.I.G.C®S.E
h
i
Prof. Dr. Fathy Abdel Galil
-
:
·.
Chemistry IGCSE
(Dr.rathyADC\el uatuJ
Contents
Ef'~
Topic L
Topic 2.
. To.pic 3.
Topic 4.
Topic 5.
Topic 6
The particulate nature of matter .........•.....................................•.
States of matter·.......... : ............................................................. .
. partie
. 1e theory ................................................................ .
K.metJc
Diffusion ............................................... , ............................... .
Experimental technique ..•.........................................................
Laboratory apparatus ................................................................. .
Safety in laboratory .................................................................. ..
Methods of purification ............................................................. ..
Separation of mixtures ............................................................... ·.
Chromatography ~ .................................................................... ..
Atoms, elements and compounds .............................................•..
Atomic structure ..................................................................... .
.Radioactive isotopes ................................................................ ..
. Electron distribution ............................................. :.. ................. .
lons and ionic bonds ................................................................. .
Molecules and covalent bonds ..................................................... .
Macromolecular (giant) structure .................................................. .
Stiochiometry ........................................................... .'.......... ..
Chemical formula .................................................................. ·.. .
Chemical equations· .................................................................. .
Chemical calculations .............................................................. ..
The mole .............................................................................. ..
Empirical formula and molecular formula ........................................ .
1
1
2
6
8
8
10
12
12
14
16
17
19
20
22
25
28
30
30
33
35
37
·44
46
The periodic table ................................................................. ..
Trends in group I [The alkali metals] ............................................. .
Transitions elements ................................................................. .
Trends in group VII [The halogens] ................. ·.............................. .
Nobel gases .......................................................................... ..
Test and collection of gases ......................................................... .
Oxidation and reduction ............................................................. .
48
51
52
55
56
58
Electricity and chemistry [Electrochemistry] ................................. .
Electrolysis ............................................................................ .
Applications of electrolysis ........................................................ ..
6D
62
67
Chemistry IGCSE
Topic 7.
Topic 8.
Topic9.
(Dr.FathyAbdel Galil)
Acids, bases and salts .-............................................................. .
Acids ............................................................ , ...................... .
Bases ................................................................................... .
The pH scale .......................................................................... .
1vfaking salts ........................................................................... .
Types of oxides ...................................................................... :.
Identification of ions ................................................................. .
69
69
71
72
73
77
79
Metals and reactivity series ..................................................... ...
Alloys .............. c •. : •.. ; •..••...•••..•.•..•••.•..•.•••.•••••••••..•..•..••.••••.••.•.
R.eacfIVI"ty senes
.
....................................................................... .
Extraction of iron ................................................... ·.................. .
Steel making .......................................................................... .
Extraction of zinc ..................................................................... .
Rusting ................................................................................. .
90
91
Chemical changes
Production of energy ................................................................ .
Electricity from chemical reactions .............................................. .
95
97
Topic 10. Chemical reactions ····································'·····························
Speed of reactions ...................................................... . :........... .
Reversible reactions ................................................................. .
Chemical equilibrium ............................................................... .
81
81
83
88
89
99
99
106
106
Topic 11. Air and water •••........••..•..••.••.•.•..••..•••••..••••.•.•••..•••.•••••..•••..••••
Purification of water supply ...................................................... ..
..
f.
·.
ComposttiOn o atr ................................................................. ..
Manufacture of ammonia .......................................................... .
Fertilisers ................................................ : ............................ .
Air pollution .......................................................................... .
108
108
109
Topic 12. Sulphur ............................................................................. .
Making sulphuric acid ............................................................. .
116
Topic 13. Carbonates ........................................................ ,..................
118
Topic 14. Organic chemistry ................................ ••.•...•.•••••• .•••..••••. .• ..... ..
120
111
ll2
113
117
- -··
Topic 1:
[Dr. Fathy Abdel Galil]
- 1-
Chemistry IGCSE
. THEPARTICULATENATUREOFMATIER
All matter is made .up of tiny particles, These may be atoms, mole_cules
or ions. Using the idea of parti?les, we can explain the way matter behaves.
States of-Matter
All matter can exist in three ·states- solid, liquid or gas. Solids have a
fixed shape. Liquids have no fixed shape, but their volume is fixed. Gases
have no fixed shape or volume. They spread out (diffuse) to fill all the
available space. Unlike solids ang liq~ids, gases are easy to compress into
· smaller size.
The state of a substance can be changed by heating or cooling.
6Jt.eez.i.ttg
c.onde.Jt6.Wg
me..Wng
so LID
w
f
y
W.r .JDI
)-
f"i
bo-U-Wg
0
0
0
0
u
0
0..
LIQUID
GAS
iodina
cry<tal$
reform
. on cool
test~tube
Sublimation
This is the change of state from solid to
vapour and back from vapour to solid
without passing through the liquid state.
Iodine, for instance, behaves like this
purple
Iodine
vapour.
lodine
cry•tal• ---.JS''fK.I
gentle
heat
heat
solid iodine
[dark grey solid]
allow to cool
iodine gas ------+solid iodine
[purple vapour]
Solid carbon dioxide behaves similarly.
(Dr. Fathy Abdel Galil)
-2-
Chemistry IGCSE
:.':
Arrangement and Movement Particles
SOLIDS
-
LIQUIDS
·')( )()J )(
T)ll
'l. X
!()"(
;-.... ..:=:
>--(-' :>--<
--'.r"[
( )[ " J: "'[_ J: J[
GASES
0
0
0
0
0
0
0·
..
.'
Arrangement
of Particles
close together
in a regular
arrangement
still close tog ether
in an irregular
arrangement
particles far
apart
Movement
of Particles
only vibrate
in their places
can move around
slowly
free moving
rapidly
Kinetic Particle Theory
1. All matter is made up of very small invisible particles (atoms, ions or molecules).
2. The particles move all the time. The higher the temperature, the faster they move.
3. Lighter particles move faster than heavier ones .
.J
4. In a gas, there is relatively large distance between the particles. They are free to
move anywhere [i.e. a gas can fill any v.olume].
Using the idea of particles and kinetic theory, we can explain the changes
of states of matter and diffusion .
...
;·..
- 3 -
(Dr. Fa thy Abdel Cali!)
Chemistry IGCSE
Changes of State
Mel.:thtg
When a sol~d ~s heated, ~ts part~cles ge~more ene,gy and
v~brate more. Th~s makes the sol~d
expand. At the melt~g po~nt
the part~cles v~brate so much that they oreak-aYay from the~r
pos~t~ons. The sol~d becomes a liquid.
nrraan·a·
o·'
" ........ ".,
'offifi8§.
heat
O:ffil..
DQO:
:a.:
DOG ·
'G ' "0'0' .
.........
heat at
melting point
·-
........
~
!he partici!"S vibcate.~~T~
a liquid is formed
Mel.:thtg Po.zn.t
~s
~nto
a
the temperature at wh~ch the sol~d melts,
~.e.
changes
l~quid.
Bo.<.Ung
When a
liqu~d
move faster.-
Th~s
is heated, its particles get more energy and
makes the
liqu~d
expand. At the boiling po~nt,
the part~cles get enough energy to overcome the forces
hold~ng
them together. They break away from the liqu~d and form a
heat
boilino point
slow-moving particles
in liquid
the particles
move faster
the particles get enough
energy to escape
Bo.<.Ung Po.ln.t
is the temperature at which the l~uids
bo~l,
i.e.· changes
into a gas.
Pure substances have fixed and definite melting points and
boiling points, e.g. pure water boils at 100°C and freezes at 0°C.
- 4 -
Chemistry l GCSE
(Dr. Fathy Abdel Cali!)
Evaporation
When left open to the atmosphere, even when a ~quid ~ Well
b~W the
boLt£ng poLnt, some particles of a liquid escape into
the gas state. -This is called evaporation.
The rate of evaporation increases vith
o
c
increasing temperature
increasing surface area.
A poht.t to Jr.emembVt ~ .tlw.t evapo~on oc.c.u.Jti. <.pon.:ta_neou&./'.q a_t
anq i:.empeJr.a..:tuAe-, bu;t boiling oc.cJLM lli:. c.elr.i:.a-Ut tempeJr.a..:tuAe wfti__cJt .U.
the boiling poht.t.
Compressing a Gas
plunoer pushed in
0
oas particles
0
0
0
0
0
0
0
0
o o
ThVte ~ a !_at a 6 .6 pa_c.e
between the p/Vr..t{_cl.u bt
a_ gil<.. You c.a_n 6oJr.c.e .the
pa_ll..U_c..tu elM Vt •••
lL_
0 0 0 0 of-, gas compressed
inlo a smaller
0
0
0 I'Oiume
0 0 0 0 0
bq ptUhlng bt the
p./'.ung Vt. The gM g ei:..6
<.queezed oJr. c.omplr.e<..6ed
.into a_ <.maUVt vo./'.ume.
·If enough force is applied to the plunger, the particles get
so close together that the gas turns into a liquid. But liquids
and solids can not be compressed. because their particles ara
already close together.
:.
....
- 5 -
Chemistry I GCSE
(Dr. Fa thy Abdel Gali!)
Temperature changes when a solid is heated
I
I
I
I
I
I
t
'Temperature
boiling _
point
}i____________
}!
~
boiling
melting
point
T
I. "3• -- -
'------y----'
melting
I
I
'
Time~
Qu.e.ction
Look at the table.
substance
state at room
. temperature
carbon dioxide
gas
iron
solid
w.ater
liquid
From the table, choose:
(i}
one substance which can be easily ccmpressed at room.temperature,
\
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•.•••1:"€\:. ~;?. :.: .Y.,;.?.6.lE.. :......................... ~---··············· .............................................. [1 J
(ii)
one substance which consists of particles which are far apart at room temperature,
(iii)' one substance which has a fixed shape at room temperature .
... i!'(tJ .....................................................................................................................[1]
Chemistry IGCSE
- 6 -
(Dr. Fathy Abdel Galil)
Diffusion
This is J,piteac:Ung oat and m.Lxhtg pMeeM, seen mainly in gases
and liquids. The particles of one substance mix with and move
through the particles of another. Diffusion goes until the mixture
is· uniform.
In otheJt. WoJtciJ,, i.;t i.A .the movemen.t an pcvd-{.de;, nJLOm JtegioM o6
/U.gheJt. c.oncen:tJtatiort .(.n.to Jteg.<.oM On loWelL c.onc.e.n.t;luztion.
Diffusion is fastest in gases. The particles in gases are moving
faster than in liquids.
The rate of diffusion· depends on the molecular mass. The smaller
the molecular mass the faster the rate of diffusion.
I. The bromine diffusion experiment:
Bromine is a red-brown liquid
which vaporises easily at room·
bromine
temperature. Some of the liquid is
liquid '\
placed at the bottom of a sealed gas
~
jar. The red-brown bromine vapour
spreads out to fill the gas jar.
bromine
vapour
. 2. Diffusion of ammonia and hydrogen chloride
a) Co.t.ton wool .60a.ked .<.n ammon.<.a.· 4olu.t!-on .U, pu.t .<.n.to one end o6
a .tong .tube. I.t g.{.ve;, o66 ammon.<.a. ga.;,.
b) A.t exactly .the <lame .tUne, c.ofton woo.t ;,oa.k.ed bt hyd!toeh.to!Uc.
aud .u, pu.t .{.n.to .the o.theJL end 0 6 the .tube. I.t g.{.ve;, 0 66
hydlt.ogen c.hlo!Ude ga.;,.
c.) The g. · e6 d.{.6tju.;, e a..tong .the .tube. Whi.;te solid o6 ammonium
chlo!Ude 6ai!Jn,l wheJLe they meet.
calion wool
soaked In ·
glass
tubing
eolian wool
soaked In
ammonia
hydrochloric
solution
acid
+
Mr
white solid
forms here
17
HCI(g)
->
NH CI (s)
4
36.5
Ammonia deffuses faster than hydrogen chloride. Why? . :~'.' ;': '..... ' ...
- 7 -
3UOI V1HJ3.T .JA T~~3Mi9.39X3
li
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3. Iffew dro~s of potassium manganat!:_.(Y.:q) solutio),! .(p,urple) are
carefully ~ded to a beaker cdfit!Jifu'W~Ate~;ftli>~&pl.!fei:oloration
will be eq#tlly distribute~ throughout the solution.
~~
U
~.
:;
H
i;,. . ~ lI
H
t\O/ 1
It is difficult?p explain t4~ above aiasetvations with,ouf using the
t'"'tes.
r ;'
z·dea o1,.{'par~
· i.. ,t
>:"'
,1 \,
~he observa#:ns _give a~ r/;Nidence~or {he movem(:nt oj:farticles 1
m gases andHzquzds.
!!
k,
!,
/
,\
I
t
:
r
,
1
-ll
!
·1-.
- 1-t
u;
~
t
1
!
'··-~--.·-'
l'-------~--)
"-----'·
,f
::.:<·~t:.A
f
1
••
The dia~ilaiiV':T'hows the diffusion of the exhau~ ..t gases from a car~ol!~•;/
~
·
;\!Lt'JJ..~-!:l..B~!:>
.
when they meet the ~I;:~J:q
.L~D.tOO:)
)/a!LL1
·.,a.SaJiv,::
;.:.'.;· (l'lJJd
i . - -•. r~.-----./
.
t..~~.j\>J Q...~!;l';i .".1-~!--!!~~J.i.~>-':..Th i·\) ~
,,:,:, up:0rr\8is'2or#s'ih 'air
/~.
'
0
q:n:;!~:r
··.,,...~~,
.,,,
.....
··-~,;..,
··;·~~
(j
,.. -%:l[e __ some other_ examples of diffusion.
\=· / '' ;/.
"~t- ~~~"f""'t
.. , .OJfo~o
·.· G]/.(1,:, 1{:-,
ct~s i:of f!"" r:><h"">i
<i.V
* • "• *
* • t\ • "•j-*<'•
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• • • • • • • . . • • //. ....•..•.•.. '.!.--~.-:---.. ...,........................... .
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1liiW blc•pil--V!ii!neb. ·uhvc!
riJiw biup-:1
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1,___,__ _ _ _ _ _•.
o o •
Topic 2.
(Dr. Fathy Abdel Galil)
- 8 -
Chemistry fGCSE
EXPERIMENTAL TECHNIQUE
Laboratory apparatus
·:.·
u
tap
beaker
conicnl flask
measuring
cylinder
pipet to
~rette
6oiL a.cClll<iLte mvw wUn9
o 6 vo.lume.o o6·Uo.u.J.d&
mo~Lta.~L
~
watch glass
evaporating
baa in
~'"'""
funnei
6
6
crucibla and lid
.bunae.n
burner
thermometer
--li<luld with
Iowa: density
liquid with
. hlohor density
{Oi!QS
balance
Chemist•·y IGCSE
(Dr. Fathy Abdel Galill
Dissolving solids in water
~a. goo<(SO"lve!}Dror many solids. Im3.gine stirring spatulas full of
copper sulphate crystals into water. At first it is easy to dissolve the solid in
the water to make a solution. Eventually, as more crystals are stirred in to
the solution, no more will dissolve, The solution·is saturated. A saturated
solution is one in which no more solute can dissolve at that temperature.
Making a solution
saturated
copper sulphate
ro!ution
water Is a
more
copper.
•ulphate
cry :;tal,
~
copper
sulphate
Is a solute
+
saturated
solution
solute
solution
liquid that docs
A solute IS the
substance that
the dissolving.
is dissolved.
A $Oiution is
fonned when a
rolute is
dissolved by
a solvent.
solvent
A solvent is the
A saturated
:rolution "is one
that will
dissolvt no more
wlutc at that
temperature.
Chemists often need to know exactly how much solu.te is dissolved in a
saturated solution. This is called the solubility. The solubility of a solid in
water is the number of grams of that solid that. will dissolve in 100 g of
water. If the saturated copper sulphate solution were heated, much inore
solid could be dissolved in it. Most cqmpounds dissolve inore in hot water
than in cold. Their solubility increases wjth increasing temperature. A
graph can be plotted to show how the solubility of a compound changes ..
with increasing temperature. This is called a: solub!Iity curve.
Solubility curves for various compounds
D1
~/- 1 -Jute
'.
,(
25 0
/
/
.g' 200
/
2m
;:
0>
8
/ .............
150
c
"
!)
ll
· ·trate
~\UI1'\~
100
r,;..
0
50
'- ...
)f:-'' '
0
4
-
..--e / /
•<..(0'\J
v
f. \\\
?'<$9\1}~.,.......,!'V~'
l:l
m
::;:
---:;
y
~
- ...:
20
40
60
Temperature/"C
80
100
.
~~-p""!v:"
,h?::-4
I' /1
D~~<"t:>I~~.L
L.-
c.cf_
,'--'. ,._,), : ,,.,,-\
L)
-
Chemistry IGCSE
- 10 -
(Dr. Fathy Abdel Galil)
Dissolving is an example of a phy¢.i.c.rtl c.!:ange.. Other physical chan:;;es
include boiling, melting, evaporation.
If the ·solvent is water, the·solution is called aqueous solution (aq).
A concentrated solution is one which contains a high proportion of
solute.
A dilute solution is one which contains only a small proportion of
solute.
How would you make a sample of sea water more concentrated 7
. .16: d... ;·?!: ~· ... r.'?f: ... ~. ';'~\ ....................................... ..
•
•
•
~
•
v
••••••••••••
0
••
0
•••••••••••••••••••••••••••
0
••
0
••••
0
.............
0
••
·safety in the Laboratory
Some chemicals are ~articularly hazardous. These are pointed out
by standard tiazard labels.
{a)
:tauc.
{b)
C.OIVW¢.f.V e
concentrated solutions
of acids ~nd alkalis such as
concentrated sulphuric acid
{c)
oucU.o.i.ng
agent
potassium dichromate~
potassium manganate.:
{d)
.£.i'.ammable
ethanol, petrol , .. hydrogen
chlorine, bromine,
carbon monoxide
Chemistry I GCSE
(Dr. Fa thy Abdel Galil)
- 11 -
Laboratory Rules for Working in a Laboratory
DO
DON'T
e keep bags and coat safely out of
the way
e tie up long hair and tuck
in ties and loose clothing
e wear goggles or safety glasses
when doing experiments
o keep your place tidy and
wipe up spills of chemicals
o ask if you are unsure about
anything
e run in the laboratory
o eat or drink in the
lzbt:re.::ory
ill> piay with fire, electrical
switches or chemicals
look down a test tube that is
being heated, or point it
at anyone
....
·,
§~~~-~~i~El_EE~~~~E~~~~-~
1- Carrying out the experiments which involve toxic gases and strong
smelling gases in fume cupboard or' in we'fl-ve'rlfilated laboratory.
a
2-
Wear gloves when doing experiments with corrosive substances
3-
For heating a flammable liquid use a hot water bath.
This diagram shows a student working in a laboratory.
Identify two safety problems In this scene.
I
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!· - ,
~-,.
\.
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S arety pro bl em 1 .................... ,............................................................................ ,;;·· .. •·•·................................. .
.·'I!... I"~
l_
\_
··~
·urr>.
·'C'.'k\0
.................................................................................................................................................................... [1 1
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Safety problem z .....
.'
0
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?.:::.::.......... ..l.R:?.!L"f..:..........::o:.......:................~..~'............ :::-~.:::::..............................
..................................................................................................................................................................... [ 1]
Chemistry IGCSE
- lZ -
(Dr. Fathy Abdel Galli)
Methods of Purification
17'--filter paper
· fimnel
residue.
a) To .5epaJta..te a. Mild (J.n.6 o.tub.te)
6Mm a. Uqr.Ud
Filtration
The solid is left on the
filter paper as the residue
while the liquid passes
through.
Just by pouring the liquid
insoluble
off from the solid,
b)
substance
To ob~ a. .5o.Ud 6Aom a. .5o.f.utLon
t:===::J-..J-salt solution
A solution consists of a
solut.e dissolved in a solvent, Sea water is a solution
solution~-_____ evop oratlng
:- .. -~_....
ba.s: 1n
/
gauze·
---
! -----
c ..... -
of salt (sodium chloride) in
K~~r
water. By heating the solution,
I
~
water evaporates and solid
'%?~~~- __.- ~'~
·salt ·is left,
:C,c;eifc!c"(
I
I
I
·
tripou·
.f1__/
/
,
u
The solution is evaporated to the crystallization point; i.e, the
point at which crystals of solute will form on cooling the solution
to room temperature and can then be f"iltered out, and dried.
What method could be used to show the crystallising point had been reached •
'I'
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••••••••'-r•:f·••••••••••·••••••••••••••••••••••••••••••••••••••••••••••••
v
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........... t
••••
Chemistry IGCSE
c)
- 13 -
(Dr. Fathy Abdel Gal!!)
To 4epaAaXe a 6olvent 6~om a 4otution
Distillation
------------
_
tharmometor
When the solution ia boiled, the
solvent changes to vapour, the
vapour passes down· a condenser
where it is converted back to
liquid and is collected as the
distillate.
sea
water
d}
To 6 epaAaXe :iJJJo .Uqu).cL6
cold W;ttcr in
pun distilled
HEAt
water
Fractional distillation
----------------------Miscible liquids (i.e. ones that
mix together completely) may be
separated by fractional distil~
thermometer
lation provided that their boiling points are different, e.g.
Cr;Jolest paQ:·
of column·---
mixture of ethanol and water,
The mixture in the flask is
heated so that it boils. Both
cold water In
fractionating ---W~
column
filled with
tilc:ss rods
go up the fractionating column.
Ethanol has a lower boiling point
Frt~ctlons
collected at
(78°C) than water (i.e, is more
lower
temperatures.
volatile), The liquid with the
lOI<er boiling point (ethanol)
and distils over and is collected
z
~8
ethanol vapour and water vapour
reaches the top of the column
1
broka_n Porcelain
HEAT
first.
Ant£-bump.i.ng gMnui.e6 [alL bMk.en polLc.eta.i.n} alLe. added .to .the. m!.xJwc.e.
.to acfU..eve 6.teady bo-UJ..ng.
Important appli<;:a·tions of fractional distillation :
a)
The separation of liquid air into oxygen and nitrogen
b)
The separation of crude oil [petroleum] into useful fractions.
3
- 14 -
{Dr. Fathy .Abdel Galil)
Chemistry lGCSE
e.)
Clvr.omCLtogJutphq
Paper chromatozraphy is used to separate a
'
mixture of similar solids dissolved in a
0
:
solvent, e.g. it can be used to_separate
the dyes in ink. It can also be used to
identify additives in foods such as
flavouring and. colouring;;.
A
- Filter paper
0
r
0
small .spot
of the solution containing the mixture
The. 6po.t nuu.t be. ab.ove
.the .tevel o 6 .the bofvent
-
is placed near the end of the filter
Solvcnl
paper. The end of the paper is dipped
into a solvent (e.g. water, ethanol). As the solvent rises up,
spots of various consti.tuents of the mixture will be collected at
di{ferent distances above the original spot. The finished paper is
called clvr.om~og~. A single p~e. substance will produce.only
one. .opa.t.
Chromatography can also be used to separate calaunle46 substances,
but .in this case the paper must be sprayed with another chemical
[tac.atilig ILge.nt) so that the position. of the s.pots. can be seen.
Example. a 6 LL!.l.Wg clvr.ama;togJutphy
3
A dye used in food colouring
f--- ---"----.--- ~- --------f
can be ide:ntified by chromategraphing it alongside some pure,
known dyes. In this way,-a public
analyst can firid out whether a dy_e
movement
of solvent
1---------------f
used iri .food is a permitted one
f
or an 'illegal' one. The figure
shows that dye: 'A' is a mixture,
and it contains dyes
1
C1 and
1
D'·.
A
8
c
0
ED
samples -of dye A. and pure chemicals B, C, 0, E.
added along !his line as shown
I 6 a. ,o po.t Jt.e.ma...i.M on. .the. ,o.ta.Jt.,ti.ng -Une., .U me.ILM ~ .the .o ub.o.ta.nce.
;_;, .{.n.Miubie. .W .the. <> otve.n.t U!.l e.d .
., •e. be. dlurWn. .w pe.n.cM:. iLn.d nat w.Uh ink ?
Why mU!.l.t .the. .o;taJLt.{.n.g V<-"
····~--~·-·······················································-····
........................................ ~ ................................... .
-
15 -
(Dr. Fathy Abdel Galil)
Chemistry IGCSE
The diagram shows a chromatogram used to find out which colourings are in a fruit drink.
.
f
I
'
I
9
'
1
fruit drink
f
2 3 4
colourings
5
Which two colourings are in the fruit drink?
A
1 and4
8
1 andS
2 and3
C
@ 2and5
Testing the purity of a substance
A puJLe substance has nothing else mixed with it. A substance is not
pure when it has other things mixed with it; these are called irup~e6.
Chemists often need to know if a substance is pure. For example, drugs
must be tested for purity before they are sold. Impurities might harm the
patient.
7. Chlr.omatog1taphy c.an be Ul>ed :to .6ee
8'--~>
\:;u_\::\::::"<>"
az
J.o \'__
~'y., <2Y'-
·, ",
~o\__
eo'"
-to a. .6!Lb.>.ta.nc.e -L.6 puJte. How ?
\\c-.~
0"-·fl"'--'
• • • 'l. . . . . . ~ •• ~--u··························::.··t···I
\\.:::
~ v.'\"
',\. , < \_ o·~\;;, <:>'0.
.............
\.j'""""'""
,
2. Ano.:the1t wa.y o 6 :te<>:ti.ng puJLUy i;, :to meMuJte :the .>ub.6:ta.nc.e' .6 me-tUng
po-i.n:t otr_ ba.i..Ung po.i.11-t. PuJLe .6ub.6:ta.n,c.e<> have de6-Lnile me.Uhtg po~
a.nd bo.LU.ng po~. I o a. .>ub.6.ta.nc.e -i..6 no:t puJte, m me..U.Utg po.ill:t otr_
bo.LUng po-Ln:t w.U.t be d.i.o oe1len:t 6Jtam :the known.
Impurities make melting points lower and boiling points higher.
The WCLte1t .ta.R.en 6Jtom ;the .6ea. 6Meze<> at a.bou:t -2'C a.nd boili at 70 1"C.
I.6 U pWLe ? No 1
..................................................................
Why ?
Gu:."-'-'S':
-,~
s"""'"\.1\ : ~f'~::·ze
:C,L
c- ) ".
··································~··········--··~
.......... .
- 16 ..
Chemist1·y I GCSE
Topic 3.
(D1·. Fathy Abdel Cali!)
ATOMS, ELEMENTS AND COMPOUNDS
Elements, Compounds and Mixtures
Element : is a substance which cannot be split up, e.g. aluminium or
sulphur. It contains atoms of only one type. There are
over 100 elements which are grouped into two main classes
metals and n'on-me tals.
Most of elemen t·s are metals. There are only 22 non-metals.
There are a few elements which are d.ifficult to classify
Because they have some metallic and some non-metallic pro-
perties.
A comparison of the properties of metals and non-metals
Property
Metal
Non-metal
state at room
temperature
solid except
mercury (liqu1.d)
solids, gases and
one liquid (bromine)
melting point
high except alkali
metals
low except carbon
and silicon
appearance
shiny
dull
.
Compound
effect of hamme ring
easily shaped
electrical and
heat conductivity
good
brittle - break into
pieces
poor or none, except
graphite
is a substance made up· of two or more elements chemically
combined together. A compound has properties different
from those of its elements, e.g. water or carbon dioxide.
Mixture
consists of two or more elements or compounds which have not
been chemically combined, e.g. air or sea water. A mixture
has the properties of the substances in it and can be separated by the methods described in Topic 2.
- 17 -
Chemistry IGCSE
(Dr. Fathy Abdel Galil)
Atomic Structure
Atoms consist of a minute nucleus, where all·the positive charge
and most of the mass of the atom is concentrated, surrounded by
electrons.
The nucleus is made up of two types of particles
p.li.o.tono and neubr.ono.
A pJto.ton is a positively charged particle.
A.neut.li.on is a neutral.particle (uncharged), with mass equal to that
of a proton.
An elec.t.li.on is a negatively charged particle; the mass of the electron
is so small that it can often be ignored,
Atoms are electrically
neutral because:
number of +ve protons =
number of -Ne electrons.
auiL-a:LomLc.
Pa.Jt.tic.te.
Rela.ti.v e. Ma.M
Cha.Jr.g e.
PILO.tort
Neu.bwn
1
1
+1
Etec.tJton
1/1810
-1
0
Ato~e (p.~to.ton) nu.mbeJt : (Z)
is the number of protons in the nucleus.
Ma..6c, (IU.Lcteon)
nu.mbe.~t : (A)
is the total number of protons and neutrons in ari atom.
Mas~ No.
(p + n)
Atomic No.
(p)
X
(symbol of
the element)
on pM.tono
Ato~e nu.mbe.~t =
nu.mbeJt
MM<l numbe.~t
.=
nu.mbeJt o6 p!W.tono
+
nu.mbe.li. o6 neu..t.li.ono
No. of neutrons = Mass no. - Atomic no.
Question ;
Work out the numbers of sub-atomic particles [protons, neutrons and electron J
of the atoms of the following element.i. ·
·
12c
6 ,
p
c
56
26Fe,
......................................... .
e =
.......... • .......................... .
n =
" ........... • •• • •• • ..... • ..... • • •••••••
- 18 -
Chemistry !GCSE
(Dr. Fathy Abdel Cali!)
Isotopes
I<> o:to p eo aJt.e a.tom<> o6 the <1 am.e. el-ement, ULU:h the <. ame numb eM
pM:to IU bu.X. cU£ {, Vtent numb eM 0 6, neu:tJr.o IU ,
_
.in o.thvr. wo.tc.do i..oo:topu h.aue .the <.ame a.tom.Z.c. nwnbvr. bu.X. cU66vr.ent
0 {,
nutM
numb Vt6 •
I<>o:topeo o6 hydJwgen
Hydrogen has 3 isotopes
()
Most hydrogen atoms are like
this, l H. It is an orcl.inarj
hydrogen atom with no
neutron.
0
But a few' are like this. It has
one neutron. It is called
deuterium, 1 H. [2D]
1
,.
0
And some are like this, with
two neutrons. It is-called
tritium, ~H. [fT]
Isotopes of an element have the same chemical properties.
IM:topu o6 c.a.Jtbon
Carbon has 3 isotopes
....... ... .....
Nwnbvr. o6 plto.toJU
= ... ... . .. . ... .
Nwnbvr. o6 dec.bta JU = . .. .. .. . . . . .
Nwnbvr. o6 neu:tJr.o JU = . ..... .. . .... . .
f.!a..66 nwnbvr.
=
"
[AJ
[C]
( B]
[A]
..............
................
..... . .. ..... ..
. .... . . . ... ...
.............. .
. ........... .
..
"
..................
...............
is called carbon~l2.
What do you think
[BJ· and
[CJ
are called ?
.......... ................................................................................ .
.,
.. . . .·...................................................... " ............................. .
,:. ..·
- 19 -
Chemistry !GCSE
(Dr. Fa thy Abde! Galli)
Relative atomic masses
Host elements contain a mixture of isot<>pes •. This explains why
their relative atomic masses are·noz whole numbers.
The relativ.e.atomic mass. of the etement[f.u] is theaverage:ma&oEits,iS@toges takiug·
into ace0unt their proporticms.
·
For example, chlorine consists.-of i:wo isotol'es with mass ·numbers
of 35 and 37. Their proportions a~e--75% of: ~fCJ: an.<! 25! of 37c1.
17
The relative atomic mass of chlorine· will be: 35-~- 75/1@0 + 37 X 25/100'= '--· •
Radioactive Isotopes
.·
· . ·· ..
·. ·Sem.e is0tepes (such a5.tri~um ami car!D0n-14].haye tmstable nuclei;
they emit certain types of radiatl&n ·[alJ!lha a, "fueta ~, anti! gamma r] in @faer ·
to Ille mere .staDle.
Some us.es ~of r:ad.i@a.etive ;iso.t€!;p,e_s :
Me.cU..c.aL 1M e.A :
--------------. e.. g.
1-
Cance-r treatment :
Tumors can be. destroyed- using controlled
doses of gamma radiation from cobalt-60.
2-
Sterilising medical equipments
I!1~~~-~~ ' e..g.
1- Detecting leaks in water pipes.
2- · Checking the thickness of paper during manufacture.
Nuc Iear Power
.. )
( 235u as a source of_ ener!iJ)'·
Nuclear fission
Some radioactive isotepes are used as nuclear fuels e.g. Uranium-235.
When they are bombarded by neutrons, they s-f)llt ·=!Jtto sutaller at·oms.
The splitting of an at<Jm is called nuclear fission. Fissiori. of
uraniuni-235 atom produces a fw{Je. am<Junt of heat energi (nuclear
· energy) wich can be used f<Jr generatio_:il ef electricity [nuclear
pewer stations] • Nu"clear fission b
done in a rw.dea.Jt lr.eitc.:toJr..
;.·
7J
(Dr, Fathy Abdel Galil)
- 20 -
Chemistry IGCSE
Uec..tMn.6 Me IVUl.anged i.n. a. ;;e}()_eo o6 ;;he.U¢ aAOW1d .the nucte.u..b.
2) Ea.c.h llheU c.a.n only c.onto:i.n. a. Li.mUed 1tW11bVT- ofJ e.t.ec.t1Wn.6.
3J The .6heU ne.aJr.e.ll.t :t6 ..the nu.cl.eu.ll 6.il.L5 6JM:t• . When U .W t]u.U,
.the e.t.ec..tMn.6 go J..n:to .the nex:t llheU, a.nd .flo on.
4 J · The fJ.iJr.b:t .6 heU c.a.n onty hold :two e.t.ec»to n.6 , .the uc.o nd 8 and
.the :t/Wui 8 04 7. 8.
The first twenty eLements in the Periodic Table and their electronic structures
~~e
H
I
Li
Be
B:
c
N
0
F
Ne ·
2,1
2,2
2,3
2,4
2,5
2,6
2,7
2,8
Na
Mg
Al
Si
p
s
Cl
Ar
2,8,1
2,8,2
2,8,3.
.. ,:2,.8,4
2,8,5
2,8,6
2,8,7
2·,8,8
K
Ca
2,8,8,1
2,8,8,2
• The outer shell is called the valency shell and the electrons of the outer shel! are the
valency electrons.
• Elements of the same group in the periodic table contZin the same number ofelectrons iii
their outer shelL For example; Jithiunl; sodium and potassium-(group I) have one electron
in their outer shell. Fluorine, chlorine and bromine (group VII) have 7 electrons in their
outer shell.
_.
What is special about· the- nobel gases 7
The nobel gMeo Me; ve:Jty (Uillea.c.tl.ve. They w.i.U not joht up wi..tft ea.clt
o.theJr. ;to 6oJUn mo.tec.ul.eo • NoJt wLU .they Jtea.d ea..ll.U.y w.U:h . o.theJr. e.temen..to
to {,oJUn c.ompound.o. The nobel gM eo Me .6.ta.b.te (ullltea.c.tl.ve) bec.auJ, e
.they ha.v e ·n uU ou.:teJr. .6 heW.
We c.oul.cl' c.onctude .tha..t o.theJr. e.t.eme.n.U Me Jtea.c:Uve bec.a.u.!Je .they do not
ha.ve {,u.tt llheUb. 'Lt <1 eemb .tha.::t e.f.!'llleJJb, Jtea.d :to f:.Jty a.nd get onf.y
6uU <>hellll.
.
:.: ~ .: :
The arrangement of electrons in the first twenty elements
. Hydrogen
atomic no. 1
"'
l)
H
Helium
He
atomic no. 2
<11
1J
.0
-<
>-
0
0
1
2
.c
....
"'
u.
'0
Lithium
a10mic no. 3
Li
I
2,1
N
Sodium
atomic no. 11
\.U
N'
c
Carbon
atomic no. 5
Nitrogen
atomic no. 7
atomic no. 6
N · Oxygen
·
atomic no. 8
0
Fluorine
atomic no. 9
F
atomic no. 10
I
Mg
I
2,3
Aluminium
atomic no. 13
AI
2,4
Silicon
atomic no; 14
j
Si
Phosphorus
atomic no, 15
. 2, 7
2,6
2,5
P
Sulphur
atomiC no. 16
S
Chlorine
atomic no. 17
2,8
Cl
Ar
Argon
atomic no, 18
(@ ~ (@). (@) (@)(@)@J@»
(/)
u
2, 8, 1
>-
Potassium
atomic no. 19
2,B,2
2,8,3
2, B, 4
2,8,5
2,8,6
2, 8, 7
l)
....'-V\
Ne
Neon
@ @ @ @ @ @
2,2
Magnesium
atomic no. 12
8
Boron
@
@
.....
Be
BeryJlium
atomic no. 4
K
Calcium
.1tomic no, 20
Ca
The numbers under each atom show the way the electrons are orranged for that element.
This is called its electronic connguratlon.
E
Q)
.c
The electronic coftfigura!ion of aluminium is 2, 8, 3. This means it has two electrons in the
first shell, eight electrons In the second shell and lhree electrons In the th'~rd shell.
u
2, o. n. 1
2, 0, 0, 2
2, 8, 8
22
Chemistry IGCSE
(Dr. Fathy Abdel Galil)
Chemical Bonding
Ions and Ionic Bonds
An ionic bond is formed when one or more electrons is transferred from
an atom of a metal to an atom of a non-metal.
Ionic compounds are made up of ions.
Sodium chloride .·(NaCl)
Na
.+
(atom)
Cl
(a tom)
2' 8' 7
2' 8' 1
sodium atom
1
chlorine atom
{Na)
{q)
+
Cl- (ion)
2' 8' 8
11 protons
10 electrons
• 11 +
u
1 a-
Overall charge = + 1
17 protons
18 electrons
- 17+
• 180verall charge • -1
chloride ion
{CI-)
sodium ion
{Na•)
Be.c.a!Ue :the· ;,odJ..wn a:tom lw..o LoU:. one. ne.ga..t<.ve. de.c.:t!ton, U be.c.ome.;, a. ·
po<..<.tive. .<.on.
Be.c.aLU e. .the c.h'-o!Une. a:tom lw..o ga.J..ne.d one de.c..tJwn. J...t ga.J..n;, a. ne.ga.Uve.
c.hM.ge a.nd be.c.ome.;, a. ne.ga..Uve. .Lon •.
SodJ..wn c.h'-oJt.l.de. .(.;, ma.de. ofJ IJodJ..wn .<.on;, a.nd c.hloJt.l.de. .Lon;, held .toge:theJL
b!f a.n e.!_e.c.Vto.;.ta..t<.c. a.:t.:Ow.c..t.Lon be..tvJe.e.n oppa.;Ue.'-!f chM.ge.d .Lon;,.
Ion :
is an electrically charged particle formed from an atom by
the loss or gain of one or more electrons.
The. a.Ma.nge.men.t o6 .the. va.J..e.nc.q e.!_e.c..tJt.on;, [.L. e. e!_ecVwn;, o 6 :the ou.teJL.;he.U) i.n :the. .<.o!Uc. compound .;od.f.wn ch'-oJt.l.de. ca.n be Jr.e.pl(.e.;,e.n.te.d a..; 6oUow.;
X X.
(2.8.1)
(2,8, 7)
(2,8)
Sodium atom
Chlorine atom
Sodium ion
(2,8, 8)
Chloride ion
- 23 -
(Dr. Fathy Abdel Galil)
Chemistry IGCSE
Magn.el>-Wm oxide (Mg 0)
XX
Mg·:~o~
~ -xx
(2,8,2)
(2,6)
. (2,8)
(2,8)
x)(
K
FX
~(·'
Mg:
+
~
(2, 7)
[Mg] 2+
<:x
~ ~F~
(2,8,2)
~
Magnesium
atom
(2, 7)
(2, 8)
2 Fluorine
Ma·gnesium
atoms ·.
ion
(2, 8)
2 Fluoride
ions
Giant Ionic Structure: [Giant Ionic lattice]
This is a regular arrangement of alternating +ve and -ve ions .in ionic crystals, giving
strong interionic forces, in other words, ions held together by an electrostatic attraction
between oppositely charged ions
This explains the high melting points of ionic compounds.
e.g. sodium chloride lattice:
0
Cl
~~~
- ++- +
Properties Of Ionic Compounds:
0
1. They are s.olids and have high m~Iting poi~ts ~nd b~gng points,
e.g. the melting point of pure sodium chlonde rs 8 0 .
2 . Solid compounds do not conduct electricity. They[' conducfrt t
electricity when melted or dissolved in water, wns are ee o
move and carry the electric current].
3. They are usually soluble in water.
- 24 -
Chemistry IGCSE
(Dr. Fathy Abdel Galil)
Molecules and Covalent Bonds
A single covalent bond is formed when a pair of electrons is shared
between two atoms (non-metals).
Covalent compounds are made up of molecules.
H- H
Hydrogen (Hzl
a hydrogen molecule, H2
two hydrogen atoms
a· shared pair of electrons
Cl
two chlorine atoms
- Cl
a chlorine molecule, Cl 2
88
Similarly,
. Br2'
12,
Fz
Hydrogen chloride (HCI)
XX
H-0-H
0
H- Cl
xx
H
\
Similarly,
PC1
3
/
N
I
H
H
- 25 -
Chemistry IGCSE
(Dr. Fathy Abdel Galil) ·
H
I
H-C-H
-
I
H
)> Draw a d.iagram which shows the arrangement of valency electrons
iJ;I tetrachloromethane [CC4J •
H
I
H-C-0-H
Methanol ( CH 0H)
3
I
H
A double covalent bond is formed when two pairs of electrons are
shared between two·atoms.
0=0
Oxygen (0 2 )
Carbon dioxide ( C0 )
2
O=C=O
H
Ethene (C H )
2 ~
\
/
c=c
I
\
H
Chemistry lGCSE
- 26 -
(Dr. Fathy Abdel Galil)
A triple covalent bond is formed when three pairs of electrons
are sha:red~
N
Ethyne [Acetylene}
N
H-C==C-H
c2 Hz
PMpeJ!.tieb a6 Caval.en.t CampoWJ.cU [simple molecular]
1.
Made up of molecules and contains no ions
2.
Do not conduct electricity
3.
Most covalent compounds are gasesandliquids,fewareso[ids.
4.
Covalent compounds are less soluble in water than ionic compo.unds ·•
5.
Usually have lower melting points and boiling points than
ionic compounds.
Diatomic Molecules
The molecule consists of 2 atoms such as H ,
2
o2 , N21 Cl 2 , Br 2 ,
rz, Fz.
Allotropes of Carbon
Carbon occuts in tw0 solid forms, diamond and graphite. These
are very different, even though they both contain carbon atoms.
Pure diamond is a l1ard, colourless solid, that sparkles in the
light, while graphite is a dark grey greasy solid with a dull
shine,
When an element has more ·than one form, it shows allotropy. The
different forms are called allotropes of carbon.
Allotropes: Different structures of the same element
Chemistr:y IGCSE
- 27 -
(Dr. Fathy Abdel Galil)
Macromolecular (Giant) Structure
Diamond
...
the centre atom
forms lour bonds
.
c
V-UJ.mond .U, a. giant structure o[ caJtbon a.to111<1. Ea.ch caJtbon a.tom
).], joi.ned :to 6oUJt o.theJt. a.tom~ .£.1i a. :t~hedJw.l. aNtangemen.t.
Diamond has these properties :
1.
It is yery hard, the hardest substance known. This because
each atom is held·in place by four strong bonds. This is
vhy diamond is used in drilling and cutting.
2.
It cannot conduct electricity because there are no ions or
free electrons in it to carry charge.
Graphite
I
1-weak
forces
CaJtbon a.to111<1 aJte aiWl:nge.d J.n hex.a.gonb J.n· pa.JrJul..(_el. .lay eM. The
.layeM ctl!-e hel.d :toge;thur. by wea.k 6oJtc.u.
- 28 -
Chemistry IGCSE
(Dr~
Fathy Abdel Ga!il)
Graphite has these properties :
1.
It is soft: and slippery vhich feels greasy. This is because
the layers can easily-slid over each other. This is why
graphite is used as a lubricant.
2.
It is good conductor of electricity. This is because each
atom has four electrons, but forms only three bonds. The
fourth electron is free to move through the graphite, carrying charge,
·.
Bo-th d.i.amond a.nd gJta.ph.Ue. have. veJr.y IU.gh meLUng po.w..t¢. ThM }J,
be.c.a.u.6e. bo-th eoitOJJ,.:t o6 g.la.n.t <>bw.e.twr.e. o6 a..:tom4.
Silicon (IV) Oxide
(Silicon Dioxide}
Silicon dioxide (Si0 ) has a giant
2
structure in which each silicon atom
is bonded to four oxygen atoms and
each oxygen atom to two silicon atoms.
This structure is similar to the giant .covalent structure of diamond.
u.ke d.i.amond, <>ilieon d..i.ox.i.de .U, luvuf., Ita<> a. IU.gh me..tti..ng po.I.n.:t
a.nd dau no-t c.ond!Le.:t e..te.c..tJr.lc.Uy.
properties ofMacromolecules:
1. High m.p. and b.p.
2. Hard [graphite is exception which is soft 1
3. Do not conduct electricity [graphite is exception 1
4. Insoluble in wat~r
Chemistry IGCSE·
(Prof. Dr. Fa thy Abdel Galil)
-29-
Metallic Bond
Giant metallic lattice - (In metals)
+ nucleus
0
electron
Giant metallic lattice consisting of the positive ions surrounded by. a
"sea" of free (mobile) electrons (i.e. the etectrons ofthe outer shells).
>·Metals are good ·conductors for electricity, the current is· carried by the
free t;lectrons.
> Metallic bonding is very strong in some metals like iron and copper (transition
elements) and is much, w~aker as in sodium and potassium (group I).
Summary of Bonding
Ionic
(be-tween metals
and no~-metals)
Bonding
1'------
1
Structures
Giant ionic
I
I
Melting point
Conduct
electricity ?
Covalent
(between non-metals)
;
7
/
\.
·
Metallic
(in metals)
.
..
T~
Simple molecular I · Giant-covalent
· '(macromolecular)
I
f
Giant metallic
High
Low·
Very high
Usually high
Not when solid, but
'No
No
Yes
(has free
.electrons)
1 they do when m:o!ten
! or dissolved in water
I
I
I
I
(when i'ons are free
I
to move)
':
Examples
.,
'
. NaCI; MgO, CaC1 2
®8CB8®
~~®~
®8+8+
Ch, h, NH3, C}L,
C02, H20
~-J:
>~
Water
diamond,
graphite, Si0 2
I
~I
!.C ~
~~~
"v~
v'l,
Diamond
Fe, Cu, Mg
~
( i·rr
·XX
- 30 -
Chemistry. IGCSE
Topic 4.
(Dr. Fathy Abdel Galil)
STIOCHIOMETRY [Formulae, Equations and Calculations]
.Valency or Combining Power
The valency of an element is the .numper which shows its ability
to combine with other elements.
In molecules (covalent compounds) it gives the number. of covalent
bonds which the atoms can form.
In ionic compounds the valency gives the charge on the ions of the
element.
Valency can be used to predict the formulae of' compounds.
1)
The. Fol!mula.e. o 6 Cova1.en.t Mo.le.c.LLte!>
Electron diagram~ ( 1 do·t and cross 1 type diagrams) or just a
knowledge of the number of shared electrons in the outer shell
can be used to work our formulae.
Complete 'the follow·ing table
Ee.emen.t
Symbol
Va1.enc'y
Carbon
c
4
Nitrogen
N
Oxygen
0
Sulphur.
s
Hydrogen
'H
Chlorine
Cl
Bromine
Br
What are the formulae· of the follwing molecules ·:
Ammonia
Methane
Hydrogen chlorid.e
........ ......... .
~
Bromine
...................
Chemistry IGCSE
(Dr. Fathy Abdel Galil)
- 31 -
._;_;·
2)
The. FolUnu.C.a.e. o o 1on.i.c Compound&
We cannot talk about molecule!! of·ionic compounds. In ionic
crystals we have an alternating arrangement of p_ositive and
. negative ·ions.
More about ions :
----------------Some elements can lose or gain electrons and change into atoms
with positive. or negative charges. These atoms are ··called ions·.
Some examples are :
..
Na+
sodium ion
)(+
potassium ion
2+
calcium ion
A13+
aluminium ion
Cl.,..
. cnlorid~. ion
02-
oxide ion·
Ca
Spmetimes, groups of atoms can have charges too~ and beh,ave
as ions. The sulphate ion, SO
2-
is made of one sulphur atom
4
and four oxygen atoms, bonded· t.oge'ther; The whole group-of
atoms has two nega.tive charges.
The nitrate ion,
No 3 - , the carbonate ion, co 3 2- , and the
ammonium ion, NH +, are other examples •
4
.Here is a lis't of· most of the ions that you are likely to meet
and will need to know :
Valency
I
2
3
Positive ions
Negative ions
H+.
hydrogen ion
u+
lithium ion
Na+
sodium ion
K+
potassium ion
Ag+
silver lqn
NH 4.+ ammonium ion •
Ca 2+ calcium ion
" .. 2+
magnesium ion
Mg.
Bal+ ·barium ion
Pb2+
iead,,ion
copper(II)
ion
Cu-7~.
Zn2+ zinc ion
Fea· irori(II) ion
oHcrBrI-
FeH
Al 3+
iron(III) ion
aluminium ion
hydroxide ion •
chlo'ride ior,
bromide ion
iodide ion
F- fluoride ion
Nol- nitrate ion
•
S2~
o2-
so/-
sulphide ion
oxide ion·
·sulphate ion
..
col2- carbonate ion •
PO/- phosphate ion •
(Dr. Fa thy Abdel Ga!il}
- 32 -
Chemlstr)' IGCSE
Predicting the formula of ionic corr Jounds
In an ionic cempound, ·th
ions are attracted to each other
-
by their opposite charges. The number of + charg.es is alYays
equal to the number of -charges. Knowing this, the formulae of
ionic compounds can be written down.
Look at these examples in which the.numbers of positive ions·
and negative ions are balanced to make the charges· the same.
·ammonium sulphate
aluminium oxide
magnesium oxide·
this is then written
&l .12-l_
Mg ~
Mg~0 2 - - - - - MgO
Remember
i) Compounds ending in 1 ide 1 are made of just 2 elements only.
ii) Compounds ending in 'ate' have a third element, 'oxygen'.
Question:
Write down the formula for each ofthese ionic compounds:
1. sodium chloride
2. aluminium nitrate
3. zinc chloride
4. sodium sulphate
5: copper (II) sulphate
6. zirlc carbonate
7. alllrniniurn carbonate
8. pctassium iodide
9 Cll!ciurn oxide
... ... .. .. ..
10. amrnonium.carbOnate
............
.............
... ... ... ...
11. calcium hydroxide
12. ammonium phosphate
.............
...............
.. ..........
............
... ... ... ...
1Liron (JII)..oxide.
...............
14~ potassiUI\1 carbonate
............
15. zinc sulphide
............
... -.........
.............
16. iron (JII) chloride
.............
.:. ...........
17. aluminium hydroxide
.... ·- ··- .....
18.. silver nitrate
.............
~
(Dr. Fathy Abde! Galli)
Chemistry IGCSE
- 33 -
When a che'mical reaction occurs, substances react together.
These reacting substances are called tne reactants. They form
new chemicals called the products.
How to write the equation for a reaction
These are the steps to follow when writing an equation
l-
Write the equation in words (word equation).
z~
Now write the equation using symbols. Make sure the· all
th~
formulae are· correct~
3-
Check that the equation is balanced, for each atom in turn;
Make b~e you do no~ change any 6okmulae.
Example l.
When hydrogen burns in oxygen or air, it forms water
hydrogen
+
oxygen
H2
+
02
>
2 H
+
02
2 H2 o
2
water
H
2
o
~V!!g111~0 :tha.:t .the c.ommon ga.<>eb (n.Ultogen, oxygen, hydMgenJ and
~lie MlogeM Me dULtom.i.c. Th.U, mean.b .:tlra.t .they .ex..U..:t a.<> motec.ul.eb
c.ol1.:ta-i.JU.ng wo <Uomb. T/UU, oxygen .i...6 02, n.o.:t 0, and· c,htoJU.ne .i...6
ct , n.o.:t CL
2
Example 2.
IVfaoonesium burns brightly in oxygen or air, it forms magnesium oxide [white powder}:
magnesium
+
Mg
+
2Mg
+
Ol)'gen ---7 magnesium oxide
2Mg0
- 34.-
Chemistry IGCSE
(Dr. Fathy Abde! Galil)
Some chemical equations include extra symbols after the formula.
They show if the surrstance is a solid (s), liquid (1), a gas (g),
or dissolved in water (aq), [aqueous]
sodium
+
water
sodium
hydroxide
+
hydrogen
2Na(~
+
2H 2 0(1)
2NaOH(aq).
+
Hz(g)
1. Balance the fo!lowing equations :
+
Na
C[z
-----'?- ••• Na C!
+
c
+
COz
-----'?- ••• CO
A1
+
Clz
-----'?- •.. A!CI,
NO
+
Oz
-----'?- ••• N.Oz
AI
+
Oz
-----'?- .. • Alz O,
Mg
+
SOz
+
C!!t
+
2.
+
-----'?-. ... KC!
+ ... 0z
COz
+ ... HzO
Ca(OH)
+
2
Complete the word equation for the above reaction :
. .. . . . . .. .. .. .. . .. . .. . . . ... . .. .. . .. . . . .
+
---'.;>-
+ ........... +
• • • • .. .. • • • • • • • • • • • • ..
..................... -........................ .
water
[Dr. Fathy 'Abdel Cali!)
- 35 -
Chemistry IGCSE
Chemical Calculations
Relative Molecular Mass [Mrl
Each element has its own relative atomic mass [Ar ]. This is the average mass of its isotopes compared with the mass of- a
standard atom of carbon, l~c.
Compounds have a relative molecular mass (sometimes called formula
mass). The relative molecular mass (formula mass) of a compound is
founq by adding up the relative atomic masses of the elements in
the compound according to the number of each element's atoms.
Look at these examples:
1 Sodium chloride, NaC!
1 X 23
1 atom of Na
1 atom of Cl
1 X 35.5
relative molecular mass
2 Calcium chloride, CaC1 2
I X 40
I atom ofCa
2 X 35.5
2 atoms of Cl
relative molecular mass
3 Zinc nitrate, Zn(N0 3)z
1 atom of Zn
1 X 65
2 atoms of N
2 X 14
2 X 3 X 16
6 atoms of 0
relative molecular mass
-
-
-
-
23
35.5 +
58.5
40
7I +
111
.65
28
96 +
189
Calculate the relative molecular masses of the following compounds :
co 2
l.
Carbon dio:cide,
3.
Sodium carbonate, Na C0
2 3
Chemistry IGCSE
(Dr. Fathy Abdel Gali!)
- 36 -
Percentage Composition by Mass
Sometimes it is important to know the exact composition of a compound.
For example, all bags of fertilizer must show the percentage of the
clements nitrogen, phosphorus and potassium they contain on the outside.
The % of an element by
Ar of the element x no. of its atoms
mass a compound in
Mr of the compound
Look at these examples:
1 The % mass of calcium in calcium carbonate, CaC0 3"
Ca
40
100 = 40 + 12 + 48. X IOO = 40 %
= C~ + C + 3XO X
40% of the mass of calcium carbonate is calcium.
2 The % mass of nitrogen in ammonium nitrate, NH.N0 3
2X N
28
=
X 100 =
ZXN + 4XH + 3XO
28 + 4 + 48 X 100 = 35%
---==---
35 % of the mass of ammonium niuate is nitrogen.
X 100
........ .... ,, ..
~
. .
(Dr. Fathy Abdel Galil)
- 37-
Chemistry !GCSE
THE MOLE
A mo.e.e. (mo.tM. ma.o.6
r o6 any .6Ub.6.ta.nc.e. )_;, w Jr.e-
.f.a.:Uve a.tom.Lc. ma.o.6 [Air.) OJt Jtel.a.tive. mo.tec.u..ta.lr.
ma.6.6 [MltJ {.<.6 i l .i..6 a. compound) mea.oUJte.d .<.n glUJJn!>.
For Elements :
1.
1 mole of· sulphur • the relative atomic mass in grams • 32 g
.2.
1 mole of calcium = the relative atomic mass in grams = 40 g
For Compounds
1.
1 mole of water = the relative molecular mass of water in grams
=2XH+O
- 2 + 16
2.
1 mole of Caco
3
- 18 g
• Ca + C + 3 X 0
= 40 + 12 +'48
= 100 g
mass
No. of
Ar
moles
Mr
or
Questions:
1. What is the mass of one mole of each of the following:
a) magnesium
Mg
.................... .
b) copper(II) oxide
CuO·
.............. · · ·
c) sodium chloride
NaCl
............... .
.·-·-·. ·.---.· . ·-·-·.
Chemistry !GCSE
- 38 -
(Dr. Fathy Abdel Cali!)
2. What is the mass of
a)
0.1 mole of carbon dioxide (C02)? .......... · - · · · ·
b)
4 moles of oxygen (02 ) ? ................ - · · · · · ·
c)
2 moles of water (H20)? ....... · ... · · · · · · · · · · · · · · · · · · · ·
3. How many moles are there in:
a)
9 g of water (HzO)? ........ · .. · · · · · · · · · · · · · · · ·
b)
1.6 g of copper (II) oxide (CuO) ? ............ - - · .
c)
117 g.qf sodium chloride (NaCI)? .. : ............ .
d)
9.8 g of sulphuric aci-d (HzS04 ) ? .... - .. · · · · · · · · · ·
e)
20 g of sodium hydroxide (NaOH) ? ............. - .
Avogadro constant [ LJ
.•• is the number of part~cles (atoms, molEcules) per mole of any
subs tan.ce • The v:alue of the constant is
A mole of iron (56 g) contains 6 X 10
23
iron atoms.
23
A mole of carbon (12 g) contains 6 X 10
carbon atoms.
~
23
A mole of sulphur (32 g) tontains 6 X 10
sulphur atoms.
23
A mole of oxygen atoms (16 g) contains 6 X 10
oxygen atoms.
.
23
oxygen molecules.
A mole of oxygen mole~ules (32 g) contains 6 X 10
23
A mole of carbon dioxide (44 g) contains 6 X 10
carbon dioxide molecules.
23 ..
A mole of water (18 g) contains 6 X 10
water molecules.
' " ' .'
..... ·•·. --.··.·
(Dr. Fathy Abdel Galil)
- 39 -
Chemistry IGCSE
Moles and chemical equations
Not only do equations tell you what substances are reacting and being
formed in a chemical reaction, but they tell you the amounts of the
substances reacting.
The equation·shows how many moles of each substance are reactipg.
Example I
.
magnesiUm
+ hydrochloric
acid
.·magnesium + h d
_...,.. chloride
y regen
MgCiz(aq). +
Mg(s)
+
2HCI(aq)
this means
1 mole
+
2 moles
and in grams
24g
+
73 g
-
H2(g)
1 mole
+ 1 mole
95 g
+
2g
the total mass on the left-hand side of the equation is equal to
the total mass on the right-hand side of the equation.
Equations can be used to predict the amount of a substanc,e that will be
used up or made in a ch~mical reaction. Look at the examples:
Example2,
Consider the reaction between magnesium and oxygen.
magnesmm
2Mg (s)
+ oxygen
+
02 (g)
-7
magnesium oxide .
2Mg0 (s)
This shows that 2 moles of magnesium react with l mole of
oxygen to give 2 moles of magnesium oxide.
Using the ideas of moles and masses we can use this information
to calculate the quantities of the different chemicals involved.
2Mg (s)
+
2 moles
+
2Mg0 (s)
1 mole
2 moles
2x24
lx (16x2)
2x (24+16)
=48g
=32g
=80crh
:
...
Chemistry IGCSE
(Dr. Fathy Abdel Galil)
40
Example 3
Lime (calcium oxide) is formed by strongly heating limestone
(calcium carbonate) until it is completely decomposed.
The equation for the process is:
CaO (s)
1 mole
I mole
1 mole
40 + 16
=56g
12 + (2x16)
=44g
[40 + 12 + (3x16)]
=IOOg
)>
•
+
CaC03 (s)
Calculate the mass of calcium oxide formed when 5 g of calcium carbonate
are strongly heated.
Pick out the substances involved in the question
CaC03 (s)
7
CaO (s)
molar ratio:
1 mole
1 mole
mass
•
The number of moles of CaC0 3 reacted
5
= -
=
•
The number of moles ofCaO formed= 0.05
•
Mass of CaO formed
= 0.05
100
Mr
why?
= number of moles x Mr
0 o.,:05 X 56
=2.8 g
=
.· .. ·..
. ·.· ·:· .
41
Chemistry IGCSE
(Dr. Fathy Abdel Galil)
Percentage Yield
Some reactions do not go to completion, i.e. not all of the reactants are converted
to products.
The amount of product formed in a non-complete reaction is known as the actual
yield of the reaction. The amount of product that would be formed if the reaction
goes to completion is known as the theoretical yield.
actual yield (given)
percentage yield .. -
X
100
theoretical yield
(calculated)
Example:
On heating 5 g of calcium carbonate, 2.1 g of calcium oxide are formed.
Using the information in example 3; what is the percentage yield of the
reaction?
>- Sodium reacts with sulphur to form sodium sulphide.
2Na + S -7 NazS
An 11.5 g sample of sodium is reacted with 10 g of sulphur. All of the sodium reacted but
there was an excess of sulphur.
Calculate the mass of sulphur left unreacted.
(i)
Number of moles of sodium atoms reacted = .................... .
[2 moles of Na react with 1 mole of SJ
(ii)
Number of moles of sulphur atoms that reacted = ..................
(iii)
Mass of sulphur reacted
(iv)
Mass of sulphur left unreacted == ................. g
= ................... g
[4]
, ..
. ·.·- '/
Chemistry IGCSE
42
(Dr. Fathy Abdel Galil)
Molar Gas Volume
The volume of one mole of any gas is 24 dm 3 (litres) at room temperature and pressure
(r.t.p.). This is known as the molar gas volume.
This rule applies to all gases. This makes it easy to convert moles of gas to volumes, and
volumes to moles.
• Calculate the number of moles a[ ammonia
gas, NH3, in a volume of7.2 dm of the gas
_.measured at r.t.p.
Volume
of gas (dml)
No. of
moles
(of gas)
24 dm 3
If the reaction involves only gases,_ then:
The ratio of volumes =the ratio of moles
•
The equaiion for the complete combustion of propane is given below. Insert the two
·
·
missing volumes.
volume of gas/cm 3
1o·
.l> · An excess of hydrochloric ·acid was added to 1.23 g of impure barium carbonate. The
volume of carbon dioxide collected at r.t.p. was 0.120dm 3 . The impurities did not reactwith the acid. Calculate the percentage purity of the barium carbonate.
BaC0 3 + 2HCl ---i- Baetz + C0 2 + H2 0
Molar gas volume at r.t.p. is 24 dm 3 •
(i)
The number of moles of C0 2 collected
...................
[1)
(ii)
The number of moles of BaC0 3 reacted
...................
[1)
(iii)
Mass of one mole of BaC0 3
................... g
[ 1)
(iv)
Mass of barium carbonate
................... g
[1]
(v)
Percentage purity of the barium carbonate
...................
[ 1)
percentage purity
=
mass of pure substance
mass of Impure substance
X
1oo
..·.
- ....
--·----~---
......
Chemistry IGCSE
(Dr. Fathy Abdel Galil)
43
Concentration of solutions
The term concentration means the mass of solute dissolved in a certain volume of the solvent.
The concentration of solutions is expressed in g I dm 3 or mol I dm 3•
For example, the concentration of a solution prepared by dissolving 58.5 g ofNaCl (1 mole) in
3
water to give a total volume of 1 dm3 is 1 mol I dm •
On dissolving 2 x 58.5 g (i.e. 2 moles), the concentration is 2 mol I dm3•
On dissolving 5.85 g (i.e. 0.1 mole), the concentration is 0.1 mol I dm3 •
Remember that 1 dm3 = I litre = 1000 cm3
No. of
moles
. )> Knowing the concentration ,
The· number of moles solute
in any volume ofsolution
can be calculated:
Cone.
Volume
(mol I dml)
· tdm 3 J
Questions:
3
1. How many moles are present in 25 cm3 of 0.1 mol I dm sulphuric acid (H2S04)?
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .
[0.0025 moles I
2. What is the concentrations of a solutio~ which contains 0.1 mole of solute in 102 cm of
solution? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
··
[1 mol I dm I
3
)>.
25.0 emS of a solution of lithium hydroxide, concentration 1. 00 mo!ldrrf3 was placed
in a beaker. A few drops of the indicator; methyl orange, were added and the
mixture turned yellow. Hydrochloric acid was added from a burette until the mixture
just turned red. 20.0 crrf3 of the acid. was needed to neutralise the alkali.
Calculate the concentration of the h)'drochloric acid.
UOH + HCt ---+ UC[ + H2 0
Number of moles of UOH in 25 cm 3 of a i .00 mol/dm3 solution
- ...........................
Therefore number of moles of HCt in 20 cm 3 = ...........................
Concentration of HCL = .......................... .
= ........................... mol/dm 3
[4]
[Dr. Fathy Abdel Galil)
-44-
Chemistry IGCSE
Empirical Formula and Molecular Formula
The empirical (ormula of a compound shows the simplest ratio of the
number of atoms of the different elements in it, while its molecular
formula shows the actual number of atoms of the different elements in it.
compound
ethane
Ethanoic acid
!fiOlecularformula empirical formula .
C2H,;
C2H402
..
CH3
CH20
_ICH3C02Hl
methane
CH4
CH4
Finding the empirical and molecular formula:
Example:
A hydrocarbon was found to contain 80% carbon and 20% hydrogen by
mass. Its relative molecular mass was 30. Find the empirical formula and
the molecular formula.
Symbols:
c
H
%
80
20 .
80
20
1. 0.-i.v.<.de.
biJ .the.
a.to mJ..c. mew.; u.
2. Divide by the sma!ler
number
12
6.67
·2o
6.67
6.67
20
to get the ratio:
empirical formula (simplest ratio):
Find mass of
empirical formula:
·Compare with M,:
Molecular formula must
be twice ·empirical formula;
molecular formula ts:
6.67
:
3
CH3
12 + 3
15 } M, is twice mass of
30 empirical formula
"" ;._;__ .· ..· ... ·.. : . .
Chemistry IGCSE
(Dr. Fathy Abdel Cali!)
- .4-5-
Questions __:
c:::•--...:c;_..,...,
1, The M, of oxalic acid is 90 and ifs composition by mass is:
carbon= 26.7%
(i)
hydrogen =2.2%
oxygen= 71.1%
Calculate the empirical formula of oxalic acid.
'••
................. ·-·····. ·······-. -· .............................. -··· ....... ······-····· ··········· .............................
·············· .......................................... ······························································· ........ [3]
(ii) What is the molecular formula of the acid?
·················································································-~·:········································-[1]
2.
The hydrocarbon benzene has an empirical formula CH and Its relative molecular.
mass Is 78. What Is its molecular formula?
.....................................................................................................................................
.........................................................................:....................................................[2]
-46-
Chemistry IGCSE
(Dr. Fa thy Abde! Gal if)
·.·.
Topic 5.
THE PERIODIC TABLE
The periodic table is obtained by arraneing the elements in order
o£ increasing atomic number and piacing them in rnws so that similar
elements fall into vertical columns. The horizontal raws are called
periods and the vertical columns are called groups.
GrCKlp1
·L
11;
Ill
1
en
''
0
f'
Ne
AI
Sl
p
s
C!
Ar
Zn
Gt
Ge
As
Se
Br
Kr
Ag
Cd
In
Sn
Sb
Te
I
Xc
""
Hg
T!
Pb
Bl
Po
"'
Rn.
N•
Mg
4
K
G.
Sc
Ti
v
Cr
Mn
Nl
Cu
Rb
Sr
y
Zr
Nh
Mo
,. Ru Rh Pd
6
c.
n.
u.
Hf
T,
w
Re
7
f'r
R2
Ac
tundtlon ttit.tlh
Fe
Os
0
,----,
N
3
,,
VI!
c
Be
""'
""' 5
VI
n
Ll
0
V
l!e
2
"d
_.,;
IV
H
Co
lr
Pt
Metals take up tlte part of the periodic table to the left of the hefiVJ' line.
1.
The periodic table showing the division into ·metals and non-metals.
The clnsa of eiernents whi"ch lies on the borderline batween me!=als
and non-metals is often classified as .o_em.(.-me;ta.t6 or me;tallo.{.dh 1
e.g. silicon, arsenic, germanium.
Fait examp.te,
aJr..~>e!U.c. {M l
.too/u, .Uk.e a. me.ta..t, .{..e . .oiU.ny bu;t
doe.o no.t belutve a..o a. me.ta..t.
He
H
"_:It,._,_
·
.,.<.'1 o.z
Non - > -
~~ o-'0::: melols
o· r
'a;q.. q.~• ~
~------c--Melols---------1>-
.t~
?J,..:
'>j.·. ".>0
\
~01.
~oy.. :.r
2.
Elements of the same group have similar properties (the same no.
of electrons in the o.utershell).
-47-
Chemistry IGCSE
3.
(Dr. Fathy Abdel Galil)
The valency (combining power) increases with_the group till
eroup -4, then decreases.
4.
Group number
1
2
3
4
5
6
7
0
Valency
1
2
3
4
3
2
1
0
The reactivity of metals increases down a group
Rb
5.
> K > Na
The reactivity.of non-metals decreases down a group
-
'·
> Br > I
F > Cl
6.
> Li
Metals react with non-metals to form ionic compounds.
Non-metals either join with other non-metals. to make :C{)I!.!I.te:n;t.
C:am)'JoWttll. or with metals to make .0J11ic. c.ompaund6.
Relation between group number and number of valency electrons.
0
,.---
0
He
III
IV
v
VI
VII
Be
B
c
N
o'-
p-
Ne
N•• M~·
!Jl+
Si
p
s'- a-
Ar
.Cu2+ Znl+
Br-
Kr
Ag•
I-
I
II
u•
K•
c.'•
Fe1+
Ba 2 +
Pbl+
r
-~
Group I elc:mcnt5. all h:ave
l electron to lo$e from
their outer shells.
They form + ions.
I
Group '\_'II elements h1ve 1 electrons
in their outer 'hells.·
They need to gain one
electron to.fill their outer Shell
and form 1 ne&:uive ion.
Group II dement' lll h:rve 2 electrons; in the:
outer .dlell. They form 2'*' iOJ'lt..
Group VI dements hne 6 elcciron11 in their outer
s:hcl!s..They need' to gi.in 2 dcctron~> to
Group lll dementt have 3
dectroos to lose.
They (arm 3 ~ ions:.
fUI their shell~. They form 2- ions:.
'
-48-
Chemistry IGCSE
(Dr. Fa thy Abdel Galil)
Group I elements: the 'alkali metals'
Density
Melting point
rc
fgcm-J
Li
Na
180
0.53
98
K
Name
Symbol
Lithium
Sodium
Potassium
Rubidium
Caesium
1.
Rb
Cs
Group lions
Lithium ion
u+
0.97
Sodium ion
Na+
64
0.86
Potassium ion
K+
39
!.53
29
1.90
Rubidium ion
Rb+
Caesium ion
cs+
They are called th!'. alkali metals because they react with water
to form alkaline solutions.
2.
The outermost shell contains one electron.
Where are Group I metals found?
The. me..ta.to .thi!Jil!>e..tvu do na.t ac.c.wr. .<.n na..twr.e.. The.£{ Me. .tao Jr.e.a.c.tive..
The.Jr.e. Me. Ve.lt.IJ many c.ompouncU a6 GJr.aup I me..ta.to
Sodillm c.htoJr..{.de., NaC.t, ~ .the. mo~.t c.ommon GJr.aup I compound.
The. MWLc.U o 6 NaC.t Me. : a) S e.a wa.te.Jr. ·
6)
GJr.aund '.Jr.Oc.k: ~aLt·· de.po.oill.
Properties of Group I elements
PhysiCal Properties
The metals .are easily cut with a
knife.· Metals further down the
group are softer.
Soft and shiny
when cut
Conduct
electricity
'
I
The metals are ail very good ciectrical conductors.
rodium. r
Low density
The metals all have low densities.
Lithium is the lightest metal known.
Lithium,. sodium and potassium. all float on
water. This is because tliey are less - dense than water.
(Dr. Fa thy Abdel Gall!)
-49-
Chemistry l GCSE
Chemical properties : very reactive metals
Reaction
with air:
The metals are stored under oil. This is because they
react with air. ·
The metals are only shiny when freshly cut. They
quickly tf!rnish as they react with air.
Metals all burn easily in air
e.g:
ssdium
+ OJeygen
4Na(s)
+ 0 2 (g)
sodium oxide
potassium + oxygen
Reaction
\vith water
--->-potassium oxide
Metals all react easily with cold water
to form alkaline solutions.
The heat from the reaction melts the metal
as it reacts:
sodium
+
water
-+
sodium
hydroxide
+
hydrogen
2Na(s)
+
2H 2 0(!)
-+
2Na®H(aq)
+
Hz(g)
potassium
+
water
-+
potassium
hyclraxide
+
hydrogen
2K(s)
+
2H 2 8(!)
--+
2K@H(a<'J)
+
H2(g)
The ob<. vr.va.:t.i.ort.O .tha/: c.a.n be ma.de when a. <>mill )!li.ec.e o 6 .the a.tka..U. meta.t i.<>
a.dded .to a. :t:Jta U!J h 0 n wa:;{:eJt :
1. UthWm fi.tow a.nd a. ga.<> 6/-zze<> Mound d.
Z. SocLWm 6.tow, meW 1J..!> d ;,hoot<> a.c.Jr.OM .the wa;tvr. a.nd a. ga.<> (i.zzu 6a.<>.t.
3. Po.tM<.i.um Jtea.W v.<.o.ten:Uy .tha/: d me.t.t<> .<.mmedi.a..te.ty a.nd c.a..tc.hu 6.0te.
-50-
Chemistry !GCSE
(Dr. ·FathY Abde! Cal ill
Reaction with chlorine:
metal
·~
chlorlne---->-gas
\
·
~
1"'~~'--~_,\.:>.~-CQ-";...n_..,..IL._ __...,l$j~
~
_,_tofume
cupboard
..
Reactivity of Group. I metals
heat
Lithium
The metals react easily to form chlorid"'>:
Sodium
Potassium
· lithium chloride
2LiCI(s)
lithium
2Li(s)
+ chlorine - +
+ Cl 2 (g) - +
sodium
2Na(s)
+ chlorine - + sodiuni chloride
2NaCI(s)
+ Cl 2 (g) - +
Rubidium
n
Caesium
potassium + chlorine - + potassium chloride
2KCI(s)
2K(s)
+ Cl 2 (g) - +
So you can see these Group· I metals have similar properties.
Lithium is said to be the, least reactive of them, because it reacts
the most slowly".· Potassium is the most reactive of the three.
Why they. ha.ve. ·~.i.mliaJI. pltopeJt.;U~ ?
In the elements of Group I, all the atoms have.! electron in the
outer shell. That is why· the elements hehave"in a similar way.
Elements behave in a similar way if" their atoms
have the same number of outer-shell electrons.
Group I compounds
Metal
Chloride
Bromide
Nitrate
Sulphate
Carbonate
Lithium
LiCI
LiBr
LiN0 3
Li 2 S0 4
Li2 C03
Sodium
NaO
NaBr
NaN0 3
Na 2 S0 4
Na 2 C0 3
Potassium
KC)
KBr
KN0 3
K2 S0 4
K2 C03
GJtoup r ~a.Lt6 {c.he.o:Ud~ I n..UJr.n.;t~ I c.aJtbona.te..o 1 e..tc.. J ivte. w!U.te.,
.<.o n..Lc ~ o.Udo, M.f.u.b.C.e. .i.n wate.Jt. [giving a colourless solution]
metals
get
more
reactive
Chemistry IGCSE
Transition Elements
- 51 -
e.g.
(Dr. Fathy Abdel Galil)
Cu, Fe, Cr, 1'-!i., V., Co.·
Typical characteristics of transitipn metals ;
1.
They .~re metals of high melting points (exceP.t Hg) and densities
(hard, strong).
2.
They.form colou_red compounds, e.g. copper (II) ions,Cu
iron (II) ions, FP.
2+
2+
(aq) are blue,
(aq), are green.
:;,
Host of them have more than one valency,
2
3
different charges,
e.B. Fe +, Fe +.
i.e. forming ions with
4.
The metals and their compounds can act as .catalysts
a)
Iron ·.is used in the m<i.nufacture of ammonia.
b)
V~nadium
(V) oxide is used in the manufacture of sulphuric acid.
Compa:tr.e. .the. .phy¢-i.c.a.l a.nd c.he.mi.c.a.l p!topeJU;{.eo bU:ween. pa.tM.t,.{.um (gJtOap I
me.tall a.nd va.na.d.wm (bw.tt.~>.uion me.ta.e.l.
Potassium
Vanadium
(Dr. Fathy Abdel Ga!H)
- 52-
Chemistry IGCSE
Group VII Non-Metals
the Halogens
D
c.o.e.oUJr.
bec.ome..t.
daltkvc.
·Halogen Molecule State at
Colour
Fluorine Fz
Gas
· Pale yellow
F
Chlorine Cl 2
Gas
Green
Cl
Bromine .Br2
Liquid
Red-brown
Br
Iodine
12
Solid
Dark gr.ey
I
Astatine
At
...
. ..
room
temperature
2
...
Symbol of
Halide ion
F
-
CI
-
-
Br
I
+
'=fry
mcreaszng
>-Bromine is very volatile [has low b;p. 59°C}. This means ihat it easily
turns into a gas.
>-
Iodine is a dark grey solid, when warmed, it turns into a purple vapour
[it sublimes]-
>- Aqueous solution of iodine is brown.
The halogens all exist as diatomic molecules. The tWo atoms in the
molecule are joined by a covalent bond.
Cl
- Cl
. a chlorine molecule, Cf2
Uses of Chlorine:
• Making bleach
.. In water purification [kills bacteria]
"' Maldn;; PVC (insulation for electric wires)
..
-53-
Chemistry !GCSE
(Dr. Fa thy Abdel Galil)
·:·:
Chemical Properties
.
Reaction with .metals:
Halogens react wi~h. most metals to make salts:
+ chlorine -+
+ Cl 2 (g) -+
sodium
2Na(s)
Reaction with.indicators:
Chlorine gas dissolves in wa\er to make a powerful bleach. Damp indicator
paper is quicldy bleached with chloiine., .
-Test for Cl
Displacement reactions:
sodium chloride
2NaCJ(s)
2
gas :
Chlorine bleaches damp litmus paper.
Chlorine can displace bromine and iodine from a solution of their salts:
chlorine gas-·===\\
v ~I>Otassium Iodide solution
·1oame belng forroed
chlorine
+
Clz(g)
+
potassium -+
iodide
2KI(aq) __,.
[colourless]
Ionic equation:
+
Clz
. chlorine
+
Cl 2 (g)
+
zr
ionic equation:
Clz
+
2 Br·
+
I,(aq)
+
potassium
chloride
2KCI(aq)
-> [.brown]
7
potassium -+
bromide
2KBr(aq). -+
[colourless]·
iodine
Iz
zcr
+
bromine
+
Br,(aq)
+
potassium
chloride
2KCl(aq)
+
zcr
-> [red]
7
Brz
In o:thvr. WOJtd.l,, a. mOJte Jtea.c:Uve hai.ogen w.Ut dUp.f.a.c.e a. leo<> Jtea.c:Uve ha..e.ogen
t)Jtom ffi compound;,.
Halogens have similar properties because their· atoms all have 7 electrons in. the
outer shell.
-54-
Chemistry I GCSE
(Dr. Fathy Abdel Gs!il)
Nobel Gases :
Helium, Neon, Argon, Krypton, Xenon
1.
The nobel gases in group 0 are very unreactive (inert), they
have complete outershell of electrons.
2.
They do not usually form compounds and exist as isolated single
atoms (i.e. monoatomic).
neon etomi"::\\\
N•
~((G
hollum atocn• ·-<--__.
He
Uses of Nobel Gases
1.
Helium is very light and. does not burn, so it is used in ballons
and air ships.
HqdJtogen WCL6 £L6ed .Ut .the pa..o.t in ba.Uo/1..6, now hel..Wm Mpl.ac.ed
hqdJtogen 601t 6-UUng ba.Uo/1..6. Whq ?
••••••••••••••••••••••••v••••••••••••••••••••••••••••••••• .. •••
2.
Argon i~ for fil1~ng_electric light bulbs as an.inert atmosphere
It is very unreactive and-helps protect the filamenc,
tung5ten
filament
3.
argon
Neon : When an electric current is passed through neon gas, it
gives out a bright light and is used in lamps and advertisement
signs.
-55-
Chel)listry I GCSE
(Dr. Fathy Abdel Galli)
Test for Gases
Test
Result
Hydrogen
Lighted splint
Burns with a pop
Oxygen
Glowing splint
Relight:s
Carbon dioxide
Limewater
Turns milky
Chlorine
Colour
Yellow-g'reen
Damp litmus paper
Bleached
Ammonia
Smell
Pungent
[ttlkq.Une gcw l
Damp red litmus
Turns blue
Formula
Gas
paper
Collection of Gases
gas -l-i>'
l.
Upward delivery over water :
For gases which are insoluble
!n water such as H ,
2
2.
o2 and N2 •
Downward delivery :
For gases which are soluble
in water and denser than air
3.
Upward delivery
For gases which are soluble
in water and less dense than
air such as NH .
3
H [Ughte;c than Wr.) Mn be
2
a-Uo c.oUec.ted bif up.wJtd deUveJty.
gas __,.._
gcw-jM
-56-
Chemistry IGCSE
(Dr. Fathy Abdel Galil)
Drying of Gases
1.
Gases that do not react with acids such as· co , so 2 may be dried
2
by pasa_ing it through concentrated sulphuric acid [dAy.i.ng agent].
11uestion :
~-""""'""'""'""'-=--
W/Uch o6 .the. 6o.UoW-Wg cuur.angeme.n.tl> 6oiL dJty,~ng a. gaJ, w.Uh concen:tJur;te.d a.cJ.d )!, co!LILe.c.t f
2
1
~===:;, r;=='d=r=y==~
concentrated
sulphuric acid
concentrated
sulphuric acid
2. Ammonia gas is dried by passing it over solid calcium oxide [drying agent]
>- [Conce./Lt!ta.te.d .sul.phU)()_c a.c<.d ca.nno.t be. tt<1 rid be.ca.W, e. U 1r.e.aw
wUh a.mmoiUa. gaJ, .]
ammonia
+ sulphuric add
-----+-
nmmonlum sulphate
(Dr. Fathy Abdel Galil)
-57-
Chemistry IGCSE
Oxidation and Reduction
excess hydrogen
burning in air
copper(II) oxide [black]
·ice
water
When hydrogen is passed over black copper(II) oxide in the apparatus
above, the blnck powder turns pink~brown (copper) •
,.._ . What is the purpose of the ice?
reduced.
1
oxidised.
I
copper( II) oxide· + hydrogen
+
CuO(s)
-7-
copper + water
Cu(s) · + H .0(g)
2
H (g)
2
Re.due-Utg ,a.ge.n.t
The copper(II) oxide is losing oxygen. It is being reduced.
The hydrogen is gaining oxygen. It is being oxidised.
In other words:
> Oxidation is defined as the addition of oxygen.
)> Reduction is defined as the removal of oxygen.
Reduction and oxidation always take place together in a reacticn.
So the reaction is called redox reaction.
Question: Which substance is oxidised and which is reduced in the following
. reactions, mention the reducing and oxidising agents.
----7 2Fe
Common reducing agents
hydrogen, carbon,
+ 3CC)z
:
carbon monoxide,
reactive metals
-58-
Chemistry IGCSE
(Dr. Fa thy Abdel Ga!i!)
)> Since hydrogen is a common reducing agent, the addition of hydrogen
is a reduction reaction, and the opposite, i.e; removal of hydrogen
is oxidation.
In which change shown has nitrogen been reduced?
B
nitrogen, N2
c
~----------~
N02
D
)> Redox in terms of electron transfer
[01 L]
[RIG]
Oxidation
Red·uction
Is
Is
Leiss of electrons
Gain of electrons
From the definitions above, it follows that:
Reducing agents give electrons.
Oxidising agents accept electrons.
Consider the reaction of magnesium with oxygen :
magnesium
+
oxygen·
2 Mg
+
02
--+ magnesium oxide
~
2 MgO
The ma.gne;,.I.wn ).), oudA.ud a.nd .the axyge.n ).), Jte.du.cvi. Vwring .tw
Jt.e.a.Ul.ott, .two el.ecbw 111> a.Jt.e. .til.aiU 6e.Med filtom ma.g lteJ>.i.wn .to oxyg e.n.
Ma.gne;,.f.wn I.on a.nd oude ion aM 6oJtmed.
0 +
Mg
2+
Mg.
2 e
oz-
+ 2 e
Ma.gne;,.f.wn, w/U.c.h ).), oufued, .to~>e;, el.ectJto111>;
oxygen, w/U.ch ).), Jte.duc.ed, ga.i..1u el.ectltoJ1-6.
-59-
Chemistry IGCSE
[Dr. Fathy Abdel Galil]
Oxidation States [Oxidation Numbers]
The oxidation state of iron in iron(II) oxide is 2 and in iron(III) oxide is 3.
The oxidation state of manganese in manganese(IV) oxide is 4 and in ·
·potassium manganate(Vll) is -7.
The oxidation state of chromium in chromium(III) oxide is 3 and in potassium
dichromate(VI) is 6.
Change in oxidation state
)>
Oxidation involves an increase in oxidation state,
e.g.
)>
Reduction involves a decrease in oxidation state,
e.g.
Oxidation and Reduction [summary]
with respect to:
O!fgen
hydrogen
electrons
oxidation state
reduction
oxidation
removal of oXygen
addition of oxygen
addition of hydrogen
removal of hydrogen
I loss of electrons [OILJ . gain of electrons [RIG] .
increase in oxidation state· decrease in oxidation state
-
Tests for oxidising and reducing agents
a) Oxidising agent (oxidant) + potassium iodide solution
The colour changes from colourless to brown [h].
b) i. Reducing agent (reductant) +.·acidified potassium magnate (yii)
solution :
The colour changes from purple to colourless.
ii. Reducing agent (reductant) + acidified potassium dichromate (VI)
solution :
The colour changes from orange to green.
- 60-
Chemistry IGCSE
Topic 6.
(Dr. Fa thy Abdel Galil)
ELECTRICITY AND CHEMISTRY [ELECTROCHEMISTRY]
Conductors and Non-Conductor:;
Solid substances that allow electricity to flow through them nre
called conductors, All metalo are good conductors of electricity. why.,
Substances that do not allow electricity to flow thr·ough them are
called non-conductors or insulators. All non-metal aubatancea such
as glass, plastic, wood, and-rubber ar~ insulators. There is, however, one very important exception, Carbon, in the form of graphHe,
is non-metal, but a very good conductor of ele.ctricity. why ?
Semi-Conductors,
They are substances which contain no "free electrons" and no
"ions" bu·t allow very small cunerit ~O··'pass through them, i.e.
they conduct weakly e.g. c,Wc.on. ·
. Electrolytes and Non-Electrolytes :
. Liquids that conduct an ele.ctric cun:ent are called electrolytes.
Those that do not conduct are called non-electrolytes.
Electrolytes are substances that contain ions which are fi:ee to
move about, so they are ionic compounds that are molten or are
dissolved in water,
Covalent compounds such as ethanol, pure water.or sugar solution
are non-electrolytes. The following figure shows the apparatus that
could be used to see if a liquid is an electrolyte .
.-----1
F
a battery
A lamp. If it glows,
electricity must be
flowing through the liquid.
electrode called cathode 8
electrodes. Generally
made of graphite or :::::::H-+--1
unreactive metal like
platinum
<±) electrode called anode
.:.
liquid under test
::'
-61-
Chemistry IGCSE
free
moving
wns
)>
(Dr. Fa thy Ab<.lel Galil)
Typ~: of su~srtmce _
Electrolyte
solutions of acids
and alkalis in water
,J
solutions of salts·
in water
,J
molten salts
,J
Non-electrolyte
ethanol
petrol
sugar solution
pure water
,J
,J
,J
oil
,J
,J
Electrolysis :
Electrolysis is the decomposition [breakdown] of a substance by electricity.
':·
During electrolysis, ions migrate towards the opposite electrodes.
)>- Can you suggest why -ve ions are called anions and +ve ions are
called cations? ........................................... .
.. ! .
.
••••••••••••
0
0
0
••••••
0
••
0
•••••••
0
0
•
0
••••
0
•••• ' •••••
0
•
0
0
....
Chemical changes take place at the electrodes. At the cathode, +ve ions gain electrons and become -atoms or molecules. At the anode,. -ve :!:ons
lose electrons and become atoms or molecules.
The electrons flow in the external circuit from the anode into the cathode.
a battery
r-~--t'I t------,
electron
flow
electron
flow
e cathode ·.
:_·anode
(£)
·negative
ions lose
electrons
at tho"·
anode
electrolyte
.
.,
/
-62-
Chemistry IGCSE
(Dr.FathyAbdel Gali!)
Electrolysis of Molten Substances using Carbon Electrodes
The compounds are decomposed into their elements. The rules for the
. electrolysis of molten compounds are :
Molten Compound
•::
At the anode +
Non-metal
At the cathode Metal
> Electrolysis of molten lead bromide [PbBr2]
+
-
a battery
;.·
carbon anode +
carbon cathode -
bubbles ~F
brown gas
{bromine)
dlr.ap.5 a 6 moLten lead
·(gJte.y}
.
~··.
-
molten lead bromide
t
heat
>:Explain. why the lead bromide needs to be melted for electrolysis to
.
:take place ........................... ·.................... .
> The. electrode reactions are summarized as follows :
Electrolyte
Lead bromide,
PbBr2
At the cathode Pbt+ + 2e- ~ Pb
At the anode +
2Br- ~ Brz + 2e·
> Complete the following table:
molten electrolyte.
lead bromide
sodium chloride
. magnesium fluoride
aluminium oXIde
Product at cathode lead
.. . . . . . . . . . . . . . . . .
. . . . . . . .... . . . . . .
. . . . . . . . . . . . . . . . ..
· Product at anode
bromine
t-
...................
..................
...................
-63-
Chemistry IGCSE
[Dr. Fathy Abdel Galil]
..-._
Electrolysis of Concentrated Uydrochloric Acid: ·
At the anode +
At the cathode -
Electrolyte
.
2W (aq) + 2 e- -7 H2 (g)
Hydrochloric acid,
HCI (aq)
2Cr (aq) -7 Ch(g) + 2e··.·.
Electrolysis of Aqueous Solutions: ·
The products of electrolysis of aqueous solutions are difficult to predict than
molten compounds. This is because as well as there is a cation and a anion
from the salt, there is a cation (H") and a anion (OH) from the water.
Electrolysis of Concentrated Aqueous Sodim Chloride :[Brine} :
At cathode. ~
Atanode +
,___
__.---,
LNa+ - - - - - _ --- \ __
d-;
FromNaCL
-- oH_.,
/
-~
~-,--
1r
·..-.+ ' ,
'
I
~
-- --
--,
--"
.
f
-- --J
Only F takes part in
electrolysis [H being
lower in the reactivity
·series than Naj
I 2 F (aq) + 2 e· -7 H (g)
2
Only Cr takes part in
electrolysis because it
is present in much greater
concentration than OH
jz Cr{aq) -7 Cl2 (g)'+ 2 e· /
This leaves a solution containing sodium and hydroxide ions (a solution of
sodiwn hydroxide, NaOH). The solution is alkaline (i.e. turns red .litmus
paper blue).
Compare the products of e./ectrolysis of:
(i)
Molten sodium chloride
(ii)
Concentrated aqueous sodi!fm chloride
)>
-64-
Chemistry IGCSE
[Dr. Fathy Abdel Galil]
Manufacture of Chlorine and Sodium Hydroxide :
The method is based on the electrolysis of concentrated aqueous
sodium chloride (brine)•.
brine
chlorine
lui~_____;
...
..... ...
.·.·. ·•·
~
pos!Uve
eleclrodo
aqueous sodium hydroxide
neg alive
elec[rode
Predicting the Products o[Electrolysis o[Aqueous Solutions :
)>
)>
At the cathode If the metal is higher than
hydrogen in the reactivity series,
then hydrogen gas is produced
If the metal is lower than hydrogen
in the reactivity series, then the
metal is deposited (formeq}.
The reactivity series
Na
Ca
Mg
AI
Zn
above hydrogen,
so hydrogen gas
is evolved at the
cathode
Fe
Pb
Cu
Ag
least reactive
Au
below hydrogen so
metal deposited
at the cathode
)>
)>
At the anode +
For concentrated
solutions of chlorides,·
chlorine gas is produced
For sulphates and nitrates,
oxygen gas is produced
-65-
Chemistry IGCSE
[Dr. Fathy Abdel Galil]
Electrolysis of Aqueous Copper(ll)sulphate :
Using carbon electrodes (i.e. inert)
Atcathode
-{ Cu +) ·
....
Atanode +
~
FromCuS04
--so
- -- ----'
• - ..:- 1
....
--·
-·
-·
... -
2
2- I
4
\.-- /
1-
....
,rr\-·-·
FromHzO
I
/
10Ir'
'r
-----
Onlythe copper ions take
part in the electrolysis.
Only the OH ions take
part in the electrolysis.
Cu 2+ (aq) + 2e· -7 Cu (s)
Copper deposited on the
cathode (as brown deposit)
Oxygen gas is given off
The solution left is dilute sulphuric acid (H2SO_J.
)>
The solution changes from blue to colourless
I
I
2)
-
cathode
anode
+
I
0
..
b~r.own
0
de.po.oU
6 c.o ppe.IC.
'
0
c
'
bubbles of
oxygen
6Oc_
c.oppe.IC. (II) .;ul..pha..te.
M.fu:ti..o n
Summary:
Electrolysis of :;:tqueous copper-(II) sulphate:
atcathode copper
The solution left is dilute sulphur~ acid (H2 S04).
atanode +
oxygen
[Dr. Fathy Abdel Galil]
-66-
Chemistry IGCSE
'•;
Types of electrodes :
. Inert electrodes: Carbon (graphite) or platinum,.
They do not take part in the electrolysis..
Active electrodes: e.g. copper, silver, zinc, nickel.
They take part in the electrolysis and the active metal anode dissolves,
(i.e. passes into solution as ions. In other words, the mass of the active·
metal anode decreases).
Electrolysis of Aqueous Copper(II)sulphate :
. Using copper electrodes (i.e. active) .
I,
ll
~
copp er
caih ode -
copper
an·ode +
1...
-7 Cu2+
-7
-7 Cu 2;-
vaqueo us copper(II)sulpltate
"""~........
(blue)
Atanode +
Atcathode -
Copper passes into solution as
ions (i.e. the anode dissolves)
[anode: decreases in mass]
Copper deposited
[cathode: increases in mass]
[ Cu (s) ~ Cu + (aq) + k
I Cu2+ (aq) + 2e- ~ Cu (s) I
2
J
The aqueous copper(ii) sulphate remains unchanged.
[Dr. Fathy Abdel Galil]
-67-
Chemistry IGCSE
Application of Electrolysis:
1} Refining of Copper:
Copper can be refined by electrolysis
using a block of impure copper as the
anode and thin sheet of the pure copper
as the cathode. The electrolyte is aqueous
copper(II)sulphate. Impurities sink to the
bottom of the container as anode sludge.
The overall result is the transfer of
copper atoms from the impure copper
to the cathode.
);>
·EB
e
an. ode.
cathode.
pU/tl!.
CO(I(Il!./t
cop.fll!./t( I I ).out.phai.e.
.oot.uil.on.
Zinc can be refined by electrolysis. The method is similar to that used to
refine copper. Complete the following statements. about refining of zinc.
The cathode is made from ................................. .
The anode is made from .................................. .
The electrolyte is aqueous ................................. .
2) Electroplating:
Many metal objects are electroplated for:
a) Protecting them from corrosion and rust
b) Making them look attractive
anode: _ _:::,-
cathode:
(object to
be plated)
(metal used to
plate the• ::>bject)
·='='""='!-·electrolyte:-
aqueous solr.{tion
contairzing.ions of
the plating metal
if the object is to
be plated with
copper
silver
.nickel
· the anode will be
made fro in
copper
silver
nickel
the electrolyte will be
aqueous copper(II)sulphate I
aqueous silver_nitrate
aqueous nickel sulphate
.
Chemistry IGCSE
-68-
[I?r. Fathy Abdel Galil]
3) Extraction of metals
Reactive metals above Zn in the reactivity series such as Na, Mg,
Ca, AI can be. extracted only by electrolysis.
Extraction of Aluminium
Ore: Bauxite.
The purified bauxite (aluminium oxide, Al 20 3) is electrolysed in
molten cryolite (Na3A1F6).
Aluminium oxide has too high melting point to be used on its
own, so it dissolves in molten cryolite at 900°C (i.e. cryolite is
used to lower the m.p. ofAl1 0J)
....
Carbon
anodes
(";),
--~,;,.,o."'l"""___ 1±/
Molten electrolyte -HI-(aluminium oxide
fil!.-l~·carbon lining
.ofccll(cathodc)
dissolved in
cryolite) ·
8.
..
AI
At cathode-
At anode +
The aluminium sinks to the
bottom.
Oxygen gas is produced.
.> As the hot oxygen escc·.pes, it burns away the graphite anode·
( C + 0 2 7 C0 2), ard so they have to be replaced from time to time.
.> Making aluminium is an expensive process because large amounts of
electricity are needed.
(Dr.FathyAbdel Galil)
-69-
Chemistry IGCSE
Topic 7.
. ACIDS, BASES AND SALTS
Acids:
An acid is a substance giving hydrogen ions, II'" (aq), in aqueous solutions.
Aqueous solutions of acids tUrn the colour of litmus red.
It is the hydrogen ions that cause the change of colour.
Remember that the hydrogen ion is simply a proton.
. In other w.ords, an acid is a proton donor.
.. ·common acids:
strong
Acid
Formula
Hydrochloric acid
HCl
Nitric acid
HN0
Sul.phur:Lc acid
{
weak <-- Ethanoic acid
(Ace tic acid)
Ions present in the acid
H+
Cl
--
[ehto.!UdeJ
H+
NO;
[ JU.:tJut.te l
H so
2 4
2H+
so 2 -
[.o ul.p fta.te J
CH COOH
3
H+
CH COO
3
3
4
- [ e..t!ta.noa.te J-
Basicity of acids:
·
Monobasic such as HCI, HN03 , CH3COOH
such as H2S04
Dibasic.
Reaction of acids
l.
f:cids reac_t. .with reactive metals to give a sa·lt and hydrogen
acid
+
metal
salt
'+
hydrogen
dilute
sulphUiic acid
magne>lum ribbon
magnesium
Mg (s)
+ ,sulphuric acid --r. magnesium sulphate + -hydrogen
+
H2SO.~ (aq)
___,. · MgSO.~ (aq) + Hz (g)
ionic equation:
Mg (s)
+ 2H+ (aq)
------'Jr
Mg+Z (aq) · + Hz (g)
- ro-
Chemistry IGCSE
2.
(Dr. Fathy Abde! Galil)
Acids react with bases (metal oxides and hydroxides) to give
a salt and water [neutralization]
Acid
+
Salt
Base·
+
Water
dilute
rulphuric acid
·:.
heat
sulphuric
acid
H 2 SO,(aq)
+
ccpper(ll)
--+-
oxide
+
CuO(s)
--+-
b.t.a.ck
copper(ll)
sulphate
CuSO,(aq)
b.fue
+
water
+
H2 0 (I)
Sulphuric acid + sodium hydroxide ~ sodium sulphate + water
H
3.
2
so 4 (aq)
Na so (aq)
2
4
+ 2 NaOH(aq)
+ 2 H 0 (.f)
2
Acids react with metal carbonates to form a salt, carbon dioxide
and water
·acid
+
carbonate
--+
salt
+
water
+
carbon
dioxide
+
calcium
carbonate
CaCO,(s)
--+
calcium
chloride
CaCl 2 (aq)
+
water
+
+
H 2 0(!)
+
carbon
dioxide
C0 2 (g)
dilute
hydrochloric
acid
2HC!(aq)
'
T
--+
>- Thing to remember about hydrochloric acid:
Hydrochloric acid is a solution of hydrogen chloride gas in water.
water
HCl (aq)
HCl (g)
[covalent]
[ionic]
•:':·
-71-
Chem_istry JGCSE
(Dr. Fathy Abdel Galil)
Bases
A base is a substance that can accept hydrogen ions, i.e·. a proton acceptor.
Ox..i..du, and hydJr.ox..i..deh of metals are bases.
Properties of bases :
1.
·Bases react ,;ith acids to form a salt and ,;ater only (see properties of acids), This reaction is called neutralization reaction.
2.
If a base is soluble in ,;ater, the solution is called an alkatl.
An aiH;ali is a base that is soluble in water
-
'
Common alkalis :
,crong {
·Alka-li
Formula
Ions present in the alkali
Sodium hydroxide
NaOH
Na+
'"'"'''= "''""""'
KOH
K+
Calcium hydroxide
Ca(OH)
weak f-- Aqueous ammonia
NH (aq) or
3
NH 0H
(often called
ammonium hydroxide)
3.
2
OH
-
Ca 2 +
20H -
NH+
OH
4
OH
4
Solutions of alkali turn the colour of lit"mus £~~~It is the hydJr.ox..i..de. ~OM that cause the chang.e of colour.
Weak and strong acids and bases
Acids
strong
Completely ionized in solution,
!.e. the solution wi!! contain
a high ·concentration of hydrogen ions,
e.g. hydrochloric acid
sulphuric acid
nitric acid
we k
Partially ionized In solution,
l ...e. some of the .. molecules
.remain un-Ionized In the
solution
e.g. ethanoic acid
citric acid [in citrus fruits]
Similar-ly;_ if an alkali completely ionizes on dissolving in water,
a ..;.tJwng alkatl is produced;
e.g. sodium hydroxide, potassium .. hydroxide, calcium hydroxide.
If an alkali does not. complet.ely ionize in· water, a
is formed; e.g·. ·ammonium hydroxide (aqueous ammonia).
we.a.k. ~
(Dr. Falhy Abdel Galil)
-72~
Chemlstiy IGCSE
nre pH scale
The strength of an acid or an alkali Is shown using a scale of numbers called the pH scale.
On this scale :
an acidic solution has a pH number less than 7
an alkalic solution has a pH number greater than 7
a neutral solution has a pH number of exactly 7
a
The pH can be measured by using universal indicator.
Unlversallnd!cator Is a mixture of dyes. Uke litmus, it can be used as a solution or as
universal Indicator paper; it goes a different colour at different pH value as shown In this
diagram:
yellow
violet
blue
orange
red
'
/
-
~r~;n
'
/
'
/
/
...__
unlversal!ndlcator colours
1
pH numbers
2...___
2
3
5
4
..... ...___
/
e.g. hydro-
o.g. otha-
chlol1c acid
nolc acid
6
7
8
11\
g 10 11 12 13 14
-"""'<trona alkall,
MUiral,
'-...
weak alkali.
a.g.water
e.g.aq.l.!TliTlOllla
The pH can be measured more accurately using
pH meter.
/
o.g.&Od!um
hydro>:ida
Salts
A salt is a compound made from ari acid when
a metal takes the place of the hydrogen in the acid
The salt made depends on the acid :
• Hydrochloric acid gives a chloride
• Nitric acid gives a nitrate
• Sulphuric acid gives a sulphate
" Ethanoic acid gives ethanoate.
Soluble and insoluble salts
Some salts dtssolve·ln water easily. They are said to be soluble. Other salts do not dtssolve
at all. They are said to be Insoluble.
Soluhle
Insoluble
All sodium, potassium,
and ammonium salts
All nitrates
except Sliver and lead chloride
Chlorides •••
except
Calcium, barium and
Sulphates ...
lead sulphate
Sodluin, potassium, and
ammonium carbonates •••
But all other carbonates
are Insoluble
Chemistry I GCSE
(Dr. Fathy Abdel Galil)
- 73-
Making Soluble Salts
1. A metal, a base or a carbonate can be added to a dilute acid. The
solution formed is then evaporated.
1.
Excess zinc is added to dilute sulphuric acid in a beaker until
the reaction stops fizzing and some zinc is left •
. 2.
The mixture is filtered, What wil~ be left in the filter paper 7
....................~.····~······································'"····
3.
The filtrate, zinc sulphate solution, is evaporated in an
evaporating basin to crystallizing point.
4.
Allow the solution to cool, crystals of zinc sulphate are formed.
5.
Separate the crystals by filtration and dry them between filter
papers (or in a warm oven).
dilute
sulphuric- -111/
acid
"-=Cd=_,
'
.
~zinc sulphate
solution
/·,zinc sulphate
/
crystals of
, solution
~~2~;;;----e:Vaporating
'i
basin
zi:!:·
Zinc sulphate-. could also have been made using· zinc carbonate instead
. of zinc. The ·sam>;! method and apparatus would. be use<;!, but the gas given
off would be carbon dioxide and not hydrogen.
Similarly, zinc oxide could have been used instead of zinc. No gas .would
be given off and warming is necessary,
- 74 -
Chemistry IGCSE
2.
(Dr. Fathy Abde! Cali!)
.Making sal!s from acids and alkalis [the titration method]
Making sodium nitrate NaN0
HN0 (aq)
3
+
N.a OH (aq)
3
-->
+
d.Uu:te.
n.U!Uc.
Cl.c).d
- - - p.{.pe.tie.
bwr.e.tie.
<.ocU.wn
/--'---\/ hyd.JW x.J..de.
&oWtion
'-----"Z.
phena.tph:dut.te..&!
<.odW.m
rU..i::Jr.JLt e.
<.olu.:Uan
Cl.ci.d.
~
l
ph. ph. j w,;t
c.hCI.ng e.6 p{.nk :to c.o.tou.!rl.e.o<>
l.
A burette is filled to the zero mark with dilute nitric acid.
2.
25 cm 3 of dilute sodium hydroxide is put into a conical flask
with a pipette.
3.
3 drops of suitable indicator such as phenolphthalein (ph.ph.)
are put into the alkali.
What. colour will it turn Z..•.•••••••..•••••••.•.•..•••••••.•••
4.
Acid is run from the burette into the alkali.
When the indicator just changes colour (from pink to colourless),
the solution is' neutral.
When me:thyi. 01r.a.ng e. (M. 0. ) .U u.¢ eel C1.6 i.ncU.c.CI.:taJt, :the. c.a.towr. c.hCI.ng e.c,
6Jtam yellow to red •
5. The experiment is now repeated, using the same volume of alkali and the same
volume of acid, that has been added, but without indicator.
6. Finally, the salt solution is evaporated to the crystallising point, allowed to cool
- 75 -
Chemistry IGCSE
(Dr. Fa thy Abdel Galil)
Making insoluble salts
Salts which do not dissolve in water have to be made by the process ofprecipitation.
Precipitation is the formation of it solid when two solutions
)>
are mixed together.
Making the insoluble salt lead sulphate [pb SO.]
1 soluble lead salt+soluble sulphate
sodiurTI sulphate
scilution
Je3d nitrate
solution
The two solutions are mixed
together. An insoluble precipitate
of lead sulphate is formed.
sodium
nitrate
solution - - - I t
precipitate of
lead sulphate···-----.;:;_,_:_"'-'-~'-'
General
reaction:
soluble
salt
Word
lead· ••.. + .. .-"sodium - +
.
••• ,
ul h
rntrate •·•· ····s p ate
equation:
+
soluble
salt
-+
insoluble . +
salt
soluble
salt
lead
sulphate
sodium
nitrate
+
Symbol
equation: Pb(N0 3 ),(aq) + Na 2 S0 4 (aq)-+ PbSO,(s) + 2NaN0 3 (aq)
i
(aq) means in aqueous
solution
(aq)
(aq)
+
(s) means an
insoluble solid
-+
(s)
+
(aq)
These state symbols show that a precipitation reaction has happened.
2
lead sulphate is filtered off
arid washed with distilled
water and then allowed to dry.
}>
Making the insoluble salt silver chloride [AgClj
AgN03 (aq)
ionic equation:
Ag+
+
NaCI (aq)
-7
AgCI (s)
+
cr
-7
AgCI
. .· .
~
+
NaN03 (aq)
Chemistry !GCSE
(Dr. Fathy Abdel Galil)
- 76 -
Water of cryst:z!lisation
Some salts contain water molecules in their crystal lattice. These salts which
contain water of crystallization are called hydrated salt.
Here are some exampl~s of hydrated salts :
Name
EalUE~
Magnesium sulphate
HgS0 4 ·7 H2o
Cobalt chloride
CoClz • 6 H20
carr~~<rr)~~irh;t~
-
c~so~:s-H;o
_____ _
If the water is removed by heatipg, the crystals often change in
appearance and the anhydrous salt is. fo-rmed;·'
Heating copper( 11) sulphate crystals (hydrated)
1 /~'
I r: ,..
--
.1/1' - - - 7.----
3. S~eam ~ g~ven a66
2. Canden.;atian a.t ~he ~ap
a6 ~e ~ube
copper(II)sulphate
crystals (hydrated},_~~::_-
I. Ca.tawr. c.ha.ng <U 61Wm b.tue -·-> wiU:te
de.hydnttion
CuS0 • 5 H 0(s)
4
+
2
hydrated copper( II) sulphate
(blue]
hydnttion
anhydrous copper( II) sulphate
[white]
Wh_-n these. blue- crystals are heated, steam is given off and the·
crystals change to a white powder called anhydrous copper(II)sulphate.
If water is added to the anhydrous powder, it gets very hot and
changes back into blue copper(II)sulphate (hydrated}.
This is a reversible. reaction. Anhydrous copper(II)sulphate can be
used in this way to test for water.
Test for Water [chemical testJ
Add anhydrous .copper(II)sulphate, the colour changes from white into blue.
Physical test for water
Pure water boils at 1oooc and freezes at ooc
Heating cobalt( I I) chloride crystals (hydrated)
CoC! • 6 H 0(s)
2
~k.
2
.-···
Chemistry lGCSE
{Dr. Fathy Abdel Galli)
- 77
TYPES OF OXIDES
1.
Acidic oxides are usually ~he oxides of non-metals·
Ac.l.d.ic. oxide.
I~:>
. co 2
so 2
(arbon ·dioxide
Sulphur .d__ioxide
-
Sulphur ·trioxide
S0
Phosphorus(III) oxide
P203
NQ
2
Si0
2
Nitrogen dioxid~
Silicon dioxide
3
qxide. ~e4-l:>otuble ?
yes
pH 6
yes
p~ l
yes
pH l
yes
pH l
yes
-··..PH l .
no
1.)
Acidic oxides dissolve in water to form acidic solutions.
2.)
Acidic oxides react with bases to form salts and water.
(vu~rbon
-y co
1
.· .
·.·.··.
dioxide + Calcium hydroxide - 7 Calcium carbonate
+ Ca(OH) 2 (aq)
(g)
(lime water)
Explain why carbon dioxide turns lime water milky 7
o.§.
... .b. ~s-AJ..t$..~.. t~ .LJ'n.S. ..+~ . ~~.Ql~te. ~r't~.p.p. h,.c.a£
2.
Basic oxides· are the oxides of metals
I..s a~~ ~~ Joluble f
Potassium oxide
K 0
2
yes
pH 14
yes
pH 14
Calcium oxide
Na o
2
CaO
yes
pH. 12
Magnesium oxid e
MgO
no
Copper(II) oxide
CuO
no
Iron(III) oxide
Fe o
2 3
nci
Sodium oxide
1.)
They react with acids to form salt and water
CuO + .H2S04
2.)
-) C)lS0 4 + H 20
If they dissolve in wat er they form alkalin~· solutions •
Na 20(s)
+
H20(l)
)
2 NaOH (aq)
Chemistry IGCSE
(Dr. Fa thy Abdel Cali!)
- 78 -
;.· ·
3.
Amphoteric oxides are the oxides of certain me tals . e.e. aluminium, zinc
7
\e.c:J
They have the properties o f both acidic and basic oxides,
i.e. they react vith both_alkalis and acids to form salts and .'Wa ter,·
Ampho.tvr.J..c. oudu 'a.Jte. .<.n.oo.tub.f.e .<.n. u.u.t.Vt.
Aluminium oxide + hydrochloric acid
+
Aluminium chloride + water
6HCI
2 AJCh
Aluminium oxide + Sodium hydroxide
4.
Sodium aluminate
+ water
Neutral oxid e s are the oxides. which do not dissolve in acids or
:.:·:
alkalis. e.g. NO_, CO ,
basic. oxides
(oxides of metals)
acidic oxides
(oxides of-non-metals)
alka~~--r-~
salt+ water
'r"-
acid
or alkali
amphoteric oxides
(Ah0 3 and ZnO)
Question: Complete the table that shows the reaction, if any, of the oxides with acid and
alkali. Indicate a reaction with "R" and no reaction with "NR".
oxide
type of oxide·
magne·sium oxide
basic
aluminium oxide
amphoteric
silicon(IV) oxide
acidic
reaction with acid
reaction with alkali
··.·
-(3)
Chemistry IGCSE
[Dr. Fathy Abdel Galil]
- 79 -
·:-·
Identification of Ions
Test for Anions
Anion
Test·
Carbonate
Add dilute acid
2
ceo; J
Result
-
Effervescence, co
produced
2
(turns limewater milky).
(e • g. dil. hydrochloric acid)
Chloride (CI-)
[In sol.ut!on]
Acidify, then ·-add
. aq. silver nitrate
White ppt.·.. of .1\gCl
Acidify, then add
White ppt. of PbCl
Ag+ + Cl- -+
AgCl
2
aq. lead nitrate
Iodide ( I )
Acidify, then add
Yellow ppt, of Agi
[In solution]
aq. silver nitrate
(or Pbi )
2
(or lead nitrate)
.
Sulphate (S0
2-
4
)
[In solution]
Acidify, then add
White ppt. of Baso
aq. barium chloride
Ba 2+ + S0 2"4
(or barium nitrate)
-+
4
naso4
..
Nitrate (NO;)
Add <J.q. sodium
Ammonia produced
Tin solution]
hydroxide, then little
(t;urns damp i:ed litmus
aluminium powder),
paper blue).
warm· carefully
)> Complete the following table to differentiate between hydrochloric acid, sulphuric acid
and nitric acid
Test
Add aq. silver hitrate
. Add aq. barium chloride
HCI (aq)
H 2S04 (aq)
HN03 (aq)
Chemistry IGCSE
(Dr. Fa thy Abdel Galil)
- 80 -
~:.
Test for Cations
{
r
Result ofadding
aqueous ammonia
Result of adding
aq: sodium hydroxide
'
Cation
.
Copper (II) [ Cu
Blue ppt. of Cu(OH) 2 ,
]
'
'
Cu2+ + 20H- -7 Cu(OH)z
[Fe 2 +J
Fe(OH)
2
- - -'
excess~
.
- - .. ------ - . -
Dirty-green. ppt ,__ inso.luble ·
Dirty-ereen ppt. of
'
~
' giving dark blue solution
' .
insoluble in excess
Iron ( II l
-
--- ---. . :Blue ppt. soluble in
~
2+
insoluble in
in excess
{tuAno -~ed-b~own
on the .OWt.6a.c.e due ;to
axJ..da.tio n)
excess
Iron (Ill)
[Fe 3+]
Red-brown ppt. of Fe(OH) 3
Red-brown ppt. insoluble
insoluble in excess
Fe3+ + 3 OH ---+ Fe(OHh
in excess
. ----- - -- - '
- - -- - - - -White
ppt. soluble '
~
2
Zinc [ Zn +J
•
I
' White ppt. of Zn(OH) 2 '
soluble in excess {g.iv.Wg 1
I
\ a. c.o.towU'.e.o.o .o o.e.u.ti.o n J / •
...
- - - -----_....
--
3
Alumlnlum [A! +]
I
'I
/
, t
I
I
-
---- of Al(OH) -
White ppt.
3 ' \
soluble in excess {g-iv-ing,'
1 a.
c.o.towU'.e.o.o 6otut£on)
\
I
in excess {g-iving
I
I
( a. c.a.to u4e.e.o.o .o o.e.u..ti.o n) ,
'
... /
- - - - -
-
-
White ppt. insoluble in
excess
' - --- - - - -- /
[A.t{OHJ 3 and Zn{OHJ 2 ~e
0111photeM.c. hyd.Ao xJ..de.o l
Calcium [ ca2+]
White ppt. of Ca(OH)
2
No ppt.
insoluble in excess
Ammonium [NH:]
Ammonia is produced
on warming with uq.
sodiu1u hydroxide
...
~
•..
~
.
- 81 -
Chemistry I GCSE
Topic 8.
(Dr. Fathy Abdel Galli)
Metals and Reactivity Series
Physical Properties of Metals _
1,
Metals are shiny (lustrous) Yhen freshly cut and polished.
2.
Hetals conduct electricity because the electrons can move about
inside the structure,
They have usually high densities
3,
because the atoms are packed
closely together in a giant
structure,
They usually have high melt'ing
4.
points and boiling points.
5.
They are malt~bte (can be hammered and rolled into shape)
and du.ctU.e (can be stretched
into wira). This is because
when force is applied to metals,
the la~Jars of a toms can slide.
over each other.
6.
Hetals are good conductor.s of heat •
...............................
.
. . . . . . . . .. . . .. . ..... .. ... ... . . . .." ......................................... .
~--y~·············~·························
Alloys
1.
An alloy is usually a mixture of two or more metals or of metal
and a non-metal.
2.
Alloys are formed by mixing molten metals together and allowing
them to cool.
Ex.ampleo on rllo y~o . :
B4aoo ~ an aLLoy on eopp~ and ~e.
&.onze ~ an aLLoy on c.opp~ and .tin.
S.teeL ~ an aLLoy o6 .UC.on and c.oJr.bon;
Chemistry I GCSE
(Dr. Fathy M. Abdel Galil
- 8 2-
Alloying often results in metal which is
stronger. than any one
of its eomponents. For example, b~L>, which is an alloy of copper
and zinc is stronger and harder than the pure metals.
The following is a diagram showing the structure of an a.lloy
·.·
0
•
me,.ta.£ a.to m6
o;thvr. metal dom6
Uses of Metals related to their Properties
Aluminium
high electrieal
conducllimy
yens;cy
(ov/
overhead
C<l.b!es
aircraft
(aeroplanes)
carengihes
Ov e.Jthea.d a1.wrU.iU.wn
el.ec..tlr)_c.al. c.a.b.te6
ha.ve a. L>.tee1. co11.e.
window frames
cans
Food containers
aluminium
The L>.teel. c.o11.e
L>.t11.eng.then6 ;the
c.a.b.f..e.
g£EE0_.:
I.t L6 u.oed e.g. : 1. In· el.ec:tiUc w.Ute6 bec.a.u.oe c.oppeJr. L6 du.c.t.Ue, a: good .c.andu.c.tolt
o6 el.ec;tJUcA.:ty, on .tow Jtea.di..vU!f a:nd haL> a. IU.gh m.p.
2. In c.oo!U.ng u;tert.6ili beCJJ.LL6e c.oppvr. L6 a. good c.ondu.c.tolt o6 hea-t.
3.
Making brass which is an alloy of copper and zinc
- 83 -
Chemistry I GCSE
(Dr. Fathy Abdel Galli)
Reactivity series
K
.l
::;
extracted by
electrolysis
a..tta.c.k
Lll:lteJL --r hy d!to :Ude.
+
Hz
Jtea.c.t.
Mg
C-+
A.t
Zn
.....-.._,. ->a..U + Hz
a.tta.ck ;,.te.a.m ---'7 o:Ude
+
..
Hz
Fe
o:Udu
a.Jte. Jte.duc ed
w.Uh c.Mbo rt
w.Uh
d.Uu..te. a.cJ.do
Pb
(H)
Cu
Ag
Au
Action of· Water on Metals
a)
Potassium, Sodium, Calcium
--------------------------
Reactive Metal + Water ----7 Metal Hydroxide + Hydrogen
Potassium and sodium react violently
+----+-Hydrogen
· with cold water, ( see page-49 J
Calc·ium reacts raadily but not violently
Water
with cold water to form hydrogen and
calcium hydroxide solution, the alkali
-U.me wct.te.Jt.
Calcium reacts
steadily wi!h walet.
calcium + water ----7 calcium hydroxide + hydrogen
Ca (s) +2H20 Q) --'-+
Ca(O~ (aq)
+ H2 (g)
St~te two observations you could make when a small piece_ ofcalciu~ Is added to cold' water.
Observation 1 ·-···-····-·····--··················--···--.--........... - ................- ................................................ ..
Observation 2 ·-·-·-·--------................................................................................................................... [2]
- 84-
Chemistry IGCSE
(Dr. Fathy Abdel Cali!)
Magnesium
Reacts very slowly with cold
water to form hydrogen and
magnesium hydroxide.·
rI
When heated in steam, magnesium
turns to a white powder (magnesium.
oxide)
Magnesium
Mg(s)
-->
+ H 2 O(g) ·->
+ _Steam
Hydrogen
burn1ng
Heal
Magnesium oxide
+
Hydrogen
• • • • • • • • • • . . • ( s)
+
• • • • • • (g)
React only with steam to form hydrogen
and the oxide.
Reaction with Dilute Acids
Metals above hydrogen in the series react with dilute acids and
hydrogen is produced. This is a displacement reaction in which the
metal displaced the hydrogen of_ the acid.
+
hydrochloric add ....-...;:. rinc chlor-ide
Zn(s) +
- - 7 .......... ..
ri nc
zinc
+
sulphuric acid --->- rlnc sulphate
+ hydrogen
+
+
hydrogen
Zn(s) +
It is too dangerous to react the very reactive metals potassium and
sodium with acids and would caitse aplosion.
)> Aluminium seems to be unreactive due to the protective layer of
Al203
.
)> Remember that Cu, Ag and Au do not react with ·,vater, steam and
dilute acids.
)>
-(Dr. Fathy-Abdel ·calif)
- 85-
Cherr:lstry IGCSE
Making hydrogen in laboratory:
Hydrogen is _prepared in laboratory by reacting zinc or magnesium with
-dilute hydrochloric acid or sulphuric acid.
acid
hydrogen
water
zinc
Reaction of Metal Oxides with Carbon
Carbon, on heating, will reduce the oxides of zinc and of metals below it
in the reactivity series.
iron (Ill) oxide _+
··Fe 0 2 3
+
carbon ---~ iron
+ carbon dioxide
.; c
+ .. co
~··Fe_
2
Competition for Oxygen :
[Reduction of metal oxides by a more reactive_ metal]
A metal oxide can be reduced tr:_ ·.:he metal by heating it ·with another
metal which is above it ir, <.:i)e reactivity series, i.e. more reactive.
iron( Ill) oxide
+ aluminium-+ Iron
+2 AI
i.-e. Aluminium is more
r~active
-------7 2 Fe
+ aluminium oxide
+ A! 2 0
3
metal than iron.
It combines with oxygen more strongly, so it can reduce iron oxide.
:;.·:
:
.
- 86 -
Chemistry !GCSE
(Dr. Fathy Abdel Gali!)
:.··
Displacement Reactions
Any metal will displace one lower in che reactivity series from aqueous
solutions containing its ions.
If a piece of iron is placed in copper(II) sulphate solution (blue), a
reddish-brown deposit of copper forms on the"iron and the blue colour of
·che solution fades.
This is a Jr.edox reaction in which iron atoms are oxidised by loosing
2+
2+
two electrons and going into solution as Fe
ions; Cu
ions are reduced by gaining tWO electrons and forming a solid deposit of Cu atoms.
Fe(s)
+
CuS0 (aq) ----7 FeS0 (aq)
4
4
ionic equation: Fe ( s)
+
Cu
2+
(aq)
----7 Fe
2+
(aq)
+
Cu(s)
+
Cu(s)
A metal cannot displace another above it in the reactivity series. Thus,
if a piece of Cu was placed in iron(II) sulphate solution, no reaction
occurs.
Similarly, copper does not displace magnesium. from magnesium sulphate
solution, but copper displaces silver from silver nitrate solution
(silver is below copper in the series).
Finding the order of reactivity of metals :
Ey placing a metal in an aqueous salt solution of the other metal
and observing if displacement takes place or not.
aqueous solution
Iron·
zinc
copper
sliver
zinc sulphate
Iron (II) sulphate
__,_______
-p~~~~ry/.07/,ry~--------4
copper( II) sulphate
silver nitrate
V
=
= no reaction
r.eaction occurred
Arrange the above elements in order of their reactivity (the most
reactive metal first)
l.
.. .
...... ..
2.
3.
. ......... .
4.
(Dr. Fathy Abdel Galil)
- 87 -
Chemistry IGCSE
.·.:
Things to remember about the reactivity series :
1. The tnore reactive the metal, the more it 'likes' to form compounds.
S~ only copper, silver and gold. are ever found as elements, i.e.
uncombined in the-earth's crust The other metals are always found as
compounds : oxides, carbonates, sulphides and chlorides.
2. The more reactive the metal, the more stable its cr.'mpounds. A stable
compound is difficult to break down or decompose.
Compare what happens when these hydroxides and nitrates are heated.
Action of Heat on Metal Hydroxides and Metal Nitrates
/Metal
II
Hydroxide
Nitrate
II
do not decompose
K
KOH
Na
NaOH
Ca
Mg
AI
Zn
Fe
heat
heat
heat
)
Ca(OHh
heat
.
I no reactwn
ZKN03(s)
I
1 metal nitrite+ oxygen
heat I ZKN02(s) + 02(g)
i no reaction
metal oxide + water
heat ) CaO+H20
decomposition gets easier down the series
heat
metal oxide,' nitrogen dioxide
(brown gas),+ oxygen
heat
2Ca(N03)2
I 2Ca0 + 4N0 2 + 0 2
decomposition ·gets easier down the seri ~s
)
Pb
Cu
Cu(OH)2
blue
heat
CuO+ H2 0
black
)
2Cu(N03)2
blue
heat ' 2Cu0+4N0 2 + 02
black
The breakdown of the compound by action of heat is called thermal decomposition.
Extraction of Metals:
Metal
Ore
Compound
Formula
Method of Extraction
A!
Bauxite
Aluminium oxide
Al203
Electrolysis of molten Al203
Fe
Haematite
Iron(III)oxide
Fe203
Reduction of the metal
oxide by coke (carbon) in a
blast furnace
.
Zn
Zinc blende
Zinc sulphide
ZnS
Ore: minenil found in the earth's crust from which metal is extracted
Chemistry I GCSE
(Dr. Fathy Abdel Ga!ll)
- 88·-
Extraction of Iron
iron(III)oxide; fe 2 o ; in
3
large quantities, by reduction in a blast furnace.
Iron is extracted from iron ore, haematite;
1.
Iron ore, coke and limestone are added at the top of the blast
furnace. A blnst of hot air causes the coke to burn.
2.
carbon
+
oxygen
carb.on dioxide
C(s)
+
o 2 (g)
C0 (g)
2
The carbon dioxide rising up the·furnace reacts with more coke·
to form carbon monoxide which reduces the iron oxide to iron.
carbon dioxide
+
+
irori oxide
.;.
carbon
C(s)
carbon monoxide
2 CO(g)
----;>->-
carbon monoxide
Iron
2 Fe
+ carbon dioxide
+ 3 Co
2
As iron reaches the lower part of the furnace it melts and runs
to the bottom of the furnace.
3.
The purpmse of limestone is Co remove the s~ndy impurities,
mainly silicon(IV) oxide [Si0 ).
2
a)
Limestone is decomposed by heat
calcium carbonate
____,..
calcium oxide
CaO
b)
Th~· basic
!1
+ carbon dioxide
+
co .
2
oxide, CaO reacts with Si0 , an acidic oxide to form
2
liquid slag which runs down to the· bottom and floats on top
of iron.
.. ·
•
calcium oxide·+ silicon dioxide --,.~) calcium silicate (slag)
Ca')
+
SI0
2
----;>
CaSJo
3
- 89 Chemistry IGCSE
(Dr. Fathy Abdel Galli)
Cast Iron
The iron produced in a blast furnace is .called cast iron. It is brittle
and impure [contains about 3 - 4~ carbon]. l1ost cast iron is converted
into steel.
Making Steel
Oxyg~n is passed tl:ir.ough the molten .rron [ containing .
3.:4% carbon], where carbon is oxidised into carbon
dioxide and pure iron remains. The required amounts
of carbon are added.
molten iron
containing
. imr:>urities
/,
~~-~~~~-1~~-~2£~-~~~~lL-l~~q-~~2~1
contains about 0.25;1; carbon, u·sed for car
bodies and machinery.
As the carbon content is increased, the steel
becomes stronger and harder. In o.ther words,
steel has a range of hardness depending on the
car body
percentage of carbon.
z.
!i~a!!-_£!¥.E2£!!_~~g.!?:f
contains about 1% carbon, used for railwey lines and _bridges and building construction
3.
e.g.
stainless steel [doe.> no.t IU(h.t},
contains nickel and chromium,
~·.
and is used for cutlery and surgical instruments.
and chemical plants
cutlery
- 90-
Chemistry lGCSE
(Dr. Fa thy Abdel Cali!)
···.,.
Extraction of Zinc
Zinc occurs as the sulphide, ·zinc blende; ZnS.
l.
The blende is roasted in air to the oxide
':.
zinc sulphide + oxygen (air) ---7 zinc oxide + sulphur dioxide
2 ZnS(s)
2;
----') 2 ZnO(s)
Zinc oxide· is then reduced with carbon (coke) 'in a blast furnace.
zinc oxide + carbon - - - 7 zinc
2 ZnO(s)
+ C(s)
+ carbon dio;x:ide
2 Zn(s) + co (g)
2
Uses of Zinc
l.
~~!~~~!~!~g-~
The metal is used to protect steel objects from rusting; the
zinc. coating (galvanising)· corrodes instead of steel.
.2.
..
~~!~~-~E~~~-~
Brass is an alloy of copper (60%) and zinc (40%).
·~
RecyCling Metals
All metal'S can be recycled, that is, to melt down used metals and
use them again rather thac throw them nway.
R~cycling
makes sense
because :
l.
It saves money and energy for extraction.
2.,
It saves mineral resources since resources of or.es are limited
and cannot last forever.
3.
<.:.
It solves the problem of waste disposal. Re.cycling metals stops
them causing pollution and spoiling the environment.
Re.cye.U.ng o:the.Jt ma.teJUaLs :
G!a..6.6, pa.pe.Jt, cl.o.th a.nd p!.a.olie.6 ca.n a.U be. Jr.e.cyc.f.e.d. Foli. e.xa.mp.C..e.,
o.e.d g!.a.o.6 bo.tte.u can be. meLted dawn :to ma.k.e. neW bo:t:Uu. T!Uo
-"a.ve.-0 Jr.e.haUJi_ce.-6 a.nd .oo.tvu paUu.tion pltob.te.m-6.
.,:
(Dr. Fa thy Abdel Galil)
- 91 -
Chemistry IGCSE
Rusting
l.
The. corrosion of iron and steel is· .called ·IULbWrg ,·
·-2..
Rust is the red-brown flaky nolid which forms ons iron and steel.
3.
Rusting is the. slow oxidation of' iron to for.rt hydrated iron(III)
oxide. This is the. chemical name. for rust.
Both ~ nnd waXe4 are needed for. rusting to occur.
4.
Iron + oxygen + water --;.-hydrated iron(lll) oxide
5.
(rust)
Rusting occurs .rnrticularly quickly in water containing dissolved ionic impurities - such as sea water.
;
);> Suggest what elements rust contains.
•oooooo••••~••••.••••••••••~•••.•••<oooooooooouoooouooooooooouooooooooouoooooooooooooooo.oooooo••••••••oooooouooOO!''"''uoonoooooooo
What happens when rust is heated 7
.........................................
······~· . ···········~·· . ,. ........ ·.
Z. _conde.Ma..Uon
Name the solid-left :
Air and water
TUBE A
TUBES
Boiled water
Dry air
TUBEC .
TUBED
oil to slop ·
air dissolving
In the water
distilled
water
sea
water
boiled
nails
heavily
rusted
naUs
rusted
no
no
rusting
rusting
An e.xperimenc co investigate the conditions needed for roscing.
'
Chemistry IGCSE
-92-
[Dr .. Fathy Abdel · Galil)
Methods of Rust Preven-tion
1.
Iron and.ateel can be protected from rusting_ by preventing air
and water from reaching the surface. This can be done by painting,
oiling, galvanising or electroplating the iron surface.
2,
s~~6icial p4ote~on
: Block of magnes~um ~r zinc are attached
to the iron, e.g. ships' hull or underground pipes. The magnesium or zinc (being !!lOre reactive than iron) ar~ oxidised in
preference to the iron.
,..
zinc blocks fixed to hull
)> Zinc blocks are attached to the steel legs of oil platforms (oil rigs)
!•
.· -·
sea
(i.) Explain why the zinc blocks prote.ct the steel legs
from rusting.
[2]
(ii) From the reactivity series name ariother metal that
could be used for the blocks in place of zinc: [1]
(Dr. Fathy Abdel Galli)
-93-
Chemistry IGCSE
Topic 9. CHEMICAL CHANGES
ENERGETICS OF A REACTION
All chemical reactions involve an energy change (ll. H). This energy is
in the form of heat.
An exothermic reaction is a reaction, which releases energy to the
surrounding, i.e. heat is given out (the reaction mixture becomes hot).
An endothermic reaction is a reaction, which absorbs energy from the
surrounding, i.e. heat is taken in (the reaction mixture becomes cold ).
exothermic reaction:
endothermic reaction:
HEAT
/
t
HEAT
HEAT
· w·here does the energy change (ll. H) come ..from ? :·
In chemical reactions bonds are broken and new bonds are formed.
Breaking bonds requires energy. It is endothermic.
Making new bonds gives out energy. It is exothermic.
If the energy given out is greater than the energy taken in, the reaction will
be exothermic.
>- the following is equation for the combustion of methane (natural gas)
CH 4
H
I
I
+
2 02
o=o
H-C-H
H
.->-
and 2 x 0=0
o=c=o
o=o
We need to break these bonds:
4xC-H
+
We need to make these bonds:
2 X C=O . . . .
and 4 x H-0
- - -
Explain using the idea of bonds forming and breaking, why the above reaction
is exothermic .........................·......................................... ·.· ...... -··.--·-........................................................................................................
[Dr. Fathy Abdel Galil)
-94-
Chemistry IGCSE
Examples (or exothermic reactions:
'
1. All neutralisation reactions are exothermic.
When dilute hydrochloric acid reacts with sodium hydroxide
solution, a neutalisation reaction happens.
hydrochloric acid
HCl(aq)
+ sodium hydroxide-+ sodium chloride + water
+
NaOH(aqj
--+
NaCl(aq)
+ HiO(l)
fmal
temperature= 34°C
initial
temperature = 21 °C
temperature rises by (34.,.. 21) = 13°C
> Why a polystyrene (plastic cup) is used instead of a beaker?
More heat resistant
....................................................
)>
Predict what the temperature of the reaction mixture in the
experiment would be after 1 hour. Explain your answer.
will be the
.21. .degrees
. . . . . .celsius
. . . . .because
. . . . . .heat
. . . will
.. . .be
. .lost
. . .to. surroundings
. . . . . . . . . and
. . . temperature
. ..
same as when it started
2. All displacement reactions are exothermic:
7
MgS04 (aq) + H 2 (g)
7
ZnS04 (aq)
+ H 2 (g)
By measuring the rise in temperature we can find mit the order of
reactivity of metals.
Chemistry IGCSE
(Dr. Fa thy Abdel Galil)
- 95-
Examples (or endothermic reactions:
2 NO(g]
1.
This means that energy is
2.
needed for the reaction to take place
Thermal decomposition..
Melting of ice and evaporation of water.
3.
PRODUCTION OF ENERGY
,·,>1
Burning Fuels
Fuels release heat energy when they burn in air or oxygen. ~
burning reactions are exothermic.
Natural gas
i~
largely methane,. When it burns,
methane + oxygen ~carbon diox1de + water
J
------1- co
)
)
CH
4
+ z 02.
2
he.a..t .{;,
given 'ocU
Ethanol (used in cars in Brazil). When i t burns,
ethanol
+ oxygen --7 carbon dioxide + water
+30
2
--72C0 .
2
+3H 0
2
) he.a..t .{;,
J given aU-t
)
What is needed for a fire ?
Hydrogen as a Fuel
Hydrogen is a possible energy source of the future. Hydrogen can be used as a fuel for cars.
It causes no pollution because the only product of combustion is water.
Nuclear Energy
Uranium- 235 as a source of energy [see page !9].
-.----~----
~-
,_
···- ..
..
Chemistry IGCSE
-96-
(Dr. Fathy Abdel Galil)
Comparing the amount of energy produced by the burning of different liquid fuels:
The apparatus below could be used. The same mass of each fuel is burnt in turn.
The initial and final temperature of the same v-;iume of water is recorded
metal
container
f--
thermometer
clam p
:.·
water
i)
wick
draught
shield
j
0:,
t
:~:~·
......"r.
r----
-----
spi rit
bu mer
l iquid
.:.-
fuel
Questions:
Suggest how you could work out which fuel produced more energy .
By seeing which fuel has the highest temperature and which fuel boils the water faster
. . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . .
. .. ... . . . .... . . .
.. . . .. . . . . . . .. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
What are the sources of errors in the above experiment?
............................................ ; ................ _- ............ .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - ... ' .
I.
-97-
Chemistry IGCSE
(Dr. Fathy Abdel Galil)
-.-.·
Electricity from Chemical Reactions :
Cell :
a device to produce electrical energy from a chemical reaction
This is the reverse of what happens during electrolysis, where chemical
reactions are brought about by the use of electrical energy.
Electrolysis (endothermic)
Electrical energy ----------__:~ Chemical reaction
t
Cell (exothermic)
Simple cells
Two metals
that are far apart from one another in the reactivity
series are placed in an electrolyte. The more reactive metal becomes
the negative pole from which electrons flow.
The amount of electricity produced (voltage) depends on the position of
the metals in the reactivity series, The rule is :
The further apart the metals are in the reactivity series
the more electricity is produced.
voltmeter
Mg
AI
copper - - - l l l
Zn
Fe
Pb
H
Cu
Ag
Au
dilute acid
:>
The voltage of an -ironicoppercell is about 0.8 volis.
Predict whether the voltage of a zinc/copper cell would be less; the s·ame ar
bigger. Explain your an?Wer.
·
It would be greater than iron/copper cell because the standard cell potential for the zinc/copper cell is
approximately 1.10 volts.
.,-.,-.-.-- "''"'"~'··-.-.··.----,-----:-..-.-;-
··--· -- -- ....
Chemistry !GCSE
(Or. Fathy Abdel Cali!)
- 98-
The simple cell can be used to compare the reactivity of two metals
l.
The more reactive metal is the one which loses electrons and
i~e.
passes as ions in the solution,
2.
becomes thinner;
The direction of flow of e- is from the more reactive metal
to the less reactive one.
Question :
:::::=========
How could the simple cell shown below be used to find out if zinc
is more reactive than cadmium ?
·-
voltmeter
zinc
cadmium
electrode
electrod.:;
-=1--- dilute sulphuric
acid
...............................................................................
•
•
•
..
•
0
•
0
.......................................
0
0
•
0
....................
0
..............
.
The Zinc Carbon Dry Cells: [Batteries]
Batteries are convenient source of energy because they are portable and
small, and are used in toys, radios, torches and many other things.
-99-
Chemistry IGCSE
(Dr. Fathy Abdel Cali!)
·.·.·
Topic 10.
CHEMICAL REACTIONS
-Rate of Reaction
The rate
l.
of a chemical reaction can be increased by :
l/,_a_king the size of reacting par·ticles smaller, i.e. increasing
the surface area of the reactants.
2.
Increasing the. concentration.
j·:
Iricreaaing the temperature..
4.
Adding a suitable catalyst.
5.
Light (applied to a few re.actions).
Plotting Graphs of Reaction Rates
FoUow.i.ng IUJ.;te o6 1r.eac.tion by mea..&UJU.ng ga..& vo.twne :
Take for example the reaction between magnesium and excess dilute
hydrochloric acid :
magnesium + hydrochloric acid--+ magnesium chloride +
Mg(s)
+
2 HCI(aq)
Measurements made are
---+
MgCI (aq)
2
+
gas volume and time.
__,.. the plunger can move out
gas s.yringe
stop clock
The volume of gas in the ayrin•;e is noted at intervals, for exal'lple
at the end of each half-minute,
How would you know when the reaction is complete ?
...........................................................................
- 100-
Chemistry I GCSE
(Dr. Fathy Abdel Galil)
Here are some typical results:
Time/minutes
0
l
1
ll
2
2!
3
3!
4
4!
5
5!
6
6!
Volume of hydrogen/em'
0
8
14
20
25
29
33
36
38
39
40
40
4D
40
These results can be plotted on a graph, as shown
'.
Shape a 6 .the GJtir.ph
I.
The 6a..o.tvr. .the II.e.ac..Uon,
curve llal,
raacllon over
.the. <>.teepvr. .the. cWLve.
curve· loss sleep,
reaction slower
, 2.
When .the II.e.a.mon ;_;, ovvr.,
.the cwr.ve goe.<> u.f.a..t.
curve steepesl,
teacllon fastest
The reaction is which a gas given off, e.g. an acid and Ciirbonate, the rate of reaction
can be followed up by measuring the decrease in mass of reactants .with time.
i.e. the balance reading decrease as the reaction takes place.
/
fast
.
add
, ..
ca.f.uwn
cMbona..te.
slow
time (s)
Chemistry IGCSE
Investigating the Rate
(Dr. Fathy Abdel Galil)
- !Ol -
of a Reaction
Effect of particle size
This effect can be examined by reacting equal masses of calcium
carbonate with different particle sizes (e.g. chalk powder and
marble chips) with equal volumes of the same hydrochloric acid.
The volume ~f. th; _produced co 2 can be measured using a_~as syringe
and is plotted against time.
B ~ U<Sing maJtb.te. chip~
A = U<Sing c.ha..£.11.
powde;t
gas syringe
2
3
Time/minutes
Curve A is steeper than curve B; this shows immediately that the
reaction is faster for the powder calcium carbonate.
The result shows :
The rate of a reaction increases when the surface area of a solid
reactant is Increased.
The danger of explosive combustion with fine powders and gases
[e.g. flour mills and mines] :
F.toW!. ht a. ba.g -L6 di£ 6-{.c.uU :to bW!.l1.. A m.ix.twr.e. o6 {toW!.-duo:t a.rid
a.Lt ma.y e.xp.tode. i6 ~paJtk.e.d.
Why 1A th-U ?
'
..•.••.••••.. • ..... • • • • • • • • • • • • • • • • · • • • • • • • • · • · • • • • •
................................................................... .
4
5
Chemistry I GCSE
(Dr. Fathy Abdel Galil)
- 102-
,.'.
Effect of concentration
A reaction can be made to go faster by increasing the concentration
of a reactant.
T/U.6 if, 6ec.aJ.L6e -<.ncJtl211ll-<.ng .the c.onc.en.tM.:t<.on on .the Jtea.cta.n:U -<-ncJteJUV>
the numbeJT. on c.oUJ.l..(.otW between pCl.ll.ti.c.tec, and, .theJT.enoJte, .(.ncJteMe6
.the tu:Lte 0 n JU!.ac.tio n.
T/U.6 a.tbo exp.taJ.iU Whlj .the gJtea.;tec,t Jta.te on Jtea.c.tion if, u.Wa.U.lj CU. Man
cu. the uacta.n:U Me nU.xed,- i.e. thelj Me both at thUJT._ JU-g hut c.one:ert.Vc.a.tio r«>. M the Jtea.c.tio n pJr.oc.eed6 the c.o nc.en.tM.:t<.o IU an the h.ea.c.t-<.ng .o u.b.ota.nc.u decJtea..o e and the tu:Lte o6 Jtea.c.tio n decJteJU e6 .
( i)
(ii)
The effect of "concentration can be shown by doing several experiments using equal masses of magnesium ribbon and hydrochloric
acid of different concentrations.
The effect of concentration can be also shown by investigating
the rate of the reaction between sodium thiosulphate and hydrochloric acid :
add dilute acid
and start timing
·view from
above the
flask
sodium
thiosulphate
solution
·....
cross drawn --f._;~_.--,
. on paper
'·-··-·· ·············-· .:
·........... ........''··.
~
At first the cross could be seen clearly. When the solution
became cloudy and the cross was no longer visible, the clock was
stopped and the time recorded.
The c.tou.fuec,.o if, due to the pJr.eup~on on .wlphu.Jr., (yellow) •
A series of experiments can be carried out using a solution of
sodium thiosulphate and hydrochloric acid of different concentration.
The results show that the more concentrated the solution, the
faster the rate of reaction.
\'
t=.
Chemistry IGCSE
- 103-
(D.r. Fathy Abdel Galli)
Effect of catalyst
A catalyst is a substance vhich speeds up the reaction but remaitls
.chemically unchanged at the end of the reaction. Enzymes are biological catalysts. [protein innnturc I
At room temperature, hydrogen peroxide decomposes very slowly·.
If a cacalyst called manganese(IV) oxide is added, decomposition takes
place very rapidly.
If the manganese (IV) oxid-e J.s ;filtered off at the end of the reaction,
washed, dried, and reweighed, it will be found that its miss· has not
changed.
ifuy 1
9tw••••••••••••••••;•••••••••~'••••OOOOOOOPO•••••••'••••oooo••••t
gas syringe
with catalyst
without
catalyst
hydrogen peroxide
lr---solution
manganese (b.Utck )
time
(IV) oxide
nuestion :
daa=•-=•"a.::
The speed of decomposition of hydrogen peroxide is investigated using
different catalysts.
State the precautions which should be taken to make this a fair test :
........ ........................................................................ .
... ... .. .. ..... .......... . ... .... . ... ..... " ........... ' .. ' ............... .
...-
" "
........................................................................ , ................. .
.. " ................................................................................... .
Chemistry I GCSE
Dr. Fathy Al:""'el Cali!)
- 104-
Effect of temperature :
A reaction goes faster when the temperature is raised. When the
temperature increases by 1o•c,- the rate approximately doubles.
Explaining the factors affecting reaction rates:
The collision theory
The reason for an increase in the rate of a chemical
reaction can be explained by the collision theory. In
order for particles to react,.they must collide, and they
must have sufficient energy to react.
92;~S!£~.,:.
··-
,
Uu. .the .Ldea. o6 .the c.o.U.U.Lon :theoJty :to ex.p.&Un .the e06 ec.t; o6 <>uJL6a.c.e
Mea.,· c.onc.ell-tlt.a.-Uon, a.nd :tempeJta.:tu!te on .the ;w;te o6 !tea.c.tion .•••.•. .•
0
0
0
I
0
o 0
o 0
o o 0 0
o o o o o o •
~ 0
o 0
o o o o o 0 o o o o o o o 0 o 0 o o o
o o o o
o •
0
o o o o o o o 0
0
o 0 o o o o
.. o 0
o
. Effect of pressure : (for gaseous reactions only)
Increasing the pressure makes the ··mo-lecules of the gases close to
each other and the fre~uency of. collis~Qn increases and the· reaction
_goes faster.
Investigating the effect of light
~-
The <.peed<. of, <.ome !tea.c.tion<>
lnc.!tea.<. ed by expo<. uJLe :to
.Ugh:t.
When a silver salt is exposed
containing white
to light, silver is formed. The
;Uver chlorid~.t
.suspension.
figure shows an _experiment with
silver chloride. Light has the
Exposed to light
REMOVE
FOil
V
effect of decomposition of
silver chloride.
2 AgCI
> 2 Ag + CI 2
Such reactions which are
affected by light are called
photochemical reactions.
TUBE A:
still while when
foil removed
TUBES:
darkens
Tne effecc of light" on che decomposicion of Silver chloride.
Chemistry IGCSE
-105-
(Dr. Fathy Abdel Galil)
Photography
The deco"mposition of silver bromide· (AgBr) to silver is the basis of
photography. The film is covered with silver bromide. When light shines
on the film, silver is formea. This is the black part of the negative.
The unexposed silver bromide stays white.
> 2 Ag
2 AgBr
white
+
Br
2
black
unexposed
Jt
photographic film
grey
black
remains white
Photosynthesis:
Photo.synthesis is one of the most important reactions involving light.
Chlorophyll is the catalyst. The; ,green chlorophyll in the leaves absorbs
light energy from the. sun and uses it to make(synthesise) sugars from.
carbon.dioxide and water..
sunlight
carbon dioxide + water
glucose + oxygen
chlorophyll
i.e. the process of photosynthesis is endothermic and the energy required
comes from the sun
Respiration:
Respiration is the reverse of photosynthesis and is an exothermic process.
The process of respiration
can be represented as:
..
glucose + oxygen --7
carbon dioxide + water + energy
(Dr. Fa thy Abdel Gal ill
- 106-
Chemistry l GCSE
Reversible Reactions
A Jtevvu.i.b.t~ Jtea.c:Uon, is one which can proc~ed in either direction
depending on the conditions under which it is carried out.
A
B
+
reactants
£o/W!a)td Jte.a.c:Uon ,
ba.dwxvr.d Jtea.c:Uo n
c
+
D
products
For example
ammonium chlaride
:;;::::=:::: ammonia + hydrogen chloride
NH3 (g) _+
NH4Cl (s)
( w:tiite solid)
HCl (g)
·.. {cptilourless gases).
·.
Energy change in reversible reactions:
If a reversible reaction is exothc1·mic in one dit•ection it will he
endothermic in the other.
For example, hydrated copper (II) sulphate (CuS.04> SH:iO) needs energy supplied ·
in the forni of heat to give i!nhydrqus copper(II). sulphate. and water~ When -viater is
ad<ie<Lto anhydrous copper(1I) stilphate·(CuSO~). energy in form of heat"is produced.
Hydrated
copper(.(!) sUlphate
(+ heat energy ]
-7
f-
anhydrous
copper(m sulphate
+water
··chemical Equilibrium __ _
When the rate offorward reaction = rate of backward reaction, the· reaction is said be
at equilibrium.·
· ··
.
At equilibrium, the concentration of reactants and products does not change, - tn fact,
both the forward and backward reactions are stilhaking place.
Factors affecting the position of equilibrium
Effect 'on "equilibrium &fthe.reailon:
Change In concentration
.A + B
ofsubstano/ ·
-
'
c + D
1ncrease in concentration
'·'Proportion o(b!uid Dincreased,
of AorB
I.e. equilibrium shifts to right
Increase In concentration
Proportion of A and B Increased,
of
Cor 0
·-
Le. equilibrium shifts
to left
,,
i
Chemistry !GCSE
-107-
(Dr. Fathy Abde! Galli)
Increasing the temperature makes the reaction !!lOVe in the direction
that takes in heat (.the err.do.theJun.i..c cUJr:e.c.tion).
In other woras,
a) For exothermic reactions, an increase in temperature favours
the· reactants,. i.-e. ma:kes the reaction move to the ];eft.
b) For ~ndothermic reactions, an increase in temperature favours
the products, i.e. makes the reaction move to the right.
N2
+
3 H
2 502
+
02
<-T
2
2 so
3
T-=:==j">
2 NO
+
3,
.. 2 N.H 3
The effect of chanee in gres·sure r for <>'aseous reactions l
:
a:::z:::z:::=m:a=:a::JZJ;:;::.:u::;::::c=a:~at••====c.-:Sit.c-=e=-==•=*'!'.*"':::.:;:a:::;J:..t;:ia;::c;;r:xi2~=~~::t=ti=:Q::=az::.;=x:=o:::.:a:J::=c:
Increasing the pressure shifts the equilibrium in the direction
in which there is decJI.e.4Ue in vohwre, i.e. th.e direction which
produces fewer gas moles.
;;:==·z NH 3 (g)
+
2mol
)> .Predict how the position of equilibrimii might ·change i f there were
an increase·in·the pressure on the f61lowin:g e-quilibria
+
CO (g)
)>
__ 02
+ 2 H2 (g)
Why an increase in pressure does not affeCt the position of fhe following
equilibrium :
2NO(g)
·~-~~·-··············································· .. ························································~········
;::'.
·.-··.
Ch~mistry
-108-
IGCSE
Topic
11.
(Dr. Fathy Abdel Galil) ·
AIR AND WATER
PuM..QJ_c.atio n a 6 wa.:teJL Mppty :
The water from rivers is. first. stored in reservoirs where the process of purification starts.
The water is still, so the larger
particles of dirt can settle out.
At the su:toface, oxygen· and sun- ·
light break down other impurities and kill some bacteria.
The water from the storage rese:z::.voirs. is treated in two stages
1-
Filtration :
===:;::========
It is filtered through heds o·f fine sands to remove suspended (insoluble)
·-
solids.
2-
Chlorination :
:ell:====-=-======
Then it is treated with chlorine to kill bacteria.
PUJte wa.:te.Jt c.a.n be ab.t.abted Mom .6e1t wa.:teJL by liU.:tUJ..a:tWn, bu:t .:tJW,
.U, cut expe.JU.<.ve p!toc.eo.6.
U.6eo o6 wa.:teJL
Household tap water is free from har~ful bacteria and insoluble dirt,
but it is not pure ·in the chemist's sense because it contains gases
and salts' in solu~ion,,
In the. home . :
===.==========
1- Drinking
2- Washing
3- Cooking
Industry uses water in many ways, e.g.
1-
Much water is used for cooling. Power stations are built near
i:ivers or coasts so that they cart. have continuous· supplies ·of.
water for the cooling. towers;
2-
As a solvent: in many industries, e.g. paper industry;
3~
Manufacture of hydrogen and oxygen by ~lectroiysis of water.
Electrolysis of water
Pure. water is a very poor conductor ofelectricity. To enqble water to
conduct eiectricity better, some dilute sulphuric acid is added
Hydrogen gas is fonned at the cathode and oxygen gas is collected at
the anode.
l :.
i·":
(Dr. Fa thy Abdel Galil}
-109-
Chemistry 'IGCSE
Composition ·of air
-
Air is a mixture of gases :
nitrogen 78%
(nearly 'A)
oxygen 21%
Gust over \1;)
-·
----=====:;;;:tt----the remainidg ·1%
I_s~n.e~.riY:.?iu:ugon (a,.8~ble gc
+ a tittle carbon'diqxid.$and.Water vapour
+ sma!l~r amounts ofh~Jium;·neon, krypton
and xe~on (the oth~r-6~blel'gases). : i
..
Sepalr'a..t.{_on a 6 oxygen a.nd /UX!wgen f/wm Uq!Ud lwr.
Fractional distillation is used to separate the pure gases from one
another ..
1-
Air is liquefied by compression._
2-
The liquid air is allowed to boil.
3-
The different components have. different boiling 'points, so ·they
can be collected in turn as they boil aff,
(1) nitrogen .
. (b.p. -: 196"C)
(2). argon
(b.p. -186"C)
(3) oxygen
. (b.p. -183"C)
.·•·
U<> e.6
l-
(Dr. Fathy Abdel Galil)
- 110-
Chemistry IGCSE
o 6 o x_ygen :
Pure, 'medical grade' oxygen is used in oxygen tents in hospitals
for persons having difficu+ty in breathing normally because· of
illness or unconsciousness.
2- In welding :
.
. .
Acetylene (which is an unsaturated hydrocarbon) burns m oxygen to
give a very hot flame "oxyacetylene flame"
welding torch
c:
Q)
.i•
--'
UJ
z
w
__J
Ol
>-
X·
r::w
0
--'
3-
()
<{
In making steel
FoJr.ma..:Uon o6 c.aJtbon d.{.oxJ..de :
1-
As a product of complete combustion of carbon-containing substances
CH
4
+ 2o ,
2
~ C0
+2 H 20
2
methane
(natural gas)
C H 0H
2 5
+ 3 0 .
2
- 7 2 C0
2
+ 3 H2 0
(ethanol) .
Some 6uw, e.g. c.a.ndte w.:L:.:, aL6o pll:oduc.e a. depo.6.U o6 c.aJtbon
(<>oo.t). TIUA p!tove.6 ..tha-t :the a»t l>!Lpply wa.o J.nllu66.f.cl.ent .to
oxJ..d.{.ze aU. .the c.a.Jtbon .tn. :the· hydJr.oc.aJtbon 6ue.t ;td c.aJtbon d;_oxJ..de.
rco 2 1.
TheJLe .iJ, a.no.theJL p!toduc.;t a6 -i.nc.omplde c.ombUl>tion w!U.c.h you c.a.nno.t
ue olt .~>me.tl. Th.iJ, .iJ, :the po.LbonoU1> :9a..6 c.a.Jtbon monoude [CO].
When pebt.ol .{..6 b!Litnt bi :the c.aJt wgine, ;the exllO.ll..il.t ga.<>e-6 c.on:tain
.~>orne c.aJcbon ·monoude, <>orne !Litbwr.n:t hydltoc.a.Jtbonll· a.nd .iome .6oo.t
-i.n a.drUtion ;to .:the ha.Jtmle-6.6 pJtod!.tU!> c.a.Jtbon d.toude and Wll.teJL.
2-
As a product of respiration :
During breathing, some of the oxygen in the air is used up, and
C0 2 , water and heat energy ·are produced.
-111-
Chemistry I GCSE
(Dr. Fathy Abdel Galil)
Manufacture of ammonia by the Haber process :
. Ammonia is made by ~yn.theo.U, i.e. nitrogen and hydrogen·are
combined together.
1.
Nitrogen is obtained from the air.
2.
Hydrogen in now obta·ined from methane (natural gas).
Hethane is heated with steam over a nickel catalysc
CO(g)
+
3 H (g)
2
> The following is the equation of formation of ammonia from Its
elements, nitrogen and hydrogen:
+
i.
1NH3 (g)
The reaction is exothermic.
ii. The reaction is reversible.
)>
Conditions:
temperature: 450°C
pressure: 200 atmosphere
catalyst: .iron
Ammonia is liquified by cooling. The unreacted gases are recycled.
:> Uses of ammonia
1.
11.
Making fertilizers
Making nitric aCid
. Chemistry IGCSE
- 112-
(Dr. Fa thy Abdel Galil)
=:
Ammonia in the Laboratory
l.
Ammonia is a colourless; choking gas, which is. formed whenever·
an ammonium salt is warmed with an alkali.
For example• :
NH,Cl(s) . + NaOH(aq) ____,.. NH 3(g) + NaCl(aq) + H 20(1)
ammonium
sodium
ammonia
sodium
water
chloride
hydro:x:ide
chloride
~p
red litmus paper
:unmonium _ _____:~,.y
chloride
t
warm
2.
Ammonia is very soluble in water and· aque·ous ammonia is .formed,.
which is a weak alkali.
NH (g)· +
3
>-
+
~---these ions make the
H 0(!) ---+NH 08(aq)
2
4
solutionalkaline
Since ammonia is an alkali, it will neutralise adds to make ammonium salts.
Ammonia +
nitric acid
---+
ammonium nitrate
Fertilisers
1. Fertilisers are substances, which added to soil to promote plant growth.
2. .The major plant nutrients include nitrogen (N), phosphorus (P) and
potassium (K).
3. Nitrogen is the most important of the three elements because plants use it to
make oroteins.
Nitrogenous fertilizers:
Ammonium nitrate
Ammonium sulphate
Ammonium phosphate
Urea
NB4N03
(NB4)2S04
(NB4)3P04
CO(NH2)2
4. Many fertilisers contain phosphorous and
potassium compounds as well as nitrogen
compounds. These mixed fertilizers are
called 'NPK' fertilisers.
16.8.24
NPK
FERTILIZER
- 113-
Chemistry .!GCSE
(Dr. Fa thy Abdel Galil)
AIR. POLLUTION
Apart from the gases normally _found in air, other gases such as
sulphur dioxide, oxides of nitrogen, and carbon monoxide can be present. These gases can cause air pollution and are called po~.
Common pollutants in the air
1.
Carbon monoxide, CO :
Carbon monoxide is produced by the .·incomplete combustion of carbon
con~aining
fuels. Much of carbon monoxide comes from the in-
complete combustion of petrol in car engines.
CaJLbon monoxide .U po.UonolLb ga.;, :thtLt pll.even;U ha.emogtobbt .<.n _.the
btood t)Jtom c.b.oo:r.bbtg oxygen. A:t a. tevet ot) H, c.aJtbon monoxide
w.Ut k..U..e.- qc:U.c.kl.y; a..t toweJt levw J.;t c.a.Mu hen.da.c.hu a.nd d.<.zz.<.nu.o. Bebtg c.oloi11!1.U.6 a.nd odoUJLteM, c.Mbon monoxide g.<.vu no
wa.Jr.nhtg on -U:.-6 pJtUenc.e~
2.
Sulphur- dioxide,
so 2 :
Fossil fuels (coal and oil) always contain sulphur. When burned,
sulphur dioxide is formed. Factories and power stations burn coal,
which contains sulphur. They send sulphur dioxide int-o the air.
Sutphwt d.<.o xide. c.a.Ub u bJr.a nc.hd.u a.nd .tung d.<.<> ea.<> u • In .the. uppeJt
a..tmo.opheJte., i l -Jtea.W wd.h. wa.teJt :to 6oJun a.dd JuU.n.
3.
Oxides of nitrogen :
When fuels are burned in the oxygen of the air, nitrogen is also
present. At high temper-ature, the result_, some nitrogen
with oxygen.
Nitrogen · + oxygen
--l>-
nitrogen· monoxide
~
2 NO(g)
Nitrogen monoxide + oxygen -nitrogen dioxide
2 NO(g)
combines
(Dr. Fathy Abde[ Galil)
- I 14-
Chemistry IGCSE
l·
About 30 - 407. of the oxides of nitrogen in the air come from
car exhausts. Other sources of nitrogen oxide pollution are
factories and fires.
NO .i..6 hJ.g hty c.aM.o~>.i.v e and ;to x.J..c..
2
Ox.J..dv, a6 n..{.;t!togen. fuM.tve .i.n. wa:te.Jt ;to 6oJUn n.J..t;Uc. ac..i.d
lead.i.n.g :to ac..i.d /W.{_n..
Catalytic removal· of oxides of nitrogen from car exhausts :
Catalytic convertors are now ·being fitted in the exhaust of cars·,
where the toxic gases are converted in the presencR of a catalySt
into carbon dioxide and nitrogen.
exhaust
from
of car
eng ina
' ·..
~\
catalytic
converter
Nitrogen
monoxide
+
2 NO(g)
+
carbo~ ~·nitrogen · +
monoxide
carbO:n
dioxide
Ca:ta.e.y:Ue eon.ve.Jt:toM !Le.qt.Wte.d :the. Me o6 l11'11.eade.d pe;t:Jtol.
4.
Lead compounds
A lead compound called tetraethyl lead·is added in small quantities
to petrol to increase the octane number·of petrol. When the-petrol
burns in the engine, lead compounds are released from car exhaust.
Lead c.ompou.nd!.. Me. n.Vtve. po.Won.~>. In. pa!L:Uc.ulM., ·:the.y c.an. eaMe.
b/W.{_n. damage .i.n. young c.hild!r.e.n..
The main way of preventing pollution from compounds of lead is
the use of lead-free petrol (unleaded petrol).
Chemistry I GCSE
- 115-
(Dr:. Fathy Abdel Galil)
Acid Rain
Acid
roln 1
I
Harmful effects of acid rain
l.
Acid rain (pll
2.
It removes minerals from the soil and increases the acidity of
=
4) makes lakes too ncidic £or fish to live in.
the soil.
3.
Acid rain attacks construction materials such f!S limestone and
4.
Acid rain can speed ujJ corrosion-of metals.
It is important to control the acidity in soil. Lime [CaOJ or
slaked lime [Ca(OH) J are used for neutralizirt(l acidic soils.
2
Finding the acidity of the soli :
I.
2.
3.
4.
A !te.p!Le..;e.n.ta.Uve. .6a111pte. o6 :the. .bOil ll. e., 6Jtont cU66e.Jte.I'Lt hl:tu
o 6 .tfte 6le..tdl l.6 :tah.w.
Wa.te.Jt .U a.dc(e.d :to .tlte <lcunpte. o 6 :tlte. <1o.U. ln a. be.a:k.e.Jt O:ftd .6:t.Ut!Led.
Some. baJtlwn .6ttipfta.te (llt.6o£.ttbte ".tn wa.te.Jt) .U, a.dde:'ll J:.o .tlte nr.i.x..ttLJte.
:to fte..tp p!Le.cA.pl:ta.tlo 11 and .to cte.M .tlte .U.q ttld.
Tlte c.i'.e.M .U.qttld l.6 :tu:te.d w.U:ft .tfte UttlveJL?a.t I ndlc.a.:to!L :to 6-Lnd
:tlte. pll.
- ll6-
Chemistry IGCSE
(Dr. Fa thy Abdel Galil)
!;
[:
Topic 12.
SULPHUR
A non-metallic element, yellol" solid, .. with low m.p., ll9°C.
Large amoun~s are produced each year by mining as it is used to
produce sulphur dioxide.
Sources :
a-
Large amounts found in certain volcanic regions of the world.
b-
From sulphide ores [e.g. zinc blende] •
c-
Under ground deposits in the United States extracted as. liquid
by pumping heated water into the sulphur depos.it.
Sulphur·dioxide, S0
:
2
=======a==============
Acidic :gas. produced by burning sulphur in air
S(s)
+
1-
As a. food presecvative
2-
B'leaching wood pulp
3-
Making sulphuric acid, H so
2 4
Food passed through an atmosphere of sulphur dioxide. The gas
kills bacteria that could spoil the food or be a danger to
human health.
When wood has been broken down to a· pulp ·it has a brown colour.
In order to make. white. paper from the pulp it has to be bleached
by passing sulphur dioxide through it. •
'
-117-
Chemistry IGCSE
(Dr. Fa thy Abdel Galli)
Sulphuric . acid ·is mad'e by the Con.ta.c.-t PMce6.6. This has 3 stages
a)
Sulphur is burnt in air_ to ·make sulphur dioxide
I·
b)
S(s)
+
Sulphur dioxide and.more air are reacted together.
);>
Conditions : temperature: 450°C ,, catalyst: vanadium(V) oxide ;
pressure: 2 atm. (for circulation ofgases),.
(no need for high pressure]
2 S0 .(g)
2
+
i>ul.phwr.
cU..ox.J..de
. c)
o2 (g)
so (g).
01(g)
2
.oxygen
6iWm tWt.
;,Ul.phliJr. .
3
ruo x.J..de
1/t :tfieblly, 46 i>ul.phwr. :tJ;;;l_ux.J..de £6 rUbi>ol.ved .:l.ll. Wod:eJL, L>u1.plu.vc.tc. a.c:id .U pJwduced•. Ba:t .thU .U. no.t dime in p}(O.c.tic.e .
on a. .ta.Jtge .6.c.al.e beaa.u.6e .:the Jt:e.a:c.tioir M :toa ex.o.the)!Jn)_e a.nd ·
boili :the <.ul.phwrJ.c. a.cU pMdU;c.ed.
. •....
.{.- · The <.iLtplit.vr. ruo:dde -M rUb.ool.v-e:d fi.i.Mt. in c.anc.e.n..tJUl:ted
;,Ul.phwUc. a.dd :to 6ollm ol.e.um.
S0 (gJ
3
+
.6 u.tphwr.
..tliJ..o x.J..d.e
..U-
H:zSb4 (IJ - ·· -.> H2SzLl 7 (1)
.6 u.tphwrJ.e
a.eld
d ··
-.- .-> 0-<.-eunl
1he ol.eum .U then d.U.t.cted wUh the eoJUr.:ic:t·. amoiut:t o6· wa.teJL
:to pJwduc.e ecmc.e:J1:tlu;(;te.d.L>u1.phwr..i,e a.ci.d.
H s o (1) . +
2 2 7
ol.eum
H 0(0
2
wa.teJL.
-~>
2 H so (!}
2 4
.6 ul.phwr..Le a.c.f..d
Since ·all three of these ·r·eaC:tiona are. exothermic, the whole process
prod~ces heat
en.e.rgy, The fact that enetgy is ·produced rather than
. '
;
'
needed means· that sulphuric acid can be produced· cheaply.
i- in-making :t~rtilisers (!'.g. ammonium sulphate)
ii- ·iri making detergents
iii- in making_paint;s
i.:iii- ·iii. car batteries.
Conc~e.d .6u1.p/w.JUe a.Ud .U paJ~y da.ngelloll.<l :to hamil.e
becO.iJ.M!. U .U a. powvr..6u1. dehydJr.a:t.Utg agen:t. I:t w.i.U Jcemove wa..teJL
6Jtom otheJc. .6ub<.~c.u,.
Chem!.~try
IGCSE
(Dr. Fa thy Abde! Galli)
-11&-
Topic 13
CARBONATES
All carbonates a~e. insoluble in water exce~t-aodium, potassium and
l.
ammonium carbon~te.
All cubonates .react wfth dilute aciqs, they all fizz and dissolve,
2.
giving off carbon dioxide and leaving a solut'ion of a .salt.·
salt·;+- .water + Cl!rbon.dioxide
Carbonate + acid
+ 2 HCI(aq)
CaC0 3(s)
. CaCI,;(-ilq). + ·HzO(lY.+ COi(g)
. ·.. - ., ...
3 •. They decompose upon heating to f_orm_-llieta'J:._.oxide .. i:md:.-;:,ar)>,on dioxide.
--......,-.;:.
+ ·cbtfg}'
C\iO(s}
bia.c.li.
Sodium and potassiurrt carbonate, however,~aretoo st<>bf~ to decompose ..
i.e. they.haye.high thermal stability.
Suggest what is meant by th~
tenn thermal stability.
.
.
.
·
............................ +···...... ·.. _.. ;; ....... ~---··
Limestone'.lime and- slaked
lime : ·
..
. . ..
~
....
Name
Fonn!Jl?
•.
'.
Limes. tone
Lime [Quick· Lime.]
Slaked Lime·
caco ·
3
CaO
.
Ca{CF!l
. ,. . 2·
'•
Colour
Chemical
. . . . Nam_e.~
Ca.rbOh~te
.(alcium
...
.
.. Calc(um OXid~
Wh!~e
··--
..
..
•.
..
White
.ca:icium Hy'droiddet
.. ··. .· ..·
·
A solution of calcit~m hyd'r<ixi,d~' i~ .c,all,)<{i{:.:);im;·~t~i":.~::w!;!¢n
Co 2 gas it; bubbled i:hrou~h 1i1!),i::.<'w~~~;~~-:ti\:~_-~@i'iihi~J.b;,;.~(;&um
carbo~S:te_ appears as a.-l{hi.c~ sifs{;-e~Ji~o~;:·:~~ 'i#i(!, ~$i~\l'i;':~(les
1
mi11W',
..-. ·.-
WJ:tlte
..
'.
Chemistry I GCSE
(Dr. Fathy Abdel Galil)
- 119-
Calcium carbonate (Limestone)
Formt.!la :
CaC0 3
Usee : ~1
M~nu6Q~~
An. important car:-bonate.
o6 cement.
Cement ·is made by heating together limestone and clay.
b) - Ma.nu.6a.c..tWL~ o 6 .<Mit. (.to JLemov~ .sa.nd hnpu.Jt.U;{.~ I.
c). neutralises acidity in the -soil
d)
Ma!1u.6a:~~ o{Um~ (C!CLtcWm ox.U!c).
Limestone is heated to a high temperature. It decomposes to
calcium ol<ide and carbon dioxide. The symbol equation for
the. reaction- is
.......... . + .. ...... .
•,
Calciuin oxide has important
to calcium hydrol<ide, Ca(OH)
·calcium oxide· +
(quicklime)
CaO··
u~ea.
2
It can be re·adily convert·ed
(slaked lime],. by adding vater
water ---+ calcium hydroXide
(slaked· lime)
"---'-'r
. .
Ca ( 0 H) 2
As both [lime and slaked lime.] form in water alkaline solutions,
they are used to : -
- Neutralize acidity in the soil ·
- Neutralize aciqic gases and industrial acidic wastes.
Question·
-:;:::======
The diagram shows a lime kiln.
· What are X and Y?
y
X
A
.lime
B
lime
slaked lime
c
limestone
lime
D
slaked lime
lime
.
limestone
heat
r
heat
t
heat
i:.
Chemistry IGCSE
(Dr. Fa thy Abdel Gal ill
- 120-
Topic 14.
ORGANIC CHEMISTRY
Org;mic chemistry includes the study of all carbon compoim.ds except
the very simple ones such as co ,co and carbonates.
2
The term 'organic' means.'living'. At first; organic chemistry was
the study of carbon chemicals from_planta and animals. Now it is "known
that complex carbon compounds can be made artificially.
Organic compounds are grouped into classes [families) such as
hydrocarbons, alcohols, organic acids, ....
HYDROCARBONS
Hydrocarbons are compounds containing hydrogen and carbon and no
other elements. They are classified into alkanes
[saturated] and
alkenes [unsaturated).
ALKANES
They have single bonds between their carbon atoms, i.e. 6~ed
Name
N!-imberof
Mol<C!!LUVL
carbon aroms 6o1Umlltz.
methane
CH,
1
.s.cw.o.tuJuiL !P;ynul.a.
H
I
H-C-H
I
H
H
ethane
C,H,
2
H
propane
butane
c,H,
3
C,HIO
4
H
.I I
H-C-C-H
I I
H
H H H
I
Gen eJ!a1. 6oJUnul.a
I
I I I
H H H
H H H H
I. I . I I
H-c~c-c-c-H
I I
H
pentane
hexane
heptane
octane ...
I
B-c-c~c-H
I
H H
5
6
7
8
. ..
[n = no, of carbon atoms]
I
H
(Dr. Fa thy Abdel Gallll ·
- l2l-
Chemistry IGCSE
::·.
ALKENES
Alkenes are IJY!4a.:tulrLLted· ·_hydrocarbons, Le. they have a double bond
between two carbon atoms. The simplest alkene. has only two carbon
atoms. It is called ethene.
No. o6 c.Mban. Malec.ulM
a.to/Jk\
6aJUnula
Name
2
e,thene
. C2H4
StJw.ctWLa£. 6Ollmula
H
H
I
I
H-C=C-H
H
I
3
propene
C3H6
H
.I
H
I
H- C- C=C-H
I
·H
but-1-ene
4
but-2-ene
4
C4H8
C4H8
I!
H
I
I
I
H
~
H
H
I
I
H
!I
I
I
H
H
H- C-C-C=C.,- H
t
l
H-C-C=C-C-H
I
I!
I
H
[ n = no. of carbon atoms]
Alkenes are characterized by. the presence of the double bond, which
is called the 6un.c.:ti.pna£. g/f.oup.
ISOMERISM
The alkene c a
4 8 .has two structures,
but-1-ene and but-2-ene.
The different structures are called .i..bomeM.
· Isomers are compounds having the same molecular formula
but. different structures
Chemistry IGCSE
(Dr. Fathy Abdel Galil)
-122-
ALKANOLS
[ALCOHOLS}
Alkanols can be.regarded·as. alkanes, in which one hydrogen atom
is replaced by a hy~oxyi g~up
[OHJ, This is called the 6unctidnal
g4oup. They are named after the alkane (with the same number of carbon
atoms) [AN¥. -> 0 L].
No. o6 caJrbon
a;tonu,
Name.
FoJrmul.a.
Sbw.e:tu!r.e.
H
methanol
1
CH 0H
3
I
H-C-0-H
I
H
ethanol
2
C H 0H
2 5
H H
I
I
H-y-y-Cl--H
H H
H
propan-1-ol
propan-2-ol
3
3
c3H70H
c3H70H
I
H
I
H
·I
H-C-C-"-C-0-H
I f I
!l H H
H .0-H H
I
I I
H-C-C-C-H
f
H
f . I
H R
[n = no. of carbon· atoms}
0
Propan-1-ol and propan-2-ol are ihom~.
Th·e alcohols butall-1-ol and butan-2-ol .whi"h have the mol1>cular
formula c H 0H are isomers. Write down their structural formulae.
4 9
...................................
. .................................... .
butan-1-ol
butan-2-ol
- 123-
Chemistry IGCSE
ALKANOIC ACIDS
(Dr. Fathy Abdel Galill
[CARBOXYLIC ACIDS]
They are organic acids and characterized by the presence'of the
carboxyl group,
0
II
[ -G-0-H]
,
which is the functional group.
They are named after the alkane (with the same number of carbon
atoms) [A N
X --> 0 I C ACID].
··---'---------------------------Name
No. o6 c.aJLbon
a..tom6
methanoic acid
1
0
II
H-C-0-H
H
I
ethimo:i.c. acid·
[acetic acid]
propanoic acid
2
0
II
H-,C- C-O__:_H
I'
H
3
H H 0
I
1 II
H-C-C-C-0-H
. j
I
H li
Question :
==:.:::======
Draw the structure· of butanoic. acid •
. . . . . . . . . . . . . .. . .. . . .... . . . .. . .. . . . ... .. .. . . . . . . .... .. . . .. .. .. . .. .. . ., ...
Homologous Series
A 6a.m.Uy o 6 .shn.ilalt OJtganic. c.ompou.n.do wLth .s.i.m.W.vr. p!WpeJL.t)_ru due :to
.the piLIUence o6 .the .sameJanc.tiona.t bu:p. AU membe!Lb Me ILepiLruen:ted
by .the .same gene!La.t 6o.IUll
, e.g. Cit
ru, a.tk.enru,. a.t/Urno.U ••.
A.s we go aLong a. homol.ogou.s .s rvr.J..ru :the bo.U'..<.ng a.nd me..Uhtg po-i.n:t.s o6
c.ompou.n.d.s · :gM,du:a.tl.y A.nc.ILe.M e.
-124-
Chem!s_try IGCSE
(Dr. Fathy Abdel Galli)
ORGANIC HALOGEN COMPOUNDS
These are compounds formed when hydrogen atoms in an alkane are
replaced by halogen atoms.
chloromethane
chloroethane
~
'I 7
H
8 8
H
I
Br
H-f-C-C-Br
I
H
I
H-f-9-y-H
H H H
1-bromopropane
2 -bromopropane
1-bromopropane and 2-bromopropane are isomers; they have the same
molecular formula c H Br.
3 7
FOSSIL FUELS
'
Fossil fuels [coal, crude oil, natural gas] have be,;n formed as
a result of the decay of plants and animals that lived long time ago.
Fossil fuel
Appearance
What it contains
Natural gas
Colourless gas
Mainly methane (CH4 )
Crude oil [petroleum]
Dark brown liquid
A miXture of hydrocarbons,
mostly alkanes
Coal
Black solid
Mainly carbon
Fossil fuels contain sulphur compounds, which form·acidic sulphur dioxide
[S0 2 l when the fuel is burned (leading to
ac~d rain).
Coal, crude oil and natural gas are -vu1~-U..e
''-'~ d Jteoowr.c.eo, 1. e. nonrenewable source of energy.
Fossil fuels and CO, emission:
co, is produced from burning fossil fuels, co, is a green house gas leading to global warming.
Chemistry lGCSE
- 125-
(Dr. Fathy Abdel Galil)
·Fractional Distillation of Crude Oil
Crude oil (sometimes called petroleum) is a mixture of alkanes.
To make best use of oil, it is separated by fractional distillation
into useful fractions according to the boiling range of the fractions._
The main fractions are :
fraction used as fuel
in cars
(C
(Kerosine)·
5
-
c 10 J
fraction for oil stoves
and aircraft.
(Cg - c16l
fraction as a fuel for
the engin·es of lorries,
trucks and some cars
(CJS - Czsl
crude
oil
__...,_
fraction for making
waxes and polishes
(over c 2·5 J
heater
Bitumen
fraction for making roads
In 6act, the demand on ughteJ~ oiUJ.moru, (pe;t;wl, piLIU1.66-i.nJ .U. gJtea.t~
.tha.n the .ou.pply fiJtam the fuWf..xti_on a6 CJw.de a.U.; . 6aJttuna.te.ty, .they
ean be made 6Jtom .the hea.vi~ 6Mc..Uaru, by ci piweu;, CaU.ed eiUJ.c.IWtg.
Cracking
The process of breaking longchained hydrocarbon molecules into
shorter ones is called c.Jt~Leking.
The reaction needs high tempeJtatulte
and a e~Lt~L./'.y;,t.
Al.kenes are
always formed as one of the products of cracking.
Chemistry IGCSE
long hydrocarbon
molecule
Octane
-126-
~.temp. >
c
y;,J; .
_CJUl~-'-cl"-u·'-"'"ng-->
(Dr. Fathy Abdel Galli)
shorter alkane
molecules
hexane
+
ethene
------>
Cracking is very Useful:
1. It' converts larger molecules from heavier, less useful fractions
into smaller molecules that are useful as petrol [more benefit]
2. It also produces alkenes, which are very useful for making plastics.
3. Hydrogen gas could be also obtained during the cracking of alkanes.
Cracking a liquid alkane:
The following figure shows a simple laboratory cracking experiment.
.The vapour of a liquid alkane is passed over a heated catalyst to make
ethene.
liquid alkane +
ceramic wool
catalyst
delivery·
tube
ethene
heal
heat
water
)>
Suggest the function ofthe ceramic wool_. .......... : ........ .
)>
The delivery tube is removed from the water before stop of heating.
Suggest why this is done? ................................. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . - .............. - ... - .... - -
- 127-
Chemistry IGCSE
(Dr. Fathy Abdel Cali!)
ALKANES
Properties of Alkanes
1.
The first four alkanes are gases, the next fifteen are colourless
liquids and the ·rest are solids.
2.
Like all hydrocarbons,, alkanes burn in air .giving co , H o and
2
2
heat energy is given out, so alkanes are useful as fuels.
+
CH (g)
4
2 o (g)
2
(methane)
--)
··
C H (g) + 5 0 (g)
3 8
2
+
(propane)
3.
Alkanes are generally unreactive.
4.
Simple alkanes react with ehta~e gab in presence of !Lght.
Thus, when methane is mixed with chlorine gas in bright light,
ehto4am~hane is slowly formed.
H
H
I
H-c-H + Cl 2
I .
I
LL h't.
g
·
> H-C-Cl
I
[,{
H
mc:thanc
·chloromethane
Similarly,
+
ethane
Cl
£<.ght
2
·
+ HCl
hydrogen chloride gas
) · C H CI
2 5
+
HCI
chloroethane
This is called. s.ubstitution reaction because the hydrogen atom
in methane molecule is replaced by chlorine atom.
Saturated hydrocarbons undergo substitution reactions.
Chemistry IGCSE
(Dr. Fathy Abdel Galli)
- 128-
f:~;
ALKENES
Alkenes (e.g. ethene, propene) are produced in large quantities
in industry from the larger molecules in oil fractions by the process of cna~g.
Properties of Alkenes
Alkanes are members· of a homologous series, so they all show
similar che"in.ical properties ..
They burn with bmok.IJ•.. yel-t_oW flame
l.
-->
+
:: ..
The double bond in alkenes make them Ve.JUj Jte.a.c.:ti.ve. They undergo
2.
a.dcU..:Uan Jte.a.c.:ti..!J no •
Unsaturate.d hydrocarbons undergo additior\ reactions:
[A]
Addition of hydrogen (hydrogenation)
If ethene gas ·(unsaturated) in mixed with· hydrogen and is
heated over a catalyst (nickel), ethane (sa.tuni.ted) is formed •.
+
ethene ,
H;
H
H
I
I
I
Nl
~
k
"'"'"' H-C-C-H
c2 H 11
ethane ,
unsaturated
(double bonds present)
c 2 H6
saturated
(all singie bonds present)
Similarly,
+
propene
propane.
Generally,
Alkene
(unsaturated)
+
hydrogen
Alkane
(saturated)
-129-
Chemistry !GCSE
(Dr. Fathy Abdel Galil)
Making Margarine
The molecules of the vegetable oils contain several double
bonds; L e·. they are poiywua..:tww..ted~ By reacting them
with hydrogen and a catalyst (nickel), they are made
-
saturated. This raises the melting point, so the liquid
oil becomes a solid fat - m~ga4Ute. The process is called
~dening
o6 oilh.
Vegetable oil
+
Ni
hydrogen
catalyst
> margarine
Large amounts of hydrogen are used in industry for making margarine.
State another large scale use of hydrogen : . _;_ .. _... _.. ____ .. ____ _
[B]
Addition of bromine (Br 2)
J\lkenes reactwith a solution of bromine in water (~q~eoub
bll.oin.Lne) , the red-orange colour of bromine goes colourless.
H
H
C=C-/
""'
H/
1,2-dibromoethane
+ bromine --+
ethene -
H H
I I
H-C-C-H
I I
Br-Br
""'H red,--orange
Br Br
colourless
colour
+
+
)
C 3 ~Br 2
1,2-dibromopropane
Similarly, ethane adds chlorine to form dichluroethane.
Aqueous bromine (bromine ~ater) is used to test for a do~bf.e
bond. It works ~ith any uMatukated moteeuf.e.
lzo- Row would you show by a chemical test that olive oil is
unsaturated 1
........................... ,. ............................... -....................................... .
-130-
Chem.istry lGCSE
(C]
(Dr. Fa thy Abdel Ga!il)
Reaction with steam [Addition of water]
EthanoL is formed in the reaction between.~!en~ nnd bt~m
at high temperature (250°C]. A catalyst is used (phosphoric acid].
ethene ·+
H..._
H
c.a.:ta.tyb;t )
water
(steam)
ethanol
/H
C= C
/
'-...
H H
I
+
H-0-H
H
C2H4
I
-> H-C-G-0-H
l l
HH
+
H 0
2
> C 2 H 5 0H
+
H o
2
>
Similarly,
i
C3H6
'
-,
ptop<mol
steam
propene
C H 0H
3 7
Generally,
catalyst
Alkene
water
+
Alcohol
(steam)
);;. Shtc~ a wcd:e.ll ritaL~cu.t~ hM .b~w add~d to th~ doubL~ bond bt
ill~n~, th~ Jtwc.:Uon .U. caLLed hyciM.:t[on,
The. Jt~v_e.M ~. Jt~c.:Uon, L ~. e.l.-Zm-ln.ation a 6 wcd:e.ll moLe.cu.t~
6Mm illanof. to 6o1Ull dhe.n~ .U. caf.f.~d de.hyciJw.:t.lon.
---::> c 2H 4 +
H 20
ethene
Dehydration can be achieved by :
(a-)
Heating the ethanol with excUb concen:tluLt~d <>u.tphwU..c
acJ.d [dehydrating agent].
{b)
[D]
Passing ethanol vapour over hot ~ o~de.
Reaction with hydrogen chloride gas-
H H
+
HCI
------,)
I
I
I
I
H -'-C--C- Cl
H H
chloroetnane
ethene
+
HCt
.· ..
-131-
Chemistry I GCSE
E]
(Dr. Fa thy Abdel Gatil)
_
Addition polymerisation [Making plastics)
F'o.tymvt-lb!Ltiott is the -process in vhich many small molecules
(manam~) join together to ~ake a large molecule
molecule)
(macro-
which is called-pa.tym~.
The polymerisation is done at high-temp~e and pressure
in presence of a
cata!.yJt.
H
H
I
H
I
C=C
I
H
I
H
I
I
C=C
+
I
H
H
I
H
l
+
l
-->- ...
C=C
I
~-~-t-6-d-d ...
I
I
I
H
H
H- Pi H H H H
H
H
ethene
[monomer]
11.6
Pa.ty (ethene)
I
H ·H· H
I
H
I
H
I
H
poly(ethene)
[polymer]
b-~iI
I
H
H
n
is used to make plas.tic bags and plastic sheets.
HCIHCIHCl
H,
n
H/
c=c
_,...CI
'H
I
I
I
I
I
I
I
I
I
I
I
I
_____,. · .. c-c-c-c-c-c · · .
H H H H H H
chloroethene
(vinyl chloride)
poly( chloroethene)
(PVC)
Polykh.taJtae.thene) known as PVC is used to make. plastic bottles,
floor tiles, raincoa-ts and electrical wire insulators.
I -Ht
l
CHJ
c_:_c
n
I. I
propene
H.
H n
poly (propene)
Paly(plwpenel is used to make plastic sheets, electric insulators
and bottles.
Monomer: A small molecule which =n be polymerised (joined together) to make a
polymer.
Poiymer:
A macromolecule (large molecule) made by polymerising (joining
together) ofmonomers.
-132-
Chemistry IGCSE
(Dr. Fathy Ab9el Galil)
.Examples o{ other addition polymers
Polymer
Monomer
formula/Name
H
I
c=c
I
. \
Name
H
\
C 6H 5
poly(phenylethene)
(polystyrene)
H
formula
f "t
I
~ n
..
STYRENE
(PHENYLETHENE)
CN
\
I
c=c
I
\
Poly(acrylonitrile)
+r 'tt
Synthetic fibre
tf-11
non-stick coating
in frying pans
c-c
I
H
H
pacKaging
c-c
c!H5
H
I
Uses
H
I
H
n
ACRYLONITRILE
F
\
I
c=c
\
I
F
F
poly{tetrafluroethene)
or PTFE
F
F
F
n
mRAFLUOROETHENE
P.ta.L>.UC-6 :
good oJi bad ?
i]QQ!!_t!Q{~
1• Qu.de cheap 1 and eM ;i.y made
2•
3.
4.
s.
Ug hte.Jt than me.ta.l
Uwr.ea.c..Uve, . They do no.•~ :coMo de .W c0t oiL wa.teJt. Many Me
not a.66ected by .a.cJ:.dl, olr.. a.eJw.Ul,
Vo not conduct hea..t olt dec:tJU.cfty 1 ;,o c.a.n be Med a.o
-Utbu1a.tolt.6
.
Can be mou:tded.1n.to any .;ha.pe and c.a.n be cowwr.ed.
§~!!_t!Q~
P.ta.L>tie-6 ca.lL6e pou.u.ti.on pJr..Ob.tem.; beC1UL6e: 1•
2.
They Me d1661c.u1.t .to d1opo1>e o6. P.la..!tic bag!> and Ca.JL.tonl> ·
do not Jtpt wh.en they Me .tlvr.own a.wa.y 1 1n o.tlvt woJull, 1 they
Me non-:b1odegJUUia.b.te1 1. e. c..a.J1J!.ot .be degltaded by rri..cJtooJt.ga.n-Winl>1 1>owey pau.u.-te the env1Mnment;
When they bwr.n, they aMen pltodu.ce ha.!tm6u.t gMel>: e.g. PVC
give~> o66 6wne.~> o6 hydltogen ch.toJU.de when 1t buJ!Ji6.
;
. i.'
;.
- 133-
Chemistry IGCSE
(Dr. Fathy Abdel Gaiil)
.ETHANOL
Making Ethanol for Industry
-1- Hydration ofethene
_
Addition of steam to ethene [obtained by the process of cracking]
at'high temperature in pr~sence of a catalyst [see page 130]
2- Makin<>
ethanol by fermentation:
.
b
FeJutre.IU:ation ~s the process where sugars (e.g.
gluco~_e)
a.re con-:'··
vei:ted to ethanol and carbon d~ox~de by· enzymes present ~n yeast:.
-:·:
The process works best at 37~C.
Sugar solution
(e.g. glucose)
C6Hli 0 6
---,) . ethanol
+ carbon dioxide.
I.t .U, hlrpolda.nt :to plte;.ve.nt· aA.Jt 6Jtom. e.n:teJU.ng .the. Ji.~d.t.or~- vv,,; eL,
e.:tlutno.i.c. add wUJ. be. 6oJtme.d.
Ye.a.i>:t -c.an ortl..if pl(.odu.c.e. a .6o.tu.tion c.o~g I 0% e.tfutno.f... k6:teJt :tha:t,
:the. ife.M:t d.i.v, 6Jtom atc.aho.f. po.i.,;ort.{.ng.
·
o:th~e.
The apparatus below can be used 1:0 ferment glucose •
. Air lock allows carbon dioxide
to escape, butpre~ents air getting
in, i.e. allows fermentation under ·
anaerobic conditions
jar
yeast
+
glucose. --1~::;:::::::;::::::~
+
.water
> What technique is used to concentrate the aqueous ethanol? ... _.. __
Dur~ng
s~nce
a fermentation process,
r~se· in
temperature is observed
the reaction is exotherm~c. Bubbles of a colourless. gas (C0 )
2
are also observed.
(Dr.FathyAbdel Galil)
- 134-
Chemistry IGCSE
A laboratory experiment to
demonstrate the fermentation:
sugar solution
andyeast -~
limewater
Wine (contains about 10% ethanol) is made by fermenting grape juice.
Beer is made by fermenting malt. Spirits (whisky, brandy, ..} contain about
30% alcohol.
Biotechnology
Microorganisms have been used in some methods of food-making fcit .many
centuries. Today these methods are often referred to as examples of
'biotechnology'. One of the oldest kriown biotechnologies isferm(mtation.
Properties of Ethanol
1. Colourless liq11id. b.p. 78°Cjrteutral to litmus.
2. Ethanol burns in air with a blue flame to form C02 and H 2 0 and heat ·
is given out.
3. Ethanol undergoes dehydra:tion and is converted into ethene when
heated with. concentrated sulphuric acid.
Uses of Ethanol
1. As a: solvent
2. As a fuel
3. In alcoholic drinks
Uses of methanol (toxic)
1. As a solvent
2. As a: fuel
- 135-
Chemistry IGCSE
Ethanoic acid >
(Dr. Fa thy Abdel Galil)
H Q'
I II
H-C-C-0-H
I
-
H
Ethano-ic acid is usually called acetic acid . (from the Latin word for
vinegar -
'acetum'). Vinegar is a 5% solui:;Lon of --.eth~noic acid.
Formation of. Ethanoic Acid from Ethanol
a)
£L~xi~~!::!:~:;-~:!,_t:!!_~tmosEheric ~?.'X~:;__:
Vinegar is made by exposing ethanol to the air in the presence of'
bacteria. Ethanol is o~ed to ethanoic acid.
~ ~
H
H-C-C-0-H
I
I
H H
Wta.noi.
I
+
0
2
0
II
H-C-C-0-H
I
+
H
e.tha.no.i.c. o.c..i..d
This is another example of 'biotechnolo'gy'.
~~g~1=~g=,;,
Suggest a reason·why wine goes 'sour' when .left open in air·?
..................................................... •.............. ............................................ .
.. . .. .. . .. .. . .. . ........................ ,. ....................... · ........................... .
~
_
b)
Ethanol can b~ ox..Ui..U,ed.much more quickly-iri the laboratory by
_heating it with an.o~.i.ng agent such as potah~ium d.i.c.hAomo.te{VT}
(adllified with sulphuric acid). On heating the colour changes
from o.lta.n.ge to. gltee:n.. In other words, when aqueous potassium
dichromate (VI) is Jteduc.ed, the colour changes from ••••••••••..•
to ................... .
Generally:
alcohol
[alkanol]'
oxidation
carboxylic ac~d
Oxidation of methanol gives _........... .
Oxidation of propanol gives ............ .
Chemist1·y IGCSE
- 136-
(Dr. Fa thy Abdel Galil)
.. :
Et}w.no.i..c. a.c.i..d .i..b a. wea.k. a.c.i..d.
Ethanoic acid (and all carboA-ylic acids) is a weak acid, i.e. partially
ionized in aqueous solution.
~~~~;!;-£liH~=,;
The pH value of ethanoic acid is ..•..••••••••••• ; •••••••••••••••••.
What is the colour produced on adding drop of universal indicator to
ethanoic acid ?
.................... • ..................................................... .
Ethano.i..c. a.c.i..d .i..b juJ.:t Uke_ MCJ o.theJt a.c.i..d. It reacts with
* Metals to form a salt + hydrogen
* Bases and alkalis to form a salt + water
* Carbonates to form a salt + water + carbon dioxide
In each case the salt is:c.alled ethanoate.
Examples_:
1>- ethanoic add + sodium hydroxide --* sodium ethanoate + water
1>- ethanokacid + sodium carbonate --* sodium ethanoate
+ water + carbon dioxide
However, the reaction of ethanoic acid is slower than of other acids such as hydrochloric acid or
sulphuric acid.
Why? ...... ········· ............................................................................................
);>
Differentiation between ethanol and ethanoic acid
test
ethanol
ethanoic acid
);>litmus paper
);> sodium carbo-nate
>potassium dichromate
);>lighted splint
no colour change
no reaction .
orange -7 green
catches fire
turns red
effervescence -7 C02
no colour change
does not catch fire
Chemistry IGCSE
[Dr. Fathy Abdel Gaiil)
- 137-
Esters:
Organic acids like ethanoic.acid react with alcohols to form
compounds called eh£~ in a reaction co~~only called an ehte4i6ieation.
organic acid
+
[carboxylic acid]
'
alcohol
ester
+
water
When e.tha.no.t is heated with e.tha.no.Lc. a.c..Ld in the presence of .Ou.t-
phuh.Lc. a.c..Ld as a catalyst, the ester ethy.t etha.noa.£e is formed.
ethanoic acid +
ethyl ethanoate + water
ethanol
·•·.
~
1;0
~ ~
.. -.
+: H;O-C-C-H
\~ .. "· ....... ·
I I.
;oH::
H
H
H-C-C
I
H
H
~
·· .... '
0 ,--the ester linkage
I
1/
H\
I
'o-+c-c-H + H2o
\..........J I
I
H-C+C
·I
\
l
H
I
H
H
H
Similarly:
ethanoic acid + methanol
~
methyl ethanoate + ·water
Ethylethanoate has a characteristic pleasant smell. Many fruits' smells are
caused by esters. Artificial flavouring are usually mixtures of esters.
The reverse reaction of esterification is called hydroly~is.
j ester + water
-·-:t
carboxylic acid + alcohol
Fats and Vegetable Oils
Fats and oils are important constituents"of our· food. They are
e..6te.Jr..6 ,. i.e contain the ester linkage [::-CQQ;..]
Making Soap (Saponification)
Soa.p is produced by heating vegetable
oils or animal fats with
.
-.sodium hydroxide solution (i.e. alka.tine hy~d.tybib).
Fats I oils +sodium hydroxide ~ soap + glycerol
Chemistry IGCSE
(Dr. Fathy Abdel Galli)
- !38-
Carbohydrates
1-
A family of energy foods including starch and sugars.
2-
These compounds consist of carbon, hydrogen and oxygen,_ the
hydroge~
and oxygen atoms are present in the sariie ratio as in
wa.ter.
3-
Sugars are carbohydrates which are soluble in water and taste
·sweet.
The chemical name for ordinary sugar is .6UCJl0.6e..
LQcto.6e. is the sugar found in milk, and fructose occurs, with
other sugars, in fruit juices. and honey.
CaJtboh!JdN:t;te.6 a.o po.tymeM : [ complex carbohydrates 1
Starch molecule consists of a long chain of g;Lucose molecules .•
Glucose HO--Q-OH (a monomer) can be j6ined by in a l.ong chain
to form starch (a polyl!ler) by condensad.on ]>o.lymerisation.
glucose rolecules .
li
(monomers)
condensation
polymerisation
hydroly•h
-o -c=J- o -c:::J- o· --c=J- o- + H2o
starch (polymer)
Ac.JJJ. hyd.Jw.tif.6.U o6 c.a.JWohydJw.;tu,, e.g. starch :
.Starch ·can be hydrolysed into gl.ucose molecul.es by boiling with
dilute hydrochloric acid
starch
hydrochloric acid
boiling
I> glucose (simple sugars)
Chemistry lGCSE
- 139-
(Dr. Fathy Abdel Galil)
Proteins
Proteins are natural macromolecules. Amino acids are the monomers from which proteins
are made.
Formation of a p;lrt of protein chain :
When proteins are formed, an amino group from one amino add reacts Vlith the carboxyl
group from another (VIith elimination of water). This-process can continue repeatedly tc
produce long chain (i.e. macromolecule).
H
0
I
II
Ii.
0
.. .:-····· ... \
II
H-N-i=t-c<oH.: + ~-H~N-~C-OH
. ..
..
....
amino acid
condensation
polyrner!satlon
H
.
···I
protein.
·
~
·-
amino ac~d
l1
hydrolysis
H
1
0
·
II
·
H-N-c::J-C-N---~- C~OH
·
~~
amide linkage
)> The linkage between the amino acids in a protein is called amide (peptide) linkage.
)> Proteins are broken down by hydrolysis into their ?mino acids. This process. occurs VI hen
protein foods are digested. This needs enzymes (biological catalysts).
In laboratory,- proteins can be hydrolysed into their amino acids by heating with dilute
· acids (e.g; HCL or HiS04).
!>-- The products of the hydrolysis of proteins and carbohydrates can be separated
and identified by chromatography. The products. are colourless so need
spraying a locating agent to be seen on the chromatogram.
)>
These constituents of food can all be hydrolysed by boiling ·with acid or alkali.
· linkage
· consliluent of food
protein
product of hydrolysis
-
fat
complex
carbohydrate
~
Complete the table.
[5]
Chemistry IGCSE
(Dr. Fathy Abdel Galli)
- 140-
CONDENSATION POLYMERISATION
Occurs when a small molecule such as ><ate.r is eliminated <1hen
the monomer unlts link together . .
s·yuthetit Macromolecule~
Polyesters
Polyesters (e.g.
~~ylene,
a man-made
fibre.) are polymers which
contain ester linkages.
Polyesters are formed when r:Uo-cl..dl. and cUa.tcofto.U combine together.
)(
? .···.-···-c.---....--·.
HO- c----[B- c-:mr·
. ..
nylon., a
contain a.m{.de UnfW.g V>.
Polyamides (e.g.
: .H.P
OH
. -Q.
.
+
man~ made
fibre) are polymers which
Polyamides. are formed when clia.cl..dl.· and cU.am.{_nu, combine· together.
.
~
H .
........~.· I
. .
H
i
(H-;- N-0~N- II
--
.
d
~ II
\
..
P:W::l
0
.11
H
I
c~I22Ld:....C-N-:
. . . . .
.
·
H
I _l_
.
0
-N)"
.
n
Nylon a.nd i:.eJtyi.R;n.e CUte examplV> of, syn.the.ilc ma.c.Jwmotecu.LV>.
Pi!.a.te.<.n a.nd <>i:aJc.c.h Me na.tu!utt ma.cJr.omo!.ecu.e.u.
ll> What is the difference between addition polymerisq:tlon and condensation
polymerisation? ·
---------······-········--------------·-----·---··--···----·-----··----··--------··-----·-··--··:.--------~; ................... [2]
Cambridge IGCSE Chemistry
Syllabus code 0620
1. Introduction ..................................................................................... 2
1.1
1.2
1.3
1.4
Why choose Cambridge?
Why choose Cambridge IGCSE Chemistry?
Cambridge International Certificate of Education (ICE)
How can I find out more?
2. Assessment at a glance .................................................................. 5
3. Syllabus aims and assessment ....................................................... 6
3.1 Aims
3.2 Assessment objectives
3.3 Scheme of assessment
3.4 Weightings
3. 5 Exam combinations
3.6 Conventions
4. Curriculum content ........................................................................ 12
5. Practical assessment. .................................................................... 28
5.1 Paper 4: Coursework
5.2 Paper 5: Practical test
5.3 Paper 6: Alternative to Practical
6. Appendix ....................................................................................... 36
6.1 Grade descriptions
6.2 Periodic Table
6.3 Notes for use in qualitative analysis
6.4 Safety in the laboratory
6.5 Glossary of terms
6.6 Mathematical requirements
6. 7 Resource list
6.8 Forms
·-·------·-·---·-----------------------
1.1 Why choose Cambridge?
University of Cambridge International Examinations ICIEJ is the world's largest provider of international
qualifications. Around 1.5 million students from 150 countries enter Cambridge examinations every year.
What makes educators around the world choose Cambridge?
Recognition
Cambridge IGCSE is internationally recognised by schools, universities and employers as equivalent to UK
GCSE. Cambridge IGCSE is excellent preparation for A/AS Level, the Advanced International Certificate of
Education IAICEJ, US Advanced Placement Programme and the International Baccalaureate (I B) Diploma.
Learn more at www.cie.org.ul</recognition.
Support
CIE provides a world-class support service for teachers and exams officers. We offer a wide range of
teacher materials to Centres, plus teacher training (online and face-to-face) and student support materials.
Exams officers can trust in reliable, efficient administration of exams entry and excellent, personal support
from CIE Customer Services. Learn more at www.cie.org.uk/teachers.
Excellence in education
Cambridge qualifications develop successful students. They not only build understanding and knowledge
required for progression, but also learning and thinking skills that help students become independent
learners and equip them for life.
Not-for-profit, part of the University of Cambridge
CIE is part of Cambridge Assessment, a not-for-profit organisation and part of the University of Cambridge.
The needs of teachers and learners are at the core of what we do. CIE invests constantly in improving its
qualifications and services. We draw upon education research in developing our qualifications.
2
1.2 Why choose Cambridge IGCSE Chemistry?
Cambridge IGCSE Chemistry is accepted by universities and employers as proof of essential chemistry
knowledge and ability. As well as a subject focus, the Chemistry syllabus enables students to:
•
better understand the technological world in which they live, and take an informed interest in science
and scientific developments
•
learn about the basic principles of Chemistry through a mix of theoretical and practical studies
•
develop an understanding of the scientific skills essential for further study at A Level, skills which are
useful in everyday life
•
learn how science is studied and practised, and become aware that the results of scientific research can
have both good and bad effects on individuals, communities and the environment.
1.3 Cambridge International Certificate of Education (ICE)
Cambridge ICE is the group award of the International General Certificate of Secondary Education (IGCSEI.
It requires the study of subjects drawn from the five different IGCSE subject groups. It gives schools the
opportunity to benefit from offering a broad and balanced curriculum by recognising the achievements of
students who pass examinations in at least seven subjects, including two languages, and one subject from
each of the other subject groups.
The Cambridge portfolio of IGCSE qualifications provides a solid foundation for higher level courses such
as GCE A and AS Levels and the International Baccalaureate Diploma as well as excellent preparation for
employment.
A wide range of IGCSE subjects is available and these are grouped into five curriculum areas. Chemistry
falls into Group Ill, Science.
Learn more about ICE at www.cie.org.uk/qualifications/academic/middlesec/ice.
3
1.4 How can I find out more?
If you are already a Cambridge Centre
You can make entries for this qualification through your usual channels, e.g. CIE Direct. If you have any
queries, please contact us at international@cie.org.uk.
If you are not a Cambridge Centre
You can find out how your organisation can become a Cambridge Centre. Email us at
international@cie.org.uk. Learn more about the benefits of becoming a Cambridge Centre at
www.cie.org.uk.
4
Cambridge IGCSE Chemistry
Syllabus code 0620
Cambridge IGCSE Chemistry candidates are awarded grades ranging from A* to G.
Candidates expected to achieve grades D, E, F or G, study the Core Curriculum only and are eligible for
grades C to G.
Candidates expected to achieve grade Cor higher should study the Extended Curriculum, which comprises
the Core and Supplement Curriculums; these candidates are eligible for all grades from A,. to G.
All candidates must enter for three papers.
Paper 4
Coursework
weighted at 20% of total
available marks
Paper 5
1 hour 15 minutes
Practical test
weighted at 20% of total
available marks
1 hour
Paper 6
Alternative to Practical paper
weighted at 20% of total
available marks
Alterations in the syllabus assessment. content and practical assessment sections for 2011 are indicated by
black vertical lines on either side of the text.
5
3.1 Aims
The aims of the syllabus listed below describe the educational purposes of this examination. The aims of
the syllabus are the same for all students and are not listed in order of priority.
The aims are:
1.
to provide a worthwhile educational experience for all candidates, through well-designed studies of
experimental and practical science, whether or not they go on to study science beyond this level
2.
to enable candidates to acquire sufficient understanding and knowledge to
3.
•
become confident citizens in a technological world, able to take an informed interest in scientific
matters
•
recognise both the usefulness and the limitations of scientific method, and appreciate its applicability
in other disciplines and in everyday life
•
be suitably prepared for studies beyond IGCSE in pure sciences, in applied sciences or in sciencedependent vocational courses
to develop abilities and skills that
•
are relevant to the study and practice of Chemistry
•
are useful in everyday life
•
encourage efficient and safe practice
•
encourage effective communication
4. to develop attitudes relevant to Chemistry such as
•
concern for accuracy and precision
•
objectivity
•
integrity
•
enquiry
•
initiative
•
inventiveness
5. to stimulate interest in the environment and caring for it
6.
to promote an awareness that
•
scientific theories and methods have developed, and continue to do so. as a result of co-operative
activities of groups and individuals
•
the study and practice of science are subject to social. economic. technological, ethical and cultural
influences and limitations
•
the applications of science may be both beneficial and detrimental to the individual, the community
and the environment
•
science transcends national boundaries and that the language of science, correctly and rigorously
applied, is universal.
6
3.2 Assessment objectives
The three assessment objectives in Cambridge lGCSE Chemistry are:
--
A
Knowledge with understanding
B
Handling information and problem solving
G Experimental skills and investigations
A description of each assessment objective follows.
A:
Knowledge with understanding
Students should be able to demonstrate knowledge and understanding in relation to
1.
scientific phenomena, facts, laws, definitions, concepts and theories
2.
scientific vocabulary, terminology and conventions (including symbols, quantities and units)
3. scientific instruments and apparatus, including techniques of operation and aspects of safety
4. scientific quantities and their determination
5. scientific and technological applications with their social, economic and environmental implications.
Curriculum content defines the factual material that candidates may be required to recall and explain.
Candidates will also be asked questions which require them to apply this material to unfamiliar contexts and
to apply knowledge from one area of the syllabus to knowledge of a different syllabus area.
Questions testing these objectives will often begin with one of the following words: define. state, describe,
explain or outline (see Glossary ofTerms).
B:
Handling information and problem solving
Students should be able, in words or using other written forms of presentation (i.e. symbolic, graphical and
numerical), to
1.
locate, select. organise and present information from a variety of sources
2.
translate information from one form to another
3.
manipulate numerical and other data
4.
use information to identify patterns, report trends and draw inferences
5.
present reasoned explanations for phenomena, patterns and relationships
6.
make predictions and hypotheses
7.
solve problems, including some of a quantitative nature.
7
Questions testing these skills may be based on information that is unfamiliar to candidates, requiring them
to apply the principles and concepts from the syllabus to a new situation, in a logical, deductive way.
Questions testing these skills will often begin with one of the following words: predict, suggest, calculate or
determine. (See the Glossary o!Terms.)
·C:
Experimental skills and investigations
Students should be able to
1.
know how to use techniques, apparatus and materials (including following a sequence of instructions
where appropriate)
2.
make and record observations, measurements and estimates
3.
interpret and evaluate experimental observations and data
4.
plan investigations, evaluate methods and suggest possible improvements (including the selection of
techniques, apparatus and materials).
3.3 Scheme of assessment
All candidates must enter for three papers: Paper 1; either Paper 2 or Paper 3; and one from Papers 4, 5 or 6.
Candidates who have only studied the Core curriculum, or who are expected to achieve a grade D or below,
should normally be entered for Paper 2.
Candidates who have studied the Extended curriculum, and who are expected to achieve a grade C or
above, should be entered for Paper 3.
All candidates must take a practical paper, chosen from: Paper 4 (Coursework), Paper 5 (Practical Test), or
Paper 6 (Alternative to Practical).
8
Paper 1
45 minutes
A multiple-choice paper consisting of 40 items of the four-choice type.
This paper will test skills mainly in Assessment objectives A and B.
Questiolrs will be based on the Core curriculum and will be of a difficulty appropriate to grades C to G.
This paper will be weighted at 30% of the final total available marks.
Paper 2
1 hour 15 minutes
Paper 3
1 hour 15 minutes
Written paper consisting of short-answer
and structured questions.
Written paper consisting of short-answer and
structured questions.
Questions will be based on the Core
curriculum and will be of a difficulty
appropriate to grades C to G.
Questions will be based on the Extended curriculum
and will be of a difficulty appropriate to the higher
grades.
Questions will test skills mainly in
Assessment objectives A and B.
Questions will test skills mainly in Assessment
objectives A and B.
A quarter of the marks available will be based on Core
material and the remainder on the Supplement.
80 marks
80 marks
This paper will be weighted at 50% of
the final total available marks.
This paper will be weighted at 50% of the final total
available ~1arks.
1 hour 15 minutes
Paper 4*
Paper 5*
Coursework
Practical Test
Alternative to Practical
School-based
assessment of practical
skills.**
Questions covering
experimental and
observational skills.
Written paper designed to test
familiarity with laboratory based
procedures.
weighted at 20% of the
final total available marks
weighted at 20% of the final
total available marks
weighted at 20% of the final total
available marks
9
Paper 6*
1 hour
*
This component tests appropriate skills in assessment Objective C. Candidates will not be required to
use knowledge outside the Core curriculum.
** Teachers may not undertake school-based assessment without the written approval of CIE. This is only
given to teachers who satisfy CIE requirements concerning moderation and who have to undergone
special training in assessment. CIE offers schools in-service training in the form of occasional faceto-face courses held in.countries where there is a need, and also through the CourseworkTraining
Handbook, avail~ble from CIE Publications.
3.4 Weightings
A: Knowledge with understanding
50% (not more than 25% recall}
B: Handling information and problem solving
30%
C: Experimental skills and investigations
20%
Teachers should take note that there is an equal weighting of 50% for skills (including handling information,
problem solving, practical, experimental and investigative skills} and for knowledge and understanding.
Teachers' schemes of work and the sequence of learning activities should reflect this balance, so that the
aims of the syllabus may be met, and the candidates fully prepared for the assessment.
A: Knowledge with understanding
25-30
48-52
0
47-54
B: Handling information and problem solving
10-15
27-32
0
26-33
0
0
40
20
C: Experimental skills and investigations
10
3.5 Exam combinations
Candidates can combine this syllabus in an exam session with any other CIE syllabus. except:
•
syllabuses with the same title at the same level
•
0652 IGCSE Physical Science
•
0653 IGCSE Combined Sde.nce:
•
0654 IGCSE Co-ordinated Sciences (Double Award)
•
5124 0 Level Science (Physics. Chemistry)
•
5126 0 Level Science (Chemistry, Biology)
•
5129 0 Level Combined Science
•
5130 0 Level Additional Combined Science
Please note that IGCSE, Cambridge International Level 1/Level 2 Certificates and 0 Level syllabuses are at
the same level.
3.6 Conventions (e.g. signs, symbols, terminology
and nomenclature)
Syllabuses and question papers conform with generally accepted international practice. In particular, the
following documents, published in the UK, should be used as guidelines:
Reports produced by the Association for Science Education lASE):
51 Units, Signs, Symbols and Abbreviations (1981)
Chemical Nomenclature, Symbols and Terminology for use in School Science (1985)
Signs, Symbols and Systematics: The ASE Companion to 16-19 Science (2000).
Litre/dm'
To avoid any confusion concerning the symbol for litre, dm' will be used in place of I or litre.
11
The Curriculum content below is a guide to the areas on which candidates are assessed.
It is important that, throughout this course, teachers should make candidates aware of the relevance of the
concepts studied to everyday life, and to the natural and man-made worlds.
In particular, attention should be drawn to:
•
the finite life of the world's resources and the need for recycling and conservation
•
economic considerations in the chemical industry, such as the availability and cost of raw materials and
..
energy
•
the importance of chemicals in both industry and everyday life.
Specific content has been limited in order to encourage this approach, and to allow flexibility in the design
of teaching programmes. CIE provides schemes of work, which can be found on the CIETeacher Support
website.
Candidates may follow the Core curriculum only or they may follow the Extended curriculum, which includes
both the Core and the Supplement.
Core
Supplement
•
Describe the states of matter and explain their
interconversion in terms of the kinetic particle theory
•
•
Describe and explain diffusion
•
Describe evidence for the movement of particles in
gases and liquids (a treatment of Brownian motion is
not required)
Describe dependence of ra<e of diffusion
on molecular mass (treated qualitatively)
2.1 Measurement
Core
•
Name appropriate apparatus for the measurement
of time, temperature, mass and volume, including
burettes, pipettes and measuring cylinders
2.2 (a) Criteria of purity
Core
Supplement
•
Describe paper chromatography
•
•
Interpret simple chromatograms
Interpret simple chromatograms,
including the use of R, values
•
Identify substances and assess their purity from
melting point and boiling point information
•
•
Understand the importance of purity in substances
in everyday life, e.g. foodstuffs and drugs
Outline how chromatography techniques
can be applied to colourless substances
by exposing chromatograms to
substances called locating agents
(knowledge of specific locating agents is
not required)
12
2.2 (b) Methods of purification
Core
•
Describe methods of purification by the use of a
suitable solvent. filtration. crystallisation, distillation
(including use of fractionating column). (Refer to the
fractional distillation of crude oil in sectioo 14.2 flnd
products of fermentation in section 14.6.)
•
Suggest suitable purification techniques, given
information about the substances involved
3.1 Atomic structure and the Periodic Table
Core
•
State the relative charges and approximate relative
masses of protons. neutrons and electrons
•
Define proton number and nucleon number
•
Use proton number and the simple structure of
atoms to explain the basis of the Periodic Table (see
section 9), with special reference to the elements of
proton number 1 to 20
•
Define isotopes
•
State the two types of isotopes as being radioactive
and non-radioactive
•
State one medical and one industrial use of
radioactive isotopes
•
Describe the build-up of electrons in 'shells' and
understand the significance of the noble gas
electronic structures and of valency electrons (the
ideas of the distribution of electrons in s and p
orbitals and in d block elements are not required.)
Note: a copy of the Periodic Table. as shown in the
Appendix, will be available in Papers 1, 2 and 3)
13
3.2 Bonding: the structure of matter
Core
•
Describe the differences between elements .
mixtures and compounds, and between metals and
non-metals
•
Describe an alloy, such as brass, as a mixture of ametal with other elements
3.2 (a) Ions and ionic bonds
Core
•
•
Describe the formation of ions by electron loss
or gain
Describe the formation of ionic bonds between
elements from Groups I and VII
3.2 (b) lvlolecules and covalent bonds
Core
Supple.ment
•
Describe the formation of single covalent bonds in
H,. C~ . H,O, CH, and HC1 as the sharing of pairs of
electrons leading to the noble gas configuration
•
Describe the formation of ionic bonds
between metallic and non-metallic
elements
•
Describe the differences in volatility, solubility and
electrical conductivity between ionic and covalent
compounds
•
Describe the lattice structure of ionic
compounds as a regular arrangement of
alternating positive and negative ions
3.2 (c) lvlacromolecules
Core
Supplement
•
Describe the giant covalent structures of graphite and
diamond
•
•
Relate their structures to the use of graphite as a
lubricant and of diamond in cutting
Describe the electron arrangement in
more complex covalent molecules such
as N 2, C,H,. CH,OH and CO,
•
Describe the macromolecular structure of
silicon(JV) oxide (silicon dioxide)
3.2 (d) lvletallic bonding
Supplement
----------·---- ·-------------------
14
•
Describe the similarity in properties
between diamond and silicon(IV) oxide.
related to their structures
•
Describe metallic bonding as a lattice
of positive ions in a 'sea of electrons'
and use this to describe the electrical
conductivity and malleability of metals
--~--~--------------
Core
Supplement
•
Use the symbols of the elements and write the
formulae of simple compounds
•
•
Deduce the formula of a simple compound from the
relative numbers of atoms present
Determine the formula of an ionic
compound from the charges on the ions
.. present
•
Deduce the formula of a simple compound from a
model or a diagrammatic representation
Construct equations with state symbols,
including ionic equations
•
Deduce the balanced equation for
a chemical reaction, given relevant
information
•
•
Construct word equations and simple balanced
chemical equations
•
Define relative atomic mass, A,
•
Define relative molecular mass, M,, as the sum of
the relative atomic masses (relative formula mass or
M, will be used for ionic compounds)
(Calculations involving reacting masses in simple
proportions may be set. Calculations will not involve
the mole concept.)
4.1 The mole concept
Supplement
•
Define the mole and the Avogadro
constant
15
•
Use the molar gas volume, taken as
24 dm 3 at room temperature and pressure
•
Calculate stoichiometric reacting masses
and volumes of gases and solutions,
solution concentrations expressed
in g/dm' and mol/dm'. (Calculations
involving the idea of limiting reactants
may be set. Questions on the gas laws
and the conversion of gaseous volumes to
different temperatures and pressures will
not be set.)
•
Calculate empirical formulae and
molecular formulae
•
Calculate % yield and % purity
Core
Supplement
•
•
Relate the products of electrolysis to
the electrolyte and electrodes used,
exempJified by the specific examples in
the Core together with aqueous copper(ll)
sulfate using carbon electrodes and using
copper electrodes (as used in the refining
of copper)
Describe the electrode products in the
electrolysis of:
molten lead(! I) bromide
concentrated hydrochloric acid
concentrated aqueous sodium chloride
between inert electrodes (platinum or carbon)
•
State the general principle that metals or hydrogen
are formed at the negative electrode (cathode). and
that non-metals (other than hydrogen) are formed at
the positive electrode (anode)
•
Describe electrolysis in terms of the ions
present and reactions at the electrodes in
the examples given
•
Predict the products of the electrolysis of a specified
binary compound in the molten state
•
•
Describe the electroplating of metals
Predict the products of electrolysis of a
specified halide in dilute or concentrated
aqueous solution
•
Name the uses of electroplating
•
Describe, in outline, the manufacture of
•
Describe the reasons for the use of copper and
(steel-cored) aluminium in cables, and why plastics
and ceramics are used as insulators
aluminium from pure aluminium oxide
in molten cryolite
chlorine and sodium hydroxide from
concentrated aqueous sodium chloride
(Starting materials and essential conditions
should be given but not technical details or
diagrams.)
-
6. 1 Energetics of a reaction
Core
•
Supplement
Describe the meaning of exothermic and
•
endothermic reactions
16
Describe bond breaking as endothermic
and bond forming as exothermic
6.2 Production of energy
Core
Supplement
•
Describe the production of electrical
energy from simple cells, i.e. two
electrodes in an electrolyte. (This should
be linked with tbe·reactivity series in
section 10.2 and redox in section 7.3.)
•
Describe the use of hydrogen as a
potential fuel reacting with oxygen to
generate electricity in a fuel cell (details
of the construction and operation of a fuel
cell are not required)
Describe the production of heat energy by burning
fuels
•
o
Describe hydrogen as a fuel
Describe radioactive isotopes, such as 235 U, as a
source of energy
7.1 Speed of reaction
Core
Supplement
•
Describe the effect of concentration, particle size,
catalysts (including enzymes) and temperature on
the speeds of reactions
•
Devise a suitable method for investigating
the effect of a given variable on the speed
of a reaction
•
Describe a practical method for investigating the
speed of a reaction involving gas evolution
•
Interpret data obtained from experiments
concerned with speed of reaction
•
Describe the application of the above factors to the
danger of explosive combustion with fine powders
(e.g. flour mills) and gases (e.g. mines)
•
17
Describe and explain the effects of
temperature and concentration in terms of
collisions between reacting particles
•
Describe the effect of light on the speed
of reactions
•
Describe the use of silver salts in
photography as a process of reduction of
silver ions to silver; and photosynthesis as
the reaction between carbon dioxide and
water in the presence of chlorophyll and
sunlight (energy) to produce glucose
'
7.2 Reversible reactions
Core
Supplement
•
•
Describe the idea that some chemical reactions can
be reversed by changing the reaction conditions
Predict the effect of changing the
conditions (temperature and pressure) on
other reversible reactions
(Limited to the effects of heat on hydrated salts.
Concept of equilibrium is not required.)
•
Concept of equilibrium-
7.3 Redox
Supplement
Core
Define oxidation and reduction in terms of oxygen
•
•
loss/gain. (Oxidation state limited to its use to name
ions, e.g. iron(! I), iron(III), copper([]), manganate(VIl),
dichromate(Vl) .)
Define redox in terms of electron
transfer
•
Identify redox reactions by changes
in oxidation state and by the colour
changes involved when using acidified
potassium manganate(VIl), and
potassium iodide. (Recall of equations
involving KMnO, is not required.)
8.1 The characteristic properties of acids and bases
Core
Supplement
•
•
Describe the characteristic properties of acids as
reactions with metals, bases, carbonates and effect
proton transfer, limited to aqueous
solutions
on litmus
•
Describe the characteristic properties of bases as
Define ac1ds and bases in terms of
•
reactions with acids and with ammonium salts and
Describe the meaning of weak and
strong acids and bases
effect on litmus
•
Describe neutrality and relative acidity and alkalinity
in terms of pH (whole numbers only) measured using
Universal Indicator paper
•
Describe and explain the importance of controlling
acidity in soil
8.2 Types of oxides
Core
Supplement
•
•
Classify oxides as either acidic or basic, related to
Further classify other oxides as neutral or
amphoteric
metallic and non-metallic character
18
8.3 Preparation of salts
Core
Supplement
•
•
Describe the preparation of insoluble
salts by precipitation
•
Suggest a method of making a given
salt from suitable starting material. given
appropriate information
Describe the preparation, separation and purification
of salts as examples of some of the techniques
specified in section 2.2(b) and the reactions specified
in section 8.1
8.4 Identification of ions and gases
Core
•
Describe the following tests to identify:
aqueous cations:
aluminium. ammonium. calcium, copper(!!), iron(fl),
iron(lll) and zinc (using aqueous sodium hydroxide
and aqueous ammonia as appropriate) (Formulae of
complex ions are not required.)
anions:
carbonate (by reaction with dilute acid and then
limewater). chloride (by reaction under acidic
conditions with aqueous silver nitrate), iodide (by
reaction under acidic conditions with aqueous silver
nitrate), nitrate (by reduction with aluminium), sulfate
(by reaction under acidic conditions with aqueous
barium ions)
gases:
ammonia (using damp red litmus paper), carbon
dioxide (using limewater), chlorine (using damp litmus
paper), hydrogen (using lighted splint). oxygen (using a
glowing splint).
19
Core
•
Describe the Periodic Table as a method of
classifying elements and its use to predict properties
of elements
9.1 Periodic trends
Core
Supplement
•
•
Describe the change from metallic to non-metallic
character across a period
Describe the relationship between Group
number, number of valency electrons and
metallic/non-metallic character
9.2 Group properties
Supplement
Core
•
Describe lithium, sodium and potassium in Group
I as a collection of relatively soft metals showing
a trend in melting point, density and reaction with
water
•
Predict the properties of other elements in Group I,
given data, where appropriate
•
Describe chlorine, bromine and iodine in Group VII as
a collection of diatomic non-metals showing a trend in
colour, and state their reaction with other halide ions
Predict the properties of other elements in Group
VII, given data where appropriate
•
Identify trends in other Groups, given
information about the elements concerned
9.3 Transition elements
Core
•
Describe the transition elements as a collection of
metals having high densities, high melting points
and forming coloured compounds, and which, as
elements and compounds, often act as catalysts
fi.4 Noble gases
Core
•
Describe the noble gases as being unreactive
Describe the uses of the noble gases in providing
an inert atmosphere, i.e. argon in lamps, helium for
filling balloons
---~·------
20
10.1 Properties of metals
Core
Describe the general physical and chemical properties of
metals
Explain why metals are often used in the form of alloys
Identify representations of alloys from diagrams of
structure
•
10.2. Reactivity series
Core
Supplement
Place in order of reactivity: potassium, sodium, calcium,
magnesium, zinc, iron, (hydrogen) and copper, by
reference to the reactions, if any, of the metals with
•
water or steam
Describe the reactivity series as
related to the tendency of a metal to
form its positive ion, illustrated by its
reaction, if any, with
the aqueous ions
dilute hydrochloric acid
the oxides
and the reduction of their oxides with carbon
of the other listed metals
•
•
Describe the action of heat on the
hydroxides and nitrates of the listed
metals
•
Account for the apparent unreactivity
of aluminium in terms of the oxide
layer which adheres to the metal
Deduce an order of reactivity from a given set of
experimental results
10.3 (a) Extraction of metals
Core
Supplement
•
Describe the ease in obtaining metals from their ores by
relating the elements to the reactivity series
•
•
Name the main ore of aluminium as bauxite (see
section 5)
Describe the essential reactions in the extraction of iron
from hematite
•
Describe the conversion of iron into steel using basic
oxides and oxygen
21
describe in outline, the extraction of
zinc from zinc blende
10.3 (b) Uses of metals
Core
Supplement
•
•
Name the uses of aluminium:
in the manufacture of aircraft because of its strength
and for making brass
and low density
•
in food containers because of its resistance to
corrosion
•
Describe the idea of changing the properties of iron by
the controlled use of additives to form steel alloys
•
Name the uses of mild steel (car bodies and machinery)
and stainless steel (chemical plant and cutlery)
Name the uses of zinc for galvanising
Name the uses of copper related to
its properties (electrical wiring and in
cooking utensils)
Supplement
Core
•
Describe a chemical test for water
•
Describe, in outline, the purification of the water supply
in terms of filtration and chlorination
•
Name some of the uses of water in industry and in
the home
•
Describe'the composition of clean air as being
approximately 79% nitrogen, 20% oxygen and the
remainder as being a mixture of noble gases, water
vapour and carbon dioxide
•
Name the common pollutants in the air as being carbon
monoxide, sulfur dioxide, oxides of nitrogen and lead
compounds
•
State the source of each of these pollutants:
carbon monoxide from the incomplete combustion
of carbon-containing substances
sulfur dioxide from the combustion of fossil fuels
which contain sulfur compounds (leading to 'acid
rain'- see section 13)
oxides of nitrogen from car exhausts
•
•
Describe and explain the presence of
oxides of nitrogen in car exhausts and
their catalytic removal
•
Describe the separation of oxygen and
nitrogen from liquid air by fractional
State the adverse effect of common pollutants on
buildings and on health
distillation
22
•
Describe methods of rust prevention, specifically paint
and other coatings to exclude oxygen
•
Describe the need for nitrogen-, phosphorus- and
potassium-containing fertilisers
•
Describe the displacement of ammonia from its salts
•
State that carbon dioxide and methane are greenhouse
gases and may contribute to climate change
•
Describe the formation of carbon dioxide:
•
Describe sacrificial protection in terms
of the reactivity series of metals
and galvanising as a method of rust
prevention
•
Describe the essential conditions for
the manufacture of ammonia by the
Haber process including the sources
of the hydrogen and nitrogen, i.e.
hydrocarbons or steam and air
•
Describe the carbon cycle, in simple
terms, to include the processes
of combustion, respiration and
photosynthesis
as a product of complete combustion of carboncontaining substances
as a product of respiration
as a product of the reaction between an acid and a
carbonate
•
State the sources of methane, including decomposition
of vegetation and waste gases from digestion in animals
Supplement
23
•
Name some sources of sulfur
•
Name the use of sulfur in the
manufacture of sulfuric acid
•
Name the uses of sulfur dioxide
as a bleach in the manufacture of
wood pulp for paper and as a food
preservative (by killing bacteria)
•
Describe the manufacture of sulfuric
acid by the Contact process, including
essential conditions
•
Describe the properties of dilute
sulfuric acid as a typical acid
Core
•
Describe the manufacture of lime (calcium oxide) from
calcium carbonate (limestone) in terms of the chemical
reactions involved
•
Name some uses of lime and slaked lime as in treating
acidic soil and neutral ising acidic industrial waste
products, e.g. flue gas desulfurisation
•
Name the uses of calcium carbonate in the manufacture
of iron and of cement
14.1 Names of compounds
Supplement
Core
•
Name and draw the structures of methane, ethane,
ethanol, ethanoic acid and the products of the reactions
stated in sections 14.4-14.6
•
State the type of compound present. given a chemical
name ending in -ane. -ene, -ol, or -oic acid, or a molecular
structure
14.2 Fuels
Core
•
Name the fuels coal, natural gas and petroleum
Name methane as the main constituent of natural gas
•
Describe petroleum as a mixture of hydrocarbons and its
separation into useful fractions by fractional distillation
Name the uses of the fractions as:
refinery gas for bottled gas for heating and cooking
gasoline fraction for fuel (petrol) in cars
naphtha fraction for making chemicals
kerosene/paraffin fraction for jet fuel
diesel oil/gas oil for fuel in diesel engines
fuel oil fraction for fuel for ships and home heating
systems
lubricating fraction for lubricants, waxes and polishes
bitumen for making roads
24
Name and draw the structures of the
unbranched alkanes. alkenes (not cistrans), alcohols and acids containing
up to four carbon atoms per molecule
14.3 Homologous series
Core
Supplement
•
•
Describe the general characteristics of
an homologous series
•
Describe and identify structural
Describe the concept of homologous series as a 'family'
of similar compounds with similar properties due to the
presence of the same functional group
isomerism
14.4 Alkanes
Core
Supplement
•
Describe the properties of alkanes (exemplified by
methane) as being generally unreactive, except in terms
of burning
•
•
Describe the bonding in alkanes
Describe substitution reactions of
alkanes with chlorine
14.5 Alkenes
Core
Supplement
•
Describe the manufacture of alkenes and of hydrogen by
cracking
•
•
Distinguish between saturated and unsaturated
hydrocarbons
•
-
from molecular structures
-
by reaction with aqueous bromine
Describe the formation of poly(ethene) as an example of
addition polymerisation of monomer units
14.6 Alcohols
Core
•
Describe the formation of ethanol by fermentation and
by the catalytic addition of steam to ethene
•
Describe the properties of ethanol in terms of burning
•
Name the uses of ethanol as a solvent and as a fuel
25
Describe the properties of alkenes
in terms of addition reactions with
bromine, hydrogen and steam
14.7 Acids
14.8 Macromolecules
Supplement
•
Describe the formation of ethanoic acid by the oxidation
of ethanol by fermentation and with acidified potassium
manganate(VII)
•
Describe ethanoic acid as a typical weak acid
•
Describe the reaction of ethanoic acid with ethanol to give an
ester (ethyl ethanoatel
Supplement
•
14.8 (al Synthetic polymers
.,
Describe macromolecules in terms of large molecules built
up from small units (mononomers), different macromolecules
having different units and/or different linkages
Supplement
•
Name some typical uses of plastics and of man-made fibres
•
Describe the pollution problems caused by non-biodegradable
plastics
•
Deduce the structure of the polymer product from a given
alkene and vice versa
•
Describe the formation of nylon (a polyamide) and Terylene (a
polyester) by condensation polymerisation, the structure of nylon
being represented as:
0
I .
0
0
I
0
I
0
I
I
-c~c-~-[]-~-c~c-~-[]-~-c~
H
H
H
H
and the structure of Terylene as:
0
0
0
0
-~~~-o-[]-o-~~~-o-[]-o(Details of manufacture and mechanisms of these
polymerisations are not required.)
26
14.8 (b) Natural macromolecules
Supplement
•
Name proteins, fats and carbohydrates as the main constituents
of food
•
Describe proteins as possessing the same (amide) linkages as
nylon but with different units
Describe the structure of proteins as:
H
0
R
H
0
I
I
I
I
I
-N-C-C-N-C-C-N-C-C1
I
I
I
R
H
0
R
•
Describe the hydrolysis of proteins to amino acids (Structures
and names are not required.)
•
Describe fats as esters possessing the same linkage as Tery!ene
but with different units
•
Describe soap as a product of hydrolysis of fats
•
Describe complex carbohydrates in terms of a large number of
sugar units, considered as Ho-D-oH, joined together by
condensation polymerisation,
e.g. -o-D-o-D-o-D-o-
-·--~-
•
Describe the acid hydrolysis of complex carbohydrates (e.g.
starch) to give simple sugars
•
Describe the fermentation of simple sugars to produce ethanol
(and carbon dioxide) (Candidates will not be expected to give
the molecular formulae of sugars.)
•
Describe, in outline, the usefulness of chromatography
in separating and identifying the product of hydrolysis of
carbohydrates and proteins
-----~
27
6.1 Grade descriptions
;
I
The scheme of assessment is intended to encourage positive achievement by all candidates.
•
relate facts to principles and theories and vice versa
•
state why particular techniques are preferred for a procedure or operation
•
select and collate information from a number of sources and present it in a
clear logical form
•
solve problems in situations which may involve a wide range of variables
•
process data from a number of sources to identify any patterns or trends
•
generate a hypothesis to explain facts, or find facts to support a hypothesis
•
link facts to situations not specified in the syllabus
•
describe the correct procedure(s) for a multi-stage operation
•
select a range of information frorn a given source and present it in a clear
logical form
•
identify patterns or trends in given information
•
solve a problem involving more than one step, but with a limited range of
variables
•
generate a hypothesis to explain a given set of facts or data
•
recall facts contained in the syllabus
•
indicate the correct procedure for a single operation
•
select and present a single piece of information from a given source
•
solve a problem involving one step, or more than one step if structured help is
given
•
identify a pattern or trend where only minor manipulation of data is needed
•
recognise which of two given hypotheses explains a set of facts or data
A Grade A
candidate
will be able
to:
A Grade C
candidate
will be able
to:
A Grade F
candidate
will be able
to:
36
6.1 Grade descriptions
The scheme of assessment is intended to encourage positive achievement by all candidates.
•
relate facts to principles and theories and vice versa
•
state why particular techniques are preferred for a procedure or operation
•
select and collate information from a number of sources and present it in a
clear logical form
o
solve problems in situations which may involve a wide range of variables
•
process data from a number of sources to identify any patterns or trends
o
generate a hypothesis to explain facts, or find facts to support a hypothesis
•
•
•
link facts to situations not specified in the syllabus
A Grade A
candidate
will be able
to:
.,
A Grade C
candidate
will be able
to:
A Grade F
candidate
will be able
to:
describe the correct procedure(s) for a multi-stage operation
select a range of information from a given source and present it in a clear
logical form
•
identify patterns or trends in given information
•
solve a problem involving more than one step, but with a limited range of
variables
•
generate a hypothesis to explain a given set of facts or data
•
•
•
•
recall facts contained in the syllabus
•
•
indicate the correct procedure for a single operation
select and present a single piece of information from a given source
solve a problem involving one step, or more than one step if structured help is
given
identify a pattern or trend where only minor manipulation of data is needed
recognise which of two given hypotheses explains a set of facts or data
~-~-------·--·--~----------~-----------
36
---
6.3 Notes for use in qualitative analysis
Tests for anions
carbonate (C0 3''1
add dilute acid
effervescence, carbon dioxide
produced
chloride (CrJ
(in solution}
acidify with dilute nitric acid, then add
aqueous silver nitrate
white ppt.
iodide WI
lin solution}
acidify with dilute nitric acid, then add
aqueous silver nitrate
yellow ppt.
nitrate (N0 3·1
[in solution}
add aqueous sodium hydroxide, then
aluminium foil; warm carefully
ammonia produced
sulfate (SO ,'·1
[in solution}
acidify, then add aqueous barium nitrate
white ppt.
Tests for aqueous cations
aluminium IAZ'•I
white ppt., soluble in excess giving a
colourless solution
ammonium (NH;J
ammonia produced on warming
calcium (Ca''l
white ppt., insoluble in excess
no ppt. or very slight white ppt.
light blue ppt., insoluble in excess
light blue ppt., solub[e in excess,
giving a dark blue solution
green ppt., insoluble in excess
green ppt., insoluble in excess
red-brown ppt., insoluble in excess
red-brown ppt., insoluble in excess
white ppt., soluble in excess, giving a
colourless solution
white ppt., soluble in excess,
giving a colourless solution
ammonia (NH 3)
turns damp red litmus paper blue
carbon dioxide (C0 2)
turns limewater milky
chlorine (CI,)
bleaches damp litmus paper
hydrogen
'pops' with a lighted splint
oxygen 10,1
relights a glowing splint
38
white ppt., insoluble in excess
6.4 Safety in the laboratory
Responsibility for safety matters rests with Centres. Further information can be found in the following UK
associations. websites, publications and regulations.
Associations
CLEAPSS is an advisory service providing support in practical science and technology, primarily for UK schools.
International schools and post-16 colleges can apply for associate membership which includes access to the
CLEAPSS publications listed below
http:/ /www.cleapss.org.uk
Websites
http:/ /www.chemsoc.org/networks/learnnet/Safety.htm
http://www. ncbe.reading.ac.uk/NCBE/SAFETYI menu.html
http:/ /www.microbiologyonline.org.uk/safety.html
Publications
Safeguards in the School Laboratory, ASE, 11 <h Edition, 2006
Topics in Safety, ASE, 3" Edition, 2001
CLEAPSS Laboratory Handbook, updated 2005 (available to CLEAPSS members only)
CLEAPSS Hazcards, 2005 update of 1995 edition (available to CLEAPSS members only)
Safety in Science Education. DIES, HMSO, 1996
Hazardous Chemicals Manual, SSERC, 1997
Hazardous Chemicals. An interactive manual for science education, SSERC, 2002 (CD)
Ul< Regulations
Control of Substances Hazardous to Health Regulations (COSH H) 2002
http:/ /www.opsi.gov.uk/SI/si2002/20022677.htm, a brief guide may be found at
http:/ /www.hse.gov.uk{pubns/indg136.pdf
39
6.5 Glossary of terms used in science papers
The glossary (which is relevant only to Science subjects) will prove helpful to candidates as a guide. but it is
neither exhaustive nor definitive. The glossary has been deliberately kept brief, not only with respect to the
number of terms included, but also to the descriptions of their meanings. Candidates should appreciate that
the meaning of a term must depend, in part, on its context.
1.
Define (the term(s) ... I is intended literally, only a formal statement or equivalent paraphrase being
required.
2.
What do you understand by/What is meant by (the term lsi .. I normally implies that a definition should
be given, together with some relevant comment on the significance or context of the term(s) concerned,
especially where two or more terms are included in the question. The amount of supplementary
comment intended should be interpreted in the light of the indicated mark value.
3.
State implies a concise answer with little or no supporting argument (e.g. a numerical answer that can
readily be obtained 'by inspection').
4.
List requires a number of points, generally each of one word, with no elaboration. Where a given
number of points is specified this should not be exceeded.
5.
Explain may imply reasoning or some reference to theory, depending on the context.
6.
Describe requires the candidate to state in words (using diagrams where appropriate) the main points
of the topic. It is often used with reference either to particular phenomena or to particular experiments.
In the former instance, the term usually implies that the answer should include reference to (visual)
observations associated with the phenomena.
In other contexts, describe should be interpreted more generally (i.e. the candidate has greater
discretion about the nature and the organisation of the material to be included in the answer). Describe
and explain may be coupled, as may state and explain.
7.
Discuss requires the candidate to give a critical account of the points involved in the topic.
8.
Outline implies brevity (i.e. restricting the answer to giving essentials).
9.
Predict implies that the candidate is not expected to produce the required answer by recall but by
making a logical connection between other pieces of information. Such information may be wholly given
in the question or may depend on answers extracted in an earlier part of the question.
Predict also implies a concise answer with no supporting statement required.
10. Deduce is used in a similar way to predict except that some supporting statement is required,
e.g. reference to a law or principle, or the necessary reasoning is to be included in the answer.
11. Suggest is used in two main contexts, i.e. either to imply that there is no unique answer (e.g. in
Chemistry, two or more substances may satisfy the given conditions describing an 'unknown'), or to
imply that candidates are expected to apply their general knowledge of the subject to a 'novel' situation,
one that may be formally 'not in the syllabus'- rnany data response and problem solving questions are
of this type.
12. Find is a general term that may variously be interpreted as calculate, measure, determine, etc.
40
13. Calculate is used when a numerical answer is required. In general, working should be shown, especially
where two or more steps are involved.
14. Measure implies that the quantity concerned can be directly obtained from a suitable measuring
instrument (e.g. length, using a rule, or mass, using a balance).
15. Determine often implies that the quantity concerned cannot be measured directly but is obtained
by, calculation, substituting measured or known values of other quantities into a standard formula
e.g. relative molecular mass.
·-
16. Estimate implies a reasoned order of magnitude statement or calculation of the quantity concerned,
making such simplifying assumptions as may be necessary about points of principle and about the
values of quantities not otherwise included in the question.
17. Sketch. when applied to graph work, implies that the shape and/or position of the curve need only be
qualitatively correct, but candidates should be aware that, depending on the context. some quantitative
aspects may be looked for (e.g. passing through the origin, having an intercept).
In diagrams, sketch implies that simple, freehand drawing is acceptable; nevertheless, care should be
taken over proportions and the clear exposition of important details.
41
6.6 Mathematical requirements
Calculators may be used in all parts of the examination.
Candidates should be able to:
•
•
•
•
add .._subtract, multiply and divide
use averages, decimals, fractions, percentages, ratios and reciprocals
recognise and use standard notation
use direct and inverse proportion
•
use positive, whole number indices
•
•
draw charts and graphs from given data
interpret charts and graphs
•
select suitable scales and axes for graphs
•
•
make approximate evaluations of numerical expressions
recognise and use the relationship between length, surface area and volume and their units on metric
scales
•
use usual mathematical instruments (ruler, compasses, protractor, set square)
•
understand the meaning of angle, curve, circle, radius, diameter, square, parallelogram, rectangle and
diagonal
•
solve equations of the form x = yz for any one term when the other two are known.
42
.J
'
'
The Periodic Table of the Elements
Group
I
II
I
I
Ill
I
IV
I
v
I
VI
I
VII
I
0
1
4
H
He
Heiiun1
Hydrogen
1
7
9
11
Li
Be
B
Beryllrum
Lrthrunl
3
,.
2
Boron
4
12
14
16
19
20
c
N
0
F
Ne
Nrtrogen
Carbon
'G·
5
7
Oxvgcn
8
No~
fluonnu
10
9
23
24
27
28
31
32
35.5
40
Na
Mg
A/
Si
p
s
C/
Ar
Aluminium
Srflcon
Sod rum
11
lvld(l<lf!SIUm
12
13
"
39
Ca
K
C~ICrum
Potassrum
19
45
48
51
52
55
56
59
59
64
65
70
" 73
Sc
Ti
v
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
Gallrurll
Scandium
20
Titamum
22
21
Vanadrurn
23
Chromium
24
85
88
89
91
93
96
Rb
Sr
y
Zr
Nb
Mo
103
106
108
112
115
Ru
Rh
Pd
Ag
Cd
In
Sn
26
Tc
I,Jrc~el
Cobalt
28
27
Z•nc
Copper
29
31
30
Sulfur
16
Argcn
Chlounc
18
17
75
79
80
84
As
Se
Br
Kr
Arsemc
33
Bromme
Selenli.Bll
34
Krypton
36
35
122
128
127
131
Sb
Te
I
Xe
Xenon
133
137
139
178
181
184
186
192
195
197
201
204
207
Cs
Ba
La
Hf
Ta
w
Re
Os
lr
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
c~esrum
Barium
Lanthanum
Hafnium
Tantalum
Tun(!sten
Rhenium
Osm•um
l<id•um
Plahnum
Gold
Mercury
Thallium
Lead
B•smulh
Polon•um
A.stat"'~
Radl>'1
Strontium
38
Fr
fronc•um
87
72
226
227
Ra
Ac
Rad•um
Nrobium
41
40
-7
56
55
Zircomum
39
73
Molybdenum Technetium
42
43
76
75
74
Rhodium
45
Palladium
46
78
77
Silver
Cadmium
48
47
79
tndrun1
49
80
';;n
51
50
81
Antimony
lod'na
Ruthenium
44
190
Rubrdium
37
Yttrium
101
Gerrnar.,um
32
119
Iron
Manganese
25
Phosphorus
15
54
53
209
83
82
Teilunum
52
"
c
86
85
actm•um
88
89
t
·ss-71 Lanthanoid series
t90-1 03 Actinoid series
Key0
140
141
144
Ce
Pr
Nd
Cerium
PraseO<jy<'ltum
Neodymium
Prometh•um
59
60
61
58
a = relat1vei.l tomic rn<.lss
X= atomic symbol
b =proton (atomic) number 90
232
Pm
150
152
157
159
163
165
167
169
173
175
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Samanum
62
Europ•um
63
Tmb<um
GadolllliUm
64
65
Dysp<osium
66
Hoi mourn
Erb1um
68
67
Thuhum
Luleuum
Yumbium
71
70
69
238
Th
Pa
u
Np
Pu
Am
Cm
Bl<
Cf
Es
Fm
Md
No
Lr
Thorium
PrO!OCII!liUffi
Uran•um
Neptumum
PlutOnium
Ameut•um
Cunum
Berkelium
Cal•fornoum
E•nsteu11um
Ferm1um
Mendelov1um
~lobelium
Lawrencoum
98
99
91
92
93
94
95
96
97
The volume of one mole of any gas is 24 dm 3 at room temperature and pressure {r.t.p.)
~
101
102
---'--
103
CHEMISTRY 0620 IGC0to ZUlu
NOTES FOR USE IN QUALITATIVE ANALYSIS
Tests for anions
anion
test
test result
carbonate (CO 3 '-)
add dilute acid
effervescence,
carbon dioxide produced
chloride (CZ-)
[in solution]
acidify with dilute nitric acid, then add
aqueous silve~ nitrate
white ppt.
iodide (J)
[in solution]
acidify with dilute nitric acid, then add
aqueous silver nitrate
yellow ppt.
nitrate (NO,l
[in solution]
add aqueous sodium hydroxide, then
aluminium foil; warm carefully
ammonia produced
sulfate (SO/l
[in solution]
~cidify, then add aqueous barium nitrate
white ppt.
Tests for aqueous cations
cation
effect of aqueous sodium hydroxide
effect of aqueous ammonia
aluminium (A1 3')
white ppt., soluble in excess giving a
colourless solution
white ppt., insoluble in excess
ammonium (NH;)
ammonia produced on warming
-
calcium (Ca2 ')
white ppt., insoluble in excess
no ppt. or very slight white ppt.
copper (Cu'•)
light blue ppt., insoluble in excess
light blue ppt., soluble in excess,
giving a dark blue solution
iron(II) (Fe ' )
green ppt., insoluble in excess
green ppt., insoluble in excess
iron(I!I) (Fe 3•)
red-brown ppt., insoluble in excess
red-brown ppt., insoluble in excess
zinc (Zn'•)
white ppt., soluble in excess,
giving a colourless solution
white ppt., soluble in excess,
giving a colourless solution
2
Tests for gases
gas
test and test result
ammonia (NH3 )
turns damp red litmus paper blue
carbon dioxide (C0 2 )
turns limewater milky
chlorine ( C 12 )
bleaches damp litmus paper
hydrogen (Hz)
'pops' with a lighted splint
oxygen (0 2 )
relights a glowing splint