1. SUMMARY - Descriptions
METALLIC
Strong malleable solids
Don’t dissolve
eg copper
IONS ONLY
IONIC
Crystals
Dissolve in water
eg sodium chloride (salt)
IONS +
FREE ELECTRONS
SIMPLE MOLECULAR
Usually Gases
eg CO2, H2O
ATOMS joined into GIANT MOLECULES
GIANT MOLECULAR
Hard strong solids
Don’t dissolve
eg diamond
(graphite – special case)
MOLECULES ONLY

2. SUMMARY - PROPERTIES Structure 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
Strong bonds between all ATOMS
No free charges/electrons
Covalent - graphite
Soft & slippery
CONDUCT: YES (fairly well)
Strong bonds between ATOMS
Weak bonds between LAYERS
Free electrons between layers
Metallic
Malleable
CONDUCT: YES (very well)
Regular structure, layers slide
Free electrons between ions

3. Structure of an Alloy Draw this picture.
What 2 things are obvious from it?
Different size atoms
Irregular structure
This makes alloys HARDER than pure metals.

4. 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.

5. 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.

6. 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.

7. Exam Question

8. Nanomaterials
Are very small but how small?

9. Human hair 9 micrometers is equivalent to 0.000009 m
40 microns
9 microns

10. Very Small Can Make Properites Very Different
m is 9 nm or micrometers
0.25 nanometers is the average length of a bond between atoms!!!
Very Small Can Make Properites Very Different

11. Some Potential Uses Filtration Catalysis Tissue engineering
Drug delivery
Diagnostics
Memory storage
Quantum computers
Optoelectronics

12. Quantum dots

13. 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.