Water Trivia
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8correct to beat the crowd
This water trivia quiz has 100 free questions with answers and covers the most important substance on Earth, from its molecule to the oceans. It takes in the chemistry of H2O and why ice floats, the water cycle, the five oceans and the deepest trench, the longest rivers, the Dead Sea and its buoyancy, icebergs and rainbows, and the surprising amount of water inside the human body. Early questions suit anyone who paid attention in science class. Later ones reward people who know the world's tallest waterfall and where most of Earth's evaporation comes from. Use it for a science-class starter, a pub-quiz nature round or a family game night. Every answer has been checked against a documented source shown under the explanation.
30 of 100 questions with answers and explanations. Play the quiz
Q 01What is the chemical formula for water?
H2O
Water is H2O: each molecule has two hydrogen atoms covalently bonded to a single oxygen atom.
Q 02About what fraction of Earth's surface is covered by water?
71%
About 71% of Earth's surface is covered by water, nearly all of it ocean; land makes up the remaining 29%.
Q 03Water is often called the 'universal' what?
Solvent
Water is called the universal solvent because more substances dissolve in it than in any other common liquid.
Q 04Unusually, water's solid form is what compared with its liquid form?
Less dense
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.
Q 05At standard pressure, water boils at what temperature?
100 degrees C
Water boils at 100 degrees C at standard atmospheric pressure, unusually high for such a small molecule because its molecules attract one another strongly.
Q 06The continuous movement through evaporation, condensation and precipitation is called what?
The water cycle
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.
Q 07Which source supplies about 86% of the water that evaporates worldwide each year?
The ocean
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.
Q 08Roughly what percentage of Earth's water is held in the ocean?
97%
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.
Q 09Which is the largest of Earth's oceans by area?
The Pacific
The oceans in order of size are Pacific, Atlantic, Indian, Southern and Arctic.
Q 10The Challenger Deep, the ocean's deepest known point, lies in which trench?
The Marianas deep
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.
Q 11Which river is generally considered the longest in the world?
The Nile
At about 7,088 km it edges out the Amazon, though it carries far less water.
Q 12Which river carries the most water of any in the world by discharge volume?
The Amazon
It discharges more than the next seven largest rivers combined.
Q 13Which is the largest lake in Africa by surface area?
Lake Victoria
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.
Q 21An underground layer of water-bearing rock or gravel from which wells draw is called what?
An aquifer
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.
Q 22Angel Falls in Venezuela holds what record?
World's tallest uninterrupted waterfall
Angel Falls is the world's tallest uninterrupted waterfall, with a total height of 979 metres and a single plunge of about 807 metres.
Q 23Earth has water in all three states because its conditions sit near what threshold?
Its triple point
Q 14The Dead Sea's shores are notable for being what?
The lowest land on Earth
The Dead Sea's shores are the lowest land on Earth; its surface lies roughly 430 metres below sea level.
Q 15The Dead Sea's very high salt content makes swimming there feel like what?
Floating
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.
Q 16About what percentage of an adult male human body is water?
60%
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.
Q 17The phrase 'the tip of the iceberg' reflects the fact that most of an iceberg is where?
Below the water
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.
Q 18A rainbow is caused by refraction, reflection and dispersion of light in what?
Water droplets
Sunlight entering water droplets is refracted, reflected off the back of each drop and dispersed into its colours, which is what produces a rainbow.
Q 19In a primary rainbow, which colour appears on the outer edge?
Red
Violet sits on the inner side of the arc.
Q 20Steam is the common name for what?
Water vapor
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.
At the triple point all three states coexist.
Q 24The Mpemba effect refers to hot water doing what faster than cold water?
Freezing
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.
Q 25Pure water reaches its maximum density at about what temperature?
4 degrees C
Below 4 C it expands again, which is why ice forms on top of ponds.
Q 26By roughly what percentage does water expand when it freezes into ordinary ice?
About 9%
Water expands by about 9% when it freezes into ordinary ice, enough force to burst household pipes and crack rock.
Q 27Water that leaves limescale in kettles because of its calcium and magnesium content is called what?
Hard water
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.
Q 28Water molecules stick to each other by forming what?
Hydrogen bonds
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.
Q 29The most remote spot in the ocean, farthest from any land, is nicknamed what?
Point Nemo
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.
Q 30On Mars, water is found mostly in which form?
Ice
Large quantities of ice sit on and under the surface, though liquid water may exist deep down.