47 Fun Facts About 10th Grade

Which country spans eleven time zones and borders fourteen others?

Russia would be even larger had it not sold Alaska to the United States in 1867, fearing Britain could seize the hard-to-defend colony.

Which organ, the heaviest inside the human body, produces bile and stores glycogen?

The liver regrows lost tissue so well that a living donor can give part of theirs, and both pieces grow back to near full size.

Which organelle, the site of aerobic respiration, has its own DNA, almost always inherited from the mother?

The mitochondrion has a genome like a bacterium's, supporting the theory that it began as a free-living microbe engulfed by an early cell.

Which 1803 deal with Napoleon's France nearly doubled the size of the United States for $15 million?

The Louisiana Purchase worked out at less than three cents an acre, and Napoleon sold because war with Britain was imminent.

Which planet hosts the Great Red Spot, a giant storm tracked since the 1800s?

Jupiter's Great Red Spot is wider than Earth, yet it has been shrinking for about a century, and no one knows exactly what makes it red.

Which explorer's fleet first circled the globe, though its commander was killed in the Philippines?

Magellan set out from Spain with five ships, but only the Victoria, under Elcano, made it home, almost exactly three years later.

Which amendment to the US Constitution, ratified in December 1865, abolished slavery nationwide?

The Thirteenth Amendment allows involuntary servitude 'as a punishment for crime', the loophole behind convict leasing and prison labor.

Which mathematician, as a boy, reputedly summed 1 to 100 in seconds by pairing numbers into 101s?

Carl Friedrich Gauss's gift won him a patron: the Duke of Brunswick gave him a stipend that put him through the Collegium Carolinum.

Australia is famously dry, but which continent is the driest of all?

Antarctica is a polar desert with little precipitation, yet its ice holds about 70% of the world's fresh water.

Which novella satirizing Stalin's Soviet Union ends with pigs walking upright and carrying whips?

Animal Farm's final commandment reads 'All animals are equal, but some animals are more equal than others', and the pigs end up indistinguishable from the men.

Which element, first identified as a distinct gas by Henry Cavendish, makes up 75% of normal matter?

Hydrogen was Cavendish's 'inflammable air'; Lavoisier later named it from the Greek for 'water-former' after showing it burns to make water.

Which photosynthetic pigment absorbs red and blue light but reflects the wavelengths in between?

Chlorophyll is why autumn leaves turn yellow: as it breaks down, the carotenoids that were there all summer finally show through.

Which property, the subject of Newton's first law, throws bus riders forward when the driver brakes?

Inertia was spotted by Galileo, who argued a ball rolling on a level surface would keep going unless disturbed, long before Newton's first law.

Which law, set out by a German physicist in 1827, makes current in a wire proportional to voltage?

Ohm's law was first dismissed by critics as empty mathematical fancy, before becoming a cornerstone of electrical theory.

Which of these common liquids is the most alkaline?

Bleach sits at pH 11 or higher, and mixing it with vinegar or other acids releases a toxic gas.

What is the approximate speed of light in a vacuum, the constant c in Einstein's equation E = mc²?

Light covers about 300,000 km/s, so the sunlight reaching Earth left the Sun a little over eight minutes earlier.

Which trait type vanished in Mendel's hybrid peas, then returned in a quarter of the next generation?

Recessive traits hide behind a dominant allele, so crossing two hybrids brings them back in one offspring in four, Mendel's famous 3:1 ratio.

Which brain structure coordinates fine movement and balance?

The cerebellum fine-tunes movement rather than starting it, so damage leaves people unsteady and clumsy.

Which alkali metal, atomic number 11, is stored under oil and is soft enough to cut with a knife?

Sodium was first isolated in 1807 by Humphry Davy, who passed electricity through caustic soda, and the element is named after soda.

Which optical effect, far stronger at short wavelengths, makes the daytime sky blue and sunsets red?

Rayleigh scattering favours violet even more than blue, but sunlight carries less violet and our eyes respond more to blue, so the sky looks blue.

Which eye defect, where distant objects focus in front of the retina, does a diverging lens correct?

Myopia in children has climbed since 1990, and studies link more time spent outdoors in daylight to lower rates.

Which leaf pores, usually more numerous on the underside, open and close to control gas exchange?

Stomata are flanked by two guard cells that bow apart as they swell with water, opening the pore, and relax to close it again.

Which gas, given off by yeast as bread dough rises, turns clear limewater milky?

Carbon dioxide reacts with the calcium hydroxide in limewater to precipitate insoluble calcium carbonate, the same compound as chalk.

Which scientist predicted gallium and germanium years before either element was discovered?

Dmitri Mendeleev reasoned that gaps in his periodic table, such as the one below aluminium, held undiscovered elements whose properties he could forecast.

Which of DNA's four bases is missing from RNA, where uracil takes its place?

Thymine sits in DNA because damaged cytosine turns into uracil, so a cell that finds uracil in its DNA knows to repair it.

Which number sequence shows up in the spirals of pinecones?

The Fibonacci sequence is named for the mathematician whose 1202 book Liber Abaci used it to model how fast rabbits breed.

What value of the discriminant b² − 4ac gives a quadratic equation exactly one repeated real root?

Zero: the ± √(b² − 4ac) in the quadratic formula then adds and subtracts nothing, so both roots equal −b/2a.

Which regular polygon with more than four sides can tile a flat surface with no gaps?

The hexagon fits three to a corner, and since equal hexagonal cells need the least total wall, a honeycomb uses the least wax.

Which Greek mathematician proved that there are infinitely many prime numbers?

Euclid's proof in his Elements multiplies any finite list of primes and adds one; the result has a prime factor missing from the list.

A 30-60-90 right triangle is exactly half of which shape?

An equilateral triangle split by its height gives two 30-60-90 triangles, so the short side is half the hypotenuse and sin 30° equals exactly 1/2.

The legend of a chess inventor who asked to be paid in wheat grains illustrates what kind of growth?

Exponential growth: the ruler laughed off the request until his treasurers found the doubling grains would outstrip his entire kingdom's wheat.

What term describes an integer such as 6 or 28 that equals the sum of its proper divisors?

Leonhard Euler proved that every even perfect number comes from a Mersenne prime, and as of 2024 no odd perfect number has ever been found.

Which medieval charter still had three of its clauses in force in English law as of 2025?

Magna Carta's surviving clauses come from the 1297 reissue; the 1215 original also named 25 barons to hold the king to his word.

Whose 1914 assassination in Sarajevo by Gavrilo Princip set off the July Crisis and World War I?

Franz Ferdinand died because his driver took a wrong turn and stalled the car while reversing, right where Princip was standing.

Which 1917 uprising, led by Lenin's Bolsheviks in Petrograd, overthrew the Provisional Government?

The October Revolution began on 7 November by today's calendar; the country still used the Julian calendar, which ran 13 days behind.

Which Mughal emperor built the Taj Mahal as the tomb of his favorite consort, Mumtaz Mahal?

Shah Jahan spent his final years imprisoned by his son Aurangzeb in Agra Fort, from 1658 until his death in 1666.

Which 1930 protest, a 24-day walk by Gandhi to the sea at Dandi, defied a British tax monopoly?

The Salt March ended with Gandhi making illegal salt at Dandi, and soon Indians across the country were making their own in open defiance.

Which circle of latitude, near 23.4° north, is the farthest north the Sun can be directly overhead?

The Tropic of Cancer is drifting south about 15 m a year as Earth's tilt wobbles, and it runs through India, Egypt, Mexico and China.

Which mountain range, pushed up by India's collision with Eurasia, is still rising today?

The Himalayas' highest peaks are capped with limestone that formed on the floor of the Tethys Ocean before the collision lifted it skyward.

Which lawyer defends Tom Robinson against a rape charge in Harper Lee's To Kill a Mockingbird?

Atticus Finch's defense of Tom brings Maycomb's anger down on his family, and Bob Ewell later attacks Jem and Scout in revenge.

In The Great Gatsby, what color is the light on Daisy's dock that Gatsby stares at across the bay?

The green light stands for Gatsby's unreachable dream of Daisy, and after his death Nick ends the story staring across the bay at it.

In Lord of the Flies, what does Ralph use to call the boys together, an object smashed when Piggy dies?

The conch stands for order and the right to speak, so when Roger's boulder kills Piggy and smashes it, the island's last rule dies too.

Which Italian city is the setting for the Montague–Capulet feud in Shakespeare's Romeo and Juliet?

Verona's famous 'Juliet's balcony' is a tourist invention: the play only puts Juliet at a window, and 'balcony' wasn't even an English word yet.

Which power, claimed in Marbury v. Madison, allows laws that violate the Constitution to be struck down?

Judicial review appears nowhere in the Constitution's text; Chief Justice John Marshall claimed it for the courts in 1803 and it has held ever since.

Which federal office does the US Constitution restrict to people aged at least 35?

President: the Constitution's age floors climb from 25 for the House to 30 for the Senate and 35 for the presidency, yet it sets no minimum age for justices.

Which UN body, with five veto-wielding permanent members, can impose sanctions and authorize force?

The Security Council backed South Korea after the North's 1950 invasion because the Soviet Union, boycotting it, was absent and cast no veto.

Which language has the most native speakers as of 2026, about double runner-up Spanish?

Mandarin Chinese leads in native speakers, but English has more speakers overall once second-language learners are counted.