chemistry test Flashcards
what are positive ions sometimes called
cations
what are negative ions sometimes called
anions
how are ions arranged in an ionic bond
positive and negative ions are held strongly together by electrostatic forces (of attraction), ionic compounds are arranged in lattices
do ionic substances have high or low melting and boiling points?
high
ionic substances are generally soluble in water, true or false?
true
ionic substances ? conduct electricity in a solid form because the ions are held in position and are ? free to ?
cannot, not, move
ionic substances ? conduct electricity in a ? or molten form because the ? are free to ?
can, liquid, ions, move
when can ionic substances also conduct electricity?
when they’re dissolved in water
what are covalent bonds?
they are bonds which are form between 2 or more non metal elements.
what do elements in covalent bonds want to do
gain electrons to gain a full outer shell
what are the two types of covalent substances
simple covalent and giant covalent
what are simple covalent substances composed of
tiny separate molecules called molecules
what do simple covalents consist of?
several atoms bonded strongly together by covalent bonds
giant covalents : contain? of atoms bonded by many ? covalent bonds to form a giant ? or ? molecule
millions, strong, molecule, macro
what are noble gases and are they reactive or unreactive?
they are the gases in the 0/8th group of the periodic table, so they have a full outer shell of electrons and are therefore incredibly unreactive.
what are forces between neighbouring molecules in covalent substances called
intermolecular forces
are the intermolecular forces in simple covalents weak or strong?
weak
do simple covalent substances have high or low melting and boiling points?
low
why is electrical conductivity poor in simple covalent substances?
because there are no ions or free electrons present since it is a covalent substance not an ionic one!!
simple covalent substances are ? in water due to no charged ? present to be ? to polar water molecules
insoluble, particles, attracted
what element is in both diamond and graphite?
carbon!!
diamond structure :
each carbon atom joins to 4 others, and there are strong covalent bonds throughout the whole substance!
Graphite structure :
Each carbon atom is covalently bonded to 3 others, has a layered structure, strong covalent bonds through layers, but weak intermolecular forces between layers
Does diamond have a high or low melting point and why
Very high, because of a vast amount of strong covalent bonds having to be broken
Diamond is very ? due to very strong ? bonds throughout the structure, and because of this structure, it has ? electrical conductivity as there are no delocalised ?
Hard, covalent, poor, electrons
What is diamond used in and why?
Drill bits for hardness and jewellery for shininess
Why does graphite have a high melting point?
Because the strong covalent bonds between the layers have to be broken
Graphite is soft, due to ? intermolecular forces ? layers, therefore layers can easily ?. Graphite is a ? electrical conductor, because it has ? electrons between the carbon ?
weak, between, slide, good, delocalised, layers
What is graphite used for?
Pencil ‘lead’
What does graphite do in pencil ‘lead’?
Lubrication can take place, the layers Slide Over each other (also used as electrodes due to good electrical conductors)
What are atoms in metals held together by
Metallic bonds
In a metallic structure what do the positive metal ions consist of
The contents of the nucleus and inner shell electrons
In a metallic structure positive metal ions are held together by the ? shell of ? which become ?
outer, electrons, delocalised
Why do metallic structures have high melting and boiling points?
Because lots of energy is needed to break the attractive forces between the delocalised electrons and positive ions
Why are metals malleable and ductile
Because the metal layers can Slide Over each other when a force is applied
Metals are good conductors of electricity- why?
The electrons in the sea of delocalised electrons are also free to move, so can flow when a voltage is applied
Why are metals good conductors of heat?
Since when heated the delocalised electrons gain kinetic energy, and so move faster through the material therefore transferring (more) heat
How are alloys different from metals
Alloys have more than one type of metal and so the different metal atoms prevent the layers from sliding over one another so the alloys are a lot harder and less malleable
Why aren’t alloys regarded as compounds?
Because there isn’t any permanent chemical change, so can separate the metals by physical means if you really want to
Meaning of ductile
Able to be drawn out into a thin wire
What type of structure does a metal have?
A lattice structure
What is graphene
A single layer of graphite, one atom thick
Graphene is an ? electrical conductor (at RTP) and has very ? electrical resistance
excellent, low
What can graphene be used to make?
Super fast electrical components and computer processors as well as strong and lightweight construction materials
What are fullerenes
3D hollow shapes of carbon, with 60 carbon atoms, they are simple molecular substances
Fullerenes have ? intermolecular forces ? the C60 molecules, meaning that fullerenes have a ? boiling point as only ? forces have to be overcome, so no covalent bonds are ?
weak, between, low, weak, broken
What can fullerenes be used for?
To deliver drugs, act as lubricants and as catalysts
What are carbon nanotubes?
Cylindrical fullerenes
Carbon nanotubes are :
Exceptionally ? and very good ? of heat and electricity. can be used as semi conductors in ? circuits, ? and for reinforcing materials eg : ? rackets
strong, conductors, electrical, catalysts, tennis
Why are catalysts often (attached to) carbon nanotubes?
Because nanotubes have a large surface area and with a larger surface area the reactants will collide more with the catalyst
What are polymers
Long chain like molecules
The atoms in the ? chain are linked to each other by ? covalent bonds so the ? forces are strong
Polymer, strong, intramolecular
In some polymers the forces between chains are relatively weak, how does this affect these chains?
The polymers have a low melting point and so are flexible as the chains can move over each other, and have weak intermolecular forces - these polymers can be used for flexible materials eg : plastic bags
