Science
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This science trivia quiz has 150 free questions with answers spanning physics, chemistry, biology, astronomy, earth science and the human body: which gas plants breathe in, what the chemical symbol for gold is, how many bones an adult has, why the sky is blue and what a light-year actually measures. Most questions sit at a middle-school level, so it works as 7th grade science trivia for a classroom warm-up or family quiz, and the harder stretch will stretch high school students and adults who think they remember it all. Every answer has been checked against a reliable reference source, and each question shows a short explanation once you have answered so the quiz teaches as it goes. Play it through for a shareable score, then try the Science Trivia for Kids and Space quizzes for more.
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Q 01What is the chemical symbol for gold?
Au
Au comes from the Latin 'aurum'; gold is so unreactive that it is one of the few metals found in nature as nuggets of pure metal.
Q 02Which planet in our Solar System is less dense than water?
Saturn
Saturn has a mean density of about 0.69 g/cm³, the only planet below water's 1 g/cm³, so it would float in a large enough ocean; Jupiter is roughly twice as dense.
Q 03Which organelle is nicknamed the 'powerhouse of the cell'?
Mitochondria
Mitochondria carry their own small genome because they descend from free-living bacteria that fused with an ancient cell; Philip Siekevitz popularised the 'powerhouse' nickname in 1957.
Q 04About how fast does light travel through a vacuum?
About 300,000 km/s
About 300,000 km/s, so a laser pulse bounced off mirrors that Apollo astronauts left on the Moon comes back in about 2.5 seconds.
Q 05Which physicist imagined a cat that is both alive and dead inside a sealed box?
Erwin Schrödinger
Erwin Schrödinger devised the cat in 1935, not as a real experiment but to show how strange quantum rules look when applied to something as big as a cat.
Q 06What is the hardest natural substance on Earth?
Diamond
Diamond, which is hard but not tough: hardness is resistance to scratching, and a hammer blow along a cleavage plane will split it. It is pure carbon, the same stuff as pencil graphite, arranged differently.
Q 07What gas makes up approximately 78% of Earth's atmosphere?
Nitrogen
Nitrogen makes up about 78% of the air, yet plants and animals can't use the gas until bacteria, lightning or industry 'fix' it.
Q 08What is the largest organ in the human body?
Skin
Skin is the largest organ, yet the surface you touch is dead: its outer layer is flattened, keratin-filled cells that are constantly shed.
Q 09Which element has the atomic number 1?
Hydrogen
Hydrogen's name means 'water-former' because the gas makes water when it burns, the property Henry Cavendish discovered.
Q 10What phenomenon causes the Northern Lights?
Solar particles exciting gases in the upper atmosphere
Solar particles exciting gases in the upper atmosphere make them glow, and auroras hug the polar regions because Earth's magnetic field steers those particles there.
Q 11What is the chemical formula for table salt?
NaCl
NaCl, sodium chloride, joins sodium, a metal that reacts vigorously with water, to chlorine, a First World War poison gas, yet together they season dinner.
Q 12Which blood type is considered the universal donor?
O negative
Only about 7% of Americans are O negative, so blood banks prize it for emergencies when there is no time to type a patient.
Q 13What is the most abundant protein in the human body?
Collagen
Collagen can't be made properly without vitamin C, which is why scurvy, a vitamin C shortage, brings gum disease and wounds that heal poorly.
Q 21What is the pH of pure water at room temperature?
7
Pure water has a pH of 7 at 25 °C, yet boiling-hot pure water reads below 7 while staying neutral, because heat splits more molecules into equal numbers of hydrogen and hydroxide ions.
Q 22On which planet do sunsets glow blue?
Mars
Mars gets its rusty colour from iron minerals in its dirt, yet fine dust in its air lets blue light through near the Sun, so Martian sunsets glow blue.
Q 23What is the function of white blood cells?
Fight infections
Fight infections: pus is largely the remains of white blood cells that died at the site, along with dead tissue and germs.
Q 14Who discovered penicillin?
Alexander Fleming
Alexander Fleming found penicillin by accident in 1928, when mould that had landed on a staphylococcus culture plate cleared a bacteria-free ring around itself.
Q 15What is the unit of electrical resistance?
Ohm
The ohm honours Georg Ohm, whose law was received so coolly that he resigned his teaching post; in 1841 Britain's Royal Society gave him its Copley Medal.
Q 16What type of rock is formed from cooled lava or magma?
Igneous
Igneous rock can even float: pumice forms when frothy, gas-filled lava cools so fast that it traps countless bubbles, leaving it lighter than water.
Q 17What is the closest star to Earth after the Sun?
Proxima Centauri
Proxima Centauri, just over four light-years away, is the nearest star after the Sun, yet it is so small and dim that you can't see it with the naked eye.
Q 18Which vitamin is produced when human skin is exposed to sunlight?
Vitamin D
Vitamin D forms when sunlight hits the skin and helps the body absorb calcium, so a shortage can leave children with the soft, bowed bones of rickets.
Q 19What is the process by which plants convert sunlight into energy?
Photosynthesis
Photosynthesis happens as much at sea as on land: tiny ocean phytoplankton carry out roughly half of all the photosynthesis on Earth.
Q 20What is the Heisenberg Uncertainty Principle about?
Position and momentum cannot both be known exactly
Position and momentum cannot both be known exactly because particles behave like waves, not because instruments are clumsy; Werner Heisenberg introduced the idea in 1927.
Q 24What force keeps planets in orbit around the Sun?
Gravity
Gravity, and an orbit is really a fall: a planet is always dropping toward the Sun, but it moves sideways fast enough that it keeps missing.
Q 25What is the most common element in the Earth's crust?
Oxygen
Nearly half the crust's mass is oxygen locked up in silicate and oxide minerals; silicon comes second at roughly 28%.
Q 26Whose 1543 book set out the Sun-centred model that Galileo defended?
Nicolaus Copernicus
Nicolaus Copernicus died the year his book came out, and in 1616 the Catholic Church suspended it until it was corrected.
Q 27Which part of the eye controls how much light gets in?
Iris
Iris patterns are as distinctive as fingerprints, which is why iris scanners can be used to confirm who a person is.
Q 28Which supercontinent joined all of today's continents together about 250 million years ago?
Pangaea
Pangaea's breakup is why fossils of the same small aquatic reptile, Mesosaurus, turn up in both Brazil and South Africa, now an ocean apart.
Q 29What do honeybees collect from flowers and turn into honey?
Nectar
Nectar is passed from bee to bee and mixed with their enzymes, then stored in the wax cells of the honeycomb, where it becomes honey.
Q 30Which athletes often have a resting heart rate in the 40s?
Marathon runners
Marathon runners and other well-trained endurance athletes can rest at 40 to 60 beats a minute, below the usual adult range, because a trained heart pumps more blood with each beat.