C3 Flashcards
if there is a higher melting and boiling point what does that mean
there are stronger forces operating between particles
what is sublimation
when a solid heats up and changes directing into a gas without going through the liquid phase
what is a compound
2 or more elements chemically combined
what is the difference between covalent and ionic bonding
covalent is sharing electrons and ionic is transferring
when are ionic compounds formed
when metals and non metals react
how is a giant lattice/structure formed
when ionic bonds between the charged particles result in an arrangement of ions
why do ionic compounds have high melting and boiling points
because it takes a lot of energy to break up a giant lattice as there are many strong ionic bonds to break
when can ionic compounds carry electrical charge
when they melt and become liquid and their ions are free to move anywhere in the liquid
or when they are dissolved in water
how does dissolving an ionic compound in water allow it to be a conductor
water molecules separate the ions from the lattice so they are free to move around
what is covalent bonding
when non metals react together, their atoms share pairs of electrons to form molecules
what are macromolecules
giant covalent structures where huge numbers of atoms are held together by a network of covalent bonds
what is the giant covalent structure of diamond
each carbon atom forms 4 bonds with its neighbours resulting in a rigid giant covalent lattice
what bonds are broken when a substance melts or boils
the weak intermolecular forces are broken/ overcome. the covalent bonds are not broken
what is the hardest known natural substance and what is its boiling point
diamond and 4827c
how can artificial diamonds be formed
by heating pure carbon under huge heat and pressure
what are properties of substances with giant covalent structures
high melting and boiling points
insoluble in water
hard and don’t conduct electricity (except granite)
what is the difference between diamond and graphite
in diamond the carbon atoms are bonded to 4 other carbon atoms but in graphite it’s only 3 bonds
why do layers in giant structures slide over each other easily
there are no covalent bonds between layers only weak intermolecular forces which is why graphite is soft and slippery
why does graphite conduct electricity
because it only has 3 carbon bonds so it has delocalised electrons which move freely along the layers
why do larger molecules have higher melting and boiling points
because the intermolecular forces increase with the size of the molecules
what are polymers
very long chain molecules with stronger intermolecular forces
what are allotropes
different forms of the same element in the same state e.g diamond and graphite are allotropes of carbon
what are fullerenes
hollow shaped molecules of carbon
what are carbon nanotubes
cylindrical fullerenes (thin cylinders with lengths greater than diameter)
