States of Matter and Intermolecular Forces

3 Phases of Matter

SolidLiquidGas

How do particles move in a solid?

Solids

Have a definite shape/structure

Very little particle movement—fixed position

Liquids

Limited structure to particles

Movement is less restricted, particles can move around and collide with each other

Conform to a container’s shape

Gases

No structure

Movement is not restricted

Particles are always in motion

Expansion occurs

Phase Changes

Physical change of a chemical compound

Change of state

Types: Melting

Freezing

Vaporization

Condensation

Sublimation

Deposition

Evaporation/Vaporization

Liquid---gas, endothermic

Liquid molecules gain enough energy to enter the gaseous state via breaking intermolecular forces.

Enthalpy of vaporization— Amount of heat necessary to evaporate a liquid at constant

temperature

kJ/mole

Table 11.1 (p. 435)

Condensation

Gas-----liquid

Exothermic process

Example 1

At 25°C, how much heat is required to evaporate 175 g of methanol?

Example 2:

Which liquid in Table 11.1 (p. 435) requires the lowest amount of heat for vaporization?

Vaporization/Condensation

Processes exist at the same time

Dynamic equilibrium is established Rate of vaporization = rate of condensation

No net change in molecular movement

Many factors determine how long it will take for equilibrium to be established

Vapor Pressure

Characteristic of liquid

Partial pressure of vapor when it exists with a liquid in dynamic equilibrium under constant temperature

Dependent on liquid type and temperature at equilibrium

INCREASE vapor pressure of liquid, INCREASE temperature

Vapor Pressure Curve

Figure 11.4 p. 439

Volatile vs. Nonvolatile Liquids

1) Volatile Liquids WEAK intermolecular forces

High vapor pressure

Ex. Gasoline, alcohols, “Whoosh Bottle”

2) Nonvolatile Liquids STRONG intermolecular forces

Low vapor pressure

Whoosh Bottle Demo Video

http://www.youtube.com/watch?v=-BtFHg-lm_M

Boiling Point

Liquid characteristic

Vaporization present throughout the liquid

Point where vapor pressure = atmospheric pressure

Aids in liquid identification

Decrease atmospheric pressure with increased altitude, lowers boiling point

Boiling Point (cont.)

Critical temperature/pressure (TC , PC)

Highest temperature with liquid and vapor present as physically different states in equilibrium

Point where increased pressure only will result in condensation

Critical Point Actual physical condition where critical temperature and pressure

achieved

Melting/Melting Point

Melting/freezing point Temperature when solid “melts”

Temperature when liquid becomes solid

For water = _________

Enthalpy (heat) of fusion– Δhfusion

Amount of heat needed to convert a certain amount of a solid to a liquid

Melting—endothermic

Freezing—exothermic (- value)

Cooling/Heating Curves

Figure 11.7 p. 444

Cooling/Heating Curves

Sublimation

Solid Gas

Some solid compounds are volatile enough to have a vapor pressure and convert to gas Ex. Mothballs, dry ice

Rate of sublimation = rate of deposition

Sublimation curve

Sublimation pressure— Pressure of a vapor existing in equilibrium with a solid

Enthalpy (heat) of sublimation

= ΔHfusion + ΔHvapn