States of MatterUnit 7

OverviewStates and Properties of MatterKinetic Molecular TheoryPhase ChangesDiagrams

Phase DiagramsHeating/Cooling Curves

Heat of Fusion/VaporizationVapor Pressure

States of MatterBased upon particle arrangementBased upon energy of particlesBased upon distance between particles

3 States of MatterSOLIDS — have rigid shape, fixed volume;

external shape can reflect the atomic and molecular arrangementReasonably well understood

LIQUIDS — have no fixed shape and may not fill a container completely Not well understood

GASES — expand to fill their containerGood theoretical understanding

Solids Definite shape & definite volume

Particles of solids are tightly packed, vibrating about a fixed position.

Not easily compressible Little free space between particles

Do not flow easily Particles cannot move/slide past one another

Infinite number of free surfaces

Solids (Types)Crystalline

Solids: highly regular arrangement of their components

Amorphous solids: considerable disorder in their structures (glass, plastic).

AllotropesSome chemical elements can exist in two or more different forms. Atoms of the element bond together differently.

Diamond, carbon atoms bond together in a tetrahedral lattice

Graphite, carbon atoms bond together in sheets

Liquids Indefinite shape but definite volume

Particles are tightly packed, but are far enough apart to slide over one another.

Not easily compressible Little free space between particles

Liquids flow easily Particles can move/slide past one another

Have one free surface

Surface Tension

Intermolecular cohesive attraction causing liquid to minimize its surface area Mostly in polar molecules and liquid metals

Capillary ActionAttraction of the surface of a liquid to

the surface of a solid, which causes the liquid to rise in a tube

Illustration of capillary action for large and

small bore capillaries.

ViscosityLiquids are fluids – they FLOW. Viscosity is the resistance to flow.

Example: Syrup has a higher viscosity than water.

High viscosity = strong intermolecular forces

Glycerine, also called glycerol, is a liquid with

a high viscosity

Viscosity decreases as temperature increases.

Gases Indefinite shape and indefinite volume

Particles are very far apart and move freely Easily compressible

There is a great deal of free space between particles

Flow very easily Particles randomly move past one another

Gases have no free surfaces

Plasma1879 - Sir William

Crookes, an English physicist, identified a fourth state of matter, now called plasma

Plasma is by far the most common form of matterPlasma in the stars and in the tenuous space

between them makes up over 99% of the visible universe and perhaps most of that which is not visible

Plasma An ionized gas Very good conductor

of electricity Composed of ions Affected by magnetic

fields Indefinite shape and

indefinite volume Particles can move past

one another. Easily compressible

Great deal of free space between particles.

Products manufacturedusing plasmas impact our daily lives:

•Computer chips and integrated circuits •Computer hard drives •Electronics •Machine tools •Medical implants and prosthetics •Audio and video tapes •Aircraft and automobile engine parts •Printing on plastic food containers •Energy-efficient window coatings •High-efficiency window coatings •Safe drinking water •Voice and data communications components •Anti-scratch and anti-glare coatings on eyeglasses and other optics

Kinetic Molecular Theory

1. pertaining to motion.

2. caused by motion.

3.characterized by movement: Running and dancing are kinetic activities.

ki⋅net⋅ic

Origin: 1850–55; < Gk kīnētikós moving, equiv. to kīnē- (verbid s. of kīneîn to move) + -tikos

Source: Websters Dictionary

Kinetic Molecular TheoryAtoms and molecules are constantly in motion.

SOLIDS — little movement between particles

LIQUIDS — more space between them than a solid does, but less than a gas

GASES — molecules are moving in random patterns with varying amounts of distance between the particles

Changes of StateChanging states requires a change in the energy of a system. Changing states may also be due to the change in pressure in a system.

Changes of State

Phase Diagrams

Phase Diagrams(T) Triple Point: temperature and pressure at

which all three phases exist simultaneously in equilibrium

(C) Critical Point: temperature and pressure beyond which the liquid and solid phase is distinguishable (supercritical liquid)molecules of a substance have too much kinetic energy

to stick together (page 453 of book = supercritical fluid)

Phase Diagrams

Water

Carbon dioxide

Carbon

Heat of Fusion (formation)Energy that must be put into a solid to melt it

Needed to overcome forces holding it togetherHeat of fusion given off when liquid freezes

Intermolecular forces within solid more stable and have lower energy than forces within liquid so energy is released during freezing

Heat of VaporizationEnergy that must be put into a liquid to turn it into a

gasEnergy needed to overcome forces holding liquid

togetherHeat of vaporization given off when gas condenses

Intermolecular forces become stronger when gas condenses so as gas becomes liquid (more stable), energy is released

Heat of vaporization larger than heat of fusionMany more intermolecular forces must be overcome in

vaporization than melting (intermolecular forces severed in vaporization but

many carry over between solids and liquids)

Heating/Cooling CurvesAs heat added to a substance in equilibrium,

temperature of substance can increase or the substance can change phases, but both changes cannot occur simultaneously

Horizontal line at melting point is heat of fusion

Horizontal line at boiling point is heat of vaporization

Heating/Cooling Curves

Vapor PressureThe pressure exerted by molecules as they escape

the surface of a liquid and become a gasAs temperature increases, vapor pressure of a liquid

increasesWhen vapor pressure of liquid increases to point

where equal with the surrounding atmospheric pressure, the liquid boils

The weaker the intermolecular forces, the easier it is for molecules to escape the surface and turn to gasWeaker intermolecular forces = higher vapor pressure

Vapor Pressure - EquilibriumAs number of gas molecules increases, higher

probability that gas molecule will hit surface of liquid and be recapturedWhen there is even exchange of liquid and gas

molecules, vapor pressure becomes constant (dynamic equilibrium)

Appears that nothing is happening in the systemVapor pressure of a liquid is the pressure exerted by its

vapor when the liquid and vapor states are in equilibrium

When liquid/solid phase is in equilibrium with the gas phase, the pressure of the gas equals the vapor pressure of the substance