Liquids & Solids

Objectives 12-1

• describe the motion of particles of a liquid and the properties of a liquid using KMT

• define and discuss vaporization

• define and discuss freezing

KMT of Liquids

FLUID - a substance that can flow and therefore take the shape of its container

• Particles have lower KE than gases

• Attractive forces between molecules is greater

• More ordered than gases

Properties of Liquids

• Relative to gases have a much higher density• Relatively incompressible• Can diffuse• Surface tension

– (force that pulls molecules together giving a smaller surface area)

– Capillary action – attraction between the surface of a liquid and a solid (meniscus)

• Vaporization – changing from liquid to gas– Evaporation – particles escaping from the surface of a non-

boiling liquid• Boiling – changing of liquid to bubbles of vapor that appear

throughout a liquid• Freezing – change of a liquid to a solid by the removal of heat

Objectives 12-2

• describe the motion of particles of a solid and the properties of a solid using KMT

• differentiate between crystalline and amorphous solids

• describe crystal symmetry and define crystal structure and unit cell

KMT of Solids

• Higher density than liquids

• More ordered

• Very strong intermolecular forces– London dispersion– Dipole-dipole– Hydrogen bonding

• Crystalline solids (very organized)

• Amorphous solids (not organized)

Properties of Solids

• Definite shape and volume

• Definite melting point– Supercooled liquids – amorphous solids

have the ability to flow over a range of temperatures

• High density/incompressibility

• Low rate of diffusion

Crystalline Solids

Ionic Crystals

• Cations and anions arranged in a pattern

• Group 1 & 2 bonded with Group 16 & 17

• Hard and brittle

• High melting points

• Good insulators

Covalent network crystals

• Single atoms bonded to its neighbor

• Can be very large

• Usually hard and brittle

• High melting points

• Non-conductors or semiconductors

Metallic crystals

• Metal atoms surrounded by a sea of electrons

• Good conductors

• Melting points vary

Covalent molecule crystals

• Covalently bonded molecules held together by intermolecular forces– If non-polar, only LDF (weak)– If polar, held together by LDF, dipole-dipole,

and maybe hydrogen bonds

• Low melting points• Relatively soft• Easily vaporized• Good insulators

Amorphous solids

• “without shape”

• Plastics and glass

Changes of State

Equilibrium

• Dynamic condition in which two opposing changes occur at the same rate in a closed system

vaporenergy heat liquid

energyheat liquid vapor

vaporenergy heat liquid

Equilibrium and Changes of State

• Solid to liquid melting

• Solid to gas sublimation

• Liquid to solid freezing

• Liquid to gas vaporization

• Gas to liquid condensation

• Gas to solid deposition

LeChatelier’s Principle

• When a system in equilibrium is stressed, it attains a new equilibrium which will minimize stress

Stresses

• Addition of liquid

• Removal of liquid

• Addition of vapor

• Removal of vapor

• Decrease in volume

• Increase in volume

• Decrease in temp

• Increase in temp

Equilibrium Vapor Pressure

• The pressure exerted by a vapor in equilibrium with its corresponding liquid at a given temperature

Phase Diagrams

• Triple point – the temperature and pressure at which all 3 phases can exist

• Critical point – indicates critical pressure and temperature – Critical Temp: temp at which a substance cannot exist in the liquid state

– Critical Pressure: the lowest pressure at which a substance can exist as a liquid at the critical temperature

Volatile vs. Non-volatile

• Volatile liquids evaporate easily (i.e – lower temperatures)

12-4: Water

Physical Properties of Water

• Clear• Colorless• Odorless• Tasteless• Molar heat of fusion is 6.009 kJ/mol (amount of

heat energy needed to melt one mole of water)• Molar heat of vaporization is 40.79 kJ/mol

(amount of heat energy needed to vaporize one mole of water)