States of Matter
Kinetic Molecular Theory
• Based on the idea that particles of matter are
always in motion
animation
KMT of Gases
• Consist of large numbers of tiny particles that
are far apart relative to their size
• Collisions between gas particles and between
particles and container are elastic (no net loss
of total kinetic energy)
• Continuous, rapid, random motion
• No forces of attraction between gas particles
• Temperature of a gas depends on average
kinetic energy
Applies to ideal gases which do not
actually exist
Properties of gases
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Expansion: gases completely fill any container
Fluidity: ability to flow
Low Density: particles are much further apart
Compressibility: Initially the particles are very far
apart but can be pushed closer together
• Diffusion: spontaneous mixing of particles of two
substances caused by their random motion
• Effusion: process by which gas particles travel
through a tiny opening
Graham’s law of Effusion (Diffusion)
• Rate of effusion is inversely proportional to
the square root of its molecular mass
• Compare the rate of diffusion of hydrogen to
that of oxygen under similar conditions.
KMT of Liquids
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Constant motion
Stronger attractive forces
Stronger intermolecular forces
Particles are closer together
Brownian movement: zigzag, irregular
motion exhibited by minute particles of
matter when suspended in a fluid
Properties of Liquids
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Fluidity
Higher density
Relative Incompressibility
Diffusion
Surface Tension: molecules at the surface of a
liquid experience attractive forces downward,
toward the inside of the liquid, and sideways;
molecules in the center of the liquid experience
uniformly distributed attractive forces
• Viscosity: friction or resistance to motion that
exists between molecules of a liquid as they
move past each other
• Capillary Action: attraction of a surface of a
liquid to the surface of a solid
• Evaporation and Boiling
• Cohesion is the term for molecules of a
substance sticking together. One of the most
common examples is water beading up on a
hydrophobic surface
• Adhesion is the force of attraction between
molecules of different substances
KMT of Solids
• Strongest intermolecular forces
• Particles closest together
Properties of Solids
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Definite melting point
High density
Incompressibility
Low rate of diffusion
Two types of solids
• Crystalline solids: consist of crystals which are
substances in which particles are arranged in
an orderly, geometric, repeating pattern
• Amorphous solid: particles are arranged
randomly
– Glass
– Plastics