SC7 Types of Substances

Structures wherein many covalent bonds have been used to join the substance together

• high melting and boiling points • no conduction of electricity • insoluble in water

They are solids at room temperature, which tells us that the covalent bonds that hold them together are strong and need lots of energy to break

They carry no overall charge, so they can’t conduct electricity

Giant covalent substances can’t form strong attractions with water, so they can’t dissolve in it

• Diamond • graphite • graphene

• each carbon atom is joined to four other carbon atoms through a covalent bond • form a regular tetrahedral structure • no free electrons

• high melting and boiling points • doesn’t conduct electricity • hard

• used to cut hard things • worn as jewellery

• each carbon atom is joined with three other carbon atom • carbon atoms form a hexagonal layered structure • layers have weak forces of attraction between them, which means that it can easily slide over each other • each carbon atom has one un-bonded outer electron • these are the free electrons, and they are delocalised

• slippery • high melting and boiling points • can conduct electricity due to the delocalised electron

A single layer of graphite

Molecules of carbon with hollow shapes. Their structures are based on hexagonal rings of carbon atoms.

• nanotubes • Buckminster balls

• low melting and boiling points • soft • slippery

A large molecule which is consists of many identical smaller molecules known as monomers

Cylinder fullerenes with a high length to diameter ratios

• can conduct electricity due to the delocalised electrons • strong • high melting point

• consists of weak intermolecular forces which need little energy to overcome • lower melting points compared to diamond or graphite

• high tensile strength, so they are strong in tension and can resist being stretched • strong • can conduct electricity

They are in a solid state because the intermolecular forces are relatively strong

• solids with high melting • shiny • malleable • high density • good conductors of heat and electricity

• solids, liquids or gases with low melting points • not usually shiny when solid • brittle • low density • poor conductors of heat and electricity

Graphite - Giant molecular structure. - Each carbon atom is bonded to three others. - Weak intermolecular forces between layers. - strong covalent bonds between atoms in a layer. Diamond - Giant molecular structure. - Each carbon atom is bonded to four others. - Strong covalent bonds between atoms. - High boiling and melting points.