structure and properties

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what state are giant structures in at room temperature?
solid (a lot of energy is needed to overcome ionic bonds)
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do ionic compounds have high melting/boiling points or low ones?
ionic compounds have high melting points and high boiling points
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can giant ionic structures conduct electricity?
only when melted or dissolved in water as ions are free to move and carry charge through the liquid
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why do some ionic solids dissolve in water?
because water molecules can split up the lattice
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why can giant ionic structures not conduct electricity when solid?
because ions can only vibrate about in fixed positions
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what are atoms in a molecule held together by?
strong covalent bonds
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simple molecules have little attraction for each other, why?
as the strong covalent bonds act only between atoms within the molecule
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why do simple molecules have low boiling/melting points?
they have weak inter molecular forces between the simple molecules
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do simple molecules conduct electricity and why?
no they do not as molecules have no overall charge so they cannot carry electrical charge
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why might large molecules be liquid at room temperature?
they have stronger attractions
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what happens when we bend/shape metals?
the layers of atoms in the giant metallic structure slide over each other
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giant metallic structures can move without breaking, how is this useful?
they are good for making wires, rods and sheet materials
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what are alloys?
mixtures of metals (harder than pure metals because layers in structure are distorted)
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what are shape memory alloys?
alloys that return to their original shape when heated
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what do delocalised electrons in metals allow metals to do?
conduct heat and electricity
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why do covalently bonded substances with giant structures have high melting points?
because it takes an enormous amount of energy to break down the lattice
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why is diamond hard/transparent?
as it is a form of carbon whose atoms each form four covalent bonds
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why is graphite slippery/grey?
it is a form of carbon where carbon atoms form layers that have no covalent bonds so they slide over each other
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why can graphite conduct electricity?
because if its delocalised electrons in its structure
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what are fullerenes?
large molecules from hexagonal rings of carbon atoms
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what do the properties of a polymer depend on?
monomers used to make it and conditions used during reactions
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what type of polyethene has a high softening temperature and is stronger?
high density polyethene
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what do thermosoftening polymers do when heated?
soften/melt easily
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what is nanoscience?
study of small particles that are between 1 and 100 nanometres in size
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how long is a nanometre?
one billionth of a metre
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how does nanotechnology use nanoparticles?
as highly selective sensors, efficient catalysts and cosmetics (sun screen)
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why does more research need to be done before nanoparticles are used in more materials?
there is a high risk of them getting into the air and bodies
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Other cards in this set

Card 2

Front

do ionic compounds have high melting/boiling points or low ones?

Back

ionic compounds have high melting points and high boiling points

Card 3

Front

can giant ionic structures conduct electricity?

Back

Preview of the front of card 3

Card 4

Front

why do some ionic solids dissolve in water?

Back

Preview of the front of card 4

Card 5

Front

why can giant ionic structures not conduct electricity when solid?

Back

Preview of the front of card 5
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