How structure influences the properties and uses of substances

Question 1

What are the properties of substances that consist of simple molecules?

Answer 1

have relatively low melting and boiling points

weak intermolecular forces in comparison to the covalent bonds

don’t conduct electricity because the molecules don’t have an overall electric charge

Question 2

What are the properties of ionic compounds?

Answer 2

have regular structures (giant ionic lattices)

these have strong electrostatic force in all direction between oppositely charged ions

high melting/boiling points because lots of energy is required to break the strong intermolecular bonds

when in a solution or molten, ionic compounds conduct electricity because the ions are free to move and carry the current

Question 3

How are giant covalent structures formed?

Answer 3

electrons are shared to form macromolecules

diamond and graphite and silicon dioxide are examples of giant covalent structures (lattices) of atoms

all the atoms in these structures are linked to other atoms by strong covalent bonds and so they have very high melting points

Question 4

Describe the structure of diamond

Answer 4

each carbon atom forms four covalent bonds with other carbon atoms atoms in a giant covalent structure

Question 5

Describe the structure of graphite

Answer 5

each carbon atom bonds to three other, this forms layers

layers can slide over each other because there isn’t a covalent bond between the layers, as a result it is soft

one electron from each carbon atom is delocalised, this allows graphite to conduct heat and electricity

Question 6

What are fullerenes?

Answer 6

carbon can also form fullerenes with different numbers of carbon atoms

based on hexagonal rings of carbon atoms

fullerenes can be used for drug delivery in the body, lubricants, catalyst and nanotubes for reinforcing materials