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.