50 Fun Facts About Water

What is the chemical formula for water?

Each molecule has two hydrogen atoms bonded to one oxygen atom.

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

Seas and oceans hold most of that water.

Water is often called the 'universal' what?

Its polarity lets it dissolve a huge range of substances.

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

That is why ice floats; water expands by about 9% when it freezes.

At standard pressure, water boils at what temperature?

That is a high boiling point for such a small molecule, thanks to hydrogen bonding.

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

It is also called the hydrologic cycle.

Which enormous salty surface supplies about 86% of global evaporation?

The sun drives the water off its vast surface.

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

Only a small fraction of Earth's water is fresh.

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

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

The deepest known part of the sea lies in which trench, near the Northern Mariana Islands?

It is the Mariana Trench, in the Pacific.

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.

The Blue and White branches are the two major tributaries of which river?

They join in Sudan before flowing to the Mediterranean.

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

The surface sits over 400 metres below sea level.

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

Its dense, briny water is one of the saltiest on Earth.

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

The water is carefully balanced inside and outside the body's cells.

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

Only a small fraction shows above the surface.

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

In a primary rainbow, red is on the outer edge and violet on the inner.

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?

It forms by evaporation or by boiling.

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

A low-permeability layer beside it is an aquitard.

Angel Falls in Venezuela holds what record?

It drops 979 metres over the edge of the Auyan-tepui.

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

At the triple point all three states coexist.

Pure water's faint blue colour comes from it absorbing light at which end of the spectrum?

Weak absorption near 750 nm removes red light, leaving a blue tint.

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?

The expansion is what bursts pipes.

Roughly what number of people lack safe drinking water, according to Wikipedia?

Unsafe water is a major cause of disease and death.

Water molecules stick to each other by forming what?

These bonds give water its high surface tension and boiling point.

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

It lies in the South Pacific and is used as a 'spacecraft cemetery'.

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.

Water is described as a polar molecule. What does that let it do to salts?

The polarity pulls apart ions and dissolves many other polar substances.

Before the Andes rose, the world's largest river by discharge drained toward which ocean?

The mountains blocked its old path, sending it east to the Atlantic.

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

From the ground the lower half is hidden by the horizon.

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

The tint only becomes visible in large volumes.

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

The Auyan-tepui sits 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 lake sits in the endorheic Jordan Rift Valley with no outlet.

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

Ice already floating displaces its own weight, so it adds little when it melts.

Two of the world's ten largest rivers by discharge are tributaries of which river?

Its flow is greater than the next seven biggest rivers combined.

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

It includes the Pacific, Atlantic, Indian, Southern and Arctic oceans.

How fast do the molecular bonds in liquid water break and reform?

That constant flicker is why water flows.

Water is described as a compound of which type?

Despite being essential to life, it contains no carbon backbone.

Along with 'water', what is the other official chemical name for H2O?

Changing phase directly from ice to vapour is sublimation, while vapour to ice is called deposition.

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

At 1,524 metres cooking time must rise by about a quarter; in a vacuum, water boils at room temperature.

How many crystalline phases of ice had been experimentally confirmed as of 2024?

Ordinary ice is ice Ih with hexagonal crystals; ice XVIII, a superionic phase, was made by shocking a water droplet.

Up to how many hydrogen bonds can one water molecule form with its neighbours?

Hydrogen bonds are about ten times stronger than the Van der Waals forces in most liquids, explaining water's high boiling point.

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

The Red Sea sits at the other extreme at about 4.0%; average seawater is roughly 3.5% sodium chloride.

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

Cotton uses 2.4% of world water, often in already water-stressed regions; Soviet diversions for cotton shrank the Aral Sea.

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

A metal standard a thousand times heavier, the kilogram, was then made, requiring precise measurement of a litre of water.

Which Siberian body of water is the largest drinkable freshwater resource by volume?

Until May 2019 the Kelvin scale itself was defined by water's triple point at exactly 273.16 K.