zone where the temperature is almost at freezing point and no sunlight can penetrate covers the majority of the ocean floor.
  1. Hadalpelagic Zone
  2. Abyssopelagic Zone
  3. Bathypelagic Zone
  4. Mesopelagic Zone

Question 20

Flowering plants first appeared on earth 130 million years ago during which period?
  1. Triassic
  2. Jurassic
  3. Cretaceous
  4. Paleocene