C3h - Allotropes of carbon and nanochemistry Flashcards
Explain why diamond, graphite and fullerenes are allotropes of carbon
they all consist of the same element (C) in the same state (solid) but they have different structural forms and physical properties
What are allotropes
different structural forms of the same element in the same physical state with different physical properties
Why is diamond used in cutting tools and jewellery? (2)
very hard and high melting point so can be used effectively in drill bits, glass cutters, dental drills without
transparent and can be cut into shapes that allow light to refract in a way that they sparkle, making them lustrous and desirable as jewellery
Why does diamond not conduct electricity? (2)
each carbon atom is joined to 4 other carbon atoms
-no free, delocalised electrons to conduct electricity by carrying a current
Why is diamond hard and has a high melting point? (2)
each carbon atom forms 4 covalent bonds to form a very rigid giant covalent structure where the atoms cannot move - hard
strong covalent bonds take a lot of energy to break, so high melting point
Why is graphite used in pencil leads
layers are held together weakly, so are slippery and can be easily rubbed off onto paper to leave a black mark
Why is graphite used in lubricants
the layers are held together weakly so are slippery, helping moving parts in machinery slide past easily, even at high temperatures
(unlike oil) because of its high melting point
Why does graphite conduct electricity(2)
each carbon atom only forms 3 covalent bonds
-as only 3 out of each carbon’s 4 outer electrons are used in bonds, each carbon has a free, delocalised electron that
can move and carry electrical charge through the material
Why is graphite slippery
there are only weak intermolecular forces between the layers of carbon molecules, so the layers can slide over each other easily, so it is slippery
Why does graphite have a high melting point
each carbon atom forms 3 strong covalent bonds thattake a lot of energy to break, so high melting point
Why do diamond and graphite have giant covalent structures?
each molecule contains many carbon atoms joined together by covalent bonds in a repeating pattern
Properties of substances with a giant molecular structure (3)
high melting and boiling points (high energy needed to break the strong covalent bonds)
-also makes it strong and insoluble in water
apart from graphite, they do not conduct electricity (no free electrons or ions)
Why can fullerenes be used in new drug delivery systems(2)
fullerenes hollow and has space inside large enough to contain drug molecules(caging the drug molecules)
drug can be delivered to target without damaging normal cells
What else can fullerene be used for
to trap dangerous substances in the body and remove them
Why are nanotubes used as catalysts? (2)
huge surface area compared to volume, allowing high collision frequency with reactant molecules
atoms of the catalyst can be attached to the large surface on the nanotubes
