Engineering Materials PDF

Chemistry
of
Engineering Materials
By: Jacqui Lou Valenzuela, RCh

Assoc. Prof., Chemistry Department
Western Institute of Technology
Bonding in Solids:
Metals
Insulators
Semiconductors
1. Classify solids in terms of
bonding/intermolecular forces
2. Relate bonding/intermolecular forces
with properties of solids
Solid State Band Theory
Insulator Semiconductor Conductor

Definition of Terms
Valence band -
• band of electron orbitals that electrons can jump out of, moving into the
conduction band when excited
• the outermost electron orbital of an atom of any specific material that
electrons actually occupy
Conduction Band -
• partially filled band or a band of vacant energy levels just higher in energy
than a filled band
• a band within which, or into which, electrons must be promoted to allow
electrical conduction to occur in a solid
Recall: Physical Properties of Metals
Physical Property Discussion

high melting point and boiling electrostatic attraction between the
point lattice of positive ions immersed in the
Strength of material fluid of valence electrons

good conductors of heat and electrostatic attraction between the
electricity lattice of positive ions immersed in the
fluid of valence electrons

malleable non-directional nature of the attractions between
the kernel atoms and the electron fluid

ductility non-directional nature of the attractions between
the kernel atoms and the electron fluid
Which of the following illustrations show
malleability of metals? ductility of metals? Explain
this property of metal in the context of metallic
bonding?
Physical property Discussion

lustrous oscillation of the polarized sea of electrons by the
incoming light
Why are metals shiny?
Physical property Discussion

color closely-spaced levels in the bands allow metals to
absorb all wavelengths equally well
Other properties:
• Can be polished
• Solid at room temperature (except mercury)
• Hard (except Mg, Na, and K)
• Heavy
• Sonorous
Why is gold yellow in color if most metals are
supposed to be black?
E= mc2
Crystalline
Solids
1. Differentiate crystalline from
amorphous solids
2. Identity the types of crystalline solids
3. Identify the types of primitive lattices
Types of Crystalline Solids
Type Bonding Example Physical Structure
Property
Ionic Coulombic forces NaCl Hard but brittle
between ions that
are systematically
arranged
Covalent electron sharing C (diamond) hard
between atoms
connected by
covalent bonds
Types of Crystalline Solids
Type Bonding Example Physical Structure
Property
Molecular molecular/intermol ice soft

ecular interactions
or H-bonding
between polar or
non-polar molecules
Metallic Metallic bonds Metals and Ductile

alloys malleable
Unit Cell
Simplest Repeating Unit
in a Crystal
Crystalline
Solids
Unit cell - simplest repeating unit in a crystal
Lattice points - the points in space about which the particles are free
to vibrate in a crystal
Space lattice
lattice points
3-D arrangement of atoms

edge
corner
face
Position No. Shared
Corner 8 1/8
Edge 0
Face 0
Body 0
TOTAL no. of atoms 8(1/8) = 1
per unit cell
Primitive cubic
Position
Position No.
No. Shared
Corner
Corner 8 1/8
Edge
Edge 0
Face
Face 0
Body
Body 1 1
TOTAL no. of atoms 8(1/8) + 1 = 2 atoms
Body-centered Cubic (BCC) per unit cell
Position
Position No.
No. Shared
Shared
Corner
Corner 8 1/8
Edge
Edge 0
Face
Face 6 1/2
Body
Body 0 0
TOTAL
TOTALno.
no.ofofatoms
atoms 8(1/8) + 6(1/2) = 4 atoms
Face-centered Cubic (FCC) per
perunit
unitcell
cell
Solving for Empirical Formula of Ionic Solids
1. Find the empirical formula of an

ionic solid with the following unit
cell.
Answer: XY3
2. Determine the net number of Na+

and Cl– ions in the NaCl unit cell.
What is the EF of the compound?
Answer: 4 Na+ ions, 4 Cl- ions, EF: NaCl
Topic: Close Packing of Spheres in Crystalline Solids
References:
• Brown, L. S., Holme, T. (2014). Chemistry for Engineering Students. Stamford, CT
Brooks/Cole Cengage Learning
• Pahari, A.K., Chauhan, B.S. 2006. Engineering Chemistry. pp. 316-349. New Delhi. Laxmi
Publications
• Structures of Solids. Available from
http://wps.prenhall.com/wps/media/objects/3311/3391416/blb1107.html
• Shah, K.P. Structure of Atoms and Crystals. Available from
http://practicalmaintenance.net/?p=1051
Prepare for: Graded hands-on demonstration on the next lab

meeting
Polymers
Notes to Remember:
 giant molecules of repeating units
 from the Greek poly and meros,
meaning "many parts"
 basic structural units - monomers
 formation process -
polymerization
 Plastic is the property of a
material that allows it to
be molded into almost any
shape.
 Although many plastics
are polymers, many
polymers are not plastics.
styrene
(2-methylbut-1,3-diene)
Synthetic Polymers
Polymerization: Addition and Condensation
Addition polymerization involves the linking of monomers
with double bonds.
Condensation polymerization involves monomers reacting
together and releasing a small molecule in the process. The
small molecule is commonly water or hydrochloric acid (HCl).
Below is a polymerization reaction to form nylon.
Classify if the reaction is addition or condensation
polymerization.
Answer:
Condensation reaction
 Polymers based on skeletons with only
carbon are all synthetic.
 The relative lengths of the chains and any
branches control the properties of
polyethylene.
 For example, higher numbers of branches
produce a softer, more flexible, lower-
melting-point polymer called low-density
polyethylene (LDPE).
 High-density polyethylene (HDPE)
contains few branches.
 Substances such as glass that melt at
relatively low temperatures can also be
formed into fibers, producing fiberglass.
Polyethylene is used in a wide variety of products, including
beach balls and the hard plastic bottles used to store solutions
in a chemistry laboratory. Which of these products is formed
from the more highly branched polyethylene?
A highly branched polymer is less dense

and less rigid than a relatively
unbranched polymer.
Thus hard, strong polyethylene objects
such as bottles are made of HDPE with
relatively few branches.
In contrast, a beach ball must be
flexible so it can be inflated. It is
therefore made of highly branched
LDPE.
Topic: Nanomaterials
References:
• Brown, L. S., Holme, T. (2014). Chemistry for Engineering Students. Stamford, CT
Brooks/Cole Cengage Learning
• Nanomaterials. Available from http://www.essentialchemicalindustry.org/materials-and-
applications/nanomaterials.html
• Nanomaterials and Their Applications. Available from
https://www.understandingnano.com/nanomaterials.html
• Rogers, M.A. 2015. Naturally occurring nanoparticles in food. Current Opinion in Food
Science. 7:14–19. DOI: 10.1016/j.cofs.2015.08.005.
Use the information to answer the questions in your lab activity on

Nanomaterials.

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Chemistry

By: Jacqui Lou Valenzuela, RCh

Insulator Semiconductor Conductor

Physical Property Discussion

Physical Property Discussion

Physical Property Discussion

Physical Property Discussion

Physical property Discussion

Physical property Discussion

Molecular molecular/intermol ice soft

Metallic Metallic bonds Metals and Ductile

3-D arrangement of atoms

1. Find the empirical formula of an

2. Determine the net number of Na+

Prepare for: Graded hands-on demonstration on the next lab

A highly branched polymer is less dense

Use the information to answer the questions in your lab activity on

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