C2.3: Properties Of Materials Flashcards
What is an allotrope?
Different forms of an element in the same state but different atomic arrangements
What are 2 examples of allotropes?
Diamond and graphite are both allotropes of carbon
What are organic compounds?
Compounds that contain carbon
Why does diamond have a high mp?
There are strong covalent bonds between atoms that are hard to break
Why doesn’t diamond conduct electricity?
No free electrons or ions
Why do you need delocalised electrons to conduct electricity?
Because delocalised electrons can move freely and carry an electrical charge
What is the layered structure of graphite like?
Interlocking hexagons over each other in layers - forces between layers are weak making graphite slippery
What is the carbon bonding like in graphite?
1 carbon is bonded to 3
What is the electronic structure of graphite like?
One electron in the outer shell is not involved in bonding (delocalised)
What is the mp like of graphite?
High melting point
What is graphene?
A carbon allotrope that resemble a single layer of graphite
What are the features of graphene?
Almost transparent
Strong
Conducts electricity
How do the physical properties of diamond make it useful?
Useful for cutting tools
Are ionic compounds conductive?
They conduct electricity when molten or aqueous but NOT when solid. Ions are charged particles, free to move about when a substance is molten or dissolved
What are 3 examples of covalent substances that conduct electricity?
Graphite
Graphene
Fullerenes
What is a fullerene?
A molecule made of carbon atoms that form a hollow shape
What happens to the bonding when a substance melts or boils?
Forces of attraction are overcome. Some bonds break and change state.
What type of materials are solid at room temp?
Metals
Ionic compounds
Giant covalent substances
Why are metals malleable?
There is a sea of delocalised electrons surrounding metal ions. They slide over one another when a force is applied.
Why are giant covalent structures brittle?
They contain any atoms held together in a giant lattice by strong covalent bonds. They break once a force is applied. Similar to ionic compounds
What are nanoparticles?
A particle between 1nm and 100nm across, and consists os just a few hundred atoms
The small size of nanoparticles also makes them useful for…
New paints
New cosmeticcs
Medicines
Sunscreens
What are risks from nanoparticles?
Small size makes it possible to breathe in or pass into cells
Catalyse harmful reactions
Toxic substances may fit onto their surface
What are examples of simple molecules?
Water
Oxygen
What are examples of non-simple molecules?
DNA
Plastic
