polymers and giant covalent structure Flashcards
what are polymers
large molecules, or macromolecules, made up of many repeating units called monomers (long chains of repeating units)
how do you find the molecular formula of a polymer
write down the molecular formula of the repeating unit in brackets and put and ‘n’ outside
what is the molecular formula for poly(ethene)
(C2H4)n
what are giant covalent structures
three-dimensional networks of atoms that are joined by covalent bonds in a regular pattern (also known as macromolecules)
what are the intermolecular forces like in polymer molecules
larger than simple covalent molecules, so more energy is needed to break them.
This means most polymers are solid at room temp.
However the intermolecular forces are still weaker than ionic or covalent bonds, so they generally have lower boiling and melting points than ionic or giant molecular compounds.
what happens in giant covalent structures
all the atoms are bonded to each other by strong covalent bonds
properties of giant covalent structures
very high melting and boiling points as lots of energy is needed to break the covalent bonds between the atoms
They do no not contain charged particles meaning they don’t conduct electricity - not even when molten.
what are the main example of giant covalent structures
diamond and graphite, which are both made from carbon atoms only , silicon dioxide (silica)
structure of a diamond
each carbon atom forms 4 covalent bonds in a very rigid giant covalent structure
structure of graphite
each carbon atoms form three covalent bonds to create layers of hexagons. each carbon atom also has one delocalised (free) electron.
structure of silicon dioxide
what sand is made of. each grain of sand is one giant structure of silicon and oxygen
does diamond or poly(ethene) have a higher melting point
diamonds because lots of energy is needed to break the covalent bonds between the atoms, however for poly(ethene) you only need to break the weak intermolecular forces, which needs less energy.
