Kinetic Molecular Theory of Liquids and Solids
Kinetic Molecular Theory
1. All matter is composed of tiny particles.
2. These particles are in constant motion.
3. The amount of motion is proportional to temperature. Increased temperature means
increased motion.
4. Solids, liquids, and gasses differ in the freedom of motion of their particles and the extent
to which the particles interact.
Characteristic Properties of Gasses, Liquids and Solids
Phase
- is a homogeneous part of the system in contact with other parts of the system but
separated from them by a well-defined boundary.
Intermolecular Forces
● Intermolecular forces are attractive forces between molecules.
● Intramolecular forces – holds atoms together in a molecule.
● Intramolecular forces - stabilizes individual molecules; intermolecular forces –
responsible for the bulk properties of matter (melting point and boiling point)
● Melting point and boiling point of substances can be used as indicators of strength of
intermolecular forces.
Different Types of Intermolecular Forces
Dispersion Forces
● These forces of attraction result from temporary dipole moments induced in an
ordinarily nonpolar molecule or atom.
● These forces are present between all types of molecules due to the movement of
electrons. As electrons move around the nucleus, an uneven distribution causes
, momentary charge separations. Slightly positive sides of a molecule are attracted to
the slightly negative sides of the adjacent molecule.
● The extent to which a dipole moment can be induced in a molecule is called its
polarizability.
● Polarizability of the atom or molecule refers to the ease with which the electron
distribution can be distorted.
● Generally, the larger the number of electrons and the larger or more diffused the
electron cloud in the atom or molecule, the greater its polarizability.
● Thus, dispersion forces may be the weakest of intermolecular forces that can exist
between two molecules, but the larger the atoms present, the stronger the dispersion
forces.
This will cause the neighboring atoms to be attracted to one another. This is called the
London dispersion force (or just dispersion force). It is significant only when the atoms are
close together.
Dipole-Dipole Forces
● are attractive forces between polar molecules (molecules that possess dipole
moments).
● In polar molecules the electrons are unevenly distributed because some elements
are more electronegative than others.
● The partial negative side of one molecule is attracted to the partial positive side of
another molecule.
● This type of force is stronger than the dispersion forces because polar molecules
have a permanent uneven distribution of electrons.
● The nature of attraction is electrostatic and can be understood in terms of Coulomb’s
law: The larger the dipole moment, the stronger the attraction.
Kinetic Molecular Theory
1. All matter is composed of tiny particles.
2. These particles are in constant motion.
3. The amount of motion is proportional to temperature. Increased temperature means
increased motion.
4. Solids, liquids, and gasses differ in the freedom of motion of their particles and the extent
to which the particles interact.
Characteristic Properties of Gasses, Liquids and Solids
Phase
- is a homogeneous part of the system in contact with other parts of the system but
separated from them by a well-defined boundary.
Intermolecular Forces
● Intermolecular forces are attractive forces between molecules.
● Intramolecular forces – holds atoms together in a molecule.
● Intramolecular forces - stabilizes individual molecules; intermolecular forces –
responsible for the bulk properties of matter (melting point and boiling point)
● Melting point and boiling point of substances can be used as indicators of strength of
intermolecular forces.
Different Types of Intermolecular Forces
Dispersion Forces
● These forces of attraction result from temporary dipole moments induced in an
ordinarily nonpolar molecule or atom.
● These forces are present between all types of molecules due to the movement of
electrons. As electrons move around the nucleus, an uneven distribution causes
, momentary charge separations. Slightly positive sides of a molecule are attracted to
the slightly negative sides of the adjacent molecule.
● The extent to which a dipole moment can be induced in a molecule is called its
polarizability.
● Polarizability of the atom or molecule refers to the ease with which the electron
distribution can be distorted.
● Generally, the larger the number of electrons and the larger or more diffused the
electron cloud in the atom or molecule, the greater its polarizability.
● Thus, dispersion forces may be the weakest of intermolecular forces that can exist
between two molecules, but the larger the atoms present, the stronger the dispersion
forces.
This will cause the neighboring atoms to be attracted to one another. This is called the
London dispersion force (or just dispersion force). It is significant only when the atoms are
close together.
Dipole-Dipole Forces
● are attractive forces between polar molecules (molecules that possess dipole
moments).
● In polar molecules the electrons are unevenly distributed because some elements
are more electronegative than others.
● The partial negative side of one molecule is attracted to the partial positive side of
another molecule.
● This type of force is stronger than the dispersion forces because polar molecules
have a permanent uneven distribution of electrons.
● The nature of attraction is electrostatic and can be understood in terms of Coulomb’s
law: The larger the dipole moment, the stronger the attraction.
