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.
vaporization condensationevaporation equilibrium vapor pressureboiling point heat of vaporization freezingpoint heat of fusionsublimation deposition heatingcurve phase diagram
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.
|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 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|
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|
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.
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|endothermic reactions move from left to right as the products increase in kinetic energy and become less organized|
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|