C2.2 Flashcards
Why do ionic compounds have high melting points and boiling points?
Because tot takes up a lot of energy to break a giant ionic lattice. There are lots of strong ionic bonds to break.
Why can ionic compounds conduct electricity when they are molten or dissolved in water?
The lattice is split up by the water molecules.
Then the ions are free to move around in the solution formed.
Ions are able to move to an oppositely charged electrode dipped in the solution.
What is an intermolecular force?
Small attraction between individual molecules in a covalent substance.
How strong are the forces between the atoms in a covalent substance?
Relatively small.
Why don’t simple molecular substances conduct electricity?
There is no overall charge so their molecules cannot carry electrical charge.
What do we call the structures which contain many millions of atoms joined together by a network of covalent bonds?
Giant lattices.
What kind of physical properties do these substances have?
- very hard
- high melting and boiling points
- insoluble in water
What type of electrons enable graphite to conduct electricity?
Delocalised electrons.
How are the carbon atoms in graphite’s layers arranged?
In hexagons.
What are fullerenes?
Large carbon molecules containing cage-like structures.
Why can metals be bent, shaped and pulled out into wires when forces are applied?
Atoms are able to slide easily over each other.
How are metal atoms held together?
By a sea of delocalised electrons.
Why do metals conduct electricity and heat so well?
Because the delocalised electrons can flow through the giant metallic lattice.
What are shape memory alloys?
Metals that can return to its original shape by themselves.
Why are shape memory alloys used in braces?
To pull teeth into the right position.
How are polyamory chains arranged in poly(ethene)?
Monomers join together to make much bigger molecules called polymers.
As they join together they produce a tangled web of very long chain molecules.
What are monomers?
Small molecules.
Name two different monomers:
- monomer that has acidic groups at each end
- monomer that has basic groups at each end
Name two different types of poly(ethene):
- high density (HD)
- low density (LD)
How does bonding in polymers happen?
They’re held together by very strong covalent bonds.
What are thermosoftening polymers?
Polymers that will reset when they cool down.
What are thermosetting polymers?
Polymers that don’t melt when heated.
How many nanometres make up 1 millimetre?
1 million.
Why would nanoparticles make very efficient catalysts?
They have large surface areas.
