Properties of Materials

What group is carbon located in the periodic table?

How many covalent bonds is it allowed to form?

What does this ability allow it to form?

What as a result of this can be formed?

• Group 4

• 4

• Families of similar compounds that contain chains or rings

• A large number of natural and synthetic organic compounds can be formed

What are allotropes?

Different forms of the same element

Name 5 well-known allotropes of carbon

• diamond

• graphite

• graphene

• fullerenes

• nanotubes

In diamonds how many carbon atoms does each carbon atom bond with and what shape occurs?

• 4

• tetrahedron

Describe 2 things about all of the covalent bonds

Are there intermolecular forces?

• identical and very strong

• no intermolecular forces

Name 3 physical properties of diamond

• does not conduct electricity

• has a very high melting point

• extremely hard (density of 3.51 g/cm³ - a little higher than that of aluminium)

Are there a freely moving charged particles in diamond and why?

• no

• all the outer shell electrons in a carbon are held in the 4 covalent bonds around each carbon atom so there are no freely moving charged particles

The 4 covalent bonds are very … and extend in a … …, so a very large amount of … energy is required to break the lattice

• strong

• giant lattice

• heat

What does diamond’s hardness make it very useful for? (Give 2 examples of where its used)

Purposes where extremely tough material is required (used in jewellery, and for coating blades in cutting tools)

What are the cutting edges of discs used to cut bricks and concrete tipped with?

Diamonds

Name 2 other things that are also diamond tipped

• heavy-duty drill bits

• tooling equipment

In graphite, hoe many carbon atoms is each carbon atom bonded to?

What shape is formed?

How many free electrons are there per carbon atom?

• 3

• layers of hexagons

• 1

Why can graphite conduct electricity?

Because these free electrons migrate along the layers and are free to move and carry charge, hence graphite can conduct electricity

Describe all of the attractions and forces in graphite and what properties they mean

• strong covalent bonds within layers

• layers attracted to each other by weak intermolecular forces

  • this means the layers can slide over each other making graphite soft and slippery

Name 3 physical properties of graphite

• conducts electricity and heat

• has a very high melting point

• soft and slippery and less dense than diamond (2.25g/cm³)

What makes graphite a useful material?

Name two ways it is used in everyday life

Name another way it is used

• Graphite's weak intermolecular forces make it a useful material

• It is used in pencils and as an industrial lubricant, in engines and in locks

• It is also used to make inert electrodes for electrolysis, which is particularly important in the extraction of metals such as aluminium

What is graphene?

Graphene consists of a single layer of graphite which is a sheet of carbon atoms covalently bonded forming a continuous hexagonal layer

Graphene is essentially as 2D molecule since it is only … … …

one atom thick

Name two areas it is used in

• fabricating composite materials

• electronics

Name 4 properties of graphene

• It is extremely strong but also amazingly light

• It conducts heat and electricity

• It is transparent

• It is flexible

Why is it so strong?

Due to its unbroken pattern and the strong covalent bonds between the carbon atoms. Even when patches of graphene are stitched together, it remains the strongest material out there

Why can it conduct electricity?

It has free electrons which can move along its surface allowing it to conduct electricity

Why is it flexible?

Those strong bonds between graphene’s carbon atoms are also very flexible

How is it transparent and what does this give it potential for (an example)?

• Graphene absorbs 2.3 percent of the visible light that hits it, which means you can see through it without having to deal with any glare

• This gives it the potential to be used for making computer screens of the future

What are fullerenes?

a group of carbon allotropes which consist of molecules that form hollow tubes or spheres

What are fullerenes usually made up of and in what shape?

carbon atoms arranged in hexagons but can also contain pentagons or heptagons

What was the first fullerene discovered?

In it how many carbon atoms are there and what do they form?

• buckminsterfullerene

• 60, 20 hexagons and 12 pentagons which produce a hollow sphere and is the exact shape of a soccer ball

Name 3 examples of what fullerenes are used for and why they are good for it

• Drug delivery systems - they can be used to trap other molecules by forming around the target molecule and capturing it

• catalysts - they have huge surface areas

• some are excellent lubricants and are starting to be used in many industrial processes - weak van der Waal forces between molecules and spherical shapes

What are nanotubes?

Graphene rolled into a cylinder to produce an interesting type of fullerene

What are some properties of nanotubes and what can they be used for?

• high tensile strength and resistant to breaking or stretching

• can conduct electricity - makes them useful in composites and specialised materials, electronics and nanotechnology

What does the amount of energy to change state between solid to liquid and liquid to gas depend on?

the strength of the forces between the particles

What type of melting and boiling points do simple molecules have and why?

• LMPS AND LBPs

• they have weak intermolecular forces that need little energy to break

What type of melting and boiling points do other structures such as giant ionic lattices and macromolecular structures have and why?

• HMPs and HBPs

• have very strong bonds which need lots of energy to break

Describe melting

• Melting is when a solid (s) changes into a liquid (l)

• The process requires heat energy which transforms into kinetic energy, allowing the particles to move

• It occurs at a specific temperature known as the melting point which is unique to each pure solid 

Describe bioling

• Boiling is when a liquid (l) changes into a gas (g)

• This requires heat which causes bubbles of gas to form below the surface of a liquid, allowing for liquid particles to escape from the surface and from within the liquid

• It occurs at a specific temperature known as the boiling point which is unique to each pure liquid 

Describe freezing

• Freezing is when a liquid (l) changes into a solid (s)

• This is the reverse of melting and occurs at exactly the same temperature as melting, hence the melting point and freezing point of a pure substance are the same

  • Water for example freezes and melts at 0 ºC

• It requires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature which is unique for each pure substance 

Describe evaporation

• When a liquid (l) changes into a gas (g)

• Evaporation occurs only at the surface of liquids where high energy particles can escape from the liquids surface at low temperatures, below the boiling point of the liquid

• The larger the surface area and the warmer the liquid/surface, the more quickly a liquid can evaporate

• Evaporation occurs over a range of temperatures, but heating will speed up the process as particles need energy to escape from the surface

Describe condensation

• When a gas (g) changes into a liquid (l), usually on cooling

• When a gas is cooled its particles lose energy and when they bump into each other, they lack energy to bounce away again, instead grouping together to form a liquid

Describe sublimation

• When a solid (s) changes directly into a gas (g)

• This happens to only a few solids, such as iodine or solid carbon dioxide

• The reverse reaction also happens and is called desublimation or deposition

What are bulk properties?

Give 2 examples

• Different compounds have different structures and bond types/strengths that give rise to bulk properties

• -electrical conductivity

• melting/boiling points 

Why do bulk properties arise and do they arise from individual atoms?

• Individual atoms do not possess these physical properties

• They arise due to many atoms, ions or molecules acting together

For ionic substances,

give 2 examples

can it conduct and why?

high or low MPs and BPs and why?

• sodium chloride, aluminium oxide

• No when solid, yes when molten or aqueous, because the ions in a solid are not free to move and carry a charge but when molten or dissolved they are

• High, because of strong electrostatic forces of attraction between oppositely charged ions that require lots of energy to break

For simple molecules substances,

give 2 examples

can it conduct and why?

high or low MPs and BPs and why?

• carbon dioxide, water

• no, because there are no free charged particles

• low, because weak intermolecular forces require little energy to break

For giant covalent substances,

give 2 examples

can it conduct and why?

high or low MPs and BPs and why?

• graphite, diamond

• no (except graphite and fullerenes), because there are no free charged particles (graphite and fullerenes have delocalised electrons that are free to move and carry a charge)

• high, because strong covalent bonds between atoms require lots of energy to break

For metallic substances,

give 2 examples

can it conduct and why?

high or low MPs and BPs and why?

• copper, magnesium

• yes, because delocalised electrons are free to move and carry a charge throughout the structure

• high, because strong attraction between metal ions and delocalised electrons require lots of energy to break

What is the difference between a brittle and malleable substance? (give examples for each)

• a brittle substance cracks or breaks when an external force is applied (ionic and giant covalent structures)

• malleable substances change shape without cracking or breaking (metals)

Why are metals malleable?

What happens if a force is applied to giant covalent structures and ionic structures?

• Their atoms are arranged in layers which slide over each other when force is applied

• they have their bonds broken if force is applied and as a result break

What state are polymers at room temperature?

What bonds are there?

How are they compared to other substances’ bonds?

• solid

• strong covalent bonds between atoms but intermolecular forces between polymer molecules

• the intermolecular forces are larger than those between simple covalent molecules and therefore need more energy to break but weaker than ionic or covalent bonds

What three groups can particles be placed into according to their diameter?

What are the ranges for each?

• coarse particles (also called particulate-matter or dust) 2500-10000 nm diameter

• fine particles  100-2500 nm diameter

• nanoparticles  1-100 nm diameter

nanoparticles are usually between … and … nanometres in size and usually contain a … … atoms

• 1 and 100

• few hundred

how many times are atoms and simple molecules larger than nanoparticles?

around 100 times larger

nanoparticles are much … than fine particles which have diameters of between … and … nm

• smaller

• 100 and 2500

What is the research into the production and application of nanoparticles called?

nanoscience

What is one of the most interesting features of nanoparticles?

As particles decrease in size, their surface area … in relation to their volume

• Their very high surface area to volume ratio

• increases

As the side of a cube decreases by a factor of 10, the surface area to volume ratio increases by a factor of …

10

What do nanoparticles’ high surface area to volume ratio mean as for their relation to properties to those for the same materials in bulk and the quantities need to be effective than for materials of normal particle sizes?

Give an example of this

• different

• smaller quantities are needed

• fullerenes (nanoparticles of carbon) behave very differently to larger compounds of carbon like diamond and graphite

What 2 areas is surface area to volume ratio an important feature in and why?

• catalysis - higher the ratio, more surface area available for reaction, hence better the catalyst

• surface chemistry

What’s the main industrial application of nanoparticles?

catalysis

Give one example of a chemical that has different properties in bulk and nanoparticle form and what it is it used for in the different forms?

• titanium dioxide

  • nanoparticles: sunscreens as it blocks UV light but leaves no white marks on the skin while providing better coverage than other sun creams

  • bulk: white pigment in paints

Name 3 areas fullerenes are used in

• medicine and drug design - more easily absorbed than other particles and can deliver drugs to target areas more effectively

• electronic circuitry

• coatings for artificial limbs and joints

Nanoparticles of … are sprayed onto the fibres of medical clothing and surgical masks which gives them the flexibility of a material but with the added benefit of the … properties of silver metal

silver, antibacterial

Why are there a lot of unknown risks to nanoparticles and what are some?

• it is in its early stages being used in science

• there is a lack of understanding on how it may affect health

• although no short term side effects, there may be long term side effects which we haven’t detected yet as they haven’t been in use long enough

• even a small amount of toxicity in a particular nanoparticle would be multiplied due to the high surface area to volume ratio

• they are not easily disposed of by the body, linking to other risks