C2 Flashcards
What is ionic bonding?
Metals bonded to non-metals. Atoms become charged either by losing or gaining electrons.
What is covalent bonding?
Occurs between two non-metals when atoms share electrons to achieve a full outer shell.
What is metallic bonding?
Occurs between metal atoms. Electrons become de-localised and free to move (a sea of free electrons is created).
What type of structure does ionic bonding have?
lattice
What type of structure does covalent bonding have?
simple molecular and Giant molecular
What type of structure does metallic bonding have?
lattice. There is a strong electrostatic attraction between the ‘sea’ of negatively charged electrons and positive metal ions.
Why do ionic compounds have a high melting point?
They have a strong electrostatic attraction between two oppositely charged ions and therefore requires lots of energy to break.
What substances have a giant covalent structure?
Diamond, graphite, SiO2 (silica)
What are the properties of a giant covalent structure?
- Many strong covalent bonds which are difficult to break and require lots of energy to do so.
- Each atom is bonded to four atoms creating an interconnected lattice where no atom can move independently from each other.
- does not have layers so cannot slide
- no free electrons
What are the properties of graphite?
- conducts electricity as it has free electrons
- each atom is bonded to three others creating a layered structure with weak intermolecular forces between the layers allowing them to slide over each other
What are polymers ?
made of many monomers and produced from cracking and alkenes.
What is polymerisation?
when many monomers form a long chain called a polymer (a much more useful substance)
Compare High Density Polyethene to Low Density Polyethene
hdpe will pack together tighter as the polymers can line up easily. Therefore, hdpe will be able to form a higher number of intermolecular bonds and will have a higher melting point as more energy is required to break the bonds.
The properties of polymers depend on:
what they are made from (monomers)
and the conditions in which they were made ( eg hdpe and ldpe)
Describe thermosoftening
Good if wanting to recycle the plastic as they are easy to separate due to the weak intermolecular forces being broken down and heated. When a polymer cools intermolecular forces pull the molecules back together hence it can be re-shaped
Describe thermosetting
polymers fixed together by strong covalent bonds and stop the polymers being separated. When heated strongly the polymers will char.
Whats nanotechnology?
nanoparticles are particles sized between 1 and 100 nanometres. This is roughly 100 atoms in size
what is collision theory?
in order for a reaction to occur, the reacting particles must collide with enough energy to react
activation energy is the minimum amount
how does increasing pressure increase rates?
increased collisions=quicker rate
same no.of atoms, smaller volume
how does increasing concentration increase the rate?
more particles, more collisions, increased rate
what is effect 1 of increasing temperature?
atoms have more energy, move faster, more collisions, more reactions
what is effect 2 of increasing temperature?
atoms have more energy, more have sufficient energy to react, more numbers of successful collisions, increased rate of reaction
how does surface area affect rates?
bigger area available to react, increased frequency, increased rate
how does adding a catalyst affect rates?
lowers activation energy, successful collisions increase, rate of reaction increases
