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Chapter 2
materials science and dentidtry
23
Archaeology
Undergraduate 4
06/20/2013

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Cards

Term
What are the 3 phases of materials and how do they differ?
Definition
Gas, liquid, solid weak-strong attraction between molecules
Term
what is long and short range order?
Definition

Short range(Liquid) – spatial relationship between atoms 5-10 neighbors apart

Long range(solid) – spatial relationship of molecules repeated millions of times

**gases have no order**

Term
What is an example of long range order? Short range?
Definition
Crystalline – long range
Amorphous – short range
Term
What is an ionic bond and what is an example of it?
Definition
ionic bond is where one molecule gives an electron to another molecule, EX: table salt
Term
What is a covalent bond?
Definition
two molecules sharing electrons
Term
What is an example of a covalent bond?
Definition
plastic and rubber
Term
What is a metallic bond?
Definition
Valence electrons are shared by all the atoms that make up the object
Term
What is: Positive cores surrounded by a cloud of negative mobile valence electrons.
Definition
metallic bond
Term
What is an example of a metallic bond?
Definition
gold
Term
What are secondary bonds?
Definition
Partial charges from an uneven distribution of electrons around an atom or molecule
Term
What is another name for a secondary bond?
Definition
Van der walls forces
Term
What are secondary bonds important in determining?
Definition
the properties of polymers
Term
What is a permanent dipole? What do these result in?
Definition
one atom has permanent positive charge and one has negative charge – result in weak bonds
Term
What is a fluctuating dipole?
Definition
uneven distribution of electrons around atoms resulting in weak bond
Term
What is a hydrogen bond?
Definition
special permanent dipole, only one electron and when pulled away hydrogen nucleus left partially unshielded, strong dipole results
Term
How do the atomic bonds of metals allow them to be ductile?
Definition
Electron cloud allows atoms to slide past each other with little difference
Term
Explain how the ionic bonds of ceramics make this material strong but brittle.
Definition
Atoms slide past each other encounter an atom with same charge – repulsion (brittle when pulled apart) strong when compressed
Term
Why are ceramics suited to replace lost tissue structure?
Definition
Translucent and comes in many colors/shades
Term
What is the atomic structure of polymers like?
Definition
Long chains of covalently bonded, repeating units
Term
What are polymers used for in dentistry?
Definition
Mouthguards, bleaching tray, dental instruments, composite filling material
Term
What is a composite?
Definition
mixture of ceramic and polymer
Term
What is a colloid?
Definition
suspensions of one material in another (impression material & fluoride foam)
Term
What is an emulsion?
Definition
2 liquids that do not blend together to form one liquid (transformation from liquid to a gel)
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