Water: More Than Meets the Eye

At the top of Mount Everest, water boils at roughly what temperature?

100 °C

70 °C

120 °C

110 °C

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That's right!

Right! Lower air pressure at altitude lets water boil at about 70 °C, so tea up there is never piping hot.

Not quite!

It's about 70 °C. The boiling point depends on air pressure, and at Everest's summit the pressure is only a third of that at sea level.

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A large iceberg floats in calm blue sea, with its submerged part visible beneath the surface.

Why do icebergs float?

Ice is less dense than liquid water

Ice is denser, but currents hold it up

Trapped water vapour lifts the ice

Salt water freezes into lighter ice

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That's right!

Correct! When water freezes, its molecules lock into an open lattice, making ice about 9% less dense than water.

Not quite!

Ice is less dense than liquid water. Freezing arranges molecules into an open hexagonal lattice, which takes up more space.

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Where is most of Earth's fresh water found?

In lakes and rivers

In underground aquifers

In ice caps and glaciers

In clouds and the atmosphere

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That's right!

Yes! Around 69% of fresh water is locked up in ice caps and glaciers, mostly in Antarctica and Greenland.

Not quite!

It's ice caps and glaciers, holding about 69% of fresh water. Lakes and rivers hold well under 1%.

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Scratch the card to reveal a fact about water

Some of the water in your glass may be older than the Sun, formed in interstellar clouds before our solar system existed.

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How well does perfectly pure water conduct electricity?

Very well, like a metal

Fairly well, like tap water

Very poorly

Well, but only when warm

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That's right!

Spot on! Pure water has very few ions; it's the dissolved salts and minerals in everyday water that carry the current.

Not quite!

Pure water conducts very poorly. Dissolved ions from salts make ordinary water conductive, which is why it's still dangerous near electrics.

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At what temperature is liquid fresh water at its densest?

0 °C

4 °C

−4 °C

100 °C

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That's right!

Correct! Water is densest at about 4 °C, which is why deep lakes stay around 4 °C at the bottom in winter.

Not quite!

It's about 4 °C. Below that, water expands as it cools, so colder water rises and lakes freeze from the top down.

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Flip the card to reveal a fact about water

Ice can exist in at least nineteen different crystal forms, most created only under extreme pressures in laboratories.

Did you know?

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What shape is a single water molecule?

Straight line

Bent, like a V

Flat triangle

Four-sided pyramid

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That's right!

Right! The two hydrogen atoms sit at an angle of about 104.5°, making water a polar molecule.

Not quite!

It's bent, at about 104.5°. That bend makes water polar, which explains why it dissolves so many substances.

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A large white cloud floats in a bright blue sky above a range of snow-capped mountains.

What are clouds mostly made of?

Water vapour gas

Tiny droplets and ice crystals

Steam from the oceans

Dust with vapour around it

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That's right!

Yes! Water vapour is invisible; clouds are what we see once it condenses into droplets or freezes into ice crystals.

Not quite!

Clouds are tiny liquid droplets and ice crystals. Water vapour itself is an invisible gas.

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Roughly what share of all water on Earth is fresh?

About 3%

About 30%

About 50%

About 15%

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That's right!

Correct! Only about 3% is fresh, and most of that is frozen or underground.

Not quite!

Only about 3% is fresh; the other 97% is salty ocean water.

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Drag the slider to reveal a fact about water

How much water does a beef burger need?

Producing one beef burger takes around 2,400 litres of water, mostly for growing the cattle's feed.

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What does a pinch of salt in a pan of water actually do?

Makes it boil much faster

Barely changes its boiling point

Lowers its boiling point a lot

Stops it from ever freezing

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That's right!

Right! A pinch raises the boiling point by a tiny fraction of a degree; the salt is there for flavour.

Not quite!

It barely changes anything. Salt actually raises the boiling point slightly, but a pinch adds only a fraction of a degree.

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A polished stainless steel kettle with a blue handle and a purple spout stands on a kitchen worktop.

The white cloud above a boiling kettle is…

pure invisible steam

water vapour gas

condensed water droplets

hot air rising

or press Enter ⏎

That's right!

Correct! True steam is invisible; the white plume forms when it cools and condenses into droplets.

Not quite!

It's condensed droplets. Real steam is invisible—look closely and there's a clear gap right at the spout.

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Perfect! Every answer right!

11 of 11 right

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Question 1:
At the top of Mount Everest, water boils at roughly what temperature?
100 °C
70 °C
120 °C
110 °C
Right! Lower air pressure at altitude lets water boil at about 70 °C, so tea up there is never piping hot.
It's about 70 °C. The boiling point depends on air pressure, and at Everest's summit the pressure is only a third of that at sea level.
Question 2:
Why do icebergs float?
Ice is less dense than liquid water
Ice is denser, but currents hold it up
Trapped water vapour lifts the ice
Salt water freezes into lighter ice
Correct! When water freezes, its molecules lock into an open lattice, making ice about 9% less dense than water.
Ice is less dense than liquid water. Freezing arranges molecules into an open hexagonal lattice, which takes up more space.
Question 3:
Where is most of Earth's fresh water found?
In lakes and rivers
In underground aquifers
In ice caps and glaciers
In clouds and the atmosphere
Yes! Around 69% of fresh water is locked up in ice caps and glaciers, mostly in Antarctica and Greenland.
It's ice caps and glaciers, holding about 69% of fresh water. Lakes and rivers hold well under 1%.
Question 4:
How well does perfectly pure water conduct electricity?
Very well, like a metal
Fairly well, like tap water
Very poorly
Well, but only when warm
Spot on! Pure water has very few ions; it's the dissolved salts and minerals in everyday water that carry the current.
Pure water conducts very poorly. Dissolved ions from salts make ordinary water conductive, which is why it's still dangerous near electrics.
Question 5:
At what temperature is liquid fresh water at its densest?
0 °C
4 °C
−4 °C
100 °C
Correct! Water is densest at about 4 °C, which is why deep lakes stay around 4 °C at the bottom in winter.
It's about 4 °C. Below that, water expands as it cools, so colder water rises and lakes freeze from the top down.
Lightning round 1
Question 6:
What shape is a single water molecule?
Straight line
Bent, like a V
Flat triangle
Four-sided pyramid
Right! The two hydrogen atoms sit at an angle of about 104.5°, making water a polar molecule.
It's bent, at about 104.5°. That bend makes water polar, which explains why it dissolves so many substances.
Question 7:
What are clouds mostly made of?
Water vapour gas
Tiny droplets and ice crystals
Steam from the oceans
Dust with vapour around it
Yes! Water vapour is invisible; clouds are what we see once it condenses into droplets or freezes into ice crystals.
Clouds are tiny liquid droplets and ice crystals. Water vapour itself is an invisible gas.
Question 8:
Roughly what share of all water on Earth is fresh?
About 3%
About 30%
About 50%
About 15%
Correct! Only about 3% is fresh, and most of that is frozen or underground.
Only about 3% is fresh; the other 97% is salty ocean water.
Question 9:
What does a pinch of salt in a pan of water actually do?
Makes it boil much faster
Barely changes its boiling point
Lowers its boiling point a lot
Stops it from ever freezing
Right! A pinch raises the boiling point by a tiny fraction of a degree; the salt is there for flavour.
It barely changes anything. Salt actually raises the boiling point slightly, but a pinch adds only a fraction of a degree.
Question 10:
The white cloud above a boiling kettle is…
pure invisible steam
water vapour gas
condensed water droplets
hot air rising
Correct! True steam is invisible; the white plume forms when it cools and condenses into droplets.
It's condensed droplets. Real steam is invisible—look closely and there's a clear gap right at the spout.

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