Heat

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HEAT

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The "Reason Why" Books

HEAT Irving and Ruth Adler

The John Day Company

:

The "Reason Why" Books by Irving and Ruth Adler AIR

ATOMS AND MOLECULES COAL COMMUNICATION EVOLUTION FIBERS

HEAT HOUSES INSECTS AND PLANTS IRRIGATION: CHANGING DESERTS TO GARDENS

LEARNING ABOUT STEEL THROUGH THE STORY OF A NAIL MACHINES

MAGNETS NUMBERS OLD AND NEW NUMERALS: NEW DRESSES FOR OLD NUMBERS OCEANS RIVERS SETS

SHADOWS STORMS TASTE, TOUCH AND SMELL THE EARTHS CRUST THINGS THAT SPIN TREE PRODUCTS WHY? A BOOK OF REASONS WHY AND HOW? A SECOND BOOK OF REASONS YOUR EARS YOUR EYES

© 1964 by Irving and Ruth Adler must not be reproany form without permission. Published by The John Dav ir ' " stlV(,t New York 36 x Y an(1 l' lf 'lL si muTt a n e orT?rC'^P^i a d a by Longmans Canada Limited, Toronto.

All rights reserved. This hook, or parts thereof,

duced

in

Si>Pw

L^'

W

-

'

i

Congress Catalogue Card Number: 64-13788

MANUFACTURED

IN'

THE UNITED STATES OF AMERICA Third

Impression

:

Contents Level of Heat and

Amount

of

Heat

6

Broken Jars

8

Popping Milk Cartons

9

The Thermometer The Dance of the Molecules Burning: Molecules Take New Motion Makes Heat Heat Makes Motion Heat Makes Light Electricity

10 12 Partners

16

18

19

20

Makes Heat

21

The First Rule of Energy: Energy The Second Rule of Energy

Is

Never Lost

22

24

Taking Pictures Without Light

26

Gas and Plasma Measuring High Temperatures The Highest Man-made Temperatures Taking the Temperatures of the Sun and the The Heat of the Earth Heat and Life The Fire That Burns Inside You Heating Our Houses Refrigerators and Air Conditioners Taking Heat Away

28

Solid, Liquid,

Engines with the Fire Inside

Word

List

Them

30 32 Stars

33 34 36 38

40 42

44 47

In places where

it is

cold

we

We

houses to keep ourselves warm. ourselves T~l

r~-

y

warm,

too,

heat our

by wearing

keep

clothing.

Clothing keeps in the heat of our bodies.

it

We

heat our food to cook

soft

and

it

and make

tasty.

We heat metals and glass to make them Then we can work them and shape

soft.

them

We make run.

into useful things.

use the heat of burning fuels to airplanes,

We

ships

and automobiles

use the heat of burning fuels to

carry rockets into space.

We can even use

heat to take pictures.

The heat alive.

of burning food keeps animals

The h n.at

of the sun

warms

the earth

and gives us bright daylight. Plants and animals cannot live without the heat and light of the sun.

The heat

of the stars

we can

bright that

though they are

What

is

heat?

see

makes them

many

of

them even

billions of miles

How

does

it

so

do

away.

all

these

things?

How can we tell that something is hot? How can we tell how hot the air is? How can

we

tell

how

hot the sun

is?

What

is

the hottest thing on the earth? In this book on heat

we

answers to these questions.

shall find the

.

A

liquid flows

from a higher place

..

/

/

lower place

W

Amount

Level of Heat and

Water to

of

Heat

comes from a hot-water faucet

that

A

your hand.

drawer

... to a

feels hot

spoon that you take from the kitchen

feels cool to

your hand.

If

you put the spoon

into

a glass of hot water, the spoon begins to get hot. It gets hotter

and hotter until

got hot because

it is

The spoon water and went into

as hot as the water.

some heat

left

the

the spoon.

The heating

of the

spoon makes

heat behaves like a liquid. place to a lower place.

A

it

seem

stops

if

level of heat in a hot object

is is

as the

Heat seems

level of the liquid in the higher place.

same way. There

the level of

same

the liquid in the lower place becomes the

flow in the

though

from a higher

liquid flows

The flowing

as

heat in every object. higher than

it is

to

The

in a cool

object. If a hot object touches a cool object, heat flows

from the hot cool object,

flowing

object,

where the heat

where the heat

when

level

is

level

low.

is

high, to the

The heat

stops

the two objects have the same heat level. 6

.

The

level of heat in

an object

is

called

(TEM-per-a-chnre). Temperature

its

temperature

measured

is

in de-

crees.

The

level of heat in

in the object are

and a quart

jar

an object and the amount of heat

not the same. Suppose you

with hot water from a

perature, or level of heat, in both jars

kettle.

is

a pint jar

fill

The tem-

the same.

Now,

every pint of water at that temperature has a certain

amount

of heat in

it.

But a quart of water

much as a pint. So the quart much heat in it as the pint jar. The amount ories

(

jar of

of heat in something

is

twice as

water has twice as

is

measured

in cal-

KAL-o-rees ) --£

the temperature of the

If

water

In

both jars

is

the

same

...

A 1

QUART

.

.

.

then the level of heat

in

both jars

is

the same, but the

amount of heat is different. The water in the quart as much heat in it as the water in the pint jar.

jar

has twice

Broken Jars Every housewife knows that she must never pour a very hot liquid into a cold glass jar. To do so might

Heat flows from the hot liquid

crack the

jar.

glass.

makes the

It

makes the

the heat

makes the glass

glass try to take

A very hot

expand so quickly that the

Most things expand

know

warmer. At the same time,

glass

glass expand.

this, so

into the cold

as they

up more

liquid

space.

may make

It

the

glass will crack.

grow warmer. Engineers

they build concrete highways in sections

with spaces between them. The spaces give the concrete sections

room

in

which

there were no spaces

rails

expand during hot weather.

between the

mer sun would make Railroad

to

the

sections, the hot

If

sum-

highway buckle and

crack.

between them

for the

are laid with spaces

same reason.

x

8

After

a

while

little

the

cover of the carton will

pop open by

itself.

Popping Milk Cartons

Take a and

set

it

partly filled milk carton out of the refrigerator

on the kitchen counter. After a

cover of the carton will pop open

by

all

little

itself.

while the

Here

is

the

reason why.

Because the carton is

air

is

only partly

above the milk. The

filled

air presses

milk. It also presses against the sides

How

carton.

called

its

hard the

pressure

with milk, there

down

and the top

air presses against

(PRESH-er) on the

The warm kitchen makes the wanner. As the air gets warmer

air it

against the of the

the carton

is

carton.

inside the carton

presses harder and

harder against the sides and top of the carton. So the pressure of the air on the inside of the carton increases. Finally the pressure

is

so great that

it

makes the cover

pop open.

What happened

inside the milk carton

wanner

a gas like air

walls ol

its

container.

is,

the harder

it

shows that the

presses against the

The Thermometer

The

most things expand as they grow warm-

fact that

er gives us

ways

of measuring temperature.

measuring temperature

is

called a

The

tool for

thermometer

(ther-

MOM-eh-ter). Some thermometers use expanding to

measure changes

in temperature.

use expanding gases.

expanding

solids

Other thermometers

The weather thermometer

uses an

liquid.

-LThe weather thermometer

is

made

of a thin tube of

glass.

The tube

glass

bulb at the other end. The glass bulb of the ther-

mometer

is

is filled

sealed at one end. It

is

joined to a small

with a liquid. Alcohol (AL-ka-hall)

usually used for cheap weather thermometers. hol

is

colored red or blue to

make

it

The

is

alco-

Good

easy to seel

weather thermometers and doctors' thermometers are

MER-cure-ee)

filled

with a liquid metal called mercury

The

may be mounted on a scale with numbers Or the numbered scale may be printed right on the

on

glass

it.

(

tube

glass tube.

When

the temperature near a thermometer increases,

the liquid inside the thermometer expands. There

one way that the liquid can take up more space.

is

It

only takes

up more space by climbing up the tube of the thermometer. The warmer it becomes, the more the liquid expands.

The more

in the glass tube.

the liquid expands, the higher

The temperature 10

is

the

it

rises

number on the

scale to

Two

which the liquid reaches.

numbered

different

scales are usually

used on

thermometers. Both scales are based on the temperature at

which water freezes and changes

perature at which

it

boils

to ice

and changes

to

and the tem-

steam or water

vapor (VAY-per). The scale used in Great Britain and in the scale.

United States

On

the Fahrenheit (FARR-en-hite)

is

the Fahrenheit scale water freezes at 32 de-

grees and boils at 212 degrees. There are 180 degrees be-

tween the freezing point and the boiling point of water. Because

we

use a

number system based on

ter to use a scale that has

is

also

used

in

is

it is

bet-

100 degrees between the freez-

ing point and the boiling point of water.

with a scale like this

ten,

used for

A

thermometer

scientific experiments. It

most of the countries of the world. This

thermometer

is

thermometer.

It is also

called the Centigrade (SEN-tih-grade) called the Celsius (SELL-see-us)

thermometer, after the

man who

invented

it.

Centigrade or Celsius scale 10

20

30

40

50

60

70

80

90

4

1

t

T

32

100

50

70

90

110

130

150

Fahrenheit scale 11

170

190

212

_

The Dance of the Molecules Everything in the world (

is

made up

MOLL-eh-kules ) The smallest .

cule of water.

bit of

The smallest bit of salt

Molecules are so small that

water were put

in a row,

Molecules are moving

water

is

a mole-

a molecule of

salt.

forty million molecules of

they would take up only an inch. all

by

cules are held in place

if

is

of molecules

the time. In solids, the mole-

electrical forces.

cules of a solid are not free to

So the mole-

wander but they can

spin

and swing back and forth or vibrate (VY-brate). In

They can wander but they are kept close to each other by the electrical forces. In gases, the molecules are separated by big spaces and move about freely. You can see the movement of the molecules of a liquid liquids, the molecules are not held in place.

with the help of a microscope. First sprinkle a fine powder in some water. Then take a drop of water with powder in

it

powder

and look

at

it

under the microscope. The

bits of

They move this way and that. The bits of powder move because molecules of water keep bumping into them and push them around. If the water

is

are never

still.

They move

faster

because heating the water has

the molecules of water

The

powder move even

heated, the bits of

move

faster.

made

faster.

fact that molecules are

12

moving

all

the time helps

what heat

explain its

is.

The heat

of a

body

is

the motion of

molecules.

The plains

fact that molecules are

why

a spoon gets hot

The molecules

hot water.

moving

when

it is

in the hot

all

the time ex-

put into a glass of

water are moving

faster than the molecules in the cool spoon.

Where

the

water touches the spoon, the fast-moving molecules of

water give the slow-moving spoon molecules next to

them a hard push. The push makes the spoon molecules

move

faster.

These faster-moving spoon molecules,

~

The path

of a

look under a

molecule as microscope

it

would

13

B

in

The faster-moving water molecules make the spoon molecules move faster. So the spoon gets hot.

spoon molecules that they

turn, give

way

push. In this

and

faster

time,

faster

all

bump

into a hard

move

the molecules in the spoon

and the spoon gets warmer. At the same

when water molecules bump

into

spoon molecules,

the water molecules slow down. So the water gets cooler,

because

its

molecules are moving more slowly.

spoon molecules are moving as cules, the

The plains

and

why most

water mole-

fast as the

is

tions. So, as

heated,

a

body

they is

all

the time ex-

when they

are heated.

move

faster

make bigger and bigger

vibra-

molecules begin to

its

heated,

more and more. Because up more

moving

bodies expand

faster. In a solid

takes

the

spoon and water have the same temperature.

fact that molecules are

As a body

When

its

molecules swing out

of these wider swings, the

space. 14

body

The plains

fact that molecules are

why, the warmer

on the walls of

its

a gas

is,

container.

moving

the greater

fast.

against the walls of the container.

faster.

When

pressure

of air in a

They

When

often

the air

warmer, the molecules of

inside the container gets

move

is its

The molecules

milk container are moving around very

hump

the time ex-

all

the molecules

move

the walls of the container harder and

faster,

more

air

they hit

often.

When

they hit the walls of the container harder and more often, their pressure

on the walls

the air becomes warmer,

increases.

its

That

is

why, when

pressure on the walls of the

container increases.

=.-.

Fast driving

makes the

sure on the inside of the

air inside a tire tire

increases.

15

warmer. Then the pres-

Burning: Molecules Take

We

burn cooking

gas,

oil,

coal

New Partners and wood

to give us

heat for cooking and for heating our homes. Cooking gas, oil,

coal

and wood are

For

fuels.

fuels to burn, they

need

oxygen (OX-i-jen). Fuels usually get the oxygen they

need is

for

burning from the

air.

About

one-fifth of the air

oxygen.

The molecules of cooking gas, oil, coal and wood are made up of atoms of carbon C AR-bun and hydrogen Carbon and hydrogen are chemical eleHY-dro-jen ments. There are 102 different chemical elements. Atoms (

)

(

.

of chemical elements

Two

)

come together

to build molecules.

atoms of hydrogen and one atom of oxygen join to

make one molecule of water.

When a fuel burns, a chemical change takes place. The chemical elements in the fuel join with oxygen to change the fuel into something else.

When

gas, oil

and wood

burn, their carbon atoms join with atoms of oxygen in the air to

make molecules

of a gas called carbon dioxide

A hydrogen atom

An oxygen atom 16

(CAR-bun dy-OX-ide). Their hydrogen atoms join with oxygen in the air to make molecules of water vapor. These chemical changes take place

When these chemical off.

Scientists

in the flame.

changes take place, heat

have measured

this

amount

is

given

of heat.

They

have found that every time two atoms of hydrogen and

one atom of oxygen water, the

join together to

same amount

of heat

is

make

a molecule of

always given

off.

The chemical changes in which heat is given be made to work the other way around. For this pen, heat must be put

make water vapor entists

split into

oxygen

amount

join to

Two atoms molecule

of

to hap-

hydrogen and oxygen.

water into hydrogen and oxygen

as the

can

So heat has to be supplied to

have found that the amount of heat that

to split

same

in.

off

of heat given off

is

is

Sci-

needed

exactly the

when hydrogen and

fonn water vapor.

hydrogen and one atom

of water.

17

of

oxygen join

to

make

a

Rubbing your hands together makes them warm.

Motion Makes Heat

Whenever you fact that its

match, you make use of the

motion makes heat. To

tip against

made

"strike" a

something rough. The

of chemicals that

makes the

tip

strike a

burn

match, you rub

tip of a

easily. Striking

match

is

the match

hot enough to burst into flame.

There are many other things you do that show that

warm hot when pump hot

motion makes heat. You rub your hands together to

them up

in the wintertime.

you hammer

it.

You make a

nail

You make the barrel of a tire the piston in and out. You make a

when you pull hot when you drill

drill

a hole in wood.

Why do these motions make heat? The motion

of rub-

bing your hands makes the molecules in your skin vibrate harder. But the heat of a cules.

body

is

the motion of

its

mole-

So when your skin molecules vibrate harder, your

hands become warmer. The motions of drilling, hammering and pulling a piston in and out all make molecules

move

bicycle

faster, too.

pump

are

all

So the

drill bit,

made warmer by 18

the nail and the

these motions.

Heat Makes Motion

We use the fact that heat makes motion to make

auto-

mobiles, ships and airplanes run and to carry rockets into space. In

Making Tin

i

all

of these cases,

we

first

make

a gas very hot.

a gas very hot increases the pressure of the gas.

the great pressure of the gas gives the push that

makes the thing move.

The

first

machine that changed heat

into

motion was

the steam engine. In a steam engine a burning fuel

used to heat a boiler of water. turns to steam.

back and is

The

When

the water boils

is it

pressure of the steam pushes a piston

forth. This back-and-forth

motion of the piston

the motion of the steam engine that

makes machinery

run.

The earliest locomotives were steam used wood or coal as fuel.

On

pages 44, 45 and 46

we

shall learn

gines that change heat into motion.

This steam locomotive

was

built

about

1

50 years

ago.

locomotives.

They

about other en-

Heat Makes Light

When wood burns, it gives out a warm reddish-orange light. A burning gas flame glows with a pale blue light. Burning all

salt gives

out a bright yellow

light.

examples of another fact about heat.

thing If

is

made

hot enough

an empty iron pan

time, the light.

pan becomes

We

it

is

a volcano

is

red-hot, too.

When

begins to give out

on a hot stove

left

so hot that

say that the pan

These are

is

light.

for a long

glows with a reddish

"red-hot."

The

volcano on an island north of

it

some-

The

lava inside

lava inside Stromboli, a

Sicily, lights

up the sky

at

night with a red glow.

Some things are so hot that they give out a white light. Then we say they are "white-hot." The sun and the stars are great masses of hot gases. They are so hot that they give out a bright white light that

we

call "sunlight"

"starlight."

^^

— 20

and

Electricity

We

Makes Heat

use electric irons, electric toasters and electric

We

coffee makers.

even cook and heat our homes with use electricity to

electricity. All of these things

heat. In all of

an

them there are metal

electric current

tric

is

coils

make

through which

allowed to flow. The flowing elec-

You can see the red stove and an electric

current makes the coils red-hot.

glow

of the hot coils of an electric

toaster.

Electricity also

When

the bulb

is

makes heat

in

it

glows with a white

on for a while,

it

oxygen inside ah

electric light bulb.

turned on, an electric current begins to

flow through a fine wire inside that

an

light.

it.

The wire

After the bulb has been

becomes too hot

to touch.

electric light bulb.

docs not burn up even though 21

it

gets so hot

There

is

no

So the wire inside

gets hot

enough

it

to glow.

The First Rule of Energy: Energy Is Never Lost There

is

energy stored in your muscles. The energy

makes your muscles do work, There

is

is

hammer can

drive a nail into a piece of wood.

energy in an electric current. The energy of an

electric current

can ring a

bell, light

up a room

The energy in your muscles, the energy

stove.

ing

swinging a hammer.

energy in a swinging hammer. The energy of a

swinging

There

like

hammer and

or heat a

in a swing-

the energy in an electric current are

different forms of energy. Sound, light

all

and heat are forms

of energy, too.

Energy appears

in

many

forms. However,

all

of the

forms are related, because energy keeps changing from

one form to another. Heat, as one of the forms of energy, can be changed into every other form. In a steam engine, the heat of a burning fuel tion.

fuel

At an is

electric

changed

power

is

changed

into energy of

plant, the heat of a

mo-

burning

into electrical energy.

Other forms of energy can be changed into heat. The energy of motion of a swinging heat

when

changed

the

into

through the

hammer hits the heat when an

hammer

is

changed

nail. Electrical

electric

into

energy

is

current passes

coils of a stove.

Although the form of energy keeps changing, the

amount

of energy never changes.

22

The energy

stored in

your muscles

is

not

been changed into

When

a

changed

hammer into

energy of motion has been

hits a nail,

an equal amount of heat energy. Scientists

call this rule that

tion of

when you swing a hammer. It lias an equal amount of energy of motion. lost

energy

is

never

lost

the law of conserva-

energy (KON-sir-VAY-shun). To conserve means

to save.

The energy stored in

your muscles.

...is

changed

.

into

an equal amount of energy of motion

...which

is

of heat energy.

/

23

.

changed

an equal amount

w

.

into

The Second Rule of Energy

When

you hammer a

wood, you

nail into a piece of

change the energy of motion of the hammer into energy of heat.

On

page 13 you learned that heat

of the molecules.

A hammer

is

made up

is

the motion

of billions of

when you swing a hammer, its molecules are moving. Then how is the motion of a swinging hammer different from the motion we call heat? molecules. So

When you swing a hammer,

all

of the molecules of the

hammer swing together. They all move in the same direction. Thev all move toward the nail. All of the molecules in the hammer move at the same speed. They all move with the speed of your swing. The motion of the molecules in the swinging

mer

strikes

hammer

orderly.

When

the ham-

the nail, the orderly motion disappears.

Molecules in the

hammer and

by the blow. They begin

many

is

nail

have been

to vibrate wildly,

stirred

up

moving

in

directions at different speeds. Their motion

*

#

The motion swinging

in a

+m

of the

hammer

is

dls-

molecules isorder/y.

They all move at the same speed in the same direction.

24

orderly or scattered. This disorderly motion of the molecules

is

what makes the hammer and the heat

this reason,

sometimes called disorderly or

is

For

nail hot.

scat-

tered motion.

The

rule of energy taught us that energy

Energy

lost.

When

the

is

which

hammer

all

hit the nail, all of the

be used

of the energy of heat can

to

any way

be changed

into

hammer and

the

push the hammer up again? According

the second rule of energy, this this rule,

never

energy of mo-

into energy of heat. Is there

energy of motion? Can the heat in the nail

is

only changed from one form to another.

was changed

tion in

first

more and more

things around us

is

isn't possible.

to

Because of

of the orderly motion of the

being changed into heat or disorderly

motion. Because of this rule, scientists think the motions of the sun, the planets little

bv

and the

stars are

slowing

down

little.

When

the

hammer

the molecules

and

nail are given

in

25

the

hammer

disorderly motion.

So the hammer and

•WT

hits the nail,

nail get hot.

Taking Pictures Without Light

When

you take a picture with your camera, you make

sure that there

is

enough

light.

you are taking a picture of

Light rays from the object

strike the film inside

your

camera. The light makes a chemical change in the

film.

The chemical change

when

dark areas light

in the film

the film

and dark areas on

is

it is

developed.

as light

The

and

film with

the negative from which a

black and white printed picture It is

shows up

is

made.

The It was

possible to take pictures without light, too.

picture on this page of a car

was taken

in the dark.

taken with the help of heat rays.

When

an

electric light

You can

bulb

is

turned on

it

gives out

They are visible VIZ-ibble ) It gives out heat rays, too. You cannot see the heat rays. They are invisible ( in-VIZ-ibble Heat rays and light rays are both caused by vibrations inside the atoms and molecules of an object. They are both radiations RAY-dee-AY-shuns ) caused by these vibralight rays. (

see the light rays.

.

)

(

26

.

An

tions.

The

Infrared

camera

make

the vibrations that

heat rays

make heat

vibrations that

is

rays are slower than

light rays.

Another name

for

infrared rays.

Infrared rays are used for taking pictures without light.

Here

is

how. Different parts of the car give out different

amounts of heat tion that

rays.

So there

is

An

infrared cam-

and changes them

into electrical

matches the shape of the

era receives these rays signals. It

makes

a strong signal

strong.

makes

a

It

weak. In

a pattern of heat radia-

this

way

parts of the car nals that

is

signal

where the heat rays are

where the heat rays are

the pattern of heat rays from different

changed

into a pattern of electrical sig-

matches the shape of the

electrical signals

weak and

weak

car.

is.

in turn,

car.

changed

The

pattern of

into a pattern of

strong rays of light. This pattern of light rays

strikes the film inside the

matches the shape of the

camera, making a picture that

ear.

Solid, Liquid,

Water

is

in a liquid state

kitchen faucet. it

becomes the

When solid

comes the gas we

You

Gas and Plasma

you freeze

we

call

when

call ice.

it

it

comes out of your

in

your refrigerator,

When

you

boil

it, it

be-

steam or water vapor.

are used to thinking of water as being in three

different states,

depending on

temperature. However,

its

you may have the idea that iron

may have

the idea, too, that air

is

is

always a

solid.

You

always a gas. Both of

these ideas are wrong. Iron and air can be in other states, too,

depending on

until

it is

If air is it

their temperatures. If iron

about 1500 degrees Celsius,

cooled until

becomes a liquid,

it is

it

becomes a

liquid.

140 degrees below zero Celsius,

too.

In a solid, the molecules are held in place forces.

heated

is

When a solid is heated,

its

by

electrical

molecules vibrate more

and more. After a while, the molecules vibrate

so hard

enough

to hold

that the electrical forces aren't strong

them

in place

any more. Then the molecules are free to

move around. The

solid melts

and becomes a liquid that

can flow.

When faster

a liquid

and

faster

is

made warmer,

and

pull farther

its

and farther

Finally, the molecules are so far apart

28

molecules

move apart.

from each other

that the electrical forces are too all.

When

or-ates)

molecules split

is

open and is

at

gas.

their

fast.

When

atoms separate. At

split into

its

they hit each other they this

temperature

hydrogen and oxygen atoms. At

20,000 degrees Celsius even the atoms

Then

them

heated to about 4000 degrees Celsius,

move very

water vapor

to bother

happens the liquid evaporates (ee-VAP-

and becomes a

gas

If a

this

weak

the gas becomes a plasma

MB*?***.

•

V

split into pieces.

(PLAZ-ma).

"

Melted iron being poured into a converter 29

to

make

steel

Measuring High Temperatures

We

can measure the temperature of boiling water by

We

putting a thermometer into the container of water.

cannot measure the temperature at which iron melts by putting a thermometer into the liquid iron because the

thermometer would melt,

too.

Nor can we use ordinary

thermometers for measuring the temperatures of plasmas.

How,

do

then,

measure very high tem-

scientists

peratures?

Something that

is

hot

is

called a hot body.

tures of very hot bodies can

tance. This can radiation.

Tempera-

be measured from a

dis-

be done by catching and measuring their

A tool for doing this is called a pyrometer

(

py-

ROM-eh-ter).

One kind hotter a

of

body

pyrometer makes use of the fact that the is,

the

more energy

it

radiates. This kind

of pyrometer measures temperature

by measuring the

energy in the rays

it

receives from the hot body. It

changes the energy

it

receives into an electric current.

The amount

of current flowing through the

pyrometer

is

a clue to the temperature of the hot body.

Another kind of pyrometer uses the out by a very hot body to measure is

done by comparing the

the light given out

light

its

temperature. This

from the hot body with

by the glowing wire 30

visible light sent

of a special kind

of electric light bulb.

The temperature and

brightness of

the glowing wire are changed by changing the amount of current flowing through til

it.

The

current

is

changed un-

the glowing wire and the visible light from the hot

body have the same

brightness.

Then

the current

clue to the temperature of the very hot body. eter like this

lava as

it

was used

came out

to

mouth

of a volcano.

-•:-•

'

;

I v.,

The temperature of the lava in the mouth of this volcano was measured with a pyrometer. 31

of hot

The tem-

perature of the lava was 1200 degrees Celsius.

-

a

A pyrom-

measure the temperature

of the

is

The temperature

of the hot

gases that surround the sun is about 1 million degrees.

temperature inside the sun is

20

about

million degrees.

The temperature on the surface of the sun is about 6000 degrees.

The Highest Man-made Temperatures Scientists ries that

have made temperatures

are higher than the temperature on the surface

of the hottest star.

has been

in their laborato-

made

The

highest laboratory temperature

inside a shock tube.

A

shock tube uses a

gas under very high pressure to push against a second

gas under low pressure. in the

are

a shock

wave

second gas. In a shock wave, the molecules of gas

moving very

depends on how to see

The push produces

why

fast.

Since the temperature of a body

fast its

molecules are moving,

it is

easy

the second gas gets very hot. Temperatures 32

more than 500,000 degrees Celsius have been made

of

this

way.

The

man-made temperature is the temperahydrogen bomb when it explodes. The tem-

highest

ture inside a

perature

about 100 million degrees Celsius. That

is

why hydrogen bombs can do

so

is

much damage.

Taking the Temperatures of the Sun and the Stars

The sun

is

93 million miles away. The nearest

billions of miles

star

is

away. Even though they are so far away,

their surface temperatures

kind of pyrometer

can be measured.

used for doing

is

this.

A

special

This kind of

pyrometer has a telescope that catches radiation from the sun or the

star.

It

then measures temperature by

measuring the amount of energy hottest stars

in the radiation.

have a surface temperature of about 80,000

degrees Celsius. The surface of the sun Its

temperature

The to the

rays

we

is

is

much

is

cooler.

only about 6000 degrees Calsius.

receive from the sun or a star are a clue

temperature inside the sun or the

star, too.

omers have figured out that the temperature sun

The

Astron-

inside the

about 20 million degrees Celsius. The temperature

inside the hottest stars

is

about 2 33

billion

degrees Celsius.

The Heat

of the Earth

The highest air temperature ever measured on the surface of the earth was at a place in northern Africa. It once was 136 degrees Fahrenheit there. The lowest air temperature ever measured on the surface of the earth

was near the South

once was 126 degrees below

Pole. It

zero there. Temperatures inside the earth are higher.

They

The

like

inside of the earth gets

some

These

at the center of the earth

may be

3000 degrees Celsius.

as high as

gets

are higher even than the temperature of

The temperature

lava.

much

of

its

its

heat in two ways.

It

heat from certain rocks inside the earth.

rocks, called radioactive rocks, contain elements

radium and uranium. The radium and uranium

atoms break up and send out energy. This energy warms

up the

earth.

The

inside of the earth also gets

some heat

from the pressure of rocks near the surface on rocks deep

The pressure on the rocks deep inside The great pressure makes them very hot.

inside the earth. is

very great.

The surface of the earth The most important way earth gets

its

heat

is

gets in

its

heat in two ways, too.

which the surface of the

from the sun. Some of the heat of

the earth's surface comes from the inside, too.

Heat

comes up

same

way

to the surface

from inside the earth

in the

as heat rises in a room.

All

around the earth, the

stars,

34

the sun and the plan-

ets

is

space.

The temperature

in

space

is

very low. Since

heat flows from a higher level to a lower level, the earth is

some

losing

of

its

surface heat into space

However, the surface heat that the earth is

all

the time.

loses into space

balanced by the heat the earth receives from the sun

and by the heat that comes from the

inside. This

The surface losing

space

some all

is

of the earth of

.

is

off.

getting

heat from the sun and heat that rises up from the inside

.

Why the

the earth does not cool

... but the surface

is

heat into

its

the time

why

to the surface of the earth

earth does not cool off .35

Heat and Life Nothing can too

much

live

without heat. Nothing can

live

with

heat either. Most things can live only within

a narrow band of temperatures. Nothing can live at a

temperature lower than 100 degrees below zero Fahrenheit.

Nothing can

live at a

temperature higher than 225

degrees above zero Fahrenheit. Most things live in the

even narrower band of temperatures between 32 degrees

and 122 degrees Fahrenheit. At lower temperatures,

would

most

living things

most

living things

A

freeze.

At higher temperatures,

would be cooked

alive.

long time ago people did not live in houses or wear

clothing. So they

had

people began to wear

to live

warm

where

it

When

was warm.

clothing and learned

how

to

heat their houses, they could live almost anywhere on the earth.

Now,

they can even

in

heated rockets and

fly off

into space that

warm is

space

suits,

colder than any

place on the earth.

Most animals

live

where

it is

warm. But there are some

animals that can even live in the Far North at freezing temperatures. These animals are kept coats of fur or feathers.

tered places.

when (

it

Some

)

,

or

their

homes

thick

in shel-

of these animals cannot get along

gets very cold

M Y-grate

They make

warm by

move

and food

is

scarce.

to places that are

36

So they migrate

warmer.

Many

birds migrate in the wintertime. There are flies

that migrate, too.

wintertime

When

because

Some animals can they

hibernate

an animal hibernates,

body temperature in its shelter all

falls.

it

curls

This saves

its

the

in

HY-burr-nati

in a ball

body

heat.

and

its

It

rests

is

ve r y

winter long.

There are a few animals that can cold or where

butter-

get along (

up

some

it is

live

where

very hot without any

it

difficulty.

The

polar codfish swims in the icy polar seas at 29 degrees

Fahrenheit. There

water

at a

is

a sea plant that lives in hot pools of

temperature of 190 degrees Fahrenheit.

A hibernating ground 17

squirrel

The Fire That Burns Inside You Your body There the

is

a

fire is

is

fire

made up

of

many

different kinds of cells.

that burns inside every cell.

The oxygen

the food you eat.

The

fuel for

for the fire

is

in

the air you breathe.

The there

fire

is

that burns inside

you has no flame. Although

no flame, the chemical changes that take place

when food burns

in

your

changes that take place eat has carbon

cells are a lot like

when wood

and hydrogen

in

it.

burns.

the chemical

The food you

When the food burns,

make water vapor. The carbon joins with oxygen to make carbon dioxide. The water vapor and carbon dioxide leave your body when you breathe out. The fire that burns inside you makes the heat that the hydrogen joins with oxygen to

keeps your body warm.

It also

makes the energy

that

makes your muscles move.

Even

if

you were

to lie

still all

need a sceady supply of food

day long, you would

in order to stay healthy.

There are muscles inside you that are working

all

the

The muscles of your heart are working all the time to make your heart beat. The muscles of your diaphragm (DY-a-fram) are working all the time to make you breathe. Your body is kept warm all the time. It is kept time.

at

about 98.6 degrees Fahrenheit by a heat regulator

side your brain. So even

when you 38

lie still,

in-

you are burn-

up food

ing

to

keep your body going and

keep you

to

warm.

The amount

of food a person must eat

size.

So a grown-up must eat more than a

who

is tall

must eat more than

a person

depends on child.

who

A

is

his

person

short.

A

son

who has a broad body must eat more than a perwho has a narrow body. An average-sized man must

eat

more than an average-sized woman.

person

The amount does.

A

person

a person eat

of food a person eats

who

who works

more than

People get

depends on what he

does hard work must eat more than

A

sitting at a desk.

ballplayer must

a radio announcer.

less active as

they grow older. So old peo-

ple should eat less than they ate

when

they were young.

who eat more food than their bodies burn get fat. That is why many people get fat as they grow older. People

The amount sex,

of food a person should eat

body build and the kind

of

depends on

work he does. 39

his age,

Heating Our Houses In order to heat a room, heat from a hot

body must

spread through the room. This happens in three ways.

A

hot body gives

carry

some

in the

off infrared rays.

from the hot body

of the heat

room. This

The

way

infrared rays

to cooler bodies

of spreading heat

is

called radia-

The sun heats the earth by radiation. A hot body also warms the air around it. Some of the warm air spreads through the room by the motion of the molecules of air. This way of spreading heat is called Conduction of heat is conduction kon-DUCK-shun

tion.

)

(

.

slow.

Some

warm air spreads through the room when warm air rise and flow away from the hot

of the

currents of

body. Currents of cool

air sink

and flow

hot body to take the place of the

spreading heat

is

warm

called convection

in

air.

toward the This

way

of

(kon-VECK-shun).

Convection spreads the heat more quickly than conduction does.

People

first

houses. Stoves

used stoves and fireplaces to heat their

and

fireplaces could heat only

Modern houses have

one room.

central heating systems.

A

central

heating system has a furnace in which a fuel like

cooking gas or coal

is

burned. The furnace

the basement of the house. Heat produced ing fuel

is

is

usually in

by the burn-

carried to other rooms of the house

40

oil,

by

pipes.

Heating by

.

.

1

.

.

.

There are several ways of doing

this.

In a hot-air heating system, air

A

convection

I* ^ ^

* + *I nace.

.

is

heated

in the fur-

fan blows the hot air through large pipes called

The ducts lead Each room has

ducts.

the hot air to openings called regis-

ters.

a hot-air register placed near the

floor.

has a cold-air register near the ceiling. Other

It

ducts carry cold air back to the furnace to again.

A

hot-air heating system heats mostly

warm

it

up

by convec-

tion.

In a hot-water heating system, water

furnace.

An

pipes to radiators in each room.

Heat

also radiates

boils

The heat

passes from the

from the

and changes

radiator. is

heated

to steam.

in

the furnace until

The steam Hows through

the pipes to the radiators. Steam radiators the

same way

in the

by both conduction and convection.

In a steam system, water it

heated

motor pushes the hot water through

electric

radiators to the air

is

that hot-water radiators do. 41

warm

a

room

and Air Conditioners: Taking Heat Away

Refrigerators

An

electric stove

and an

make

of an electric current to

and a

On

it is

When

heat

is

An

air conditioner

taken away from some-

cooled.

page 29 you learned that

enough por.

heat.

energy

refrigerator use the energy of an electric current to

take heat away.

thing

electric toaster use the

it

Heat

if

a liquid

is

made

hot

begins to evaporate or change to a gas or va-

used up

is

changing a liquid to a

in

gas.

So

when a liquid evaporates, the molecules that leave it to become a vapor are taking heat out of the liquid all the time. The liquid gets the heat it needs to make it evaporate from its surroundings. That is why you wet your you cool

skin to help

your skin evaporates, cools

you

off.

things in the

off it

on a hot day. As the water on

takes heat out of your skin

Air conditioners and refrigerators cool

same way.

Cooling coils inside the refrigerator

Outside coils on the back of the refrigerator refrigerator

is

where the

cooled by

air

Compressor

How a

and

refrigerator

works

42

Here

how

is

a refrigerator works.

A

liquid that evap-

orates easily flows through small pipes, or coils, inside

the refrigerator.

The

liquid

called a refrigerant

is

FRIJ-er-aut). As the refrigerant evaporates it

uses

up

heat.

gets the heat

It

it

ree-

the coils.

in

needs by taking heat

out of the air and the food in the refrigerator. In

this

way

the inside of the refrigerator gets very cold.

More and more coils

of the refrigerant evaporates in the

and keeps cooling the

inside of the refrigerator.

As

the refrigerant evaporates, the vapor flows through the

compressor (com-PRESS-er). The compress-

coils to the

or is

is

run by an electric motor. The job of the compressor

to press

and squeeze the vapor. Pressing and squeez-

ing the vapor turns frigerant liquid

is

into a liquid again.

compressed,

refrigerant

through

it

coils

it

warms

up.

away from

flows

on the outside of the

it off.

Then

the re-

The warmed-up the

compressor

refrigerator. Air

the outside then takes heat out of the frigerant, cooling

When

warm

on

liquid re-

the cooled liquid refriger-

ant flows back into the coils inside the refrigerator, where it

way

evaporates again. In this

out of the food and

air inside

the heat to the outside

An

air

the refrigerant takes heat

the refrigerator and carries

air.

conditioner uses a refrigerant to take heat out

of the air inside a house'

and carry the heat

outside the house. 43

to the air

Engines with the Fire Inside

Them

In the steam engine you read about on page 21, the fire

that heats the boiler of water

is

in a separate firebox

outside the engine. There are other engines in which the fire is

inside the engine

car or an airplane, the

itself.

jet

The

gasoline engine of a

engine of an airplane and the

rocket engine of a spaceship are

all

examples of

this

kind

of engine.

A gasoline engine has one or more cylinders ders) in which the burning takes place. six cylinders.

vapor and

Most

air enters

A

the cylinder (1).

by pushing

it

v*

have

the spark plug,

The spark

is

sets the

piston com-

into a small space at

one end of the cylinder (2). Then an mixture.

cars

In a gasoline engine, a mixture of gasoline

presses the mixture

made by

(SILL-in-

electric spark,

allowed to pass through the mixture on

fire in

=====

Inside the cylinder of a gasoline engine

44

an explo-

The burning mixture produces hot gases at high pressure. The great pressure of the burnt gases pushes sion.

the piston back to the other end of the cylinder

Then

the piston

moves up

again, pushing the burnt gases

out of the cylinder (4). After the burnt gases have been

pushed

out, the cylinder

reach For a new explosion. In

is

a car, the up-and-down motion of the piston

is

used to

turn gears that turn the wheels of the car. In a gasoline engine, hot gases are produced at high

pressure in order to push pistons. tons

is

The motion

of

the pis-

used to turn the wheels of a car or the propeller

of an airplane. In a jet plane, the push of the hot gases

used to push the plane forward without the help of tons.

Here

is

how

the engine of a

enters the engine at

making

it

comes inhere

front end.

The

compressed

air.

Fuel

n Compressor

is

V

When

pis-

plane works. Air air

is

compressed.

very hot. Then gasoline or kerosene

into the hot

Air

its

jet

is

is

sprayed

the spray hits the hot.

sprayed

_

^inhere...

me

Tur f

Burnt v

gases

Fuel burns here

Diagram of a rocket

compressed

air,

the spray starts to burn. Burning pro-

duces hot gases at high pressure. The pressure forces the burnt gases out through a narrow opening at the back of the engine.

The

against the plane

way

out, the

bin).

way push

gases pushed out in this

and make

it

move

forward.

On

their

burnt gases pass through a turbine (TUR-

The turbine

is

a wheel with

burnt gases push against the

many

little

little

vanes.

vanes and

make

The the

The turning turbine makes the compressor work. When the compressor works, more fresh air comes turbine turn.

into the jet engine to

keep the

fire

inside the jet engine

going.

A

rocket engine works like a

jet

engine, except that

it

drawn in from the outside. Rockets travel space where there is little or no air. They do

doesn't use air

high up in

not get oxygen from the space around them. So rockets take along their rocket needs

oxygen

in

it.

is

own

supply of oxygen. The oxygen a

carried in a tank.

Liquid oxygen

is

used because then a

oxygen can be compressed into a 46

The tank has

little

space.

liquid lot of

Word

— The

(KAL-o-ree)

Caloric

amount

List

for

unit

measuring

the

of heat in something. 252 calorics arc needed

temperature of one pound of water one

to raise the

degree Fahrenheit.

Conduction (kon-DUCK-shun)

—The way

heat

is

spread

heat

is

spread

by the motion of the molecules. Convection (kon-VECK-shun)

— Thewa)

when warm air rises and cool air sinks to take Degree — The unit for measuring temperature. Evaporate

(

—To

ee- VAP-or-ate )

its

place.

change a liquid

to a

gas.

Expand

— To

take

up more

space.

Hibernate (HY-burr-nate)

— What

body

up

save

its

temperature Infrared rays

Molecule

(

heat. It curls

Heat

and

in a ball

shelter

falls. It rests in its

—

an animal does to

all

its

body

winter long.

rays.

MOLL-eh-kule

)

— The

smallest bit of

any

chemical.

Pressure

(PRESH-er)

against the walls of

Pyrometer

— How its

container.

(py-ROM-eh-ter)

very high temperatures

Temperature

hard something pushes

—A

tool

for

measuring

at a distance.

TEM-per-a-clinre

I

—

The level

of

heat

in

something. Vibrate (VY-brate)

—To

move back and IT

forth quickly.

About the Authors and Ruth Adler have written more than fifty books about science and mathematics. Dr. Adler has been an instructor in mathematics at Columbia University and at Bennington College, and was formerly head of the mathematics department of a New York Irving

City high school.

Mrs. Adler,

who

formerly taught

mathematics, science, and art in schools in the

York area, recently also taught dition to

in

New

Bennington. In ad-

working with her husband writing

this

book,

she drew the illustrations.

Books by Irving Adler alone and books by him collaboration with Ruth Adler have been printed 77 different foreign editions,

in 10

in in

languages and in

9 paperback editions.

The Adlers now

live in the

country in Shaftsbury

Township, near Bennington, Vermont.

PHOTOGRAPH CREDIT Pages 26 and 27

-

Barnes Engineering

48

Company

v^

by

Series They

are excellent"— New York Herald Tribune

The best of the matter is

One can -be scientific

and Ruth Adler

Irving

that,

with authors like the Adlers, their

certain that not only

is

name is

a guarantee.

the exposition clear and logical, but that the

Horn Book Magazine

matters presented are correct and up-to-date— The

THINGS THAT SPIN "A

vital

if

somewhat complex subject handled with

clarity

and

precision."

—Virginia Kirkus

— The Horn Book Magazine

"A helpful and stimulating book."

THE STORY OF A NAIL 'Presenting a truly excellent account of the historical development of the steel industry. Clear, well-labelled drawings accompany the simple and meaningful text;

-Library Journal

recommended."

SHADOWS "An

easily

understood explanation of the causes and uses of shadows."

—ALA Booklist

NUMBERS OLD AND NEW "A fascinating book

for the student interested in mathematics."

—American Library Association "Exceptional book about

how we came

to

count as

we

do."

—Child Study Association

WHY? A

America

of

Book of Reasons

"This takes the kinds of questions continually asked by children in 2nd-3rd-4th grades and answers them, so that each topic is complete in itself, within the limitations of the age level and scope. I'd suggest that it be given to a child with an inquiring mind and acquisitive instinct for collecting unrelated facts." —Virginia Kirkus

RIVERS simple "Contains a wealth of information, and the illustrations add clarification enough for third-graders and informative enough for fifth-graders. Recommended." —Library Journal .

.

.

OCEANS AIR "These

fine additions to the series are well written

Schools and public libraries will find

INSECTS

,johndat|

'VHSw'/

^ .^

The

interrelation of plants

illustrations in

two

colors.

and

.

.

.

and

scientifically accurate.

-Library Journal

these useful."

AND PLANTS

insects, for the

middle grades. Attractive and useful

-The Horn Book Magazine