C2.3 - Properties Of Materials Flashcards
Why can carbon from so many different compounds?
- Carbon can form four covalent bonds.
- A carbon atom can join with other carbon atoms
and also form covalent bonds with other
elements producing many different compounds.
What are allotropes?
Allotropes are different forms of an element in the same state but with different atomic arrangements.
Give two allotropes of carbon.
- Diamond - Transparent very hard
2. Graphite - Grey-black and soft
Describe the structure of diamond.
- Giant covalent structure.
- Each carbon atom is covalently bonded to four
other carbon atoms. - Many covalent bonds means that diamond has a
very high melting point and is very hard - Makes
them suitable for the drills of dental drills. - No delocalised electrons - Cannot conduct
electricity.
Describe the structure of graphite.
- Giant covalent structure.
- Each carbon atom is covalently bonded to just
three other carbon atoms. - One electron in the outer shell of each atom is not
involved in bonding - Becomes delocalised
instead - Free to move throughout the structure
and therefore graphite can conduct electricity - Layered structure.
- Atoms in each layer form interlocking hexagons.
- High MP - Many strong covalent bonds.
- Forces between each layer are weak - Layers can
slide over each other.
What is graphene?
- A carbon allotrope that resembles a single layer of graphite. - Almost transparent. - Extremely strong. - Conducts electricity.
What are fullerenes, nanotubes and buckyballs?
Fullerenes form a large family of carbon allotropes
in which the molecules are shapes like tubes or
balls.
- A nanotube resembles a sheet of graphene
rolled into a tube - Strong and used to reinforce
sports equipment. - A buckyball resembles a sheet of graphene
closed to make a hollow ball - Potential uses as a
lubricant - Molecules acting like tiny ball bearings -
Could be used for drug delivery systems
What happens when a substance melts or boils?
- Forces of attraction between its particles are
overcome. - Some bonds break going from the solid to liquid
state. - Nearly all of the remaining bonds break going
from the liquid to the gas state.
What happens when a substance condenses or freezes?
- Some bonds form going from the gas to liquid
state. - Many bonds form going from the liquid to the
solid state.
What is sublimation and deposition?
- Sublimation - Solid to gas.
- Deposition - Gas to solid.
Gives examples of the bonds involves in state changes and their strengths.
Type of substance
Bonds involved in state changes
Relative strength
Examples of substances
- Metals
- Metallic Bonds
- Strong
- Iron, Mercury - Ionic compounds
- Ionic Bonds
- Strong
- Sodium Chloride - Giant covalent structures
- Covalent bonds
- Strong
- Diamond, Silica - Simple molecules
- Intermolecular forces
- Weak
- Oxygen, Water & Wax
What is the difference between a brittle substance and a malleable substance and what does the difference depend on?
- A brittle substance cracks or breaks when an
external force is applied. - A malleable substance can change shape without
cracking or breaking. - The difference depends on how easily the
particles in the substance can change their
position in the lattice structure.
Why are metals malleable?
- Layers of metal ions slide over one another.
- No bonds are broken.
Why will diamond shatter if hit with a hammer?
- Giant covalent structure with very many atoms
held together in a giant lattice by strong covalent
bonds. - Large enough force applied = Many covalent
bonds break at once and the substance breaks. - Similar with ionic compounds.
Why can metals conduct electricity?
- A substance can conduct electricity if it has
charged particles that are free to move. - The delocalised electrons in the structure of the
metal are free to move through the structure.
