179121479125786First_Children__s_Encyclopedia

Check here for the answer.

Using this book

5

Buttons contain mini

facts: quick information

at your fingertips.

Weird or what? are

packed with extra weird

or wonderful facts.

Every page is

colour coded to

show you which

chapter it’s in.

Quick quiz

questions are

at the bottom

of each page.

Colour coding

identifies each

chapter at

a glance.

Text gives you

information

about a subject.

Photographs

show you

information

about a subject.

Han

ds on

Want to try

something for yourself?

Then look at a

“Hands on” tip.

Hands on tells you
how to get stuck in
and try an experiment
for yourself.

224 225

Some materials are hard and

brittle, while others are flexible.

Some materials are colourful, while

others are transparent. These kinds

of features are called “properties”.

Properties of matter

BrittlenessSome materials, such as glass, are

very brittle and will break when pushed out of shape. Safety glass is

designed to crack rather than break.

Does it float?It’s easy to learn about

some properties, such as the ability to float.

The amount of matter in a certain volume of

an object is called its density. Objects and

liquids float on liquids of a higher density and

sink through liquids of a lower density.

Is a diamond harder than quartz?

Materials science Properties of matter

Safety glass

Yes, a diamond is the hardest mineral of all. It will scratch quartz.

Freezing pointtemperature at which is the

a liquid becomes a solid.

Plasticitya solid can be reshaped. is how well

Conductivitya material lets electricity is how well

or heat travel through it.

Boiling point hottest a liquid can get is the

before becoming a gas.

What they are...

There are many different

properties of matter.

A smooth flowSome liquids flow more

easily than others. It depends on their “stickiness”, or viscosity.

Hot lava from a volcano flows slowly because it is sticky.

An onion sinks through oil and water, but floats on syrup.

Syrup sinks below water.

A cork floats on oil. Oil floats on water.

Talc^1

HardnessA scientist called Friedrich Mohs created a

scale of ten minerals to compare how hard they are. Many materials are graded on this scale.

Tensile strengthmuch a material can is how

stretch without breaking.

Flammabilityeasily and quickly a is how

substance will catch fire.

Reflectivity a material reflects light. is how well

Water reflects well.

Malleabilitya solid can be shaped is how well

without breaking.

Flexibilitya material can be bent. is how easily

Solubilitya substance will dissolve, is how well

such as salt in water.

Transparencywell a material will let is how

light pass through it.

CompressibilityGases can be

squashed, or compressed, by

squeezing more into the same

space. This is what happens when you

pump up a tyre.

A plastic building brick sinks through oil but floats on water.

Gypsum^2 

Calcite

Fluorite^4

Apatite^5 

Feldspar Quartz^7 Topaz^8

Corundum^9

Diamond^10

Gas can be compressed because its particles are far

apart. A bicycle pump pushes the particles closer together.

Diamond is the hardest

mineral.

Hands^ on

Foot pump

Gas particles

Heat cannot easily pass A good insulator

through some materials. These are known as

insulators. For example, aerogel can completely

But don’t try this at home!block the heat of a flame.

Softest mineral

different pebbles Collect some

hardness. A pebble is harder and put them in order of

than another if it scratches it. This is how Mohs worked

out his scale.

The lunar module was

nicknamed the Eagle.

(^280) Why is there no blue sky on the moon?
Men on the moon
281
The universe
Because the moon has no atmosphere.
On 20 July 1969, Neil Armstrong became the first
person to walk on the surface of the moon. He was
joined by Buzz Aldrin. A third astronaut,
Mike Collins, remained in orbit with the
command and service modules.
Men on the moon
What did they do?Armstrong and Aldrin
spent almost 22 hours on the moon. About
2.5 hours of this was spent outside
rock and soil samples, the Eagle, collecting
and taking pictures. setting up experiments,
Neil Armstrong
Here comes EarthInstead of the moon rising,
the astronauts saw Earth rising over the
moon’s horizon – it looked four times
bigger than the moon looks
from Earth.
What was it like?Buzz Aldrin described
the moon’s surface as like nothing on
Earth. He said it consisted of a fine,
talcum-powder-like dust, strewn with
pebbles and rocks.
We have transport!Three later Apollo missions
each carried a small electric car, a lunar rover, which allowed the
astronauts to explore away from the lander. These were left on the
moon when the astronauts left.
SplashdownThe astronauts returned to
Earth in the module. This fell through the Apollo 11 command
atmosphere and landed in the Pacific Ocean. A ringed float
helped to keep it stable.
One lunar rover reached a top
speed of 22 km/h (13.5 mph).
This dish antennae
allowed the astronauts to
send pictures to Earth.
How did they talk?There’s no air in space, so
sound has nothing to travel through. Lunar astronauts
use radio equipment in their helmets.
(^)
(^)
We
ird^ or^ what?
module computer The lunar^
on71K of memory. Some Apollo 11 had just
calculators can now store more
than 500K.
W
ei
rd^
or^ wh
at
?
Want to know
something surprising?
Then look at a “Weird or
what?” tip.