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Quizzes > Science

Hard Science Questions Quiz: Test Your Knowledge

Quick, free way to test your knowledge. The hardest science quiz with instant results.

Editorial: Review CompletedCreated By: Phil LyonsUpdated Aug 27, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration for a challenging science trivia quiz on a dark blue background

This quiz helps you take on hard science questions across physics, biology, and chemistry and see where you stand. Warm up with our basic science quiz, then push deeper with hardest chemistry questions, or mix it up with a chemistry trivia quiz. You get instant results.

Which cell organelle contains the genetic material in eukaryotic cells?
Ribosome
Mitochondrion
Golgi apparatus
Nucleus
The nucleus houses chromosomal DNA, which carries genetic information for cell function and replication. It is separated from the cytoplasm by a nuclear envelope. Other organelles like mitochondria or ribosomes do not contain the cell’s main genome.
What does the atomic number of an element represent?
Atomic mass
Number of electrons and neutrons
Number of neutrons
Number of protons
The atomic number equals the count of protons in an atom’s nucleus and defines the element. In neutral atoms, it also matches the number of electrons. Neutrons vary and contribute to isotopes.
According to Newton’s First Law, an object in motion remains in motion unless acted upon by what?
Its own inertia
A net external force
Gravity alone
Friction only
Newton’s First Law states that an object continues at constant velocity unless a net external force changes its state. Inertia is the property enabling this, not the cause of change. Both friction and gravity can be forces but are specific examples.
What is the approximate speed of light in vacuum?
3.00 × 10^8 m/s
1.50 × 10^8 m/s
1.00 × 10^9 m/s
3.00 × 10^6 m/s
The speed of light in vacuum is defined as 299,792,458 meters per second, often rounded to 3.00×10^8 m/s. This constant underpins relativity and electromagnetic theory. No known signal travels faster.
What is the chemical formula for water?
H3O
HO2
H2O2
H2O
Water consists of two hydrogen atoms covalently bonded to one oxygen atom, giving the formula H2O. Hydrogen peroxide is H2O2 and has different properties. The arrangement results in a polar molecule responsible for many of water’s unique traits.
How long does Earth take to orbit the Sun once?
Approximately 10 years
Approximately 30 days
Approximately 365 days
Approximately 24 hours
Earth completes one full orbit around the Sun in about 365.25 days, defining a solar year. This period causes seasonal cycles. Leap years correct the extra quarter day.
At what temperature does pure water boil at sea level?
0°C
100°C
212°C
50°C
At standard atmospheric pressure (1 atm), pure water boils at 100°C (212°F). Changes in elevation or pressure alter the boiling point. Lower pressure reduces boiling temperature.
What pH value is considered neutral at 25°C?
7
1
0
14
At 25°C, a pH of 7 indicates neutrality where hydrogen and hydroxide ion concentrations are equal. Values below 7 are acidic and above are basic. Temperature can slightly shift the neutral pH.
What is the SI unit of force?
Newton
Joule
Pascal
Watt
The SI unit of force is the newton (N), defined as the force needed to accelerate 1 kg of mass at 1 m/s². Joule measures energy, Pascal measures pressure, and Watt measures power.
What is the fundamental unit of heredity in living organisms?
Gene
Cell
Protein
Chromosome
A gene is a sequence of DNA that encodes functional products, typically proteins. Chromosomes carry many genes, but the gene is the basic unit of heredity. Cells and proteins serve other roles.
Which planet is the largest in our solar system?
Saturn
Jupiter
Neptune
Earth
Jupiter is the most massive and largest planet in the Solar System, with a diameter of about 143,000 km. Its composition is mainly hydrogen and helium. It is over twice as massive as all other planets combined.
Which gas is most abundant in Earth's atmosphere?
Carbon dioxide
Argon
Oxygen
Nitrogen
About 78% of Earth's atmosphere is nitrogen, making it the most abundant gas. Oxygen is next at around 21%. Argon and carbon dioxide form small percentages.
What is the lowest layer of Earth's atmosphere where weather occurs?
Stratosphere
Troposphere
Mesosphere
Thermosphere
The troposphere extends from Earth's surface up to about 8–15 km and contains most atmospheric water vapor and weather phenomena. Temperatures decrease with altitude here. Above it lies the stratosphere.
What is the metric prefix for 1,000 times a unit?
Centi
Kilo
Milli
Mega
The prefix kilo- denotes multiplication by 1,000 in the metric system. Mega- is 1,000,000; milli- is one-thousandth. Centi- is one-hundredth.
What process do plants use to convert light energy into chemical energy?
Respiration
Transpiration
Fermentation
Photosynthesis
Photosynthesis in chloroplasts converts light energy into chemical energy stored in glucose. Respiration breaks down glucose for energy. Transpiration is water loss and fermentation is anaerobic energy production.
What natural satellite orbits Earth?
Titan
The Moon
Phobos
Europa
Earth has one natural satellite known as the Moon. Phobos orbits Mars, Europa orbits Jupiter, and Titan orbits Saturn. The Moon’s gravitational pull affects tides.
Which element is a noble gas at room temperature?
Argon
Fluorine
Oxygen
Chlorine
Argon is a noble gas with complete valence electron shells, making it inert. Chlorine and fluorine are halogens and highly reactive. Oxygen is a reactive nonmetal.
What is the standard enthalpy change of formation for an element in its standard state?
One kilojoule
Negative
Depends on temperature
Zero
By convention, the standard enthalpy of formation for an element in its standard state is zero. This provides a reference for calculating reaction enthalpies. Compounds have non-zero values.
Which law states that pressure of a given mass of gas is inversely proportional to its volume at constant temperature?
Gay-Lussac’s Law
Boyle’s Law
Avogadro’s Law
Charles’s Law
Boyle’s Law describes how pressure and volume vary inversely for a gas at constant temperature. Charles’s Law relates volume and temperature. Avogadro’s Law involves volume and moles.
What type of bond involves sharing electron pairs between atoms?
Covalent bond
Hydrogen bond
Metallic bond
Ionic bond
Covalent bonds form when atoms share pairs of electrons to achieve stable configurations. Ionic bonds form via electron transfer. Metallic bonds feature delocalized electrons. Hydrogen bonds are weak attractions.
What is the primary role of ribosomes in a cell?
Protein synthesis
Lipid storage
DNA replication
Energy production
Ribosomes translate mRNA sequences into polypeptide chains, synthesizing proteins. DNA replication occurs in the nucleus. Lipid storage involves lipid droplets. Energy production is mainly in mitochondria.
Which law of thermodynamics states that entropy of an isolated system never decreases?
Second Law
First Law
Zeroth Law
Third Law
The Second Law of Thermodynamics asserts that total entropy in an isolated system can only increase or remain constant. The First Law covers energy conservation. The Third Law addresses entropy at absolute zero.
What is the term for a change in an object's speed or direction?
Velocity
Momentum
Acceleration
Force
Acceleration is defined as the rate of change of velocity with time, encompassing speed or direction changes. Velocity is speed with direction. Force causes acceleration. Momentum is mass times velocity.
Which biomolecule category includes enzymes, hormones, and antibodies?
Nucleic acids
Proteins
Carbohydrates
Lipids
Proteins are polymers of amino acids that serve as enzymes, hormones, and antibodies. Carbohydrates are sugars and starches. Lipids include fats and oils, and nucleic acids store genetic information.
What is Avogadro’s number?
6.022×10^23 particles per mole
3.00×10^8
1.67×10^-27
9.81
Avogadro’s constant is defined as 6.022×10^23 entities per mole, linking atomic scale to macroscopic amounts. The other values correspond to different constants or quantities.
Which process describes the movement of water across a semipermeable membrane?
Filtration
Active transport
Diffusion
Osmosis
Osmosis is the passive movement of water from low solute concentration to high across a semipermeable membrane. Diffusion is general solute movement. Filtration requires pressure. Active transport uses energy.
What phenomenon explains the bending of light as it passes from one medium to another?
Interference
Refraction
Reflection
Diffraction
Refraction is the change in direction of a wave passing between media with different refractive indices. Reflection is bouncing back. Diffraction is bending around obstacles. Interference is wave overlap.
Which type of reaction involves the transfer of electrons between reactants?
Neutralization reaction
Acid–base reaction
Precipitation reaction
Redox reaction
Redox reactions involve oxidation (loss of electrons) and reduction (gain of electrons). Acid–base involves proton transfer. Precipitation yields a solid. Neutralization is acid–base producing salt and water.
In genetics, what is the observable physical trait called?
Chromosome
Genotype
Allele
Phenotype
Phenotype refers to the expressed characteristics of an organism due to genotype and environment. Genotype is the genetic makeup. Alleles are gene variants. Chromosomes are DNA carriers.
What is the pH of a 0.01 M HCl solution at 25°C?
2
7
12
0.01
Hydrochloric acid is a strong acid that dissociates completely, giving [H+] = 0.01 M. pH is ?log10[H+], so pH is 2. Solutions with pH 7 are neutral.
Which principle explains why ice floats on water?
Surface tension
Density difference
Viscosity
Capillary action
Ice has a lower density than liquid water due to its crystalline structure, allowing it to float. Surface tension and capillary action involve surface phenomena. Viscosity is flow resistance.
What is the Heisenberg Uncertainty Principle about?
Energy and time relationship
Wave–particle duality
Speed of light constant
Simultaneous measurement limits of position and momentum
The principle states that one cannot precisely know both position and momentum simultaneously for a particle; the more precisely one is known, the less precisely the other can be known. It arises from quantum mechanics.
In organic chemistry, which functional group characterizes ketones?
Hydroxyl group
Amino group
Carbonyl group bonded to two carbons
Carboxyl group
Ketones feature a carbonyl (C=O) group connected to two carbon atoms. Aldehydes have at least one hydrogen bonded to the carbonyl. Hydroxyl is -OH, amino is -NH2, carboxyl is -COOH.
What phenomenon causes the redshift observed in distant galaxies?
Gravitational lensing
Interstellar dust absorption
Expansion of the universe
Doppler effect due to galaxy rotation
Cosmological redshift arises from space expansion stretching light wavelengths from distant galaxies. The Doppler effect is similar locally but cosmic expansion dominates at large scales. Gravitational lensing bends light but doesn’t shift color.
Which structure in mitochondria generates most of the cell’s ATP?
Outer membrane
Matrix
Cristae
Intermembrane space
Cristae are folds of the inner mitochondrial membrane that increase surface area for the electron transport chain and ATP synthase, producing ATP. The matrix hosts the Krebs cycle.
What is the primary mechanism of action for antibiotics like penicillin?
Disruption of DNA replication
Protein synthesis interference
Inhibition of cell wall synthesis
Inhibition of folic acid metabolism
Penicillin and related beta-lactam antibiotics block peptidoglycan crosslinking in bacterial cell walls, causing lysis. Other drugs target DNA replication or protein synthesis.
Which astrophysical object is formed by the collapse of a massive star beyond the neutron star stage?
Brown dwarf
Supernova remnant
Black hole
White dwarf
When a massive star’s core collapses past neutron degeneracy pressure, it becomes a black hole from which not even light escapes. White dwarfs and neutron stars form from less massive cores.
In quantum mechanics, what is the name of the equation that describes how the quantum state evolves over time?
Heisenberg equation
Klein–Gordon equation
Dirac equation
Schrödinger equation
The Schrödinger equation governs the time evolution of a quantum system’s wavefunction. The Dirac and Klein–Gordon equations extend quantum theory to relativity. Heisenberg formulated matrix mechanics.
What type of biological molecule are deoxyribonucleic acids:
Nucleic acids
Proteins
Carbohydrates
Lipids
DNA (deoxyribonucleic acid) is a nucleic acid carrying genetic instructions. Carbohydrates, proteins, and lipids serve other cellular roles.
Which process describes the fixation of nitrogen by bacteria into ammonia?
Nitrogen fixation
Denitrification
Ammonification
Nitrification
Nitrogen fixation converts atmospheric N2 into biologically usable ammonia via bacterial enzymes like nitrogenase. Nitrification and denitrification are other steps in the nitrogen cycle.
What is the critical angle in optics?
Angle at which light refracts at 90°
Angle of incidence above which total internal reflection occurs
Angle of maximum dispersion
Angle between incidence and reflection
The critical angle is the minimum incidence angle in a denser medium where the refracted ray runs along the boundary, beyond which total internal reflection occurs. It depends on refractive indices.
Which eigenvalue problem underlies the hydrogen atom solution in quantum mechanics?
Klein–Gordon equation for spin-0 particles
Dirac equation for spin-½ particles
Time-independent wave equation in free space
Solution to the radial Schrödinger equation with Coulomb potential
The hydrogen atom’s bound states come from solving the time-independent Schrödinger equation with a Coulomb potential, yielding quantized energy levels. The Dirac and Klein–Gordon equations are relativistic extensions.
In general relativity, what tensor describes the curvature of spacetime?
Einstein tensor
Riemann curvature tensor
Metric tensor
Stress-energy tensor
The Riemann curvature tensor fully characterizes spacetime curvature in general relativity. The Einstein tensor relates curvature to matter. The metric tensor defines distances.
What is the key step in PCR (polymerase chain reaction)?
Thermal cycling with DNA denaturation, primer annealing, and extension
Gel electrophoresis to separate fragments
Ligation of DNA fragments
DNA methylation analysis
PCR amplifies DNA by repeated cycles: heating to denature strands, cooling to anneal primers, and extension by DNA polymerase. Gel electrophoresis is downstream analysis.
Which phase of matter occurs at extremely low temperatures where quantum effects appear macroscopically?
Bose–Einstein condensate
Fermionic liquid
Quark–gluon plasma
Plasma
A Bose–Einstein condensate forms near absolute zero when bosons occupy the same quantum ground state, showing macroscopic quantum phenomena. Plasmas exist at high temperatures.
What is the Weinberg angle associated with in particle physics?
Spin coupling in quantum chromodynamics
Threshold energy for nucleosynthesis
Mass ratio of up and down quarks
Mixing of electromagnetic and weak forces in electroweak unification
The Weinberg angle (weak mixing angle) quantifies the mixing between electromagnetic and weak interactions in the electroweak theory, defining the coupling strengths.
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Study Outcomes

  1. Analyze interdisciplinary science concepts -

    Break down and interpret challenging questions from biology, physics, and chemistry to deepen your understanding of complex scientific principles.

  2. Evaluate your science knowledge -

    Assess your proficiency across key scientific domains by tackling the hardest question about science and related hardest science trivia questions, pinpointing areas for improvement.

  3. Apply critical thinking skills -

    Use logical reasoning and problem-solving techniques to confidently approach and solve tough science trivia challenges.

  4. Identify knowledge gaps -

    Recognize specific topics where your understanding falls short, allowing you to focus your study efforts and boost overall performance.

  5. Strengthen memory retention -

    Reinforce recall of essential science facts and theories through engaging, high-difficulty trivia that enhances long-term retention.

  6. Demonstrate science mastery -

    Showcase your expertise by achieving top scores in the hardest science trivia quiz and proving your command of tough science trivia content.

Cheat Sheet

  1. Second Law of Thermodynamics -

    When approaching the hardest science trivia questions in physics, remember that the second law dictates ΔS ≥ 0 for isolated systems, meaning entropy (disorder) never decreases. For example, calculating ΔS=S_final−S_initial lets you predict spontaneity in reactions; reversible heat flow Q_rev at temperature T gives ΔS=Q_rev/T. Mnemonic: "Order Loves Chaos" helps you recall that systems naturally progress toward higher entropy.

  2. Time-Dependent Schrödinger Equation -

    This cornerstone of quantum mechanics often features in tough science trivia - iħ ∂ψ/∂t = Ĥψ describes how a particle's wavefunction ψ evolves over time. In a one-dimensional infinite potential well, the stationary states ψ_n(x)=√(2/L)sin(nπx/L) and energy levels E_n=n²π²ħ²/(2mL²) are classic examples from MIT and Caltech course notes. A quick tip: "IHateIceCream" helps you recall iħ∂ψ/∂t.

  3. Chemical Equilibrium Constant (K_eq) -

    Hardest question about science in chemistry often asks you to derive K_eq for aA + bB ⇌ cC + dD as K_eq=[C]^c[D]^d/[A]^a[B]^b at equilibrium. Using data from NIST, you can calculate ΔG°=−RT lnK_eq to predict reaction spontaneity. Mnemonic "AC/DC" (Add Concentrations/Divide Concentrations) makes the equilibrium expression stick.

  4. Mass - Energy Equivalence (E=mc²) -

    One of the most iconic formulas from Einstein's 1905 paper, it often appears in hardest science trivia rounds. Converting 1 g of mass entirely to energy yields E=(0.001 kg)(3×10^8 m/s)²≈9×10^13 J, illustrating nuclear power's potency. Think of "Energy Comes from Mass" to cement the concept whenever you tackle a tough science trivia question.

  5. Central Dogma of Molecular Biology -

    In biology-themed hardest science trivia questions, recall that DNA → RNA → Protein underpins gene expression; transcription by RNA polymerase and translation on ribosomes are core processes detailed by NIH resources. A handy mnemonic is "Drip" (DNA → RNA In Protein) to remember the information flow. Don't forget proofreading by DNA polymerase reduces replication errors to ~10^−10 per base!

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