States of Matter

States of MatterStates of Matter

LiquidGas

Solid

What causes the differences in solids, liquids, and gases?

What causes the differences in solids, liquids, and gases?

Kinetic Molecular TheoryKinetic Molecular Theory

Describes behavior of matter in terms of particles in motion.

Makes assumptions of gas particles:• separated by empty space

• particles are not attracted to each other• are in constant, random motion• collisions are elastic• kinetic energy determined by mass & velocity

KE = ½ mv2

C. Johannesson

Liquids & SolidsLiquids & SolidsLiquids & SolidsLiquids & Solids

I. Intermolecular Forces(between molecules)

(Ch. 6, p.189-193)

C. Johannesson

A. Definition of Intermolecular Forces

A. Definition of Intermolecular Forces

Attractive forces between molecules.

Much weaker than chemical bonds within molecules.

a.k.a. van der Waals forces

Intermolecular ForcesIntermolecular Forces

Attraction between

molecules

C. Johannesson

B. Types of IMFB. Types of IMF

C. Johannesson

B. Types of IMFB. Types of IMF

London Dispersion Forces

View animation online.

DispersionDispersion

Weak forces caused from temporary shifts in e- density

Polarity (Differing Electronegativities)

Polarity (Differing Electronegativities)

Eletronegativity Difference Bond Character

> 1.7 ionic

0.4 – 1.7 polar covalent

< 0.4 Nonpolar covalent

C. Johannesson

B. Types of IMFB. Types of IMF

Dipole-Dipole Forces

+ -

View animation online.

Dipole-DipoleDipole-Dipole

Between partial positive area of one molecule with the partial negative area of another

Occurs in polar molecules

C. Johannesson

B. Types of IMFB. Types of IMF

Hydrogen Bonding

Hydrogen BondingHydrogen Bonding

Special dipole-dipole Between H and a highly

electronegative atom (O, N, F) SPECIAL NOTE – THE H atom has to be

directly chemically bonded to an O, N, or F

Your DNAYour DNA

C. Johannesson

C. Determining IMFC. Determining IMF

CH2Cl2• polar = dispersion, dipole-dipole

CH4

• nonpolar = dispersionHF

• H-F bond = dispersion, dipole-dipole, hydrogen bonding

C. Johannesson

II. Physical PropertiesA. Liquids vs. Solids

II. Physical PropertiesA. Liquids vs. Solids

LIQUIDS

Stronger than in gases

Y

high

N

slower than in gases

SOLIDS

Very strong

N

high

N

extremely slow

IMF Strength

Fluid

Density

Compressible

Diffusion

C. Johannesson

B. Liquid PropertiesB. Liquid Properties

Surface Tension• attractive force between particles in a

liquid that minimizes surface area

C. Johannesson

B. Liquid PropertiesB. Liquid Properties

Capillary Action• attractive force between the surface of

a liquid and the surface of a solid

water mercury

C. Johannesson

C. Types of SolidsC. Types of Solids

Crystalline - repeating geometric pattern• covalent network• metallic• ionic• covalent molecular

Amorphous - no geometric pattern

decreasingm.p.

C. Johannesson

C. Types of SolidsC. Types of Solids

Ionic(NaCl)

Metallic

C. Johannesson

C. Types of SolidsC. Types of Solids

CovalentMolecular

(H2O)

CovalentNetwork

(SiO2 - quartz)

Amorphous(SiO2 - glass)

C. Johannesson

III. Changes of StateA. Phase Changes

III. Changes of StateA. Phase Changes

C. Johannesson

A. Phase ChangesA. Phase Changes

EvaporationEvaporation• molecules at the surface gain enough

energy to overcome IMF

VolatilityVolatility• measure of evaporation rate• depends on temp & IMF

C. Johannesson

A. Phase ChangesA. Phase Changes

Kinetic Energy

# o

f P

art

icle

s

p. 477

Boltzmann Distribution

temp

volatility

IMF

volatility

C. Johannesson

A. Phase ChangesA. Phase Changes

EquilibriumEquilibrium• trapped molecules reach a balance

between evaporation & condensation

C. Johannesson

A. Phase ChangesA. Phase Changes

Vapor PressureVapor Pressure• pressure of vapor above

a liquid at equilibrium

IMF v.p.temp v.p.

• depends on temp & IMF• directly related to volatility

p.478

temp

v.p

.

C. Johannesson

A. Phase ChangesA. Phase Changes

Boiling Point• temp at which v.p. of liquid

equals external pressure

IMF b.p.Patm b.p.

• depends on Patm & IMF

• Normal B.P. - b.p. at 1 atm

C. Johannesson

Which has a higher m.p.?• polar or nonpolar?• covalent or ionic?

A. Phase ChangesA. Phase Changes

Melting Point• equal to freezing point

polar

ionic

IMF m.p.

C. Johannesson

A. Phase ChangesA. Phase Changes

Sublimation

• solid gas

• v.p. of solid equals external pressure

EX: dry ice, mothballs, solid air fresheners

C. Johannesson

B. Heating CurvesB. Heating Curves

Melting - PE

Solid - KE

Liquid - KE

Boiling - PE

Gas - KE

C. Johannesson

B. Heating CurvesB. Heating Curves

Temperature Change• change in KE (molecular motion) • depends on heat capacity

Heat Capacity• energy required to raise the temp of 1

gram of a substance by 1°C• “Volcano” clip - water has a very high

heat capacity

C. Johannesson

B. Heating CurvesB. Heating Curves

Phase Change• change in PE (molecular arrangement)• temp remains constant

Heat of Fusion (Hfus)

• energy required to melt 1 gram of a substance at its m.p.

C. Johannesson

B. Heating CurvesB. Heating Curves

Heat of Vaporization (Hvap)

• energy required to boil 1 gram of a substance at its b.p.

• usually larger than Hfus…why?

EX: sweating, steam burns, the drinking bird

C. Johannesson

C. Phase DiagramsC. Phase Diagrams

Show the phases of a substance at different temps and pressures.

Phase DiagramsPhase Diagrams

Triple point - The temperature and pressure at which the solid, liquid, and vapor phases of a pure substance can coexist in equilibrium.

*Be able to know what phase change occurs when pressure and/or temperature changes when looking a phase diagram.

C. Johannesson