From atoms and cells to the laws of physics and chemical reactions, this science quiz covers biology, chemistry, physics, and earth science. Whether you're a student revising for exams or a lifelong learner, sharpen your scientific thinking one question at a time.
Questions range from easy school-level facts to trickier university-level concepts.
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Science Quiz: All Questions & Answers
Browse all 50 science trivia questions with the correct answers and a detailed explanation for each. Use it as a study guide, an answer key, or to read up before you play the timed quiz above. Questions are picked at random each round, so every playthrough is different.
1. What is the chemical formula for water?
- A.HO
- B.H2O✓ Correct
- C.H2O2
- D.OH
Answer: H2O. Water (H2O) is composed of two hydrogen atoms bonded to one oxygen atom. Its bent molecular shape gives it a slight electrical polarity, making it an excellent solvent — which is why it is called the 'universal solvent'.
2. What is the powerhouse of the cell?
- A.Nucleus
- B.Ribosome
- C.Mitochondria✓ Correct
- D.Golgi apparatus
Answer: Mitochondria. Mitochondria generate most of the cell's supply of ATP (adenosine triphosphate), the molecule used as a source of chemical energy. They have a double membrane and their own DNA, supporting the theory that they were once independent bacteria.
3. What does DNA stand for?
- A.Di-Nucleic Acid
- B.Deoxyribonucleic Acid✓ Correct
- C.Dynamic Nucleotide Array
- D.Dual Nano Atom
Answer: Deoxyribonucleic Acid. DNA (Deoxyribonucleic Acid) is a molecule that carries the genetic blueprint for living organisms. Its famous double-helix structure was discovered by Watson, Crick, Franklin and Wilkins in 1953, earning Watson and Crick the Nobel Prize.
4. What is the approximate speed of light?
- A.300,000 km/s✓ Correct
- B.150,000 km/s
- C.3,000 km/s
- D.30,000 km/s
Answer: 300,000 km/s. Light travels at approximately 299,792 km/s (often rounded to 300,000 km/s) in a vacuum. This is denoted as 'c' in physics. According to Einstein's theory of special relativity, nothing with mass can travel at or beyond this speed.
5. Which gas do plants absorb during photosynthesis?
- A.Oxygen
- B.Nitrogen
- C.Carbon Dioxide✓ Correct
- D.Hydrogen
Answer: Carbon Dioxide. During photosynthesis, plants absorb carbon dioxide (CO₂) from the air and water (H₂O) from the soil, using sunlight to convert them into glucose and oxygen. The oxygen is released as a byproduct — providing the air we breathe.
6. What is the most abundant gas in Earth's atmosphere?
- A.Oxygen
- B.Carbon Dioxide
- C.Argon
- D.Nitrogen✓ Correct
Answer: Nitrogen. Nitrogen makes up about 78% of Earth's atmosphere, followed by oxygen at 21%, and argon at nearly 1%. Despite being so abundant, nitrogen gas (N₂) is largely inert and must be 'fixed' by bacteria or lightning before plants can use it.
7. What is the boiling point of water at sea level?
- A.90°C
- B.95°C
- C.100°C✓ Correct
- D.105°C
Answer: 100°C. Water boils at 100°C (212°F) at standard atmospheric pressure (sea level). At higher altitudes where pressure is lower, water boils at a lower temperature — which is why cooking times in mountains are longer.
8. What is the atomic number of Carbon?
- A.4
- B.6✓ Correct
- C.8
- D.12
Answer: 6. Carbon has atomic number 6, meaning it has 6 protons in its nucleus. It is the backbone of all organic chemistry and life on Earth. Carbon can form millions of different compounds due to its ability to bond with itself and many other elements.
9. Which planet in our solar system has the most confirmed moons?
- A.Jupiter
- B.Saturn✓ Correct
- C.Uranus
- D.Neptune
Answer: Saturn. Saturn holds the record with 146 confirmed moons as of 2024, edging out Jupiter's 95. Saturn's largest moon, Titan, is the only moon in the solar system with a dense atmosphere and liquid lakes on its surface — though of methane, not water.
10. What force keeps the planets in orbit around the Sun?
- A.Magnetism
- B.Electrostatic force
- C.Gravity✓ Correct
- D.Nuclear force
Answer: Gravity. Gravity is the force of attraction between objects with mass. The Sun's enormous mass creates a gravitational field strong enough to keep all the planets in stable elliptical orbits. This relationship was first described mathematically by Isaac Newton in 1687.
11. What is the chemical symbol for oxygen?
- A.Ox
- B.O✓ Correct
- C.Og
- D.On
Answer: O. Oxygen's chemical symbol is simply 'O'. It is the third most abundant element in the universe and essential for respiration in most living things. In its common form it exists as a molecule of two atoms, O₂.
12. What is the chemical symbol for potassium?
- A.P
- B.Po
- C.K✓ Correct
- D.Pt
Answer: K. Potassium's symbol 'K' comes from its Latin name 'Kalium'. It is a soft, reactive metal vital for nerve function and is found in foods like bananas. The symbol 'P' is reserved for phosphorus.
13. What is the pH of a neutral solution?
- A.0
- B.7✓ Correct
- C.10
- D.14
Answer: 7. A neutral solution, such as pure water, has a pH of 7. Values below 7 are acidic and values above 7 are alkaline (basic). The pH scale is logarithmic, so each step represents a tenfold change in acidity.
14. Which blood cells help the body fight infection?
- A.Red blood cells
- B.White blood cells✓ Correct
- C.Platelets
- D.Plasma cells
Answer: White blood cells. White blood cells (leukocytes) are the body's defenders, attacking bacteria, viruses and other invaders. Red blood cells carry oxygen, while platelets help blood to clot.
15. What is the central part of an atom called?
- A.Electron
- B.Nucleus✓ Correct
- C.Proton
- D.Shell
Answer: Nucleus. The nucleus is the dense centre of an atom, containing protons and neutrons. Electrons orbit around it in regions called shells. Almost all of an atom's mass is concentrated in its tiny nucleus.
16. What type of energy does a moving object possess?
- A.Potential energy
- B.Kinetic energy✓ Correct
- C.Thermal energy
- D.Chemical energy
Answer: Kinetic energy. Kinetic energy is the energy of motion, and it increases with both mass and speed. A stationary object at height has potential energy, which converts to kinetic energy as it falls.
17. What is the green pigment in plants that captures light for photosynthesis?
- A.Carotene
- B.Chlorophyll✓ Correct
- C.Melanin
- D.Keratin
Answer: Chlorophyll. Chlorophyll is the green pigment found in the chloroplasts of plant cells. It absorbs red and blue light while reflecting green, which is why plants appear green, and it powers the conversion of light into chemical energy.
18. What is the smallest basic unit of life?
- A.Atom
- B.Cell✓ Correct
- C.Molecule
- D.Tissue
Answer: Cell. The cell is the smallest structural and functional unit of life. Some organisms, like bacteria, consist of a single cell, while humans are made of trillions. The cell theory states all living things are composed of cells.
19. Which scientist formulated the three laws of motion?
- A.Albert Einstein
- B.Isaac Newton✓ Correct
- C.Galileo Galilei
- D.Nikola Tesla
Answer: Isaac Newton. Isaac Newton published his three laws of motion in 1687 in the 'Principia'. They describe the relationship between an object and the forces acting on it, forming the foundation of classical mechanics.
20. What is the most abundant element in the universe?
- A.Oxygen
- B.Carbon
- C.Hydrogen✓ Correct
- D.Helium
Answer: Hydrogen. Hydrogen is the most abundant element in the universe, making up about 75% of its normal matter. It is the fuel of stars, which fuse hydrogen into helium — the second most abundant element.
21. Which state of matter has a definite volume but no definite shape?
- A.Solid
- B.Liquid✓ Correct
- C.Gas
- D.Plasma
Answer: Liquid. A liquid keeps a fixed volume but takes the shape of its container. Solids hold both a fixed shape and volume, while gases expand to fill any container they occupy.
22. What word describes animals that are active mainly at night?
- A.Diurnal
- B.Nocturnal✓ Correct
- C.Crepuscular
- D.Hibernal
Answer: Nocturnal. Nocturnal animals, such as owls, bats and many cats, are active at night and rest during the day. The opposite is 'diurnal'. Nocturnal creatures often have heightened senses of hearing and smell to navigate the dark.
23. What is the SI unit of force?
- A.Joule
- B.Newton✓ Correct
- C.Watt
- D.Pascal
Answer: Newton. Force is measured in newtons (N), named after Isaac Newton. One newton is the force needed to accelerate a 1 kg mass by 1 metre per second squared. The joule measures energy and the watt measures power.
24. Which gas is produced when baking soda reacts with vinegar?
- A.Oxygen
- B.Hydrogen
- C.Carbon dioxide✓ Correct
- D.Methane
Answer: Carbon dioxide. Mixing baking soda (sodium bicarbonate) with vinegar (acetic acid) produces carbon dioxide gas, which creates the familiar fizzing and bubbling. This reaction is often used in model volcanoes and homemade science experiments.
25. Which subatomic particle carries a negative electric charge?
- A.Proton
- B.Neutron
- C.Electron✓ Correct
- D.Photon
Answer: Electron. Electrons carry a negative charge and orbit the atom's nucleus. Protons carry a positive charge and neutrons carry no charge. In a neutral atom, the number of electrons equals the number of protons.
26. What is the process by which a liquid turns into a gas called?
- A.Condensation
- B.Evaporation✓ Correct
- C.Sublimation
- D.Freezing
Answer: Evaporation. Evaporation is the process where a liquid changes into a gas, usually at its surface and below boiling point. It is a key part of the water cycle, lifting water vapour into the atmosphere where it later forms clouds.
27. Which vitamin is essential for blood clotting?
- A.Vitamin A
- B.Vitamin C
- C.Vitamin D
- D.Vitamin K✓ Correct
Answer: Vitamin K. Vitamin K is essential for producing the proteins that allow blood to clot, preventing excessive bleeding. The 'K' comes from the German word 'Koagulation'. It is found in leafy green vegetables like spinach and kale.
28. Which metal is the best conductor of electricity?
- A.Copper
- B.Gold
- C.Silver✓ Correct
- D.Aluminium
Answer: Silver. Silver is the best electrical conductor of all metals, slightly better than copper. Copper is used more widely in wiring, however, because it is far cheaper while still being an excellent conductor.
29. What is the scientific study of living organisms called?
- A.Geology
- B.Biology✓ Correct
- C.Chemistry
- D.Ecology
Answer: Biology. Biology is the study of life and living organisms, from microscopic cells to entire ecosystems. It includes branches such as zoology (animals), botany (plants) and microbiology (microorganisms).
30. What is the chemical formula for common table salt?
- A.NaCl✓ Correct
- B.KCl
- C.NaOH
- D.CaCO3
Answer: NaCl. Table salt is sodium chloride (NaCl), formed from sodium and chlorine ions arranged in a cubic crystal lattice. Despite being made of two dangerous elements on their own, the compound is essential to life in small amounts.
31. How many chambers does the human heart have?
- A.Two
- B.Three
- C.Four✓ Correct
- D.Five
Answer: Four. The human heart has four chambers: two upper atria and two lower ventricles. The right side pumps oxygen-poor blood to the lungs, while the left side pumps oxygen-rich blood to the rest of the body.
32. What force opposes motion between two surfaces in contact?
- A.Gravity
- B.Friction✓ Correct
- C.Tension
- D.Magnetism
Answer: Friction. Friction is the resistive force that acts when two surfaces slide or try to slide past each other. It generates heat and wear, but it is also essential — without it, walking, driving and gripping objects would be impossible.
33. What is the basic physical unit of heredity?
- A.Cell
- B.Gene✓ Correct
- C.Protein
- D.Enzyme
Answer: Gene. A gene is a segment of DNA that codes for a specific trait or protein, and it is the basic unit passed from parents to offspring. Humans have an estimated 20,000–25,000 genes.
34. What is the process of cell division that produces two genetically identical cells?
- A.Meiosis
- B.Mitosis✓ Correct
- C.Osmosis
- D.Fertilisation
Answer: Mitosis. Mitosis is the process by which a single cell divides to produce two identical daughter cells, used for growth and repair. Meiosis, by contrast, produces sex cells (gametes) with half the number of chromosomes.
35. Which scientist proposed the theory of evolution by natural selection?
- A.Gregor Mendel
- B.Charles Darwin✓ Correct
- C.Louis Pasteur
- D.Carl Linnaeus
Answer: Charles Darwin. Charles Darwin proposed the theory of evolution by natural selection in his 1859 book 'On the Origin of Species'. Based partly on his observations during the voyage of HMS Beagle, it remains the unifying theory of biology.
36. What is a substance that speeds up a chemical reaction without being used up called?
- A.Catalyst✓ Correct
- B.Solvent
- C.Reactant
- D.Product
Answer: Catalyst. A catalyst increases the rate of a chemical reaction by lowering the energy needed for it to occur, and it emerges unchanged at the end. In living organisms, biological catalysts called enzymes perform this role.
37. What type of rock is formed when molten magma or lava cools and solidifies?
- A.Sedimentary
- B.Metamorphic
- C.Igneous✓ Correct
- D.Mineral
Answer: Igneous. Igneous rock forms from cooled magma or lava — examples include granite and basalt. The other two main rock types are sedimentary (formed from compressed sediments) and metamorphic (rock changed by heat and pressure).
38. What is the most abundant metal in the Earth's crust?
- A.Iron
- B.Aluminium✓ Correct
- C.Copper
- D.Gold
Answer: Aluminium. Aluminium is the most abundant metal in the Earth's crust, making up about 8% of its mass. Although common, it is rarely found in pure form because it bonds readily with other elements, mostly as part of minerals.
39. What is the SI unit of energy?
- A.Watt
- B.Joule✓ Correct
- C.Newton
- D.Volt
Answer: Joule. Energy is measured in joules (J), named after physicist James Prescott Joule. One joule is roughly the energy needed to lift a small apple one metre. The watt, by contrast, measures the rate of energy use (one joule per second).
40. What do bees collect from flowers to make honey?
- A.Pollen
- B.Nectar✓ Correct
- C.Sap
- D.Water
Answer: Nectar. Bees collect nectar, a sugary liquid produced by flowers, and convert it into honey through evaporation and enzymes. They also gather pollen as a protein source, accidentally pollinating plants as they travel between flowers.
41. What is the process by which water vapour turns back into liquid water?
- A.Evaporation
- B.Condensation✓ Correct
- C.Precipitation
- D.Sublimation
Answer: Condensation. Condensation is the change from gas to liquid, such as water vapour forming dew or clouds. It is the opposite of evaporation and a key stage in the water cycle that leads to rainfall.
42. Which human sense is associated with the cochlea?
- A.Sight
- B.Smell
- C.Hearing✓ Correct
- D.Taste
Answer: Hearing. The cochlea is a spiral-shaped, fluid-filled structure in the inner ear that converts sound vibrations into nerve signals for the brain — making it essential for hearing and also helping with balance.
43. What is the term for animals that have a backbone?
- A.Invertebrates
- B.Vertebrates✓ Correct
- C.Mammals
- D.Arthropods
Answer: Vertebrates. Vertebrates are animals with a backbone or spinal column, including mammals, birds, reptiles, amphibians and fish. Invertebrates, which lack a backbone, actually make up around 97% of all animal species.
44. What is the chemical symbol for iron?
- A.Ir
- B.In
- C.Fe✓ Correct
- D.Fr
Answer: Fe. Iron's symbol 'Fe' comes from its Latin name 'Ferrum'. It is the most widely used metal in the world, essential for making steel, and also a key component of haemoglobin, which carries oxygen in our blood.
45. What term describes the variety of living species within an ecosystem?
- A.Biomass
- B.Biodiversity✓ Correct
- C.Biosphere
- D.Biome
Answer: Biodiversity. Biodiversity refers to the variety of life in a given area, including the range of species, their genes and the ecosystems they form. High biodiversity generally makes ecosystems more resilient and stable.
46. What is the SI unit of electrical resistance?
- A.Volt
- B.Ampere
- C.Ohm✓ Correct
- D.Watt
Answer: Ohm. Electrical resistance is measured in ohms (Ω), named after physicist Georg Ohm. Ohm's law states that voltage equals current multiplied by resistance (V = IR), one of the most fundamental relationships in electronics.
47. What is an animal that eats both plants and other animals called?
- A.Carnivore
- B.Herbivore
- C.Omnivore✓ Correct
- D.Detritivore
Answer: Omnivore. An omnivore eats both plants and animals — humans, bears and pigs are examples. This flexible diet allows omnivores to survive in a wide range of environments where food sources may vary.
48. In which part of a plant does most photosynthesis take place?
- A.Roots
- B.Stem
- C.Leaves✓ Correct
- D.Flowers
Answer: Leaves. Most photosynthesis happens in the leaves, which contain large numbers of chloroplasts packed with chlorophyll. Their broad, flat shape maximises the surface area available to capture sunlight.
49. What is the process by which plants release water vapour into the air called?
- A.Respiration
- B.Transpiration✓ Correct
- C.Germination
- D.Pollination
Answer: Transpiration. Transpiration is the loss of water vapour from a plant, mostly through tiny pores in the leaves called stomata. It helps draw water up from the roots and plays a major role in the global water cycle.
50. How many pairs of chromosomes does a typical human cell contain?
- A.21
- B.23✓ Correct
- C.46
- D.12
Answer: 23. Human cells normally contain 23 pairs of chromosomes — 46 in total — with one of each pair inherited from each parent. The 23rd pair determines biological sex: XX for female and XY for male.