Chemistry Midterms

• Gas - High kinetic energy

  Solid - Low Kinetic energy
• Attractive forces between neighboring particles of one or more substances

  Intermolecular forces
• The type of IMF present depends on the type of

  particles present
• Attractive force between molecules. Responsible for keeping matter in solid or liquid phase

  Intermolecular Forces
• Forces that hold atoms together in a molecule

  Intramolecular Forces
• Forces within a molecule or ionic compound

  Intermolecular Forces
• Forces between molecules or ions and molecules

  Intramolecular forces
• Intramolecular > Intermolecular
• Intramolecular bonds are stronger because it would take a lot more energy to overcome covalent bonds and break apart the molecule than to overcome intermolecular forces in between the atoms
• Intermolecular forces of attraction in a pure substance are collectively known as

  Van der Waals Forces
• intermolecular forces of attraction between neutral molecules

  Van der Waals
• Won Nobel prize in physics 1920


  Johannes Van der Waals
• known for his work on the equation of state for gases and liquids

  Johannes Van der Waals
• ability of an atom to attract electrons toward itself in a chemical bond.

  Electronegativity
• The higher the electronegativity value for an element, the stronger its ability to attract shared electrons
• The larger the electronegativity difference between two atoms, the more polar the bond will be.
• Tendency of electron clouds to shift, depends on the electronegativity of each atom
• Covalent bond can be polar or nonpolar
• attractive forces between polar molecules, that is, between molecules that possess dipole moments.

  Dipole - Dipole Forces
• are a strong type of dipole-dipole interaction.

  Hydrogen Bonds
• about five to ten times stronger that the other dipole-dipole attractions.

  Hydrogen bonds
• is attached to a highly electronegative atom (N,O,F).

  Hydrogen
• Hydrogen bond acceptor should be small highly electronegative atom (N,O,F).
• result from the interaction between an ion and a polar molecule.

  Ion-dipole Forces
• Present in solutions where an ionic compound is dissolved into a polar solvent.

  Ion-dipole Forces
• Exist between ALL atoms and molecules.

  London Dispersion Force
• These are the only forces present in nonpolar molecules.

  London Dispersion Force
• They arise from the continuous movement of electrons inparticles.

  London Dispersion Force
• attractions between an instantaneous dipole and an induced dipole.

  London dispersion forces
• This intermolecular attraction happens between charged particles (ions) and molecules with positive and negative ends (polar molecules).

  Ion-Dipole Forces
• This occurs between a hydrogen atom bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine) and another electronegative atom in a nearby molecule.

  Hydrogen bonding
• This occurs when there is an interaction between a ion and an induced-dipole molecule.

  Ion-Induced Dipole
• This is the interaction between a polar molecule and non-polar molecule that was induced to have a dipole moment.

  Dipole-Induced Dipole
• The size of molecule can affect the London dispersion force between two molecules.
• The bigger the molecule, the stronger the attraction between two molecules
• A larger surface-to-surface contact between molecules results in stronger-dispersion force attraction and a higher boiling point
• Intermolecular forces that bind like molecules to one another (e.g. hydrogen bonding).

  Cohesive Forces
• Intermolecular forces that bind a substance to a surface.

  Adhesive Forces
• Concave Meniscus Formed by Polar Water
• Convex Meniscus Formed by Nonpolar Liquid Mercury