100 Fun Facts About Water

What is the chemical formula for water?

Water is H2O: each molecule has two hydrogen atoms covalently bonded to a single oxygen atom.

About what fraction of Earth's surface is covered by water?

About 71% of Earth's surface is covered by water, nearly all of it ocean; land makes up the remaining 29%.

Water is often called the 'universal' what?

Water is called the universal solvent because more substances dissolve in it than in any other common liquid.

Unusually, water's solid form is what compared with its liquid form?

Ice is less dense than liquid water: as it solidifies, the molecules lock into an open hexagonal lattice with more empty space, so solid ice rests on top of liquid water.

At standard pressure, water boils at what temperature?

Water boils at 100 degrees C at standard atmospheric pressure, unusually high for such a small molecule because its molecules attract one another strongly.

The continuous movement through evaporation, condensation and precipitation is called what?

The water cycle, also called the hydrologic cycle, is the continuous movement of water between Earth's surface and atmosphere through evaporation, condensation and precipitation.

Which source supplies about 86% of the water that evaporates worldwide each year?

The ocean supplies about 86% of global evaporation; the sun drives water off its vast surface, and most of it falls straight back as rain at sea.

Roughly what percentage of Earth's water is held in the ocean?

About 97% of Earth's water is salty ocean water; only around 2.5% is fresh, and most of that is frozen in glaciers or stored underground.

Which is the largest of Earth's oceans by area?

The oceans in order of size are Pacific, Atlantic, Indian, Southern and Arctic.

The Challenger Deep, the ocean's deepest known point, lies in which trench?

The Marianas deep, better known as the Mariana Trench, holds the Challenger Deep, which at nearly 11 kilometres below sea level is the deepest known point in any ocean.

Which river is generally considered the longest in the world?

At about 7,088 km it edges out the Amazon, though it carries far less water.

Which river carries the most water of any in the world by discharge volume?

It discharges more than the next seven largest rivers combined.

Which is the largest lake in Africa by surface area?

Lake Victoria, shared by Tanzania, Uganda and Kenya, is Africa's largest lake by area, the world's largest tropical lake and the second-largest freshwater lake on Earth by surface area.

The Dead Sea's shores are notable for being what?

The Dead Sea's shores are the lowest land on Earth; its surface lies roughly 430 metres below sea level.

The Dead Sea's very high salt content makes swimming there feel like what?

Floating is effortless in the Dead Sea: its water is roughly ten times saltier than seawater, so it is far denser than a human body.

About what percentage of an adult male human body is water?

Water makes up about 60% of an adult male's body weight, a little less in women, and is split between the inside and outside of cells.

The phrase 'the tip of the iceberg' reflects the fact that most of an iceberg is where?

Roughly 90% of an iceberg's mass sits below the water; ice is only about a tenth lighter than seawater, so most of the berg stays submerged.

A rainbow is caused by refraction, reflection and dispersion of light in what?

Sunlight entering water droplets is refracted, reflected off the back of each drop and dispersed into its colours, which is what produces a rainbow.

In a primary rainbow, which colour appears on the outer edge?

Violet sits on the inner side of the arc.

Steam is the common name for what?

Steam is water vapor, the gas phase of water; the white plume seen above a kettle is actually vapor that has already condensed back into a fine mist.

An underground layer of water-bearing rock or gravel from which wells draw is called what?

An aquifer is a body of permeable rock, gravel or sand that holds groundwater; wells and springs draw from it, and a low-permeability layer beside it is an aquitard.

Angel Falls in Venezuela holds what record?

Angel Falls is the world's tallest uninterrupted waterfall, with a total height of 979 metres and a single plunge of about 807 metres.

Earth has water in all three states because its conditions sit near what threshold?

At the triple point all three states coexist.

The Mpemba effect refers to hot water doing what faster than cold water?

The Mpemba effect is the observation that hot water can finish freezing faster than cold water under some conditions; it is named after Erasto Mpemba, who noticed it as a Tanzanian schoolboy in the 1960s.

Pure water reaches its maximum density at about what temperature?

Below 4 C it expands again, which is why ice forms on top of ponds.

By roughly what percentage does water expand when it freezes into ordinary ice?

Water expands by about 9% when it freezes into ordinary ice, enough force to burst household pipes and crack rock.

Water that leaves limescale in kettles because of its calcium and magnesium content is called what?

Hard water carries high levels of calcium and magnesium picked up from limestone and chalk; heating deposits them as limescale, and they stop soap lathering easily.

Water molecules stick to each other by forming what?

Hydrogen bonds form between the slightly positive hydrogen of one water molecule and the slightly negative oxygen of another, giving water its high surface tension and boiling point.

The most remote spot in the ocean, farthest from any land, is nicknamed what?

Point Nemo, the oceanic pole of inaccessibility, lies about 2,688 km from the nearest land and serves as a 'spacecraft cemetery' for de-orbited satellites.

On Mars, water is found mostly in which form?

Large quantities of ice sit on and under the surface, though liquid water may exist deep down.

What does water's polarity let it do to salts like table salt?

Polar water molecules pull salts apart and dissolve their ions, surrounding each charged particle; this is why sodium chloride vanishes into a glass of water.

Which ocean has the highest average salinity?

The Atlantic is the saltiest of the major oceans on average, because over much of its surface evaporation removes more water than rain and rivers return.

A rainbow seen from the air, with enough mist, can appear as what shape?

A rainbow is really a full circle around the antisolar point; from the air, with mist below, the whole ring can be seen, while on the ground the horizon hides the lower half.

Water is nearly colourless but has an inherent hint of what colour?

Pure water has an intrinsic faint blue tint, visible only through several metres of it, because water absorbs slightly more light at the long-wavelength end of the spectrum.

Angel Falls plunges over the edge of which type of flat-topped mountain?

Angel Falls drops from Auyan-tepui, a tepui or table-top mountain of ancient sandstone in Venezuela's Canaima National Park.

In a double rainbow, the second arc appears where relative to the first?

The secondary arc appears about 10 degrees outside the primary.

The main tributary that feeds the Dead Sea is which river?

The Jordan River is the Dead Sea's main inflow; the lake lies in an endorheic basin with no outlet, so water leaves only by evaporation.

Losing which kind of ice is the main driver of rising sea levels?

Melting grounded land ice, such as the Greenland and Antarctic ice sheets and mountain glaciers, adds new water to the sea; floating sea ice already displaces its own weight, so its melt adds almost nothing.

Which African river plunges over Victoria Falls?

The Zambezi plunges about 108 metres over Victoria Falls on the border of Zambia and Zimbabwe; locals call the falls Mosi-oa-Tunya, 'the smoke that thunders'.

'The sea', used without specification, refers to the single interconnected body of what?

The sea is the world's single interconnected body of salt water, divided by convention into five named oceans plus many marginal seas.

What name is given to the H3O+ ion formed when a water molecule gains a proton?

Hydronium, H3O+, forms when a water molecule gains a proton; in pure water a tiny fraction of molecules split into hydronium and hydroxide ions, giving a neutral pH of 7.

Water is described as a compound of which type?

Water is an inorganic compound: it contains no carbon, so despite being essential to life it falls outside organic chemistry.

Along with 'water', what other name does IUPAC accept for the water molecule?

Oxidane is the systematic IUPAC name for the water molecule, used mainly as the parent name for derivatives, while 'water' remains the accepted everyday name.

By roughly how much does water's boiling point drop for every 274 metres of altitude gained?

Water's boiling point falls by roughly 1 °C for every 274 metres of altitude, so at about 1,500 metres it boils near 95 °C and cooking takes longer.

The ordinary ice found in snow and freezers is which crystalline phase?

Ordinary ice is ice Ih, whose molecules sit in a hexagonal lattice; nearly all ice on Earth takes this form, while the other phases need high pressure or very low temperatures.

One water molecule can bond to at most how many neighbouring water molecules at once?

Each water molecule can link to up to four neighbours, donating its two hydrogen atoms and accepting two through the lone pairs on its oxygen, building a tetrahedral network.

Which sea has the lowest salinity of the major seas, at about 0.7%?

The Baltic Sea is the least salty major sea at about 0.7%, because heavy river inflow and only a narrow link to the North Sea keep it diluted; average seawater is about 3.5% salt.

Roughly how much water does it take to produce 1 kg of cotton, about a pair of jeans?

Producing 1 kg of cotton takes roughly 10.9 cubic metres of water, about 10,000 litres, which is why irrigated cotton farming helped drain the Aral Sea.

The gram was defined in 1795 as the weight of a cube of pure water with sides of what length?

In 1795 the gram was defined as the weight of a cube of pure water one centimetre on a side at the temperature of melting ice; the kilogram standard followed in 1799.

Which lake holds more fresh water than any other on Earth?

Lake Baikal in Siberia holds about 23,600 cubic kilometres of water, roughly a fifth of the world's unfrozen surface fresh water, and is also the deepest lake at 1,642 metres.

A camel's hump is widely believed to hold water, but what does it actually store?

Fat fills the hump, a calorie reserve that goes limp and droops as a hungry camel uses it up. The water from a camel's huge drinks, up to 140 litres at a time, travels in its bloodstream instead.

Which human organ is about 83% water, more than the brain and heart at roughly 73%?

The lungs are about 83% water, well ahead of the skin at 64%. Even bones, which seem as dry as anything in the body, are roughly 31% water.

Which continent's ice sheet locks up about 61% of all the fresh water on Earth?

Antarctica is 98% covered by an ice sheet averaging more than 2 kilometres thick, far larger than Greenland's, the only other ice sheet on the planet.

Which human activity accounts for roughly 70% of the fresh water people withdraw worldwide?

Agriculture takes about 69% of global withdrawals, mostly to irrigate crops. Industry uses around 19%, and towns and cities just 12%.

Which brainless, heartless sea animals have bodies that are about 95% water?

Jellyfish are only about five percent solid matter, which is why one lifted out of the sea slumps into a shapeless blob. They also get by without blood.

Which ancient Greek is said to have cried 'Eureka!' on noticing his bath water rise as he got in?

Archimedes, the story goes, saw that the rising water could measure the volume of a king's crown and reveal whether cheaper metal had been mixed into its gold. 'Eureka' is now California's state motto.

Which doctor traced London's 1854 cholera outbreak to a contaminated water pump on Broad Street?

John Snow mapped the deaths clustered around the pump and persuaded the parish to take off its handle, at a time when most doctors blamed cholera on bad air.

Which Scottish landmark holds more water than all the lakes of England and Wales combined?

Loch Ness is only the second-largest Scottish loch by surface area, behind Loch Lomond, but its great depth makes it the biggest by volume in the British Isles.

Which alarming chemical name for plain water has fuelled decades of hoax campaigns to ban it?

Dihydrogen monoxide simply describes water atom by atom. In 1997 a 14-year-old's science project persuaded 43 of 50 classmates to vote for banning it.

Which fixture uses more water than any other inside the average North American home?

The toilet accounts for about 24% of household water use, flushed around five times a day by each person. Showers come second.

Cancer and Scorpio are two of astrology's three water signs; which sign completes the trio?

Pisces completes the trio, while Aquarius, despite being the water-bearer, counts as an air sign alongside Gemini and Libra.

Old Faithful, a geyser that hurls boiling water up to 185 feet, erupts in which national park?

Yellowstone's Old Faithful was the first geyser in the park to be named, in 1870, and erupts about every 92 minutes on average. The park's less predictable Steamboat Geyser shoots higher.

Which waterfall did teacher Annie Edson Taylor, aged 63, ride over in a barrel and survive?

Niagara Falls made her the first person to survive the plunge in a barrel, on her 63rd birthday. Two days earlier a cat had been sent over in the same barrel to test its strength.

Pure water scores a neutral 7 on which scale, which runs from 0 to 14?

pH was introduced in 1909 by the Danish chemist Søren Sørensen at the Carlsberg Laboratory. He never explained what the letter p stands for, and its meaning is still disputed.

Which element has disinfected American tap water since Jersey City first treated its supply in 1908?

Chlorine went into continuous use in the United States at the Boonton Reservoir. The English town of Maidstone got there first, treating its entire supply in 1897.

Which body's gravity is the main cause of the sea's twice-daily rise and fall, known as the tides?

The Moon does most of the work, since the Sun's tidal pull is only about 46% as strong. When the two line up, their forces combine into the extra-large spring tides.

Which author said his pen name came from a riverboat call meaning the water was two fathoms deep?

Mark Twain was the leadsman's cry for a depth of twelve feet, safe water for a steamboat. Samuel Clemens heard it daily while working as a Mississippi riverboat pilot.

Which disease was long called 'hydrophobia' because its victims panic when offered water to drink?

Rabies sets off painful, uncontrollable throat spasms whenever a sufferer tries to swallow. The same inability to swallow saliva produces the notorious foaming at the mouth.

Which process do most desalination plants use, squeezing fresh water out of seawater under pressure?

Reverse osmosis forces seawater through a membrane that lets water pass but holds the salt back. Desalination produces most of the drinking water consumed in Israel, Saudi Arabia, Oman and Kuwait.

Which of North America's Great Lakes covers more area than any other body of fresh water on Earth?

Superior is the largest freshwater lake in the world by surface area, yet it ranks only third by volume because two far deeper lakes elsewhere hold more.

Which element makes up nearly 89% of water's mass, despite supplying only one atom in every three?

Oxygen atoms are about sixteen times heavier than hydrogen atoms, so the single one in each molecule outweighs its two lighter partners eight to one.

Which fish knocks insects off overhanging branches by spitting a well-aimed jet of water at them?

Archerfish adults almost always hit their target with the first shot. Youngsters start spitting when barely an inch long, miss a lot, and have to learn from experience.

Which Central Asian lake shrank to a tenth of its size after Soviet irrigation diverted its rivers?

The Aral Sea was once among the four largest lakes in the world, until the rivers feeding it were turned onto desert cotton fields in the 1960s. By 2007 it had broken up into separate, far smaller lakes.

Which poet wrote 'Water, water, every where, nor any drop to drink' about a becalmed ship's crew?

Samuel Taylor Coleridge gave the line to the narrator of The Rime of the Ancient Mariner, whose shipmates blame their thirst on him for shooting an albatross.

Which toxic metal leached from ageing pipes into the tap water of Flint, Michigan, from 2014?

Lead reached around 100,000 residents after the city began drawing from the Flint River and officials failed to add the corrosion inhibitors that stop old pipes shedding it.

Which desert rodent never needs to drink, making all its water from the dry seeds it eats?

Merriam's kangaroo rat gets enough water from breaking down seeds to survive, and it saves more by slowing its metabolism to cut losses through its skin and breath.

Which effect lets a paper towel soak up a spill and helps draw water up through the stems of plants?

Capillary action pulls a liquid along narrow gaps, and the narrower the gap, the further it travels. Candle wicks and sweat-wicking sports fabrics work the same way.

China's Three Gorges Dam, the world's largest power station, holds back the water of which river?

The Yangtze turns generators with a capacity of 22,500 megawatts, and the dam also helps protect millions of people downstream from the river's severe floods.

Which French Impressionist painted about 250 canvases of the water lilies in his garden at Giverny?

Claude Monet made the lily pond the main focus of his last 31 years, painting many of the canvases while cataracts clouded his eyesight.

Grand Rapids, Michigan, was the first US city to add which tooth-protecting mineral to its water?

Fluoride went into the Grand Rapids supply in January 1945 as a controlled experiment to test whether it would prevent cavities. It leaves the look, taste and smell of the water unchanged.

Which process, performed in 1800 with Volta's newly invented battery, splits water into its two gases?

Electrolysis of water with a battery was achieved by William Nicholson and Anthony Carlisle only weeks after Alessandro Volta unveiled his voltaic pile. The International Space Station uses it to make oxygen.

Which reptile, nicknamed the 'Jesus Christ lizard', flees danger by sprinting upright across water?

The common basilisk stays up on large hind feet fringed with flaps of skin. Youngsters can cover up to 20 metres on water, while heavier adults sink after only a few.

Which South African city braced for 'Day Zero' in 2018, when its taps were due to be switched off?

Cape Town never reached it: residents cut their water use so sharply that the date kept being pushed back, and strong rains from June 2018 let the dams recover.

A snowflake's arms reflect the way water molecules lock together, giving it which kind of symmetry?

Six-fold symmetry comes from the hexagonal lattice the molecules settle into, though real flakes are rarely tidy: studies suggest fewer than 0.1% show the ideal form.

Which bitter compound, once taken against malaria, makes tonic water glow under ultraviolet light?

Quinine tasted so bitter that British officials in India mixed their dose with soda and sugar, creating tonic water. Modern tonic contains far less of it.

Which of Saturn's satellites sprays water into space from 'tiger stripe' cracks at its south pole?

Enceladus has more than 100 identified geysers, first spotted by the Cassini spacecraft in 2005. Together they hurl about 200 kilograms of material into space every second.

Which Swedish astronomer's temperature scale originally ran upside down, with water boiling at zero?

Anders Celsius had colder readings score higher. His scale was turned the modern way up around the time of his death in 1744, a change often credited to the botanist Carl Linnaeus.

Which toy did engineer Lonnie Johnson invent after a test nozzle shot water across his bathroom?

The Super Soaker was a by-product of Johnson's experiments on a new kind of refrigeration system. He was an engineer for the Air Force and NASA when the stray jet gave him the idea in 1985.

Which nickname is given to seabed vents that gush mineral-laden water heated above 400 °C?

Black smokers take their colour from the sulfur-bearing mineral particles they pour out. The superheated water rises from beneath the crust, and the vents cluster in fields hundreds of metres wide.

Which English chemist invented fizzy water by hanging a bowl above a beer vat at a Leeds brewery?

Joseph Priestley made nothing from the discovery, yet it launched the soft drink industry: Johann Jacob Schweppe founded Schweppes in 1783 to sell bottled soda water.

Which hydrogen isotope replaces the ordinary kind in the 'heavy water' of some nuclear reactors?

Deuterium atoms weigh twice as much as ordinary hydrogen atoms. Reactors built around heavy water have the advantage of being able to run on natural uranium.

Which Greek philosopher from Miletus taught that water is the one substance underlying all nature?

Thales is remembered for the idea thanks to a passage in Aristotle's Metaphysics. He also pictured the Earth itself resting on water.

Which name is given to the water-filled limestone sinkholes that dot Mexico's Yucatán Peninsula?

Cenotes number an estimated 10,000 on the peninsula. The ancient Maya depended on them for their water supply and occasionally cast sacrificial offerings into them.

Which part of the brain plays the key role in triggering thirst when the body runs short of water?

The hypothalamus matters so much that damage to one part of it can wipe out the urge to drink, even when the body's fluids have become extremely salty.

Which Canadian bay has the world's highest tidal range, with water rising about 16 metres?

The Bay of Fundy moves about 100 billion tonnes of water in and out on each tide, twice the combined flow of all the world's rivers over the same period.

Which term describes snow or frost vanishing straight into the air as a gas, without melting first?

Sublimation also explains the fog that pours off dry ice, which is solid carbon dioxide turning directly into gas at about −78.5 °C.

Drinking far too much water too quickly dangerously dilutes which mineral in the blood?

Sodium diluted below a safe level is called hyponatremia, a known risk for marathon runners who overdrink: 13% of finishers tested at the 2002 Boston Marathon had it.

Which ancient timekeeper takes its name from Greek words meaning 'water thief'?

Clepsydra clocks kept time by letting water drain at a steady rate out of a vessel. The oldest surviving example was made in Egypt around 1400 BC.

Which famously reclusive scientist discovered the 'inflammable air' that forms water when it burns?

Henry Cavendish was so shy that, by one account, he had a back staircase added to his house to avoid meeting his housekeeper. His inflammable air is the gas we call hydrogen.

Which term describes the shape of a water molecule, set by its two lone pairs of electrons?

Bent, rather than a straight line, is the geometry that makes water polar: one end of each molecule carries a slight negative charge and the other a slight positive one.