CH110

Chapter 11 Notes

We've studied chemical bonds which are INTRAmolecular forces....in this chapter, we explore the forces between molecules, or INTERmolecular forces (see Fig. 11.1) which you might rightly assume to be weaker since they are over longer distances

We did discuss the ideal gas law in Chapter 5, but what MAKES something a gas?

Space between molecules determines state, but what determines the spacing?

Vaporization- going from a liquid to a gas

Requires energy (endothermic- a POSITIVE number since energy is being supplied to the system FROM the surroundings)

Reverse is condensation, which gives off energy (exothermic- a NEGATIVE number since energy is coming OUT of the system into the surroundings)

The vaporization-condensation cycle is the basis of refrigeration and air conditioning- the study of energy changes involved in this phenomenon is called calorimetry

Vapor pressure- the partial pressure exerted by the vapor when it is in DYNAMIC EQUILIBRIUM with a liquid at constant temperature (Fig. 11.3)

Boiling point- occurs when vapor pressure = atmospheric pressure (Fig. 11.4)

Critical point and supercritical fluids

Phase changes

FUSION is the reverse of melting

Melting point and freezing point are the same temperature, just different direction (warming or cooling)

Sublimation- going directly from solid to gas (reverse is deposition)

Phase diagrams

Shows phases of a substance at various temperatures and pressures (Fig. 11.10)

Triple point

Polymorphs can exist in more than one form per phase

Hydrogen bonds

Why does ice float? (see Fig. 11.21)

Structure determines function!! (proteins, DNA)

Wan der Waals forces

Polarizability (Fig. 11.16)

Dispersion forces (induced dipole-induced dipole forces)

Dipole-dipole forces

Ion-dipole forces (not in book)

Liquid crystals- the thrust of your instructor's thesis

Not quite solid, not quite liquid....a true 5th phase of matter

Surface tension (see Fig. 11.27- this is how Rain-X^© works)- OMIT

Viscosity- OMIT

Network covalent solids- OMIT, though the C₆₀ discussion (see Fig. 11.33) is topical

Ionic bonds- section is just common sense- strength of interaction increases as charges increase and distance decreases- OMIT

Crystals- OMIT