stpm chemistry chapter 3

8/3/2019 Stpm Chemistry Chapter 3

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STPM CHEMISTRY CHAPTER 3

GROUP 14:C,Si,Ge,Sn,Pb

Prepared by : LEE WEI SHAN/U6F



Analysis of the STPM Chemistry

Questions (2001-2009);group 14

years 2005 2006 2007 2008 2009

Number ofquestionsppr 1:ppr 2

2 ; ½ sec B 2 ; ½ sec A 1 ; 1 sec A 2 ; 1 sec A 2 ; ½ sec B



Allotropes

• An allotrope is a variant of a substanceconsisting of only one type of atom asdifferent form under different condition.

• This dictinctive form of the same elementare known as allotropes.



Graphite – used as lubricant (powder or oily suspension)

• layered lattice structure

•

hexoganal for the crystal system• density is 2.25 g cm-3

• each carbon atom is bonded by strong covalent bonds (sp2hybridisation / trigonal planar) with three other carbon atoms

to formed hexagonal ring.• the layer are held together by weak van der Waals forces.

• graphite is soft and slippery due to weak van der Waalsforces allow the layer to slide over one another.

•

graphite is a moderate conductor of electricity along its layer(in the direction parallel but not perpendicular to the laver)due to a free electron (per carbon atom) which can movethroughout the solid lattice. (Each carbon atom has oneouter shell electron (unhybridised p electron) which is notused to form covalent bonds.)



Diamond – used as abrasives (high velocity cutting tools) and

ornaments (high refractive index)

• crystallises in a face-centred cubic structure.

• single giant molecule.

• density is 3.50 g cm-3

• each carbon atom is bonded by strong covalent bonds (sp3

hybridisation) withfour other carbon atoms to formed three-dimensional giant structure.

• diamond has great hardness and high melting point due to the strong covalent bonds

in the 3-D structure.

• diamond is a non-conductor of electricity due to all the four valence electrons of thecarbon atoms are involved with covalent bonding, therefore no free/delocalised

electrons.



Fullerene / Buckyball / Buckminsterfullerene – used as

lubricant, semi-conductor, superconductors and catalyst

• Molecular formulae of fullerene areC20 (smallest member), C32, C60 (most

common member), C70, C76, C78, C84 and

C90.

• spherical molecules of 20 –

90 carbon atoms(32 sides, 12 pentagons and 20 hexagons).

• simple molecular solid.

• each carbon atom is bonded by strongcovalent bonds (sp2 hybridisation / trigonal

planar) with three other carbon atoms.

• Fullerene is a superconductor when it mixed

with other metals.



USES OF CARBON ININDUSTRY

Composite materials, often shortened tocomposites or called composition materials, are

engineered or naturally occurring materials made

from two or more constituent materials with

significantly different physical or chemicalproperties.Examples of carbon compounds and

their uses are :

COMPOSITE COMPOUND USES

CARBON LAMINATES AIRCRAFTS,BOAT HULLS

KEVLAR CANVAS FOR TENT,ARMOUR

CARBON AND FIBREGLASS SPORTS EQUIPMENT

TUNGSTEN CARBIDA CUTTING TOOLS,ABRASIVE

CARBON CONCRETE CONSTRUCTION



USE OF SILICON AND SILICATE ININDUSTRY

Silicon is use:

• in the electronics industry as asemiconductor,

• in alloys used in the electrical industry,

and• for the manufacture of Silicones, which are

use as fluid,elastomer,resin.



Silicate is use In:

• primary raw material for industrialPortland cement

• production of glass for windows, drinking

glasses, beverage bottles, and many otheruses



• Silicates are compounds where Si and O areabundant and are major mineral components of

the earths crust and mantle• The basic unit for all silicates is the (SiO4)4-

tetrahedron.

• eg: zircon,ZrSiO4 which can be cut to

look like diamond

calcium silicateCa2SiO4,important component in cement.



• Inosilicates -(chain silicates)

• The most important two mineral groups

• are the pyroxenes and the amphiboles.



Ring and chain silicates

SiO2

/ \

O O

| |

O2Si SiO2 \ /

O

• The precious stone beryl Be3Al2(SiO3)6 contain six-silica rings.

• Single chain silica are called pyroxenes. The natural pyroxenesinclude enstatite, MgSiO3; diopside, CaMg(SiO3)2; and jadeite,NaAl(SiO3)2.



SHEET SILICATES

• Is formed when each silicate tetrahedron is linked tothree other by sharing 3 oxygen atom per unit,an infinite2D sheet structure is formed.

• Bonded weakly together

• Cleave heavily on to one another

• Weak van der waal forces causes

it to “glide” and give a slippery feel.



FRAMEWORK STRUCTURES

• Formed when all 4 angles of SiO4 are shared by 4 otherunit

• Quartz shape

• Used as oscilators, optic instruments and glass



KAOLIN

• Label given due to high quality clay

• Al2Si2O5(OH)4

• Formed by removing 1 layer of SiO2 are removed so 1 layer of SiO4

shares corner with 1 layer of AlO6.

• used in ceramics, medicine, coated paper, as a food additive intoothpaste, as a light diffusing material in white incandescent light

bulbs, and in cosmetics. It is generally the main component in

porcelain.



MOMTMORILLONITE

• Molecular formula of (Al,Mg)2(Si4O10)(OH)2

• Consist of identical sheets

• Forms semi-solid gel in water

• Used in cation-exchange chromatography

SILICA IS THE MAIN COMPONENT OF GLASS



SILICA IS THE MAIN COMPONENT OF GLASS

GLASS COMPOSITION CHARACTERISTIC USES

SODA GLASS SiO2,

NA2C03,CACO3 Transparent,lowmelting point,notresistent to heat andchemical reaction

bottles, jars,everydaydrinkingglasses, andwindow glass.

Borosilicate glass SIO,B203,NA2O,A

L2O3

Heat resistent,low

thermalexpansion,transparent to coloured light andinfra-rays

Test

tube,cookingware

Quartz glass SiO2 Low thermalexpansion,hightransparency

Optical studies

Lead glass(crystalglass)

Sio2,PbO2,Na2O High refractiveindex,high density

Lens andprisms

METAL OXIDES ARE SOMETHIMES ADDED TO GLASS TO

PRODUCE COLOURED GLASS eg: co2+ for dark bluecolour,it aslo softens over a wide rang of temperatures



USES OF TIN ALLOYS

• Tin is extracted from cassiterite ore (SnO2),

• Used in making cans and alloys



STPM 2003/P1/Q23

Carbon fibres is one of the components of acomposite substance which is used to makebullet-proof jackets.Which if the following isnot a property of carbon fibres?

A low density

B inert towards chemical cubstances

C stable at high temperaturesDelastic



STPM 2007/P1/Q27

• Which of the follwing statement is true ofglass?

a.It consist of well arranged silicate units

b.It withstand the actions of strong alkali

c.It softens at a wide range of temperatures

d.It can be coloured by adding soda limes

stpm chemistry chapter 3

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