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VISUAL SCIENCE THIRD BOOK
ISOTYPE I
Parrish INSTITUTEVISUAL CIENCE
1 FIRST BOOK A SCIENCE IN THE COUNTRY
Living things: how young animals begin life; The life-histories o f plants and animals in more
where plants store Food; life-cycles o f plants detail; introduction to the chemistry o f the soil;
and animals. Water: its role in nature; ice, how seeds form and germinate; the nitrogen
water, steam; floating and sinking. Earth and cycle; the carbon cycle; first lessons in animal
sun: seasons, climates, day and night. Sound: and human physiology; further aspects o f the
how it is caused and how it travels; loud and behaviour o f liquids; how water rises in plants;
soft sounds; high notes and low. introduction to study o f weather.
2 SECOND BOOK 5 MOVING ABOUT
Air: its weight and power; burning and breath Devices which assist movement: the wheel, the
ing. Heal: its sources; how heat travels through screw, the propeller, the jet, the oar. Stopping,
air, through liquids, through solids; using and starling and turning (acceleration and inertia).
keeping heat. Light: how it travels; brightness Movement o f animals in water, in the air, on
and colour; rclleciion. Weight and work: fall land, underground; limbs, muscles, nerves.
ing and gliding; levers; arms and legs. Pressure in air and in liquids. The magnet.
3 SCIENCE IN THE HOM E 6 MACHINES WHICH WORK FOR MAN
Water: how it com es to our homes; hard and The sun as a source o f power: from coal to
soft water; water and rust. Food: the role o f steam and steam engines, to the turbine and
cooking; digestion and nutrition; why food electricity, to coal gas; watermills and wind
must be kept clean. Glass: how it is made; its mills. Simple chemical changes as sources o f
properties; its value in the home. Electricity: power. Electrolysis and electro-magnetism.
heating and lighting; the electric bell; the fuse. Gravity and work. Sources o f power compared.
VISUAL SCIENCE
SCIENCE IN T H E H O M E
1951
IN ASSOCIATION WITH ADPBINT LIMITED LONDON CHANTICLEER PRESS NEW YORK
SET IN G R E A T B R I T A I N . P R I N T E D IN A U S T R I A BY 1 V A L D H E I M - E B E R L E
SCIENCE IN THE HOME
PREPARED BY
MARIE NEURATH
D IR E C T O R OF THE ISOTYPE INSTITUTE
J. A. LAUWERYS
P R O F E S S O R OF C O M P A R A T I V E E D U C A T I O N UNIVERSITY OF LON DON
MAX PARRISH LONDON
sou b m u i i n o i u ; G E O R G E G. H A R R A P A CO LTD iS z m oil ih h .w » n w c i y r o N i rW l l i i M I T MLIST OF C O N T E N T S
H ow to Use this Book Page S
The Water from the Tap 6
The Power o f Water 8
H ow Different Things Mix with Water 10
H ow Soap Cleans when Water W on’
t 12
Water and Rust 14
H ow Iron is Made from its Ore 15
What W e Have Learned about Water 16
A Fire Burns, a Man Breathes 18
C ookin g in Water and Cooking in Fat 20
The F ood W e Eat 22
The Story o f a L oaf o f Bread 24
Why We Must Protect Food 26
What W e Have Learned about F ood 28
Windows, Warmth and Light 30
Making and Shaping Glass 32
Som e Qualities o f Glass 34
What W e Have Learned about Glass 36
H ow Electricity is Carried to Our Homes 38
Light and Heat from Electricity 40
Getting Just the Heat W e Need 42
H ow Electricity Rings the D oorbell 44
Dangers from Electricity 46
What W e Have Learned about Electricity 48
Som e Books to Read 49H O W T O USE T HI S BOOK
Science is not simply a “subject" which you read and understood in a short time, but this
learn in the classroom, in the laboratory or by is quite wrong. Isolype pictures, like engineers*
reading books. It is a way o f observing, o f blueprints or navigators' charts, are packed with
understanding, o f doing things. In your own interesting information, and the more carefully
home, am ong the things you see and handle you examine them the m ore you will learn from
every day, there are many opportunities to them. O n som e pages we have asked a number
observe, to understand and to d o things in o f questions. Y ou will not be able to answer
a scientific way. The purpose o f this book is to all o f them after a quick glance at the pictures,
help you to make use o f these opportunities, but you will after you have examined the pic
not only so that you will learn something about tures thoroughly. O n other pages we have used
science, but also so that you will find more text to add to the information given in the
enjoyment in seeing everyday things and doing pictures.
everyday jobs. W e hope that you will enjoy studying this
The pictures are not intended to show you book and that you will want to read som e o f
how things look, but to give you scientific in the others we have listed on page 49. But you
formation about them. Every line and every will find that the best ways o f increasing your
patch o f colou r has something to tell you, just knowledge o f science are by observing and
as in a g o o d map. In the charts about food, for studying real things and by conducting simple
instance, carbon is always shown in black, experiments. See for yourself how things behave
oxygen in red, hydrogen in blue. Certain simple under different conditions and test for yourself
drawings, called “Isotype sym bols" are used whether the same things always behave in the
over and over again, always with the same same way under the same conditions. When
meaning, so that you will recognise and under you have done that, you will find that this book
stand them quickly and easily every time you helps to make your knowledge m ore orderly
see them. and useful, by showing you how the results o f
It is easy to imagine that because this book your observations and experiments all fit in with
contains many pictures and few w ords it can be certain laws o f nature.
The EditorsThe Water from the Tap
6
Look at the picture on the left 6 Has the wSter to be cleaned again before it
reaches the second town? H ow did the dirt
1 Whal d o the yellow patches stand Tor? What get into the water?
do the blue lines on the yellow patches stand
Tor? 7 Has the water to be cleaned after it leaves
the second town?
2 What happens to the rain when it falls on
the earth?
3 H ow d oes the waier get into the well below Look at the pictures below
the pump? T o the reservoir above the dam?
6 When the boy turns on the lap, where does
4 H ow is dirty water shown? Is the water dean the dean water com e from? What d o you
or dirty when it reaches the houses in the think happens to the dirty water from the
first town? kitchen sink?
5 H ow are dangerous impurities from sewage 9 Which colour shows the washer in the tap?
shown? Point out the filters which remove What happens to the washer when the tap
them. is turned on?
7The Power of Water
T o keep the tanks in houses full, the level o f water in the reservoir must be higher than in the tanks.
Water will not rise higher than the water level in the lank it is drawn From. What happens when the
jet from the hose reaches that height? Can water be drawn from Lhe highest tap on the right?
8
When this tank is almost full, the water
holds up a hollow ball fixed to a rod. the bottom and m oves’the rod. The
Attached to the rod is a lever which lever turns and opens the inlet pipe.
keeps the inlet pipe closed. Water pours in to fill up the tank.
The water in the bath supports part o f this If there is no water, the whole o f his weight
man's weight; his body feels slightly lighter. rests firmly on the bottom o f the bath.
The ball pushes aside a volume o f water as
In air the ball weighs as much as the block large as its own. The weight it loses is equal
In water it weighs less than the block. to the weight o f the water pushed aside.
9How Different Things M ix with Water
The blue oblongs stand f o r water; the red patches show various things mixed with water; (he broken
black lines show fillers.
Whai d o we mean when we say something o f fat are not solid. They will squeeze through
“mixes" with water? These pictures show four the pores o f the paper. A mixture o f water
things which mix with water in different ways. and drops o f another fluid is called an emulsion.
Chalk mixes with water, but most o f it can When lea is mixed with boiling water some
easily be separated again. Strain som e o f the o f it breaks into very small particles which
mixture through a filter-paper. Water trickles colour the water. These particles are too small
through and chalk remains on the paper. The 10 be separated from the water by any filler.
solid particles o f chalk are too big to pass This kind o f mixture is called a colloid.
through the pores o f the paper. They were In water, sugar breaks up into the smallesL
simply floating about in the water. They were, particles possible— into what are called m ole
as we say, “in suspension". cules. These liny particles cannot be separated
In milk, globules o f fat are suspended in by filtering, but only by boiling the mixture
water, but you cannot separate them from the until all the water is driven off. A mixture o f
water by means o f a filter-paper. The globules this kind is called a solution.
10JELLY GLUE
One form o f colloid which is often used in When glue is boiled in water and allowed to
ihe hom e is table jelly. When the jelly cubes are cool, something very similar happens. But the
placed in hot water, separate particles o f jelly cells formed by the glue are smaller and much
float about in the water. As the water cools these firmer than those formed by the jelly. When glue
particles jo in together to form little cells, each cools it is hard enough and strong enough to
containing som e o f the water. hold two pieces o f w ood together.
11How Soap Cleans when Water W on’
t
Next look as the pictures below.
If you add soap to the water the par
ticles o f soap will mix with particles o f
butter and form an emulsion. The
emulsion washes off in the water.
There is always a certain amount o f
oily substance on our bodies to which
the dirt clings. Clear water alone will
not wash off the oil and dirt. We must
use soap to keep ourselves clean.
First look at the pictures above.
Why d o we use soap? Can we not clean
things just as well with cold water only?
Some things can be cleaned with clear cold
water, but not all. Take a spoon smeared with
treacle and leave it in water. The water grad
ually dissolves the treacle, and the spoon is left
quite clean. N ow leave a dirty butter-knife in
cold water. The butter still clings to it. Butter
will not mix with or dissolve in cold waLer.
12Carbon dioxide from the
air dissolves in this stream.
It becom es slightly acid and
dissolves chalk particles,
making the water hard.
Rain water is always soft.
If it is left to stand in a
water butt, it may dissolve
carbon dioxide from the
air, but so lon g as there is
Soap causes a chemical If hard water is boiled the no chalk in it, it does not
change which throws the chalk will separate and form becom e hard. Soap does
dissolved chalk out o f solu a “fur” inside the vessel. not have the jo b o f softening
tion. It forms a scum on The water becom es soft. such water. It can form a
lop o f the water. Soap lathers well in it. lather at once.
13Water and Rust
\ 1 What metal d o you think the ring is
made of? What metal d o you think
the blade o f the spade is made of?
2 Is the ring clean when the rain first
falls on it? Is the spade?
3 D oes the ring change in any way
when it is left out in the rain? Does
the spade?
4 What colours are used to show rust
on the spade? D o you think the
water helped to make the spade
rusty?
Red dots show air, blue lines water,
5 L ook at the first picture. D oes any
water touch the spade? Any air?
6 L ook at the second picture. D oes
air touch the spade? D oes water?
7 L ook at the last two pictures. D oes
air touch the spade? D oes water?
What happens to the iron?
8 L ook at the colours o f the dots
which are used to show rust in the
last picture. What two things d o you
think are necessary before rust can
form on iron?How Iron is M ade from its Ore
Y ou d o n ol find iron metal in the earth. You
find a rocky mineral called “ore”. M ost iron
ores contain iron chemically joined to oxygen.
T o get the iron from the com pound oxide,
layers o f iron ore are placed in a blast furnace
with layers o f coke. The coke and iron ore are
healed strongly in the furnace and the heal
causes chemical changes in both o f them.
C oke contains a high proportion o f carbon,
and carbon will very readily jo in itself to
oxygen.
In the blast furnace there is plenty o f oxygen
— oxygen com bined with iron in the iron oxide.
As the heat passes up through the furnace the
carbon in the cok e com bines with the oxygen
from the iron ore to form a colourless gas
called carbon monoxide. When the oxygen is
taken away from the iron oxide pure iron
remains.
The diagram above shows you wftar happens. The
bodom strip shows iron combined with oxygen.
Oxygen is taken away and pure iron remains.
The top strip shows carbon. Oxygen combines
with carbon and produces carbon monoxide.
15What W e Have Learned about Water
SCREEN
TOWN
FIRST TANK
SEWAGE
FILTER
As the sewage flow s slowly through the pit, grit sinks to
the bottom; next a screen removes paper and vegetable peel,
S E C O N D TANK
RIVER jf .
hi the first tank much o f the remaining matter settles at the
bottom. The top liquid passes through a filter into a second
cleansing tank before it reaches the river.
1, If we live in a town, the water we use for reservoir it com es from. Therefore the water
washing and drinking has probably had lo soak level in the reservoir must be higher than the
through the soil and flow along the bed o f som e highest water tank in the houses it supplies.
stream or river. It has gathered dirt and im In the water-pipes in our homes, the water is
purities which must be removed before it com es always pushing up towards the same level as the
to our homes. This is usually done by making water in the reservoir. If we allowed it lo reach
the water pass through filter-beds at the water that level, the water-storage tanks would
works. It is sometimes also necessary to add overflow.
chemicals to the water to help purify it. T o prevent this, we make use o f the power o f
If a town lies near the source o f a stream or water lo support weight. When the tank is
river, its waLer will collect fewer impurities. almost full, the water lifts a ball. This ball
There will be less need to lake so much trouble moves a lever which closes the inlet water-pipe,
to get it clean. 3. Different things mix with water in different
When waste water leaves our homes som e o f ways. Chalk (or sand or sawdust) can be held in
it may once m ore soak through the earth and suspension in water. The solid particles can be
find its way into a river. Therefore water is separated from the water by filtering.
cleaned not only before it reaches our homes, In milk (or in broth) globules o f fat mix with
but also after it leaves them, water to form an emulsion. The globules cannot
2. N o matter how many twists and bends and be separated by filtering; since they are soft
joints in the pipes, the water in our hom es will they usually squeeze through the pores o f
not rise higher than the level o f water in the the filter.
16Table jelly, and glue form colloids when first cause chemical changes which produce a
mixed with w ater Particles form themselves chalky scum on the surface o f the water.
into small cells, each containing a little water. 5. Neither air alone nor water alone will
4. Greasy things cannot be cleaned properly cause rust to form on iron. Both air and water
in clear cold water. I f we use soap, particles o f must be present. In nature both air and water
soap mix with particles o f grease to form an usually ore present. Unless iron is protected it
emulsion in the water. Because there is always com bines with oxygen and water to form rust.
a certain amount o f oily substance on our skins, Iron ore usually contains iron oxide, a co m
we must use soap as well as water to keep our pound o f iron and oxygen. In the blast furnace,
bodies clean. layers o f ore and layers o f cok e are strongly
Carbon dioxide from the air dissolves in heated. The carbon in the cok e lakes the oxygen
water and makes it slightly acid. It then dissolves from the iron oxide and com bines with it to
particles o f chalk which make it hard. Before form carbon m onoxide gas. Pure iron remains
soap can form a lather in hard water it must in the furnace.
THINGS TO DO
1. Put som e washing soda crystals in an old funnel into one side o f the lube, and try to fill
iron spoon. Heat slowly over a gas flame. the funnel to the brim. What happens?
Describe carefully what happens and try to 4. Many houses in the country collect rain
explain it. Take the while pow der which remains water in a water butt. This water is used for
and dissolve it in a little w a ter; pour into a washing but not usually for drinking. Try to
saucer and leave for a few days. explain this.
Repeat this experiment with som e crystals o f 5. Sea water cannot be used either for washing
blue copper sulphate, which you can get from a or for drinking because o f the amount o f sail
chemist if you show him a note from your teacher. dissolved in it. H ow can pure water be obtained
(Remember that copper sulphate is poisonous.) from sea water?
2. Place a heavy stone in a bucketful o f water. 6. G el a bottle o f som e fluid used for cleaning
Lift the stone from the bottom o f (he bucket greasy clothes. Invent a way o f finding out
right out o f the water. What d o you notice whether it will dissolve rust, butter, mar
about its weight when it leaves (he water? garine, mutton fat, ink, the green colouring
3. Take a U-shaped glass tube, and half fill it matter o f plants. Try out your method. N ow
with water. What d o you notice about the level explain what kinds o f stain could be removed
o f water in each arm o f the lube? N ow insert a from clothes by using this fluid.
17A Fire Burns, a Man Breathes
The stick o f carbon burns in the open air. H old it above a fire and it goes out. Why? T o burn, the
carbon must be able lo gel oxygen from the air and com bine with it to form an invisible gas called
carbon dioxide. The air above the fire contains a large amount o f carbon dioxide from the
burning coal, and only a little oxygen. Without enough oxygen the carbon cannot burn.
18
1 D o the logs contain carbon? What is taken 6 I f there were no free oxygen left in the air,
from the air as the fire burns? would fires still burn? What would happen
to human beings and animals?
2 Whai gas is produced as the fire burns?
Where d oes it g o to?
Every time a fire burns, every lime an animal
3 D oes the wheat contain carbon? D oes the or a human being breathes, free oxygen is taken
loa f o f bread? from the air and carbon dioxide added to the
air. But all the lime plants are taking in carbon
4 In our bodies carbon com bines with oxygen
dioxide and giving out free oxygen.
and produces carbon dioxide. Where d o our
Plants cannot get the carbon they need from
bodies get this oxygen? H ow d oes it enter
the soil. Instead, every green leaf absorbs carbon
our bodies?
dioxide from the air. During daylight carbon
5 What would happen to the supply o f free dioxide acts with water inside the leaf to p ro
oxygen in the air if nature produced no duce starch and free oxygen. The starch contains
more? What would happen to the supply o f carbon in a form which the plant can use, and
carbon dioxide? the oxygen returns to the air.
19Cooking in Water and Cooking in Fat
stands fo r steam
35$ stands fo r ice
I L ook at the top row of pictures.
What is the temperature o f the mix
ture o f ice and water when it is first
placed over the flame?
0_ 2 What has happened to the ice in
picture two? What caused this? Has
\ r ^ / the water become warmer?
/VN
3 Is the water warmer in picture three?
6 The second row o f pictures shows fat instead Has any other change laken place?
o f water. Which reaches a temperature o f
100° more quickly, the fat or the water? 4 Is the water hotter still in picture
Which d o you think needs less heal to melt four? What other change is taking
it, solid fat or ice? place?
7 Will the temperature o f water rise above 5 The water is still being healed in
100° if it is heated for a long time? Will the picture five. D oes its temperature
temperature o f fat? go on rising? What happens instead?
20When potatoes are boiled, changes
lake place in Ihem which we cannot see.
A raw potato contains many particles
o f starch which are valuable as food.
But it also contains a hard substance
called cellulose which makes the potato
difficult to digest.
These three pictures show what
happens when the potatoes boil. At
first each particle o f starch is completely
surrounded by a thin, hard shell o f
cellulose. After a time the shell softens
and breaks. As boiling goes on, the
starch particles break up into smaller
pieces which can easily be digested.
When meaL is cooked in fat we can
see the changes which take place. A thin
crust forms around it. This crust keeps
the juice and flavour inside the meat.
(Do you think this will happen if we
pul it in cold water and then boil it?)
Part o f the meal which is valuable as
food is a substance called “protein*1.
When meat is roasted, som e o f the pro
tein particles join together to form the
crust. Our bodies can digest the protein
in raw meal, but cook in g makes meat
tender by breaking down stringy parts.
It also destroys many impurities.
21The Food W e Eat
©
The row o f drawings at the top o f this column Protein particles are not changed much by
shows som e o f our main sources o f food. The cooking, but they join together in new ways.
next row shows what som e o f our food is made Protein helps to make an egg hard when it is
of. Solid black slands for carbon, red for boiled, and to form a crust round roasting meat.
oxygen, blue for hydrogen. (Pure hydrogen is Fat, which is hard to digest when it is raw
an invisible gas. When com bined with oxygen and solid, changes to liquid when it is cooked
it forms water.) and forms an emulsion with other liquids. The
The first drawing shows protein from animal emulsion is easier to digest. Starch panicles are
foods , the second fat, and the third starch broken up by cooking into smaller pieces, but
from vegetable foods . Each contains carbon, each piece still contains carbon, oxygen and
oxygen and hydrogen in different proportions; hydrogen.
the protein also contains a substance called In cooking, the salts in our food mix with
nitrogen. The shaded paLch shows salts. water to form a solution.
22
In our insides, foo d is acted upon and dis
solves in digestive juices. The solution passes
through the walls o f the intestine to other parts
o f the body. Protein goes mainly direct to the
cells o f our bodies, where it helps to build and
repair tissues. Fat and starch g o partly to the
liver to be stored, partly direct to body cells.
The foo d which enters the cells contains
carbon, hydrogen and oxygen. Free oxygen
from the air we breathe also enters the cells. It
combines with the carbon to form carbon
dioxide. Hydrogen and oxygen remain and
com bine to form water.
When carbon combines with oxygen in the
air it produces fire and warmth. In the same
way, the chemical changes which take place in
our body cells provide our bodies with warmth
and energy.
When we sit still we need little energy. W e
breathe rather slowly and the chemical changes
in our body cells take place rather slowly. When
we walk fast o r run about we need m ore energy.
We breaihe faster and the chemical changes in
our body cells g o on faster. M ore warmth and
energy is produced.The Story o f a L oaf o f Bread
The pictures below show how yeast grows.
Every ounce o f yeast is made up o f millions o f
tiny living cells. When oxygen and food are
present, each cell quickly bulges out to form a
"bud”. The bud rapidly grows, breaks off from
the old cell and forms a separate new one.
The pictures above the line show how bread is made. First the
!•
•
•
stalks and husks o f the wheal are separated from the kernels;
<5 0r>
then the kernels are ground inlo flour. The flour goes to the
bakery where it is mixed with yeast and waler to make dough.
The dough is left to “work”for a time to allow it to rise. Then
it is shaped into loaves and baked.
Now look at the pictures below the line. When the husk is
removed from the wheat, the kernel that remains contains
starch and protein.
<4 0 0 Dough, then, contains protein, starch, yeast and water. The
protein forms a colloid which makes the dough stodgy and
“heavy’ *. T o enable them to grow, the yeast cells take oxygen
from som e o f the particles o f starch. This causes chemical
changes which produce carbon dioxide and alcohol. The carbon
dioxide makes the dough rise.
0! 4 if In the oven, heal kills the yeast cells and so slops the chemical
Q> changes. The carbon dioxide makes the bread light; the alcohol
evaporates; the proLein helps to form the crust.
24The baker’ s oven must
be hot before the dough
goes into it.
When the bread is bak
ing the heal must not
be lo o fierce.
25Why W e Must Protect Food
In the fou r centre pictures on the leftypin-mould
is growing on moist food.
1 Look at the first o f these four pictures. What
do you notice about the threads o f mould
in the air?
2 What change has taken place in the second
picture? What d o you think the blue dots
stand for?
3 What happens when the seed-pods break?
Does the amount o f mould on the food
increase?
4 In the top picture you see these seeds falling
on food. Look at the bottom picture and
say how we can prevent this.
5 Look at the pictures on the right. Name
some o r the things flies may visit before they
alight on food.
6 What creatures hatch from the eggs the fly
lays in the garbage? When the maggots
have gone through all stages o f growth,
what d o they turn into?
7 D o flies also lay eggs on food? D o maggots
hatch out?
8 H ow can we slop flies laying eggs around
dustbins? On food? Name a m odem way
o f killing flies.
2627
What W e Have Learned about Food
1. Nearly all fuels and all foodstuffs con other liquids; it also makes particles o f starch
tain carbon. In fires and in the cells o f our smaller and easier to digest.
bodies carbon combines with oxygen from the Here is a little sum which reminds you what
air and produces carbon dioxide. Every day happens when free oxygen from the air we
burning and breathing take more and more breathe acts on the food particles in the cells
oxygen from the air and put more and more o f our body:
carbon dioxide into it. I f all the free oxygen in (carbon + hydrogen -f-oxygen)+ oxygen
the air were used up, no fire could burn and no makes (carbon -boxygen)-l-(hydrogen-f-oxygen)
animal or human being could live. This chemical change produces the warmth and
The oxygen in the air is replaced by growing energy our bodies need.
green leaves. During daylight, carbon dioxide 4. The dough from which our bread is made
taken from the air acts with water inside the leaf contains protein and starch from ground wheat-
and produces starch and oxygen. The starch feeds kernels, plus yeast and water.
the plant and the oxygen goes into the air. The yeast cells take oxygen from some o f the
2. Fat gets hot more quickly than water, and starch particles to enable them to grow and
reaches a much higher temperature before it multiply. This causes chemical changes which
boils. When meat is cooked in fat the protein produce carbon dioxide and alcohol. Baking
particles help to form a crust round it which kills the yeast cells and so stops the chemical
keeps in the juice and flavour. changes. The alcohol evaporates; the carbon
Many vegetables contain particles o f starch dioxide bubbles make the bread light; the pro
surrounded by tiny hard walls o f cellulose. tein helps to form the crust.
Boiling first breaks the cellulose walls and then 5. On certain moist foods pin-mould grows
splits the starch into smaller pieces and changes and produces pods full o f tiny seeds called
some o f it chemically. This makes the vegetables spores. When the pods break the spores may
easier to digest. float quite a long way in the air, fall on other
3. The fats, starch and protein in our food all food and begin to grow there. We can protect
contain carbon, hydrogen and oxygen combined moist food from these airborne spores by keeping
with one another. Protein particles are not it covered.
changed very much by cooking. We can digest Houseflies visit all kinds o f filthy places. They
them quite well uncooked. may be carrying disease germs when they alight
Cooking makes fat easier to digest by chang on our food.
ing it into liquid which forms an emulsion with Flies lay eggs in heaps o f garbage and some-
28
limes in meat. M aggots from the eggs turn meal safe or under a wire-gauze cover. W e can
first into chrysalises then into flies. M eal can help to stop the number o f flies from increasing
be protected from flies by keeping it in a by keeping all rubbish in a closed dustbin.
THINGS TO DO
1. Mix a little starch into a paste with cold 4. Put a few lumps o f chalk in a two-necked
water and pour the paste slowly into a cupful jar, fitted wilh a thistle funnel in one neck and
o f boiling water. A llow to cool. Pour into this a length o r glass tubing in the other, placing the
one drop o f iodine solution. N ote what happens. lower end o f the glass tubing under water, as
This lest allows you to find out whether or not shown in the diagram. Fill a jam jar with water
various food s contain sla rch : i.e. add a sp ot o f and hold its neck under water, just above the
iodine and see whether you get a colour change tubing. N ow pour a lillle dilute hydrochloric
and what kind o f change. acid down the funnel. The acid acts on the
2. Test for the presence o f starch in (1) bread chalk and produces carbon dioxide which
(spot with iodine solution); (2) potato (boil in bubbles into the jar. When the jam jar is full
water first); (3) roots o f carrot and turnip. o f carbon dioxide, place a lighted taper at
3. Leave a piece o f moist bread in a saucer its mouth. What happens? Why is this?
for a while. At the same time, leave another 5. Fill a second ja r with carbon dioxide;
piece on which you have sprinkled a little without letting any gas escape, place a few
bleaching powder. A lso leave a piece o f moist green leaves in it and stopper it up firmly.
bread under a saucer. At the end o f a week, Leave it in brighl light for a few hours, then
com pare the three pieces and explain what has place a lighted taper at its mouth. D oes the
happened in each case. taper g o out? Explain what happened in the jar.
29Windows, Warmth and Light doy
HOUSE W ITHOUT GLASS
In all the pictures on these two
pages yellow standsf o r warm air,
blue f o r cold air, black shading
for shadow; stands f o r heat. nigh!
doy
night
Many years ago houses had no glass in the windows. This picture
shows how such a house was warmed on a winter day.
1 L ook at the two columns o f small pictures. 4 In which house are the shadows darker?
Which has the larger window, the house What do you think is the reason?
with glass or the house without? 5 H ow was the old house lighted at night?
2 Which is colder by day? Why is this? Why How is the modern one lighted?
is its window small? 6 Why were shutters placed over the window
3 Which house gets more direct light during o f the old house on a cold night? Why were
the daytime? they not used during the day?
30HOUSE W fTH GLASS
This picture shows how heat circulates on a winter day in a
modern house with glass windows.
7 L ook at the large picture on the left. How 10 For simplicity, no chimneys are shown on
does cold air enter the room? these pictures. What difference d o you
8 Why is the air warm at the lop o f the room ? Ihink a chimney makes to the movement
H ow does heat escape? o f the warm air?
9 L ook at the large picture above. Is there 11 When som e o f the warm air passes up a
any cold air in the room ? What happens chimney, how d o you think fresh air com es
to hot air rising up from the fire? into the room to replace it?
31Making and Shaping Glass Glass is useful in our homes mainly because
it is transparent. Certain transparent substances
called crystals are found in nature, but few o f
them are as transparent as glass, and none can
be shaped so easily or used in so many ways.
Nowadays, partly in order not to waste it,
broken glass forms an ingredient o f glass
making. The second ingredient is sand, which
contains many semi-transparent crystals; the
third is usually limestone, a form o f hard
chalk, and the fourth soda.
To make lenses and heavy glass ornaments,
lead oxide is used instead o f limestone; to make
glass for ovenware, less soda is used and a
substance called boron oxide is added.
The mixture is heated strongly in a large
lank until it melts into a thick liquid.
/"V > /V N / V S /V N /V'N
Delicate vessels are made by blowing glass.
First the glass is left to cool until it becomes
plastic, like soft modelling clay. (Even then it is
still white-hot!) A blob o f glass is placed over
one end o f a blow-pipe and the glass blower
blows through the other end until the blob is
roughly the size and shape he wants. He finishes
shaping it with tools and then breaks it off
from the pipe.
32The first row o f pictures below shows you in A m ould shaped like a thin bottle is sealed
a simple way how plate glass for large windows at the neck end and held upside-down while a
is often made. blob o f hot glass is dropped into it. Air is blown
Molten glass from the furnace is passed be into the open end o f the m ould and the glass is
tween a pair o f cast-iron rollers which are cooled pushed down to form the shape o f the neck.
by water. The rollers co o l the glass enough to M ore air is now blown into the neck end to
make it plastic, and press it into a long, flat shape the bottom o f the bottle. But the glass
strip which slides on to a table. The strip is is not yet hollow except just inside the neck.
cut into lengths, then ground and polished While the glass is still hot it is placed in a
ready for use. larger mould. M ore air blows it up like a
The bottom row o f pictures shows you one balloon until it fils the mould. When the second
o f the m odern ways o f making bottles. It is mould is opened the bottle has only to be cooled
called the “blowing-and-blowing” method. before it is ready for use.
33Some Qualities o f Glass
1 Which is made o f thinner glass, the
flask or the tumbler? Which will
break when it is lapped lightly?
Which needs a harder knock to
break it?
2 The flask, the tumbler and the metal
pot are filled with cold water. Can
you boil ihe water in the flask? In
the tumbler? In the metal pol?
3 What happens to the tumbler o f cold
water when it is placed over a flame?
D o you think heat would break a
pot made o f thick metal?
A Look at the pictures at the bottom.
The first two show thin glass, the
second two thick glass, the last two
thick metal. D oes the thin glass ex
pand when it is healed? D oes thick
glass? D oes thick metal?
5 D oes heat travel through the whole
thickness o f the metal? O f the thin
glass? O f the thick glass?
6 Why does only a part o f the chick
glass expand? What happens as a
result o f this?
7 Can you think o f a way o f keeping
very hot water in a thick glass
tumbler?
34GLASS POLISHED METAL POLISHED W O O D
■ '
SCIENCE 30M 3D2
8 Is polished metal transparent, like glass? Is polished w ood?
9 What are m ost mirrors made of? Is it possible to make a
mirror o f polished w ood? O f polished melal? Is any light
reflected from polished wood?
10 Look at the letters seen through the magnifying glass. What
do you notice about them? D o you think the last letter o f
the word is really as far to the right as it appears to be?
11 Is the lens o f a magnifying glass o r even thickness?
12 Behind the first wedge-shaped piece o f glass is a strip o f red
paper. When you look through the side o f the glass what
appears to happen to the strip?
13 Behind the second wedge o f glass is a beam o f while light.
If you look at it through the glass what d o you see?
14 From whi te light, lights o r different colours can be oblai ned.
Can you think how the glass breaks up the white light into
the separate colours?
15 What d o we see in the sky when rain-drops split the light
from the sun into separate colours?
35What We Have Learned about Glass
1. At the very dawn o f history men already by different substances to produce different
knew how to make glass. Almost six thousand qualities o f glass.
years ago glass was used in Egypt and M eso The glass-blower uses a blow-pipe to blow a
potamia for coaling beads made o f stone, and blob o f hot glass into a bubble roughly the size
more than three thousand years ago the ancient and shape o f the vessel he wants to make. He
Egyptians knew how to mould vases from glass. uses tools to finish the shaping.
Glass-blowing began, probably near Syria, just When many jars or bottles all o f the same
before the time o f Christ. But it was not until shape and size are to be made, Lhe glass is blown
about eight hundred years ago that clear glass inside a mould by machinery.
windows were first made, and even after that Plate glass for large windows is made by
several hundred years passed by before the passing molten glass between water-cooled
houses o f ordinary people had them. rollers and rolling it into long strips which are
The window o f a house during (he middle (hen cut into lengths, ground and polished.
ages was simply a hole in (he wall through 3. Lemonade bottles, jam jars, milk bottles,
which light and air could pass. On a winter day, tumblers are not always handled very gently.
however big the fire might be, warm air was They are made o f thick glass, since thick glass
always escaping from the window, and cold air does not break so easily as thin glass when it is
blowing in through it. Therefore people did not knocked. Electric light bulbs, test-tubes, retorts
want their windows to be lo o large, and the all have to withstand heat. They are made o f
result was that little sunlight came into the thin glass, because heat will not crack thin glass
rooms. as easily as it will thick glass.
In a modern house with large glass windows, Glass is not a good conductor o f heat. If we
we can enjoy plenty o f daylight, even on the place thick glass over a flame, the side nearest
coldest days, without suffering from cold the flame will become hot and expand while the
draughts. The warm air from our fire does not other side remains cool and does not expand.
escape through the window; it rises towards the The result is that the glass cracks. When very
top o f the room and, as it cools a little, comes thin glass is placed over a flame the heal can
down again and is then again warmed by the fire. travel the short distance from one side to the
2. The main ingredients which go into the olher much m ore rapidly, and (he glass is less
melting tanks at the glassworks are sand and likely to break.
broken glass. Other ingredients are usually 4. When rays o f light pass through a lens
limestone and soda, but these may be replaced (except through its centre) they are bent. Look
36
at something through a sloping lens; its position glass, it is split up into the separate colours from
will seem to have shifted. This also happens which il is made. This is because in passing
when the rays pass through a wedge o f glass. through the glass, each colour is bent by a
When white light passes Lhrough a wedge o f different amount.
THINGS TO DO
1. When you are in a very warm room on a vex lenses (thin at the edges, thick in the centre)
cold day open the window slightly at top and may be slipped into them. H old the cardboard
bottom. H old a strip o f thin paper near the top together with sticky tape. N ow slide one tube
o f the window then near the boLtom. What d o into the other. Point one lens towards a distant
you notice? Where does cold air com e in more object. L ook through the other lens. Y ou have
quickly? made a m odel telescope.
2. H alf fill a glass jar with water. Place a long 7. Replace the lens nearer to the eye with a
straight stick in the jar. What d o you notice? concave lens (that is, thicker at the sides than
H ow w ould you explain this? in the middle). This time you will have made a
3. Take two beads o f exactly the same size model o f what is called a “Galilean” telescope.
(or two pen nibs). Thread on e on a piece o f 8. I f you can gel a thick block o f glass, you
cotton and suspend it in a round glass flask can trace the path o f a ray o f light through
full o f water. H old the other bead near the the block by using pins. The picture will explain
flask. D o Lhey still look the same size? Try to the method. T o the eye all four pins appear to
explain what has happened. be in one straight line.
4. Obtain som e glass tubing from the chemist
and by heating it over a gas flame (1) bend it
(2) close the end (3) blow a bubble at the closed
end. Take care not to burn yourself with the
hot glass.
5. M ake a list o f all the uses o f glass which
you might com e across during a walk between
hom e and school,
6. Obtain two rolls o f cardboard o f such
sizes that on e slides easily inside the other.
Make slits near on e end o f each so that con-
37H ow Electricity is Carried to Our Homes
Red stands f o r electricity, yellow f o r heat.
1 What d o we call the flashes we sometimes
see in the sky on a hoi, stormy day? D o we
ever see smaller flashes rather like these in
our homes?
2 D o you think electricity existed before men 4 D oes electricity flow along the wires behind
learned how lo produce it? the socket when the plug o f the electric fire
is pulled out? When it is pushed in?
3 H ow many wires must be used to carry
electricity from the power station to our 5 D oes electricity flow along the wires leading
homes? H ow many wires lead to the electric lo the bulb when the light switch is off?
socket in the wall? T o the electric light bulb? When it is on?
386 In the first iw o pictures below, trace (a) the 8 N ow trace the red lines leading from the
lines showing the wires leading to the socket, power station (a) to the fire and (b) to the
and (b) those showing the wires leading to bulb in the bottom pictures. Is it possible
the bulb. Can you, in either case, get from now, in either case, to get from one wire to
one wire to the other without lifting your the other without lifting your pencil from
pencil from the paper? the paper?
7 D oes elecLricity flow when there is no con 9 Say what must happen before electricity can
nection between the two wires? flow along wires.
39Light and Heat from Electricity
Inside an electric light bulb is a thin wire,
made o f a metal called tungsten. When the light
is switched on, electricity flows along the tung
sten wire and makes it white-hot, so that it
gives out a bright light. There is no oxygen
inside the bulb, so the wire cannot burn.
A long, thin wire is also used to heat the
water in an electric kettle. If this wire touched
the metal part o f the kettle or the water inside
the kettle, electricity would flow Lhrough the
metal or the water instead o f travelling all the
way along the wire. T o prevent this, the wire is
coiled round a ring made o f som e material
which will not carry electricity, and covered
with an outer ring o f similar material.
40If you were to take an electric flat-iron
to pieces, you would find that the bottom
part o f it is made up o f five separate
layers, bolted together. The centre layer
is a flat frame with a long, thin wire
wound round it, and on each side o f
this frame is a thin, flat plate. The two
outer layers are the thick steel plates
which give the flat-iron the weight
which is needed for ironing.
When the electric iron is plugged in,
the wire quickly becom es red-hot. Heat
passes through the two thin plates and
makes the heavy steel plates hot enough
to make the linen quite smooth.
But although heat can pass through
the two thin plates, electricity cannot.
They are made o f material which will
not carry electricity. Materials o f this
kind are called “non-conductors” o f
electricity. When a wire which carries
electricity is surrounded by a non
conductor we say it is “insulaled”.
Electricity can travel more easily
through thick metal than it can through
thin wire.
If the wire in the electric iron were not
insulated, the electricity would travel
through the steel plates instead o r
through the wire.
The current would then be much too
large and the fuses would melt.
41Getting Just the Heat We Need
The round diagrams show the wires which
heat a hot-plate. The thicker the red
lines, the more electricity is flowing
along the wires.
1 H ow many healing wires are there
i under the plate? D oes electricity flow
MEDIUM
along any o f them when the switch
is off? Why is this?
2 When does the plate produce most
heat? When does it produce m od
OFF
erate heat? When does it produce
I little heat?
LOW - HIGH
I
MEDIUM
3 In which position is the total flow o f
electricity greatest? In which least?
4 How many heating wires carry
electricity when the switch is at
“high”? At "m edium ”? At “low”?
5 When the switch is at "low ” does
MEDIUM
electricity flow along the heating
wires in the same way as it does
when the switch is at “high”?
6 D oes more electricity flow along one
short wire or along three shorl
OFF
I wires side by side? D oes more flow
LOW - HIGH
through a long wire than through a
I
MEDIUM short one?
427 L ook at the first two pictures. Are the two
strips o f metal equal in length when they
are cold? What happens when both o f them
becom e hot?
8 L ook at the next two pictures. A length o f
brass is firmly joined to a similar length o f
steel. Is the whole strip straight while it
is cold?
9 What happens when it becom es hot?
10 N ow look at the pictures below. While the
water in the boiler is cold, electricity for
the heater flows through the brass-and-
sleel strip. What happens to the strip when
the water becom es hoi?
11 What happens to the electric current when
the strip bends away from the screw?
Blue stands f o r cold, yellow f o r heat
12 What d o you think will happen when the
water becom es co o l again?
43How Electricity Rings the Doorbell
Why docs ihe electric bell ring when Ihe
button at the d oor is pressed? Wires behind the
bell-push lead to a box near the gong. In the
circuit is a battery which supplies electricity.
When nobody touches the button, Lhere is a gap
between the wires and no electricity can flow
along them. Press the button and the gap closes;
the current flows and the bell rings.
When electricity flows along a coil o f wire Above the rod is an iron striker held up by
wound round an iron rod, the rod becomes a a weak spring. When the current flows along
magnet. It attracts sleet or iron just as a the coil, the magnetism in ihe rod overcomes
horseshoe magnet does. Inside the box near the weak upward push o f the spring and pulls
the gong there is just such a magnet. the striker down so that it hits the gong.
44-----E*3
% % % % %
But while the bell is pressed, the striker hits the gon g not once but many limes. L ook carefully at
the pictures below and you will sec how this com es about.
At the first instant the button is
pressed, electricity flows right round the
wire and through the striker itself.
The rod becom es a magnet and pulls
the striker down so that the bell rings.
This causes a gap between the wires.
No current flows and the rod is no longer
a magnet,
The spring pushes the striker up, and
again the current begins to flow.
Once more the rod becomes a magnet
and pulls the striker down, breaking the
current.
The spring again pushes the striker up.
The current flows, the rod becom es a
magnet, and so the ringing goes on.
45Dangers From Electricity
1 Are ihe hoi wires o f an eleclric fire
insulated? Why is ihis?
2 L ook at the pictures on the left,
Whal may happen if you touch the
wires with a metal spoon? Wilh a
piece o f dry wood? With a piece o f
wet wood?
3 If a gap in an eteciric circuit is filled
with a metal spoon can the current
flow? Can it flow if the gap is filled
with dry wood?
4 What happens if the gap is filled with
wet wood?
5 Look at the top three pictures on the
right. What d o you notice about the
insulation between the two wires in
the first ,picture?
6 In the second picture that insulation
has broken. What happens to the
electric current? T o the w ood near
the wires?
7 What happens to the w ood in the
third picture?
B H ow can you avoid getting a shock
from an electric fire? Whal would
you d o if you noticed badly worn
insulation round a wire in an electric
circuit?
46If, for any reason, there is a sudden
increase in the flow o f electricity
through a circuit, wires may be burnt
and destroyed. Bulbs or electric fires
may be put out o f order.
We avoid this by putting a short piece
o f soft, thin “fuse-wire'' into the circuit.
If there is an increase in the flow o f
electricity now, the heat will quickly
burn through the fuse-wire. The circuit
will be broken and the flow o f electricity
will stop altogether.
47What We Have Learned about Electricity
1. Electricity will only flow where there is a the electricity has a long way to travel through
closed circuit. That is, it must be able to flow thin wire; the current is weak and the wire does
from wherever it is produced to wherever it is not becom e so hot.
needed and back again without any break in the 4. Som e metals expand more than others
wires. I f we make a break— by turning o ff a when heated. Make a strip by joining equal,
switch or pulling a plug out o f a socket— no parallel lengths o f Lwo different metals, and
electricity will flow. when it becomes hot it will bend. Electricians
2. Electricity gives us heat and light by use such strips lo make devices for automatic*
making thin wires very hot. Heating wires must ally switching ofT the current when the water
not touch anything else which will carry elec in an electric boiler becomes hoi.
tricity; if they did, the electricity would take a 5. When electricity flows along wire coiled
short cut through that substance instead o f round a piece o f iron, the iron becomes a mag
(ravelling right along the wires. net. When the current stops flowing the iron
3. Under a hot-plate are three heating wires. loses its magnetism.
When the switch is off there is a break in the 6. T o prevent damage to wires in expensive
circuit, and no electricity flows along any o f electrical apparatus, we use a short length o f
them. When it is at “high” electricity flows thin fuse-wire in the circuit. If there is a sudden
through all three at once; at “medium” it increase in the flow o f electricity, the extra heat
flows along only one; at “low ”it flows through quickly destroys the fuse-wire. The circuit is
all three, one after she other. In the last position broken and the current stops.
THINGS TO DO
I. A ttach'tw o copper wires to a 2-volt 2. Get an old electric bell, take off the cover
accumulator and to one o f these join about and trace how the current flows (1) when the
3 or A inches o f very line iron wire. Make a striker touches the bell (2) when Lhe Lwo are
little hook at the end o f this iron wire. At the apart. Take the bell to pieces, and if it is not
end o f the copper wire make a small loop. N ow broken, clean the metal parts with sandpaper
drop the hook into the loop and pull fairly and replace them. Connect a dry-cell battery
tight. (I) What d o you observe and how d o you to the terminals and try to make the bell ring.
explain it? (2) Repeal the experiment, but use 3. Ask your father or older brother to ex
about 2 yards o f the iron wire. H ow d o you plain lo you how to replace the fuses in your
account for the difference in the result? home.
48
SOME BOOKS TO R E A D
A s you have studied this b ook you have probably felt that you would like to read more
about som e o f the subjects dealt with. From the list o f book s given below you will be
able to pick out quite a number that will interest and help you. The easier ones are
marked*, but don't be afraid to look at som e o f the others as well. They are all interest
ing, and many o f them contain pictures which will help you to understand m ore about
science.
Another enjoyable way o f building up your knowledge o f science is by visiting museums.
If you live near London, or if ever you g o there, you would especially enjoy a visit to
the Science Museum at South Kensington.
Everyday Knowledge in Pictures holm es, b . and m. The Water We Use
Odhants 7/6 Pilot Press 2/6
The Wonder Book o f Science Ward Lock 12/6 money, w. b . English Glass Collins 5h
alkxander , i. The Story o f Plant Life •jarvis , a . The Things We See: Indoors
Penguin 1/6 and Out Penguin 3/6
•co les , m . ). About Your Home Blackie 2/6 •ia u w e r y s , j . a ., and glover , a . h . t .
•cro ssl a n d , j . r . (cd.) The Book of Making Light Nelson 3/-
Wonders Collins 2/3 •lauw erys , j . a ., and glover , a . h . t .
c u l i .is, w. Your Body and the Way it The Thirst o f Cities Nelson 3/*
Works Allen <S Unwin 2/6 •little , w . b . Science in the City
•f a w c e tt , r . Bread Gawthorn 3/6 Pitman 4/6
•fa w cett , r. Glass Cawthorn 3/6 m cd ou ga ll , a . t . Nature's Giant
•FAWcrrr, r. Soap Gawthorn 3/6 Forces Pitman 3/-
fortune , j . b ., and m ann , f . b . The • m o r g a n , a . p ., and s im s , j. w . The Boy
Story o f Iron Penguin 1/6 Electrician Harrap 9f-
•freeman , m . and i. Fun With Chemistry o *d e a , w. t. Electric Illumination 9d.
Pilot Press 7/6 p e a r s o n , f . j. Our Food Cassell 3/6
g e r a r d , c. The Story o f Power Nelson 4/- • p e t e r s h a m , m . and n . The Story Book
Hactings , a . b . The Biology o f Water o f Wheat Wells, Gardner, Darton £ Co. 3/6
Supply H.M. Stationery Office 1/6 • t a y lo r , f. s. The Young Chemist
h ill , F. J. Electricity Collins 2/- Nelson 5/-
•h o ll o w o o d , b . The Things Wc See: t k o r n h il l , p. The Air We Breathe
Pottery and Glass Penguin 2/6 Pilot Press 2/6
holmes , B. and m . Keeping Warm w a y , R. B. and g reen , n . d. Electricity
Pilot Press 2/6 Wells, Gardner, Darton <£ Co. 5/-A GRADED COURSE
IN GENERAL SCIENCE
aims to give a basic course in General
V is u a l S c i e n c e
Science during the years from 9 to 15; to focus activi
ties by encouraging observation and fostering a taste
for experiment. It makes a radically new approach to
the problem of science teaching in its early stages.
The first two books, a two-year course, are directed
broadly at the ages 9-11. They contain much “Nature
Study”therefore, but the clarity of the Isotype method
of visual exposition has made it possible to introduce
other aspects of science which closely touch the child's
daily life.
The next four books, which cover the ages 11-15, are
of particular value to Secondary Modern Schools and
as a background course to frame the more specialised
studies of the Grammar School or the Junior Tech
nical School. Each deals with many topics stemming
from one general theme, and illustrates them by
reference to everyday phenomena. The emphasis
throughout is on knowledge which will be of direct
practical use in later life. At the same time, exercise
is given in simple scientific reasoning, all the main
branches of organised science are represented, and the
principles of elementary science clearly emerge.
V is u a l S c i e n c e reflects the most progressive tendencies
in science teaching. The contents rest firmly on the
suggestions contained.in recent reports on the teaching
of science prepared by the Science Masters' Associa
tion, the Association of Women Science Teachers,
and the Ministry of Education. 
Isotype Archive