50 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.