Keywords
Which keywords might you use when
describing each type of bond?
Electrostatic
attraction
Ionic bond
Covalent bond
Metallic bond
Lattice
Alloy
Ionic
Bonding
Metallic
Bonding
Which keywords might you use when
describing each type of bond?
Ionic
Bonding
Strong bonds
Opposite
charged ions
Fixed position
lattice
Giant Covalent
Structures
Strong bonds
All atoms
Lattice
No electrons/charges
Simple covalent
Molecules
Strong bonds
within molecule
Weak
intermolecular
forces
No charges
Metallic
Bonding
Strong bonds
Between ions
Free electrons
Layers
Answering an exam question……
Steps to success
Why is
• What is the structure?
sodium
• What type of bonding and
chloride a
solid at room
temperature?
forces are present?
• Is the melting/boiling point
high OR low?
• How much ENERGY is needed
to break the forces/bonds?
Answering an exam question……
Why is
sodium
chloride a
solid at room
temperature?
Steps to success
• Giant ionic lattice structure
• Strong ionic bonds
• High melting point because
• Lots of energy is needed to
break the strong ionic bonds
Exam question
The boiling point of methanol is +65 °C; the boiling point of
oxygen is –183 °C. Methanol and oxygen each have an Mr
value of 32. Explain, in terms of the intermolecular forces
present in each case, why the boiling point of methanol is
much higher than that of oxygen.
(3)
Steps to success
• What intermolecular forces are
there between the oxygen
molecules?
• What intermolecular forces are
there between the methanol
molecules?
• Which is stronger?
Exam question
The boiling point of methanol is +65 °C; the boiling point of
oxygen is –183 °C. Methanol and oxygen each have an Mr
value of 32. Explain, in terms of the intermolecular forces
present in each case, why the boiling point of methanol is
much higher than that of oxygen.
(3)
Steps to success
• van der Waals’ forces between oxygen molecules;
1
Hydrogen bonding between methanol molecules; 1
H-B stronger than van der Waals’ OR stronger IMF in
methanol; 1
• (if dipole-dipole forces in O2 or methanol, allow
comparison, hence max 2)
• (if ionic/covalent etc. max 1)
• (mention of bond break = CE = 0)
Answering an exam question……
Why does
potassium
chloride
conduct
electricity
when molten
or in solution
but not when
solid?
Steps to success
• What is the structure?
• Does it contain ions or
delocalised electrons?
• Are they in fixed positions or
free to move?
• Can something be changed so
that the are free to move?
Answering an exam question……
Why does
potassium
chloride
conduct
electricity
when
molten or
in solution
but not
when
solid?
• Giant ionic lattice structure
• Contains ions
• That are in a fixed position so
they are not free to move so do
not conduct electricity
• When molten or dissolved in
water they are free to move so
conduct electricity