Science Quiz for Students: 40 Must-Know Questions

Q1. What is the powerhouse of the cell?

✅ Answer: The mitochondrion

💡 Mitochondria convert glucose and oxygen into ATP (adenosine triphosphate), the energy currency of the cell.

Q2. What is the basic unit of life?

✅ Answer: The cell

💡 All living organisms are made of one or more cells. The cell theory was established in the 1830s by Schleiden and Schwann.

Q3. What gas do plants absorb from the atmosphere during photosynthesis?

✅ Answer: Carbon dioxide (CO₂)

💡 Plants use CO₂ and water in the presence of sunlight to produce glucose and oxygen.

Q4. What is DNA an abbreviation for?

✅ Answer: Deoxyribonucleic acid

💡 DNA carries the genetic instructions for growth, development, and reproduction in all known living organisms.

Q5. How many chromosomes do humans have in each body cell?

✅ Answer: 46 (23 pairs)

💡 One set of 23 comes from each parent. Sex cells (gametes) contain only 23 chromosomes.

Q6. What type of blood vessel carries blood away from the heart?

✅ Answer: Arteries

💡 Arteries have thick, muscular walls to withstand the high pressure of blood pumped directly from the heart.

Q7. Which organ produces insulin?

✅ Answer: The pancreas

💡 Beta cells in the islets of Langerhans secrete insulin, which regulates blood sugar levels.

Q8. What is the largest organ in the human body?

✅ Answer: The skin

💡 An adult's skin covers roughly 1.5–2 m² and weighs about 3.6 kg. It acts as a barrier against pathogens.

Q9. What process do cells use to divide and produce two identical copies?

✅ Answer: Mitosis

💡 Mitosis produces two genetically identical daughter cells and is used for growth and repair. Meiosis, by contrast, produces four genetically different gametes.

Q10. What is the function of red blood cells?

✅ Answer: To transport oxygen around the body

💡 Red blood cells contain haemoglobin, which binds oxygen in the lungs and releases it in tissues.

Q11. Which part of the plant cell is not found in animal cells?

✅ Answer: The cell wall (also chloroplasts and a large permanent vacuole)

💡 The cell wall provides structural support and is made mainly of cellulose in plants.

Q12. What is the name of the process by which water moves across a semi-permeable membrane?

✅ Answer: Osmosis

💡 Water moves from a region of lower solute concentration to higher solute concentration until equilibrium.

Q13. Which vitamin is produced when human skin is exposed to sunlight?

✅ Answer: Vitamin D

💡 UV-B radiation triggers vitamin D3 synthesis in the skin. It is essential for bone health and immune function.

Q14. What structure in the cell contains the genetic material?

✅ Answer: The nucleus

💡 The nucleus houses chromosomes (DNA) and controls cell activities by regulating gene expression.

Q15. What is natural selection?

✅ Answer: The process by which organisms with advantageous traits are more likely to survive and reproduce.

💡 Proposed by Charles Darwin, natural selection is the main mechanism of evolution, often summarised as "survival of the fittest".

Q1. What is the chemical symbol for gold?

✅ Answer: Au

💡 It comes from the Latin word "aurum". Gold has an atomic number of 79.

Q2. What is the pH of pure water?

✅ Answer: 7 (neutral)

💡 The pH scale runs from 0 (strong acid) to 14 (strong alkali). Pure water is exactly neutral at 25 °C.

Q3. What are the three states of matter?

✅ Answer: Solid, liquid, and gas

💡 A fourth state, plasma, exists at very high temperatures. At school level, the three main states are solid, liquid, and gas.

Q4. What is the chemical formula of water?

✅ Answer: H₂O

💡 Each molecule contains two hydrogen atoms covalently bonded to one oxygen atom.

Q5. What is an exothermic reaction?

✅ Answer: A reaction that releases heat energy to the surroundings.

💡 Combustion is a common example. Endothermic reactions absorb heat, like photosynthesis or dissolving ammonium nitrate.

Q6. What is the atomic number of carbon?

✅ Answer: 6

💡 Carbon has 6 protons. It forms the backbone of organic chemistry and all known life.

Q7. What is the name of the bond formed when atoms share electrons?

✅ Answer: Covalent bond

💡 Covalent bonds are common in non-metal molecules like H₂, O₂, and CH₄. Ionic bonds involve electron transfer.

Q8. Which gas makes up approximately 78% of the Earth's atmosphere?

✅ Answer: Nitrogen (N₂)

💡 Oxygen makes up about 21%, with argon, CO₂, and trace gases making up the rest.

Q9. What is the periodic table arranged by?

✅ Answer: Increasing atomic number (number of protons)

💡 Dmitri Mendeleev published an early version in 1869. Elements in the same group share similar chemical properties.

Q10. What is an ion?

✅ Answer: An atom that has gained or lost one or more electrons, giving it a net charge.

💡 A positive ion (cation) has lost electrons; a negative ion (anion) has gained electrons.

Q11. What type of reaction occurs when an acid reacts with a base?

✅ Answer: Neutralisation

💡 The general equation is: acid + base → salt + water. For example, HCl + NaOH → NaCl + H₂O.

Q12. What is Avogadro's number?

✅ Answer: Approximately 6.022 × 10²³

💡 It represents the number of particles (atoms or molecules) in one mole of a substance.

Q13. What metal is liquid at room temperature?

✅ Answer: Mercury (Hg)

💡 Mercury melts at −38.83 °C. Gallium (melting point ~29.8 °C) can also become liquid in warm conditions.

Q1. What is the unit of force?

✅ Answer: Newton (N)

💡 One newton is the force required to accelerate a mass of 1 kg by 1 m/s².

Q2. What is the speed of light in a vacuum?

✅ Answer: Approximately 3 × 10⁸ m/s (300,000 km/s)

💡 Nothing with mass can travel at or faster than the speed of light, according to Einstein's theory of special relativity.

Q3. What is Newton's First Law of Motion?

✅ Answer: An object at rest stays at rest, and an object in motion stays in motion, unless acted upon by an external force.

💡 This is also called the law of inertia. A book on a table remains still until a force moves it.

Q4. What type of energy does a moving object have?

✅ Answer: Kinetic energy

💡 Kinetic energy = ½mv². It depends on both mass and velocity.

Q5. What is the unit of electrical resistance?

✅ Answer: Ohm (Ω)

💡 Resistance = Voltage ÷ Current (Ohm's Law: V = IR).

Q6. What happens to the frequency of a wave if its wavelength decreases (speed unchanged)?

✅ Answer: Frequency increases

💡 Speed = frequency × wavelength. If speed is constant and wavelength decreases, frequency must increase.

Q7. What is the acceleration due to gravity on Earth's surface?

✅ Answer: Approximately 9.8 m/s²

💡 This value varies slightly depending on altitude and location but is typically rounded to 10 m/s² in school calculations.

Q8. What is the difference between mass and weight?

✅ Answer: Mass is the amount of matter (measured in kg); weight is the force of gravity on that mass (measured in N).

💡 Your mass is the same on the Moon, but your weight is about one-sixth of what it is on Earth.

Q9. What device is used to measure electric current?

✅ Answer: An ammeter

💡 An ammeter is connected in series within a circuit. A voltmeter, by contrast, is connected in parallel to measure potential difference.

Q10. What is the law of conservation of energy?

✅ Answer: Energy cannot be created or destroyed, only transferred or transformed.

💡 The total energy in a closed system remains constant. For example, a falling ball converts gravitational potential energy into kinetic energy.

Q11. What type of wave is sound?

✅ Answer: A longitudinal wave

💡 Sound waves compress and rarefy the medium (like air). They cannot travel through a vacuum.

Q12. What colour of visible light has the shortest wavelength?

✅ Answer: Violet

💡 Violet light has a wavelength of about 380–450 nm. Red light has the longest visible wavelength at around 620–750 nm.

What age group is this quiz for?

It is aimed at secondary-school students (ages 11–16) but anyone curious about science will enjoy it.

Does the quiz cover all three sciences equally?

Roughly. There are 15 biology, 13 chemistry, and 12 physics questions to give a balanced spread.

Can teachers use these questions in class?

Yes. Feel free to copy them into worksheets, presentations, or starter activities — no attribution required.

Are these questions suitable for GCSE revision?

Many align with GCSE-level content (UK), AP-level (US), and equivalent curricula worldwide, though they are not a substitute for full syllabus revision.