Oxford Mastering Science 2A unit 7

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77 Living things and airLiving things and air

7.1 Gases in the air (Book 2A, p. 3)

A What is air made up of? (Book 2A, p. 3)

B Identifying gases in the air (Book 2A, p. 3)

The Earth is surrounded by a layer of air called the (1) ____________________.

Air is a mixture of gases. The table below lists the methods for identifying the gases in the air:

Gas in the air Method to identify the gas

Nitrogen No simle test as it is (!) __________________.

"xygen #t ($) __________________ a glowing slint.

%arbon dioxide #t turns hydrogencarbonate indicator (&) __________________.

#t turns (') __________________ mily.

ater *aour +ry cobalt chloride aer changes from (,) _______________

to (-) _______________.

Noble gases No simle test as they are () __________________.

"ther gases ///

+ifferences between the comosition of unbreathed air and breathed air:

0reathed air contains () ______________________ (more 2 less) oxygen than unbreathed

air.

0reathed air contains (13) ______________________ (more 2 less) carbon dioxide than

unbreathed air.

The amount of water *aour in breathed air is (11) __________________ (*ariable 2

saturated) while that in unbreathed air is (1!) __________________ (*ariable 2 saturated).

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7.2 Air and burning (Book 2A, p. 15)

A What is burning? (Book 2A, p. 15)

0urning is a (1) __________________ reaction between a fuel and oxygen.

"xygen suorts burning. +uring burning4 the chemical energy stored in the fuel is changed to

(!) __________________ energy and ($) __________________ energy.

The word e5uation of the rocess of burning:

B Conditions for burning (Book 2A, p. 18)

The three conditions for burning can be reresented by the fire triangle.

C Putting out a fire (Book 2A, p. 19)

To ut out a fire4 we can remo*e the () _______________4 cut off the (13) _______________

suly4 and2or lower the (11) __________________ of the fire.

%arbon dioxide/tye (1!) ____________________________ ut out a fire by releasing carbon

dioxide to dislace the oxygen/containing air surrounding the ob6ect on fire.

D Preventing and surviving fire accidents (Book 2A, p. 19)

#n case of a fire accident4 ee calm4 act 5uicly and rotect oursel*es from (1$) ___________.

7.3 How humans obtain energy(Book 2A, p. 26)

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A !btaining energy from food (Book 2A, p. 26)

7ood stores (1) ________________ energy. #t is the source of energy for suorting our daily

acti*ities.

B Amounts of energy in different foods (Book 2A, p. 28)

The (!) ____________________ of food shows the amount of energy ro*ided

by a certain 5uantity of the food. #t is measured in ($) ________________ (8)

or (&) ________________ (cal).

Taing in more energy than we need may cause health roblems.

7.4 How green plants obtain energy (Book 2A, p. 31)

A Photosynthesis (Book 2A, p. 31)

9reen lants can mae their own food by (1) ________________________.

%omlete the aragrah by referring to the diagram below:

9reen lants tae in (!) ________________________ and ($) __________________ from the

surroundings. The lants then build them into (&) __________________ (in the form of starch)

using (') __________________ energy absorbed by (,) __________________ inside the

chlorolasts in green lant cells. "xygen is released as a (-) ____________________.

The word e5uation of hotosynthesis:

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Extension



B #est for the products of photosynthesis (Book 2A, p. 32)

e can carry out the (13) ______________________ to test for the resence of starch in green

lea*es. #odine solution changes from (11) __________________ to (1!) __________________

when starch is resent.

The uroses of the stes in testing for starch in a green leaf:

$tep Purpose

1 0oil the leaf in water. +estroy the

(1$) _____________________

of the cells.

2 oa the leaf in

(1&) ___________________.

;emo*e the chlorohyll from

the leaf.

3 ash the leaf in hot water. ash away the alcohol and

(1') _________________ the

leaf.

4 Add iodine solution to the

leaf.

Test for the resence of starch.

Hydrilla undergoes hotosynthesis under light. e can test the gas

roduced by the Hydrilla with a (1,) _______________________.

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Hydrilla

oi!ing

"ater

a!coho!

hot "ater

hot "ater

iodine

so!#tion



#t relights when it is ut o*er the mouth of the bottle. This shows

that (1-) __________________ is a roduct of hotosynthesis.

C &ecessary conditions for photosynthesis (Book 2A, p. 36)

e can carry out the following exeriments to find out the necessary conditions for hotosynthesis.

0efore conducting the exeriments4 we ha*e to (1) __________________ the lant by utting it in

the dar for at least !& hours.

To show that chlorophyll is needed for photosynthesis:

<se a otted lant with (1) __________________ lea*es

in the exeriment.

=ut the destartched lant under sunlight.

%arry out the iodine test to test for the resence of starch in the

leaf.

The (!3) __________________ art of the leaf becomes blue/

blac while the (!1) __________________ art remains brown.

%onclusion:

(!!) __________________ is needed for hotosynthesis.

To show that light is needed for photosynthesis:

ra a art of a green leaf on a otted lant with a iece

of aluminium foil.

=ut the destartched lant under sunlight.

Test for the resence of starch in the leaf. "nly the art

exosed to (!$) __________________ turns blue/blac

while the art co*ered with the foil remains (!&) __________________.

%onclusion:

(!') __________________ is needed for hotosynthesis.

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Extension

"ra$$ed in a!#%ini#% foi!



To show that carbon dioxide is needed for photosynthesis:

et u the aaratus as shown. oda lime absorbs

the (!,) ________________________ in the air.

=ut the destarched lant under sunlight.

Test for the resence of starch in both lea*es.

"nly leaf (!-) _________ contains starch.

%onclusion:

(!) ________________________ is needed for

hotosynthesis.

D Importance of photosynthesis in producing food

(Book 2A, p. 41)

9reen lants con*ert (!) _______________ energy from the sun to ($3) _________________

energy stored in the food roduced by hotosynthesis.

The feeding relationshi among li*ing things can be reresented by a ($1) ________________.

9reen lants are the ($!) ___________________ because they mae their own food. Animals

obtain food by feeding on lants or other animals. They are the

($$) ___________________.

7.5 Gaseous e!hange in animals and plants

(Book 2A, p. 43)

A (espiration (Book 2A, p. 43)

>i*ing cells use (1) __________________ to brea down food and release the chemical energy

stored in them. The breaing down of food in cells roduces (!) ____________________ and

($) ____________________. This rocess is called (&) __________________ (呼吸作用).

The word e5uation of resiration:

B Gaseous e)change in anima*s (Book 2A, p. 44)

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soda !i%e

A &

!ight

Extension



9aseous exchange in the air sac:

3 The breathing mechanism (Book 2A, p.48)

"a# $reathing in

1a When we breathe in, the intercostal muscles (24) __________________

and pull the ribs upwards and outwards.

1b At the same time, the diaphragm (25) ________________ and becomes(26) __________________ .

2 These movements (2) _________________ the volume o! the chest cavit"

and there!ore

the gas pressure inside it (2#) __________________ .

3 When the gas pressure inside the chest cavit" becomes (2$)

__________________ than the atmospheric pressure, air is drawn into the

lungs.

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Extension

(!1) _________________surrounding the air sac

"xygen asses into the caillary and iscarried to body cells for carrying out

(!!) _________________.

The carbon dioxide roduced in resiration asses into the air sac and lea*es the body

when we (!$) ____________________.



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"b# $reathing out

1a When we breathe out, the intercostal muscles (%&) __________________ ,

allowing the ribs to move downwards and inwards.

1b At the same time, the diaphragm (%') __________________ and returns to

its

(%2) __________________ shape.

2 These movements (%%) __________________ the volume o! the chest

cavit" and there!ore the gas pressure inside it (%4) __________________ .

3 When the gas pressure inside the chest cavit" becomes (%5)

__________________ than the atmospheric pressure, air is !orced out o!

the lungs.

The rib cage model

hich art of the resiratory system does each art of the model reresent@

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The balloon-bell jar model:

hich art of the resiratory system does each art of the model reresent@

C Gaseous e)change in p*ants (Book 2A, p. 54)

D #he ba*ance of o)ygen and carbon dio)ide in nature (Book 2A, p.58)

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The diagram below shows how green lants and other li*ing things hel ee a balance of

oxygen and carbon dioxide in nature:

ome gases in the atmoshere (e.g. carbon dioxide) can absorb (') _____________________

from the sun and ee the Earth warm. This natural henomenon is called the

(') ____________________________.

0urning fossil fuels and clearing forests increase the amount of carbon dioxide in the

atmoshere. This enhances the greenhouse effect and causes (,3) _______________________.

7.% Air pollution and smo&ing (Book 2A, p. 62)

A 0ffects of po**uted air on our hea*th (Book 2A, p.62)

0urning fossil fuels gi*es out large amounts of (1) _________________________.

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Extension



The effects of air ollutants on health:

Air po**utant 0ffect on hea*th

ulhur dioxide4

nitrogen oxides

(!) ___________________ the eyes and throats

#rritate the lungs and causes ($) ___________________

diseases%arbon articles #rritate the lungs

>ead articles Ad*ersely affect the brain functions

%arbon monoxide >owers the amount of (&) ___________________ in the blood

and causes diiness and headaches

The (') ______________________________________ (A=#) ranges from 3 to '33 and isdi*ided into fi*e le*els. The higher the index4 the (,) ___________________ the air 5uality.

B 0ffects of smoing on our hea*th (Book 2A, p.66)

moing and assi*e smoing largely increase the ris of de*eloing resiratory diseases4

(-) ___________________ and () ___________________.

?atch the harmful substances in cigarette smoe with their effects on health:

Harmful substance ffect on health

! Nicotine a #rritates the eyes4 nose and sin

!! Tar b >owers the oxygen content in blood

!!! %arbon monoxide c %auses addiction

!" Bydrogen cyanide d tains the teeth and finger nails

e %auses coughs and other resiratory diseases

f #ncreases heart rate and blood ressure

g %auses headaches and *omitingh %auses throat and lung cancer

i >eads to heart diseases

!: () _______4 _______ and _______ !!: (13) _______4 _______ and _______

!!!: (11) _______ !": (1!) _______ and _______

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Extension



A n

s w

e r

s

77 Living things and airLiving things and air

,21

1 at%os$here #nreactive " re!ights % ye!!o"

' !i%e "ater + !#e , $ink - #nreactive

. !ess 1/ %ore 11 sat#rated 1 varia!e

,2

1 che%ica! 3 " heat 3 !ight % oxygen ' caron dioxide

+ 3 , 3 - f#e! ' oxygen ' high te%$erat#re . f#e! 1/ oxygen

11 te%$erat#re 1 fire exting#ishers 1" s%oke

,2"

1 che%ica! energy va!#e " ki!o(o#!es % ki!oca!ories

,2%

1 $hotosynthesis caron dioxide " "ater % food' !ight + ch!oro$hy!! , y-$rod#ct - caron dioxide

. food )starch* 1/ iodine test 11 ro"n 1 !#e-!ack

1" ce!! %e%ranes 1% hot a!coho! 1' soften 1+ g!o"ing s$!int

1, oxygen 1- destarch 1. variegated / green

1 non-green +h!oro$hy!! " s#n!ight % ro"n

' Light + caron dioxide , & - +aron dioxide

. !ight "/ che%ica! "1 food chain " $rod#cers

"" cons#%ers

,2'

1 oxygen 3 " caron dioxide ' "ater % res$iration

' oxygen + 3 , caron dioxide ' "ater - ronch#s

. ronchio!e 1/ air sac 11 intercosta! %#sc!e 1 nasa! cavity

1" trachea 1% !#ng 1' ri 1+ dia$hrag%

1, ri cage 1- intercosta! 1. dia$hrag% / air sacs

1 ca$i!!ary res$iration " reathe o#t % contract

' contracts + f!attened , increase - decreases

. !o"er "/ re!ax "1 re!axes " do%e

"" red#ce "% increases "' higher "+ ri

", chest one "- ackone ". intercosta! %#sc!es %/ o#t

%1 in % trachea %" ronchi %% !#ngs

%' dia$hrag% %+ in %, o#t %- higher

%. oxygen '/ caron dioxide '1 caron dioxide ' caron dioxide

'" oxygen '% $hotosynthesis '' oxygen '+ res$iration

', caron dioxide '- heat energy '. greenho#se effect +/ g!oa! "ar%ing

,2+1 air $o!!#tants ,rritate " res$iratory % oxygen

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' Air Po!!#tion ,ndex + $oorer , 3 - !#ng cancer 3 heart diseases

. c f i 1/ d e h 11 1 a g

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Oxford Mastering Science 2A unit 7

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