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Metallic Structures

metals also consist of a giant structure

metallic bonds involve free electrons- the factor which produce ALL properties of metals. these delocalised free electrons come from the outer shell of every metal atom in the structure

these delocalised electrons are the reason why metals are good conductors of heat and electricity

they also hold the atoms together in a regular structure

Strong forces of electrostatic attraction between the positive metal ions and the negative electrons

allow the layers of atoms to slide over each other, allowing metals to be bent and shaped

Alloys are harder than pure metals

pure metals are often to soft for certain jobs , so scientists mix two or more metals together to create an alloy

different elements obviously have different sizes, and so when another metal is mixed with a pure metal, the new metal atoms will distort the layers of metal atoms, making it more difficult for them to slide over each other

Smart Materials

behave differently depending on the conditions in which they are in

Nitinol - a shape memory alloy can be bent went cool, if we bend it too far then it obviously stays bent

if we add heat to the bent nitinol then it returns back to its " remembered" or original shape

good for glasses frames and for dental braces , when the mouth warms the nitinol tries to return back to its remembered shape and gently pulls the teeth with it

Nano particles

1-100 nanometers 1nm = 0.000 000 001m

contain roughly a few hundred atoms

nanoparticles include fullurenes,

fullerenes can be joined together to form nanotubes

all the covalent bonds make carbon nanotubes very strong, they can be used in tennis rackets

Nanoscience

have a huge surface area to volume ratio, so they can be used to help make new industrial catalysts

can be used to make sensors to detect one type of molecile

used to make stronger, lighter building materials

used in sun tan cream and deodorant, do the job but dont leave the white marks

Nanomedicine

New lubricant coatings can be used in places from artificial joints to gears

conduct electricity so they can be used in tiny electric circuits for computer chips

Polymers

thermosoftening polymers, dont have cross- linking between chains

forces between chains are really easy to overcome, easy to melt the plastic, when it cools, the polymers hardens into a new shape, can melt these plastics again and remould them as many times as you like

Thermosetting polymers

have crosslinks, these hold the chains together in a solid structure, the polymer doesn't soften when it's heated

two types of polythene can be made

low density polythene - made by heating ethene to about 200 degrees under high pressure - it is flexible and used for bags and bottles

high density polythene made at a lower temperature and pressure, more rigid and is used for water tanks and drain pipes

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