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Elements, compounds and
experimental techniques
• Co re
1 The t able below shows the melting points, bo iling po ints and densities of element s A to E.
Substance
Meltinq point/°C
Bollinq pointl°C
- 259
-253
1085
-7
2580
59
- 39
357
- 183
A
- 2 18
Density/q cnrl
0.09
8.93
3.1
13.6
0.0013
a Wh ich of these subst ances, A to E, a re gases at room tem pe rat ure? .
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b Wh ich of these substances, A t o E, are liq ui ds at room temperat ure?
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c Wh ich of these substances, A t o E, are so li ds at room t emperat ure?
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d Wh ich two of these substa nces, A to E, are most li kely to be metals? ...
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e Wh ich of these substances, A t o E, is most li kely to be mercury? ...
/1/
f
Wh ich of t hese substances, A to E, is t he least dense metal? ..
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g Wh ich of these subst ances, A t o E, w ill be a liquid at-2 10°C? ...
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2 a Pick t he 'odd one o ut ' in each of the fo llowing g roups of elements and explain why it is d iffere nt
fro m the others.
i
Cu,
C.
ea, Cs, Cr
Odd one out ..
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Explanation ,,,
ii nitrogen, neon, su lfu r; Iron, silicon
Odd one out ,, __ __ , ., __ ,,,
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Explanation
iii Mg, Al, Cl, Na, Ar
Odd one out
Explanat ion _,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, __,,,__ ,__ ,__ ,,,,,,,,_,,,,,_,.,,,,,, __ ,__ ,., __,__,,,_,., __ ,,,,,,,,_,.,,,_
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Cambridge IGCSE Chemistry Workbook
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b Fo r each of the fo llowi ng stat ements abo ut elements, write eithe r ·true' o r 'fal se·.
i
There are on ly 103 element s. ·--··,,
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ii
More elements are metals than non-metals . ..
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iii Each element has a chem ical name and a symbol. ..
iv Metals such as magnesi um cont ain t wo at oms joined together t o fo rm molecules.
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v Molecul es of argon cont ai n only one at o m ...
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vi Some of the sym bo ls for the element s come from their Chinese names ...
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vi i W here elements co ntain two atoms jo ined together in pairs, they are ca lled diatomic.
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3 a Distinguish between the t erm s compound and mixture, using specific examples.
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b Here is a list of substances:
stainl ess steel
ca rb o n monoxide
lemo nade
sulfuric acid
methane
sod ium hydroxide
limestone
beer
brass
ce ment
Which of these substances are:
i
co mpounds? ...
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Ii
mixtures? ...
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c Pick the 'odd o ne out ' In each of the fo llowing grou ps and expl ain w hy it is different from the
others.
i
petrol, oi l, water, air, solder
Odd one o ut ..
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Explanati on ...
ii
lead nitrate, potassium oxide, chromi um, hydrochloric acid, silicon dioxide
Odd one o ut ..
Explanati on
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iii HCI, Fi, MgO, FeS, col
Odd one o ut --···
Explanation
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2 ELEMENTS, COMPOUNDS AND EXPERIMENTAL TECHNIQUES
4 a A mixtu re of zi nc met al powder and sulfur w as heat ed stro ng ly in a test-tu be. A brig ht
red glow spread very quickl y th roughout the mixtu re duri ng t he reaction. At t he end of
the experime nt , a white powder was produced.
i
What safety precaut io ns should be taken whe n carrying out th is experiment?
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ii Explain what the 'bright red g low' indicat es . .
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iii Give the chemical name of t he 'white powder'. .
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iv W rite a word equation and a balanced chem ical equation for the react ion that has
taken place.
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v The white so lid is a com pound. Explai n the d ifference between the mixture of
zinc and sulfu r and t he compound formed by t he chemica l reaction between t hem.
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vi Many compo unds are very useful subst ances. Salt (chemical name sod ium chloride) is o ne
of t hese usefu l compo unds. It Is a wh ite crysta ll ine soli d and has been prized by people for
a very long time. Find and make a 11st of some th ings that we use sa lt for in o ur w orld t oday.
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b The met al cop per can be extract ed from Its ore, copper su lfide, In a two-st age process:
I
Copper su lf ide reacts w it h oxygen at a high temperature to fo rm copper oxide and sulf ur
dioxide gas.
II Then t he copper oxide is reacted with carbon, aga in at high temperature, to form copper
metal and ca rbon d ioxide gas.
i
Name the elements ment ioned in t he passage above.
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ii Name the compounds mentioned in the passage above.
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iii W rite word and balanced chemica l equations for t he reactio ns described in the
passage above.
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5 a The table below shows the formu lae for so me compo unds.
Complete the tab le by w riti ng in:
i
the symbols present in each formula and the eleme nts they represent
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Ii the number of atoms of each element present in t he formula
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iii t he total number of atoms present in the formu la.
The fi rst one has been done fo r you.
Formula of
substa nce
t-,S-ym~b-071- rN7~-~m,'- "" ~"'" ," ~~'-um~b-,-, o~,---< ~:!~er of
atoms
atoms
Lithium
Nitrogen
Oxygen
0
b Balance the fo llowing equations. Some of t he spaces sho uld be left blank .
. ... _Pb(s) + ..... .0/g) -+ ...... PbO(s)
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. .. .Hz{g) + . .. 0 2(g)
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...-i, • _
.Hp (I)
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....C1H. (g) + ....0 1(g) -+ ...C0 2 (g) + ... H10(1)
iv ... ...Fe(s) + ..... _.Br 1(1)
.CuO(s) +
...-i, •••••
/2/
FeBri(s)
HCl(aq)-,.
CuCl/aq) +
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Hp(I)
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Vi . .. ..SnOiCs) + . -···H1(g)-+ ····--Sn(s) + ·-·-·.HzD(I)
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2 ELEMENTS, COMPOUNDS AND EXPERIMENTAL TECHNIQUES
6 a The d iag ram on the right shows the apparatus used fo r
fractio nal d isti llati on. The labels have bee n replaced
w it h numbers.
For each number, write down the correct label from
the li st below.
i
Liebig condenser
fract io nating colum n
cold water out
distillate
cold water in
t he rmometer
mixtu re of liquids
heat
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2 ...
/1 /
3 ...
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··············-··-····--····--····--····-··---··· /1/
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6 ...
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8 ...
ii W hich of t he fo llowing mixtures can be separated successfully by fra ctiona l distillation?
Explain your answers.
crude oil
magnesium and sulfur
a mixtu re of dyes
air
b The d iag ram on the right shows a simple apparatu s used for
chromatography. The labels have been repla ced with numbers.
For each number, write down the correct labe l fro m the list in the box.
pencil li ne
beaker
chroma t ography pa per
solvent
Q
sa mp les
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1
2
.
'
~
e
/1/
/1/
2 ..
/1/
/1/
3 ...
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c W hat do you understand by the term accuracy of experimental work?
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d Which of the fo llowing are units of:
i
time ...
Ii temperature
Iii vo lume
;, ma>> .....................................................................................................................................................................................................
cm 1
kilograms
seconds
grams
hours
degrees Celsi us
litres
minutes
[BJ
e In experiments you wi ll require the use of accurate measuring instruments. What accuracy
would you expect of:
i
a st opwatch ...
ii a t herm ometer
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Ii i an electron ic balance ...
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iv a bu rette
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• Exte nded
7 The metal zinc can be extracted from Its ore, zi nc su lfid e (z inc blende), in a two-stage process.
The second part of the process involves a redox reactio n in which zinc oxide is reacted with carbon,
at a high temperature, to form zinc metal and ca rbon mo noxide gas.
zi nc ox ide+ coke (carbon)--+ zi nc+ carbon monoxide
a What do you understand by the term redox?
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b W hich of the substances shown in the word equatio n Is being :
i
oxidised? ...
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ii reduced? ..
c W hich of the substances shown in the word equatio n is acting as the :
i
oxidising agent? ..
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Ii reducing agent ? ...
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d W rite a balanced chem ical eq uatio n fo r the reactio n shown in the word equation .
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2 ELEM ENTS, COM POUNDS AND EXPERIMENTAL TECHNIQUES
e The word eq uati ons below describe reactions by w hich the meta ls lead and ti n are
obt ained fro m th ei r ores.
lead oxide+ ca rbon -+ lead+ carbon d ioxide
ti n(1v) oxide + hyd rogen gas -+ ti n + w ate r
In each of t hese reactions, wh ich of the substances show n is be ing:
i
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oxidi sed ?
ii red uced?
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iv red uci ng agent?
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Wh ich of the substances shown is acting as t he:
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iii oxidising agent? ..
v Write a ba lanced chemi cal eq uatio n fo r each of the se reacti o ns.
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Exa m focus
Core
1 The table below shows some information abou t four differen t elements, W, X, Y and Z. (Note that W,
X, Y and Z are not chemical symbols.)
a Complete the following tab le.
Element
w
z
Metal or non-metal? Shinv?
Metal
Non-metal
No
Yes
Non-metal
Conducto r of electridtv? Meltinl! ooint
Yes
High
No
Low
Yes
High
No
Low
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b Zinc is a me tal. Give one property of zinc, not shown in t/1e table, which shows that it is a me tal.
.................................................................................................................................................................................................................... (1/
c Sparklers are a type of firework. They usually consist of a chemical mixture that has been moulded
onto a thin wire. One of the main substances fotmd in the mixture is iron powder.
The word equation for one of the main reac tions that takes place during the burning of a sparkler is:
iron+ oxygen --. iron oxide
i
Give the name of one of the reactants present in the word equation above . ..
ii Give the name of the compound present in the word equation above . .
[1/
[1/
iii Give o ne reason why people should be careful when handling sparklers.
[ 1/
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iv Write a balanced chemical equation for the reac tion of iron with oxygen.
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[Tota/:10]
Core/E xte nd ed
2 Iron is usually extrac ted from its ore haema ti te (iron(m ) oxid e). The following is a brief ou tline of the
reactions involved in this extraction.
I
coke + oxygen -+ carbon d ioxide
II carbon dioxide + coke ~ carbon monoxide
Ill iron(m ) oxide+ carbon monoxide-+ iron + carbon d ioxide
a Wri te balanced chemical equa tions for:
i
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reaction! .
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ii reactionII.
b Which substance is being oxid ised in reac tion I?
111
c Which substance is being reduced in reac tion II? .
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d Balance the following equa tion fo r reaction Ill. Some spaces may be left blank.
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................... Fep 3(s) + ................... CO(g)-+ .................. Fe(!)+ .................. CO,(g)
e In reaction Ill, which substance is ac ting as the reducing agen t and which is ac ting as
the oxidising agent? ·······-·····f
····················-·····-·····-·····-·····-···············-·····-·
[21
Complete the tab le below.
Formul a of
substance
Name
Elements resent
Total number
Svmbol
Numberofato ms of atoms
co
Fe
co,
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g v\'hich of the substances shown in the table are:
i
elements? ....... _
/41
ii compounds? ...
[Total:40]
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