reading utk final test sgsb.inggris1

8/18/2019 Reading Utk Final Test sgsb.inggris1

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UNIT 7

READING COMPREHENSION

THE ATOMThe atom is a system. It consists of a nucleus and one or more electrons. The nucleus is the

center of the atom and consists of protons and neutrons. The electrons move around the

central nucleus.There is only one electron in the hydrogen atom. There are seven electrons in

the nitrogen atom and eight in the oxygen atom. An atom of iron contains twenty-six

electrons.

The concept of atom first emerged in Ancient Greece. In 400 B.. the philosopher

!emocritus theori"ed that matter could #e divided into smaller and smaller particles until a

point was reached #eyond which no further su#division was possi#le. These indestructi#le

particles were called atomos$ a Gree% word meaning indivisi#le. &e %now today that atoms

are so small that it would ta%e more than a million of them to e'ual the thic%ness of this sheet

of paper. !emocritus( theory$ however$ was not universally accepted in the ancient world$ or many #elieved in Aristotle(s theory that matter is composed of four elements) earth$ fire air$

and water.

!uring the middle Agesin *urope$ the concept of atoms was considered too a#stract and was

accordingly re+ected. ,inally$ in 04 the *nglishman /ohn !alton formulated an atomic

theory #ased on his experimentation. e claimed that all matter is made of atoms1 that all

atoms of a single element have the same shape si"e$ weight$ and #ehavior1 and that atoms of

each elements are different from those of any other element. e said that atoms are not

created or destroyed #ut rather form new com#ination in chemical reactions.

!alton thought that atoms were solid$ #ut today atoms are #elieved to consist mainly of

space$ with a dense nucleus at the center. The si"e of the nucleus inside an atom is

compara#le to the si"e of an ant on a foot#all. *ach nucleus contains proton$ which have positive electric charge$ and neutrons$ which have no charge. The nucleus is surrounded #y

electrons$ which have a negative electric charge. The num#er of protons e'ual to the num#er

of electrons in each atom$ and therefore in the entire atom has no charge. In 23$ the !anish

physicist iels Bohr proposed a model of the atom in which the electrons revolved around

the nucleus li%e the planets revolved around the sun. Today the movement of electrons is

thought to #e more li%e #ees hovering around a hive. The force of attraction #etween the

positive atoms in the nucleus and the negative electrons whirling around %eeps the electrons

in their paths.

&hat is it that ma%es iron hard$ oxygen a gas$ and mercury a li'uid5 The properties of an

elements are determined #y a num#er of electrons in an atom$ which is called the atomic

num#er. All atoms of the same element are ali%e. If you(ve seen one atom of oxygen$ you(ve

seen them all. ydrogen$ the lightest element$ has one proton and one electron. In fact$ the

hydrogen atom$ the most common atom in the universe$ is the #asis on which our entire

universe was formed. ydrogen has eight protons and eight electrons. 6ranium$ one of

heaviest$ has 27 protons and 27 electrons. All the world is made of atoms) *verything we see

and %now of is made of the #illion and #illion of these infinitesimal spec%s of matter. All life

exists #ecause atoms are continually moving$ com#ining$ separating$ colliding$ giving of f

energy and a#sor#ing energy.


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UNIT 8READING COMPREHENSION

SOUND8ound waves cannot travel through empty space #ecause they need a solid$ li'uid or gas to

pass through. Astronauts on the moon cannot tal% to each other li%e they do on *arth as there

is no air for sound to pass through$ so they have radios to spea% to each other.

8ound waves can #e produced in several different ways #y hitting1 #lowing$ pluc%ing or

ru##ing$ for example 9 a drummer hits the s%in of a drum with his drumstic%. &hen you ru#

your hand a long the ta#let it ma%es a noise. They way that a wind instrument ma%es a noise

is #y #lowing air through a pipe so that the air inside the instrument has to vi#rate in a

num#er of different ways. The strings of a guitar are pluc%ed.

The human voice is a wind instrument. Two thin pieces of s%in$ the vocal chords$ are at the

#ac% of the throat. Breathing out #etween these stretched mem#ranes ma%es them vi#rate and

produce sound waves. !ifferent sounds can #e made #y using muscles to alter the tightness of the vocal cords.

Any movement sets up vi#rations that cause changes of pressure in the surrounding air.

*verything that vi#rates at a ,re'uency of #etween a#out :0-70000 vi#ration per second

ma%es sound waves which humans can hear. A shrill$ high note is produced #y rapid

vi#ration$ a deep$ low one called its pitch$ and the pitch of a note depends on the num#er of

times the sound producer vi#rates in one second. The human ear cannot detect very low or

very high fre'uency sounds. It is sensitive to fre'uencies of from a#out 70-70$000 hert" #ut

the range varies from the person to person. ;ne hert" is e'ual to one vi#ration per second.

The loudness of a sound is the effect it has on the human ear. It depends on the si"e of the

vi#rations. The larger the vi#ration will #e the louder the sound. The amount of energy

needed to produce the vi#rations controls the intensity of the sound.


POWER OF THE SUN

The sun radiates its energy in all directions. The minute fraction of the sun(s energy received

#y the earth has provided the #asis of all life #oth the incoming energy used to %eep warm

and sustain life and the retained fossil energy in the form of coal$ petroleum$ and others typesof fuel. *volving man%ind has #ecome increasingly dependent on using our stored energy

reserves to provide the light and heat which in the past were provided exclusively #y the sun

and renewa#le energy sources. &e have extended the hours of wor% and play and the level of

thermal comfort$ independent of geography and climate. owever$ we have now learnt that

the supply of non-renewa#le energy is not infinite. &e have also #ecome aware of the cost in

pollution and other negative side effects that can result from the conversation of excessive

amount of energy. &e must therefore examine the amount of


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have an average of 30-00 foot-candles of electrics lighting. >assing through the atmosphere

of clear s%y to sea level$ the level can exceed 0.000 foot-candles of electric lighting. As a

comparison$ #rightly-lit office might have an average of 30-00 foot-candles of electrics

lighting.

The instantaneous energy of one s'uare foot of sunlight ?on a hori"ontal surface at e'uinox

noon$ see level$ 40 degrees north latitude@ is e'uivalent to the visi#le light of 3.340 wattflorescent lamps or 00 watt incandescent lamps. As heat$ this solar energy is e'uivalent to

watts from an electric heater. *ven if used inefficiently$ there is o#viously an a#undant

amount of radiant energy availa#le from the sun.


ELECTRIC FIELD

*verything seems to #e full of electricity when the weather is cold and dry. *ven wal%ingacross a rug will give your #ody a charge of electricity. If you then touch a metal o#+ect or

another person$ you may see an electric spar% and feel a small electric shoc%. om#ing your

hair ma%es it crac%le$ and stro%ing a cat in the dar% will produce showers of spar%s.

;n cold$ dry days you can do many electrical experiments without any magnets$ wires$ or

#atteries. A com# that has #een ru##ed with a cloth will attract a small stream of water

running from a faucet. A sheet of paper ru##ed against your clothes will push each other a

part #ut will #e attracted to your #ody.

>lace #its of paper$ popcorn$ or puffed cereals underneath a sheet of glass resting on two

#oo%s. u# the glass with a cloth to give it charge of electricity. The papers and other o#+ects

are attracted #y the glass #ecause they have no electrical charge first. &ithin a short time they

drop off #ecause some electrons +ump from the paper to the glass. Then paper #its are

repelled #y the glass #ecause #oth have the same %ind of electric charge.

old a charged com# #its of paper and see if you o#tain the same result. ;n a most day$ some

of these experiments may not wor% #ecause the electric charges are drained off #y water

particles in the.

8ince electrically charged o#+ects attract or reply each other$ you might guess that they are

magneti"ed. &e can #e made 'uic%ly. >ush a pin through the middle of a soda straw so

#ecomes charged with positive electricity and the other with negative electricity. 8urrounding

each o#+ect there is an invisi#le something called an electric fields. *lectric field is not the

same as a magnetic field.

;ur understanding of electric fields is still incomplete$ and scientists are not 'uite sure whythey #ehave as they do. ,or the remainder of our study of electricity$ the %ind that travels

through metal wires and other good conductors of electricity.


SOLID, LIQUIDS, GASES

Catter in physics means something that ta%es up space. *verything that is made of any

material is made of some of the elements. &e could also say is #etter this way) All matter ismade of elements.


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Catter may #e in three different forms.

Catter may #e a solid ?a #ric%@

Catter may #e a li'uid ?gasoline@

Catter may #e a gas ?air@

8ome %inds of matter can easily #e changed from a solid to a li'uid and then to a gas. &ater

is a li'uid. Ice is a solid. 8team is a gas.

Ice is +ust water in the form of a solid. 8team is +ust water in the form of a gas. Air is a gas.

But if air is made cold enough it #ecomes a li'uid. Iron is a solid. But if iron is made hot

enough it #ecomes a li'uid. ere is a fact a#out solids$ li'uids$ and gases that you already

%now$ #ut perhaps you(ve never thought a#out it in this way. A solid generally %eeps its own

si"e and shape. A li'uid %eeps its own si"e #ut changes its shape to fit whatever holds it. A

gas changes not only its shape #ut its si"e to fit whatever holds it.

,or instance$ put a #ric% in a teapot. The #ric% remains the same si"e and shape. It is a solid.

>ut some water in the teapot. The water doesn(t ta%e up any more space than it did #efore it

was in the teapot. The si"e of the water stays the same. But the water ta%es the shape of the #ottom and sides of the teapot. &ater is a li'uid.

>ut some steam in the teapot ?#y #oiling the water@. The steam fills all the empty space in the

teapot. 8team not only ta%es the shape of the inside of the teapot #ut it changes its si"e so as

to fill the whole teapot. 8team is gas.

Dou can see from ice and water and steam that heat must have something to do with solids$

li'uids$ and gases. That #rings us #ac% to molecules. Colecules in a material aren(t +ammed

solidly together. Colecules have spaces #etween them. The molecules move a#out in these

spaces. The more the molecules are heated the faster they move. In a solid molecules have

less freedom to move than in a li'uid. In a gas the molecules have so much spaces to move in

that they go shooting off in every direction.

>erhaps you can get an idea of a solid #y thin%ing of a haystac%. There are plenty of spaces

#etween the pieces of hay #ut the pieces of hay haven(t much freedom to move a#out. A

li'uid may #e more li%e a #ag of mar#les or a 'uart of cran#erries. The mar#les or the

cran#erries slide over and around each other when you pour them out. Dou cannot pour the

pieces of hay out of a haystac%. The molecules in a li'uid may #e li%e the cran#erries in the

'uart #ox.

A gas is more li%e a lot of tennis #alls flying and #ouncing around in a #ig room. They

go in every direction and if you open the window some of the #alls apt to fly out. The

molecules in a gas are something li%e the tennis #alls in a room.

reading utk final test sgsb.inggris1

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