Chapter 3: 3.3 Intermolecular Forces Flashcards
Define:
Boiling point
Temperature at which the vapor pressure equals the atmospheric pressure
Define:
Melting point
The temperature at which solid turns into a liquid
Define:
Dispersion forces
Weak interactions between molecules caused by momentary changes in electron density
How do we determine the strength of dispersion forces?
The surface area of the molecule (larger SA = stronger dispersion forces)
Define:
Dipole-dipole interactions
Attractive forces between the permanent dipoles of two polar molecules
True or False:
Dipole-dipole interactions are stronger than dispersion forces
True, dipole-dipole interactions are MUCH stronger than dispersion forces
Define:
Hydrogen Bonding
When a hydrogen atom covalently bonded to a highly electronegative atom (F, O, or N) is attracted to a lone electron pair on another such electronegative atom of a different molecule
What are dispersion forces and dipole-dipole interactions collectively known as?
Van der Waals Forces
What are electrostatic forces between permanently charged ions known as?
Ionic interactions or Ionic bonds
True or False:
Ionic bonds are stronger than electrostatic forces in dispersion and permanent dipoles
True
What is the relationship between intermolecular forces and boiling points?
Stronger intermolecular forces = Higher boiling points
What is the relationship between molecular mass and boiling points?
Larger molecular mass = Higher boiling points
True or False:
Melting point trends are the opposite of boiling point trends
False, the melting point trends generally follow the same trends observed for boiling points
Besides intermolecular forces and molecular masses, what other factor is important in determining melting points?
Symmetry
What is the relationship between symmetry and melting points?
Symmetry = Compact = Higher melting point
