SUMMARY - DescriptionsIONIC
CrystalsDissolve in water
eg sodium chloride (salt)
METALLICStrong malleable solids
Don’t dissolveeg copper
SIMPLE MOLECULARUsually Gases
eg CO2, H2O
GIANT MOLECULARHard strong solids
Don’t dissolveeg diamond
(graphite – special case)
IONS ONLY IONS +
FREE ELECTRONS
MOLECULES ONLY
ATOMS joined into
GIANT MOLECULE
S
SUMMARY - PROPERTIESStructure Property Reason
Ionic HIGH mpt/bpt
CONDUCT: Solid NO
Molten YES Dissolved YES
Strong bonds between IONS
Ions can’t move
Ions can move to carry current
Covalent –
Simple molecular
LOW mpt/ bpt (often gas at room temp). Soft when solid
CONDUCT: Never
Bonds between MOLECULES very weak.
Molecules aren’t charged
Covalent – giant molecular
HIGH mpt/bpt. Hard & strong
CONDUCT: Never
Strong bonds between all ATOMS
No free charges/electrons
Covalent - graphite
HIGH mpt/bpt
Soft & slippery
CONDUCT: YES (fairly well)
Strong bonds between ATOMS
Weak bonds between LAYERS
Free electrons between layers
Metallic HIGH mpt/bpt. Hard & strong
Malleable
CONDUCT: YES (very well)
Strong bonds between IONS
Regular structure, layers slide
Free electrons between ions
Structure of an AlloyStructure of an Alloy
1. Draw this picture.2. What 2 things are
obvious from it?
Different size atomsIrregular structure
This makes alloys HARDER than pure metals.
Smart Materials
Smart materials' 'are materials that have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as stress, temperature, moisture, pH, electric or magnetic fields.
Smart Liquids
When a magnetic field is applied to the fluid it becomes semi-solid and when the field is removed, the fluid returns to a free-flowing liquid.
• http://www.youtube.com/watch?v=kL8R8SfuXp8
Shape Memory Alloys A shape memory alloy is an
alloy that "remembers" its original,
cold, forged shape, and which returns to
that shape after being deformed by applying heat.
http://www.youtube.com/watch?v=fsBHF_j2FJ4
Exam Question
Nanomaterials
Are very small but how small?
Human hair 9 micrometers is equivalent to 0.000009 m
40 microns 9 microns
0.000000009 m is 9 nm or 0.009 micrometers
0.25 nanometers is the average length of a bond between atoms!!!
Very Small Can Make Properites Very Different
Some Potential Uses
• Filtration
• Catalysis
• Tissue engineering
• Drug delivery
• Diagnostics
• Memory storage
• Quantum computers
• Optoelectronics
Quantum dots
Nanotubes
• Cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science, as well as potential uses in architectural fields. They exhibit extraordinary strength and unique electrical properties, and are efficient thermal conductors. Their final usage, however, may be limited by their potential toxicity and controlling their property changes in response to chemical treatment.
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