Thermodynamic Properties of Ionic Liquids - Measurements and
Chapter 12 Liquids and Solids. Sect. 12-1: Liquids Properties of liquids Definite volume Takes...
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Transcript of Chapter 12 Liquids and Solids. Sect. 12-1: Liquids Properties of liquids Definite volume Takes...
Sect. 12-1: Liquids
Properties of liquids Definite volume Takes shape of its container Properties can be explained by the kinetic
molecular theory (KMT) just like gases were explained
Fluid – has the ability to flow
Properties of liquids (con’t)
Relatively high densityRelative incompressibilityAbility to diffuseSurface tension – force that tends to pull
adjacent parts of a liquid’s surface together, thereby decreasing surface area to the smallest possible size
More properties of liquids…
Capillary action – the attraction of the surface of a liquid to the surface of a solid
Vaporization – liquid changes to a gasEvaporation – vaporization occurring at
the surface of a non-boiling liquidFreezing – liquid changing to a solid
Sect. 12-2: Solids
Properties of solids Definite volume Definite shape Properties can be explained by the kinetic
molecular theory (KMT) just like gases and liquids were explained
Two types of solids
Crystalline solids – made up of crystals Crystals – particles are arranged in an orderly,
geometric fashion
Amorphous solids – particles are arranged randomly
More properties of solids…Definite melting point – temperature at
which a crystalline solid turns into a liquidSupercooled liquids – substances that
retain certain liquid properties even at temperatures at which they appear to be solid (amorphous solids)
High densityIncompressibilityVery low rate of diffusion
Crystalline solids
Crystal structure – total 3D arrangement of particles of a crystal
Unit cell – smallest part of a crystal structure that shows the 3D pattern of the entire structure
Binding forces in crystals
Ionic crystalsCovalent network crystalsMetallic crystalsCovalent molecular crystals
Sect.12-3: Changes of State
Equilibrium – a dynamic condition in which two opposing changes occur at equal rates in a closed system
Phase – any part of a system that has uniform composition and properties
Equilibrium and changes of state
If you start out with a closed container of liquid, eventually some of it will evaporate.
Over time, some of the gas will condense.If left for a long enough period of time,
equilibrium will be reached for amount of substance condensing vs. evaporating.
Represented by the following equation: liquid + heat energy vapor
System will stay at equilibrium until some outside force acts upon it.
Le Châtelier’s Principle – when a system at equilibrium is disturbed by an application of stress, it attains a new equilibrium position that minimizes the stress Stress is typically a change in concentration,
pressure, or temperature.
Equilibrium and temperature
What will happen to earlier discussed liquid/vapor system if temperature is increased? Which reaction will be favored?
What if temp is decreased? Which reaction is favored?
Equilibrium and concentration
What would happen to system if volume of container was suddenly increased?
Amount of vapor would now be in lower concentration and thus less condensation would be occurring and more evaporation occurring until system reaches equilibrium again.
At the new equilibrium, there fewer liquid molecules, but the same concentration of the gas due to larger container size. (equilibrium has shifted right)
Equilibrium and Vapor Pressure of Liquid
Equilibrium vapor pressure – pressure exerted by a vapor in equilibrium over a liquid at a given temperature (increases as temp increases)
Explained by KMTPg. 376 for illustration
Volatile vs. nonvolatile liquids
Volatile liquid – liquids which evaporate very easily due to weak forces of attraction between particles Have a relatively high equilibrium vapor
pressure
Nonvolatile liquids have stronger forces of attraction and lower equilibrium vapor pressures
Boiling
Boiling – conversion of a liquid to a gas at the surface and throughout the liquid
Boiling point – temperature at which the equilibrium vapor pressure is equal to the atmospheric pressure Pressure affects the boiling point Normal boiling point is at 1 atm pressure
During a phase change, such as vaporization, the temperature remains constant because any heat being added is going to changing the particles from liquid to gas
Molar heat of vaporization – amount of heat required to vaporize one mole of liquid at its boiling point The higher it is, the stronger the bonds are that
hold that liquid together
Freezing and Melting
Freezing point – temperature at which the solid and liquid are in equilibrium at 1 atm
Molar heat of fusion – amount of heat required to melt one mole of a solid at its melting point
Sublimation – change of state from a solid directly to a gas
Deposition – change of state from a gas directly to a solid
Both occur at low pressures and temperatures where a liquid cannot exist
Phase Diagrams
Phase diagram – a graph of pressure vs. temperature that shows the conditions under which the phases of a substance exist
Triple point – indicates the temperature and pressure at which the solid, liquid, and vapor can coexist at equilibrium
Critical point – indicates critical temp. and pressure
Critical temperature (tc)– temp above which a substance cannot exist as a liquid
Critical pressure (Pc) – lowest pressure at which the substance can exist as a liquid at the critical temperature
Sect. 12-4: Water
Water molecules have a bent structure
Solid or liquid water molecules are linked by hydrogen bonding
Ice is made up of water arranged in hexagon shapes; this allows for low density