Intermolecular Forces Flashcards
⚫ has a fixed volume that cannot be compressed into a smaller volume
⚫ is rigid with a definite shape because the
atoms, ions, or, molecules are in fixed
positions
Solid
⚫ is flowing matter with a definite volume but
an indefinite shape
⚫ takes the shape of its container
Liquid
⚫ flowing, compressible matter that has no definite volume or shape
⚫ spreads out to fill the space
⚫ particles are much farther apart than they are in solids and liquids
⚫ particles can be easily pushed together
Gas
As they drift through the air
they are seen to wobble in zigzag paths. This was first
noticed in 1827 by Robert
Brown. The effect is called _______
Brownian motion
Viewed through a microscope,
smoke can be seen to be made up
of millions of tiny bits or
particles. The bits of smoke
glint in the light from the lamp
Brownian motion
______ can explain
Brownian motion – the bits of
smoke, just large enough to be
seen, have so little mass that
they are ‘jostled’ about by
thousands of surrounding gas
particles that bump into them at
random.
Kinetic Theory
The total KE and PE of all
atoms and molecules in a
material is called the
__________. The
hotter a material, the
faster the particles move,
and the more internal
energy it has.
Internal Energy
⚫ states that submicroscopic particles of all
matter are in constant motion
⚫ Kinetic energy is the energy of moving
objects
Kinetic Theory of matter
⚫ A gas particle can change direction only when
it strikes the wall of its container or another
gas particle
⚫ Assumptions: Each gas particle rebounds
without losing kinetic energy and without
losing speed, but in a new direction
⚫ Collisions of particles in a gas are called
elastic collisions because no kinetic energy is
lost
kinetic model of gasses
⚫ Particles of a liquid can slide past each other, but they are so close together that
they don’t move as straight as gas
particles
Kinetic model of liquids
⚫ Strong forces between particles explain the rigid structure
of solids
⚫ Particles of a solid cannot move past each other, but they
are in constant motion (vibration)
⚫ Particles occupy fixed positions in a well defined, 3-dimensional arrangement
Crystal lattice- The arrangement, which is repeated throughout the solid
⚫ When a solid melts, its crystal lattices disintegrate and its
particles lose their 3-dimensional pattern
Kinetic Model of Solids
what holes molecules together
intramolecular force of attraction
intramolecular forces of attraction is also called as….
Van der Waals Forces
⚫ Occurs between polar molecules
⚫ Polar Molecule = “Permanent Dipole”
⚫ asymmetrical molecule with polar bonds
Dipole Dipole attractions
⚫ Super strong Dipole-Dipole Attraction
⚫ Occurs when molecules have hydrogen atoms
bonded to very small, highly electronegative
atoms like F, O or N
⚫ Creates a very polar bond and an “extra polar”
molecule.
Hydrogen Bonding
Hydrogen Bonding between molecules results in ______
High MB/BP temps
Hydrogen Bonding is responsible for water ______&__
surface tension and How it beads
⚫ Only attractive forces between nonpolar
molecules and noble gas atoms.
⚫ Weakest of all intermolecular forces
Dispersion Force
Dispersion force is also called as
induced dipole
How can you increase the chance for
Dispersion forces to be felt between
NONPOLARS?
High pressure/low temp. conditions
⚫ Nonpolar gas particles are so far apart, weak
dispersion forces cannot be felt.
⚫ Molecules must be close and moving slowly so
that the momentary dipoles can be created.
Why Do Ionics Dissolve in Water?
⚫ Molecule-Ion Attractions:
⚫ Attraction between polar solvent molecules and ions in an ionic crystal.
⚫ Allows polar solvent (like water) to “pull” the ions into solution, creating “hydrated” ions.
