Science MCQs

Question 1

#1

By TheQuizWire•Medium•✅ Fact Checked

The dynamic movement of Earth’s lithospheric plates, which results in continental drift and geological phenomena like earthquakes and volcanism, is primarily driven by which continuous process within the underlying mantle?

Answer

Plate tectonics is primarily driven by thermal convection. Heat from the core and lower mantle causes the less dense material in the asthenosphere (upper mantle) to rise, cool near the surface, and then sink, creating slow-moving currents that drag the overlying lithospheric plates.

Question 2

#2

By TheQuizWire•Medium•✅ Fact Checked

In the study of chemical kinetics, catalysts are crucial for achieving efficient reaction rates in both industrial processes (e.g., Haber-Bosch) and biological systems (e.g., enzymes). Which of the following mechanisms fundamentally explains how a catalyst accelerates a chemical reaction?

Answer

A catalyst functions by lowering the activation energy (Eₐ) required for a reaction to proceed. It does this by creating a new reaction pathway, thus allowing a greater fraction of molecules to achieve the necessary energy threshold to react per unit time. Catalysts affect kinetics (rate) but do not alter the thermodynamics of the reaction, meaning they do not change the ΔG or the equilibrium constant (K).

Question 3

#3

By TheQuizWire•Hard•✅ Fact Checked

The observation that the spectral lines of light from distant galaxies are systematically shifted toward the red end of the spectrum (cosmological redshift) is the primary empirical evidence supporting the expansion of the universe (Hubble’s Law). If the universe were static, uniform, and infinitely old, which established astronomical paradox would the observed universal redshift and the associated dynamic model primarily help resolve?

Answer

Olbers' Paradox asks why the night sky is dark if the universe is infinite, static, and uniformly filled with stars. The expansion of the universe (evidenced by cosmological redshift) and its finite age resolve this paradox. Expansion causes distant light to be stretched (redshifted) and diminished in energy, and the finite age means light from extremely distant regions has not yet reached us, thus limiting the total observed brightness.

Question 4

#4

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Which of the Earth’s layers is primarily composed of molten iron and nickel, generating the planet’s magnetic field?

Answer

The Outer Core is composed mainly of liquid iron and nickel. The movement of this highly conductive liquid metal creates convection currents, which are responsible for generating the Earth's protective magnetic field.

Question 5

#5

By TheQuizWire•Medium•✅ Fact Checked

The powerhouse of the cell, the mitochondrion, is responsible for producing the vast majority of cellular energy (ATP) through aerobic respiration. The inner mitochondrial membrane features extensive folds known as cristae. What is the essential functional significance of these cristae in maximizing ATP yield?

Answer

The cristae significantly increase the surface area of the inner mitochondrial membrane. This maximized surface area allows for the embedment of a greater quantity of critical components—specifically ATP synthase enzymes and the protein complexes of the Electron Transport Chain (ETC)—which are necessary to establish the proton gradient (proton motive force) that drives chemiosmosis and subsequent mass production of ATP.

Question 6

#6

By TheQuizWire•Medium•✅ Fact Checked

What fundamental observation serves as the key evidence that distant galaxies are moving away from Earth and that the universe is expanding, a core tenet summarized by Hubble’s Law?

Answer

The observed redshift of light from distant galaxies indicates that the light waves have been stretched (shifted toward the longer, red end of the spectrum) due to the relative motion away from the observer. This phenomenon, known as cosmological redshift, is the primary evidence for the metric expansion of space, as formalized by Hubble's Law.

Question 7

#7

By TheQuizWire•Medium•✅ Fact Checked

A well-designed Dewar flask (vacuum flask/thermos) is engineered to minimize thermal energy transfer across its boundary. What is the primary physical function of the vacuum layer situated between the inner and outer walls?

Answer

Heat transfer occurs primarily through three modes: conduction, convection, and radiation. Conduction and convection both require a physical medium (solids, liquids, or gases) to transfer energy. By creating a vacuum between the walls, the flask eliminates the medium, thereby effectively stopping heat transfer through both conduction and convection. Radiative heat transfer is minimized by the silvered/reflective inner surface.

Question 8

#8

By TheQuizWire•Medium•✅ Fact Checked

The tendency of an atom to attract a shared pair of electrons towards itself in a chemical bond is defined as electronegativity. Which element possesses the highest value of electronegativity on the standard Pauling scale?

Answer

Fluorine (F) is the most electronegative element on the periodic table. Electronegativity generally increases across a period and decreases down a group, and Fluorine is positioned at the top right (excluding noble gases), giving it the strongest pull on shared electrons.

Question 9

#9

By TheQuizWire•Medium•✅ Fact Checked

Which fundamental physical constant represents the speed of light in a vacuum, often denoted by the letter ‘c’?

Answer

The speed of light in a vacuum is a universal constant, often referred to as the electromagnetic radiation constant, and is approximately 299,792,458 meters per second.

Question 10

#10

By TheQuizWire•Medium•✅ Fact Checked

Which specific stage of cellular respiration is responsible for generating the vast majority of Adenosine Triphosphate (ATP), the primary energy currency, in aerobic eukaryotic cells?

Answer

Oxidative Phosphorylation, which occurs in the inner mitochondrial membrane and includes the Electron Transport Chain, is the final stage of aerobic respiration and generates approximately 90% of the total ATP yield (30–34 molecules) from the breakdown of one glucose molecule.

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