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Properties of Liquids and the KineticMolecular Theory
•A liquid can be described as a form of matter that
has a definite volume and takes the shape of its
container.
•The attractive forces between particles in a liquid
are more effective than those between particles in a
gas.
•This attraction is explained by intermolecular forces
(dipole-dipole, London dispersion, and hydrogen
bonding).
•Like gases, particles in a liquid are in constant
motion.
•Liquids are more ordered than gases because of
the stronger intermolecular forces and lower
mobility of particles.
•Relatively High Density – At normal atmospheric
pressure, most substances are hundreds of times
denser in a liquid state than in a gaseous state.
•Due to the close arrangement of liquid particles.
•Relative Incompressibility – Liquids are much less
compressible than gases because liquid particles
are more closely packed together.
•Ability to Diffuse – Any liquid gradually diffuses
throughout any other liquid in which in can dissolve.
•The constant, random motion of particles causes
diffusion in liquids.
•Diffusion is much slower in liquids than in gases
because liquid particles are close together.
•Also attractive forces between the particles slows
their movement.
•As temperature increases, diffusion increases.
•Surface Tension – A property common to all liquids
is surface tension, a force that tends to pull adjacent
parts of a liquid’s surface together, thereby
decreasing surface area to the smallest possible
size.
•The higher the force of attraction, the higher the
surface tension.
•Capillary action is the attraction of the surface of a
liquid to the surface of a solid.
•This attraction tends to pull the liquid molecules
upward along the surface and against the pull of
gravity.
•Vaporization – The process by which a liquid or
solid changes to a gas is vaporization.
•Evaporation is a form of vaporization.
•Evaporation is the process by which particles
escape from the surface of a nonboiling liquid and
enter the gas state.
•Evaporation occurs because the particles of a liquid
have different kinetic energies.
•Particles with higher kinetic
energy move faster and can
overcome intermolecular
forces.
•Evaporation occurs at the
surface of a liquid.
•Boiling is the change of a liquid to bubbles of vapor.
•Boiling occurs throughout the liquid.
•The physical change of a liquid to a solid by
removal of energy as heat is called freezing or
solidification.
•When a liquid is cooled, the average kinetic energy
of its particles decreases.
•When energy is low enough, attractive forces pull
the particles in a more orderly arrangement.