3.2 - interactions between molecules

Question 1

what are dispersion forces?

Answer 1

dispersion forces exist between all molecules, their strength depends on the size and shape of the molecule.

dispersion forces are the only type of forces that exist between non-polar molecules.

Question 2

what are intramolecular bonds?

Answer 2

intramolecular bonds are the bonds found between atoms within a molecule, they are known as primary interactions and include ionic, metallic and covalent bonding.

Question 3

what are intermolecular bonds?

Answer 3

intermolecular bonds are the forces located between molecules, these include dipole-dipole bonding, hydrogen bonding, ion-dipole bonding and dispersion forces.

Question 4

what is the difference between intramolecular and intermolecular bonds?

Answer 4

intramolecular bonds are significantly stronger than intermolecular bonds, as a result of the electrostatic forces that hold compounds together being stronger than those that hold molecules together.

Question 5

explain the trends of dispersion forces.

Answer 5

larger molecules have larger dispersion forces as opposed to smaller molecules (when molecules have a higher molecular weight, there are more available surfaces where the dispersion forces can act) and therefore, have higher melting and boiling points as more energy is required to overcome the electrostatic attraction.

Question 6

what are dipole-dipole interactions?

Answer 6

dipole-dipole interactions exist between polar molecules and their strength depends on the polarity and size of the molecules.

• the slightly positive end of one molecules is attracted to the slightly negative end of the other molecule and so on.

Question 7

what is hydrogen bonding?

Answer 7

hydrogen bonding is a stronger form of dipole-dipole interactions that exist when hydrogen is bonded to any of the three most electronegative elements, flourine, nitrogen or oxygen.

Question 8

explain the trends present within hydrogen bonds?

Answer 8

as a result of the type of interaction, the boiling points of molecules that have hydrogen bonding present is considerably higher than what would be expected for their size.

Question 9

list the secondary bonds from strongest to weakest.

Answer 9

ion-dipole interactions
hydrogen bonding
dipole-dipole interactions
dispersion forces