chemistry topic 2 bonding, structure and properties of matter Flashcards
what do ions want or try to do?
gain a full outer shell
when metals form ions do they lose or gain electrons?
lose
when non metals form ions do they lose or gain electrons?
gain
the number of electrons lost or gained is the?
same as the charge on the ion
what are the oppositely charged ions strongly attached by?
electrostatic forces
what diagram can we use to show ionic bonding?
dot and cross diagram
what do you put around every ion when drawing dot and cross diagrams?
square brackets
what do ionic compounds have a structure like?
they have a giant ionic lattice
what do the ions forming a giant regular lattice arrangement give?
a very strong electrostatic forces of attraction between oppositely charged ions
all ionic compounds have high what?
melting and boiling points
how do ionic compounds all have high melting and boiling points?
they have many strong bonds between the ions
when ionic compound are solids they cant do what?
they cant conduct electricity
when ionic compounds melt the ions are free to move and they can do what?
they can carry electric current
what do ionic compounds do easily in water ?
dissolve
when they dissolve and the ions separate, what can they do?
carry electric current
when non metals share electrons to gain full outer shells what is this called?
covalent bonding
why are covalent bonds very strong?
they are attracted by electrostatic forces
in covalent bonding, where do atom only share their electrons?
their outer shells
where does covalent bonding happen?
in compounds of non metals
what can you use to show a covalent bond?
a dot and cross diagram
the atoms within molecules In covalent structures are very strong covalent bonds, what are forces of attraction like between the molecules?
very weak
what Is the boiling or melting point of a simple molecular structure like?
low because you only have to break the weak intermolecular structures and not the covalent bonds
as molecules get bigger what happens to the strength of the intermolecular force and the boiling point?
the strength increases which means more energy is needed to break the bonds therefore the boiling point increases
do molecular compounds conduct electricity?
no
why do molecular compounds not conduct electricity?
they aren’t charged, so there are no free electrons or ions
what are polymers?
long chains of repeating units
what is in a polymer?
lots of small units that are linked together to form a long molecule that has repeating sections
how are polymers linked?
via strong covalent bonds
how can you write out a polymer?
you can draw the shortest repeating section , called the repeating units in brackets with ‘n’ on the outside
how do you write the molecular formula for a polymer?
write out the molecular formula of the repeating unit in brackets, and put an ‘n’ outside
what does ‘n’ mean when writing out a polymer?
that the unit is repeated lots of times
what are polymers like at room temperature?
solid
what is the boiling point like in polymers?
they have a low boiling point
in giant covalent structures, what are they bonded by?
strong covalent bonds
what is the melting and boiling point like in a giant covalent structures?
they have a very high melting point and boiling point as lots of energy is needed to overcome the covalent bonds
what are the main examples of giant covalent structures?
diamond, graphite and silicon dioxide
what is the structure of diamond like?
each carbon atom forms four covalent bonds in a very rigid giant covalent structure
what is the structure of graphite like?
each carbon atom forms three covalent bonds to create layers of hexagons. each carbon atom also has one delocalised electron
what is the structure of silicon dioxide like?
this is what sand is made of, each grain of sand is one giant structure of silicon and oxygen
whats an allotrope?
different structural forms of the same element in the same physical state
all allotropes are what state?
solids
diamonds carbon atoms and covalent bonds make diamond what?
really hard
whats diamonds boiling point like?
very high because it has strong covalent bonds
does diamond conduct electricity?
no because it dosent have any free electrons
what is graphite like?
soft and slippery, ideal as a lubricating material
why is graphite soft?
there aren’t any covalent bonds between the layers , they are only held together weakly
what’s graphites melting point like?
high
what is graphene?
one layer of graphite
what is the graphene sheet like?
one atom thick, making it a two dimensional compound
what is good about graphene?
its strong because of the network of covalent bonds and is also very light. this means that you can add strength to something without adding a lot of weight
can graphene conduct electricity?
yes, because it contains delocalised electrons
what are fullerenes?
molecules of carbon , shaped like closed tubes or hollow balls
what are fullerenes mainly made up of?
carbon atoms arranged in pentagons, hexagons or heptagons
what was the first fullerene to be discovered?
buckminsterfullerene
what are fullerenes used for?
to cage other molecules ( deliver a drug into the body)
why are fullerenes good catalysts?
fullerenes have a huge surface area
fullerenes are good for what like graphite?
lubricants
fullerenes can form nanotubes, what are nanotubes?
tiny carbon cylinders
what can nanotubes do?
conduct electricity and thermal energy
nanotubes have a high tensile strength, what does that mean?
they don’t break when they are stretched
what is the technology called that uses very small particles such as nanotubes ?
nanotechnology
what can nanotubes be used for?
electronics or to add strength to a material without adding a lot of weight
in metallic bonding what are the electrons in the outer shell like?
they are delocalised with strong forces of electrostatic attraction between the positive and negative metal ions
why are most metals solid at room temperature?
the delocalised sea of electrons are very strong, so lots of energy is needed to break them and the boiling point/melting point
why are metals good conductors of electricity and heat?
the delocalised electrons carry electrical current and thermal energy through the whole structure
why are most metals malleable?
the layers of atoms in a metal can slide over each other
how are alloys harder than pure metals?
different elements have different sized atoms and when elements are mixed with a pure metal it distorts the layers of metal atoms making it harder for them to slide over each other
what are the three states of matter?
solids, liquids and gases
what does the state of something depend on?
how strong the forces of attraction are between the particles in the material
what are the forces of attraction like in a solid?
strong
what is the structure of a solid like?
the particles are close together in fixed position in a regular lattice arrangement
how do solids keep a definite shape and volume?
the particles don’t move from their positions
the hotter a solid is?
the more the particles vibrate
what are the forces of attraction like between the particles in a liquid?
theres a weak force of attraction
what are the arrangements like in a liquid?
they are randomly arranged and free to move past each other but they tend to stick closely together
what is the volume and shape of a liquid like?
the volume is definite but it doesn’t keep a definite shape so it will flow to the bottom of a container
how do particles in a liquid move?
they constantly move in a random motion
what happens when a liquid is heated?
the hotter the liquid gets, the faster they move which means liquids expand when slightly heated
what is the forces of attraction like in a gas?
they are very weak - free to move and far apart
what Is the structure of a gas like?
gases don’t keep a definite shape or volume and will always fill a container
what does aqueous mean?
dissolved in water
when asking to predict a state of matter, how do you know its a solid?
if the temperature is below the melting point of the substance
when asking to predict a state of matter, how do you know its a liquid?
if its between the melting and boiling point of the substance
when asking to predict a state of matter, how do you know its a gas?
if the temperature is above the boiling point of the substance
how do you work out surface area to volume ratio?
surface area to volume ratio= surface area divided by volume
as particles decrease in size what happens to their surface area to volume ratio?
it increases
what is the surface area to volume ratio of a nanoparticle like?
nanoparticles have a very high surface area to volume ratio
what does it mean to have a large surface area to volume ratio?
the surface area is very large compared to the volume
when using nanoparticles as a catalyst, do you need a lot?
you need less of nanoparticles rather than if you were using normal sized particles
what is Nano medicine used for?
drug capsules as tiny particles are more easily absorbed into the body
how are nanoparticles used in electricity?
nanoparticles can conduct electricity therefore they can be used in tiny electric circuits for computer chips
what do silver nanoparticles have?
antibacterial properties
what can silver nanoparticles be added to polymer fibres to make?
surgical masks, wound dressings and add to deodorants
how are nanoparticles used in cosmetics?
they’re used to improve moisturisers without making them oily
why is it important that nanoparticles are tested thoroughly?
the way the affect the body isn’t fully understood
why are people worried about products that contain nanoparticles?
they are worried that they have been made available without the effects on human health being investigated long term
since people don’t know the long term impacts of nanoparticles on health what do many people think should happen?
nanoparticle objects should be clearly labelled .
what type of creams are nanoparticles being used in?
sun creams as they are thought to have been better at protecting skin from harmful UV rays
what is unclear about nanoparticles in the body?
whether they can get in your blood stream or damage your cells
what other thing can nanoparticles potentially destroy?
they might damage the environment when they are washed away
