2. Compare the different states of matter in terms ofpotential and kinetic energy

3. Describe the major events that occur along a heatingcurve.

You are watching: Is water evaporating endothermic or exothermic

4. Interpret a phase diagram.

Key Terms:

vaporization condensationevaporation equilibrium vapor pressureboiling point heat of vaporization freezingpoint heat of fusionsublimation deposition heatingcurve phase diagram

Notes: (14-4)

Matter on Earthexists as either liquid, solid, or gas. Other than water, most matterexists in a single phase (liquid, solid, or gas) but can be made to change phaseby adding or deleting pressure or temperature.

Energy and PhaseChanges

According to thekinetic-molecular theory, a substances phase is determined by the balance of itskinetic and intermolecular forces. What this means is that you can convertmatter from one phase to another by simply adding or deleting kinetic energy(heat). When attempting to understand the phase changes it is important toremember what is occurring in endo and exothermic reactions. Endothermic - Energy is being absorbed - bonds are breaking - products are less ordered Exothermic - Energy is being released - bonds are being formed - products are more ordered

*

(server.chem.ufl.edu/~itl/2045_s99/ lectures/FG11_024.GIF)

Changesin State:

liquid to gas - vaporization, by process of evaporation
solid to gas - sublimation
liquid to solid - freezing
gas to liquid - condensation
gas to solid - deposition

Evaporation

Evaporation is again explained by theKinetic-molecular theory. When the kinetic energy of the molecules in aliquid become greater than the intermolecular attractions between them,evaporation occurs.

within a liquid, evaporation is always occurring to some extent at the surface of the liquid
Temperature and evaporation rate are directly related
Liquids with high evaporation rates are said to be volatile - usually flammable due to the presence of organic materials and oxides
Evaporation cools a surface or solution by removing the molecules with the highest kinetic energy
Most solutions in a closed container are in liquid-vapor equilibrium
condensation and evaporation rates are equal
rate of molecules leaving the solution are equal to the molecules entering the liquid
The solution is at equilibrium vapor pressure

Boiling Point:

The boiling point of a liquid is directly relatedto the vapor pressure of the liquid. Vapor pressure is a measure of thevapor present in a liquid. When the vapor pressure equals the atmosphericpressure boiling occurs. It is important to remember that vaporization isan endothermic process as heat is removed from the liquid through boiling.

vapor pressure of a liquid is directly related to the temperature applied to the liquid
the boiling point is directly related to the atmospheric pressure exerted on the solution
boiling occurs when the vapor pressure = atmospheric pressure
the temperature of a liquid will remain constant at the boiling point until all of the liquid is vaporized.

Freezing and Melting:

The freezing and melting points of a liquid existat the same temperature and represent an equilibrium between the liquid andsolid phases.

melting and freezing points are not greatly affected by atmospheric pressure
melting depends on the heat of fusion which like the boiling is an endothermic process
freezing uses the same amount of energy as the heat of fushion bu is an exothermic process

Heating Curves:

*

((server.chem.ufl.edu/~itl/2045_s99/ lectures/FG11_024.GIF))

The heating curve is a representation of thephases of a substance compared to the temperature and internal energy of asubstance. The blue lines represent the different phases of a substancewhile the red lines represent the heats of fusion and vaporization.

See more: What Is The Greatest Common Factors Of 12 And 18 Gcf(12,18), Greatest Common Factor (Gcf)

endothermic reactions move from left to right as the products increase in kinetic energy and become less organized

Phase Diagrams

*

((server.chem.ufl.edu/~itl/2045_s99/ lectures/FG11_024.GIF))

The phase diagram is another representation ofthe internal energy of a substance compared with the pressure and temperature ofits surroundings.

temperature and pressure are inversely related to the process of vaporization
pressure has little effect on the melting and freezing of a substance
the triple point is a point where all three phases occur in equilibrium