LIQUIDS

Properties of Liquids and the Kinetic-Molecular 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.