A. A graph of the temperature of the system versus the amount of heat added (or temp vs time if the heat is added at a constant rate) is called a ______ _____.

A. We can calculate the energy change of the system for each of the segments of a heating curve using ________. In segments AB, CD, and EF we are heating a ______ phase from one temperature to another.

1. The ______ the specific heat of a substance, the more heat we must add to accomplish a certain temperature increase.

Example with H2OH2O AB: 100. g 2.10 J/gºC 20.0ºC = 4,200 J

Example with H2OH2O CD: 100. g 4.18 J/gºC 100.ºC = 41,800 J

Example with H2OH2O EF: 100. g 1.70 J/gºC 25.0ºC = 4,250 J

A. In segments BC and DE we are converting one phase to another at a _________temperature. The temperature remains constant during these phase changes, because the added energy is used to overcome the attractive forces _________ molecules rather than to increase their average kinetic energy.

1. The energy required to make the solid to liquid transition is called the Heat of ______ (∆H fus ). For segment BC, in which ice is converted to water, the enthalpy change can be calculated by using ∆H fus.

2. The energy required to make the liquid to gas transition is called the heat of ____________ (∆H vap ). For segment DE we can use ∆H vap.

Q=n∆H fus or Q=n∆H vap (where n is number of moles)

Example with H2OH2O BC: Q = (100 g 1mole/18g) (6.01 kJ/mole) = 33.4 kJ

Example with H2OH2O DE: Q = (100 g 1mole/18g) (40.7 kJ/mole) = 226 kJ

a. There is no ∆T because during a phase change, the substance remains at a _______ temperature (the plateau on the graph) and no temperature change occurs.

b. These values are _____ to each particular substance and are measured in kJ/mole (or g/J).

A. The______ of the plateau is directly related to the amount of heat required to make the phase change. If more substance was making the phase change, the plateau would be _____.

B. Remember the angle of the sloping portion is directly related to the ______ ____ of the phase of the substance.

1. The slope of the graph will be ______for substances with a lower specific heat. 2. The slope of the graph will be______ for substances with a higher specific heat.

C. Similar information can be portrayed in a ______ curve.

A. Since temperature is a measure of ________ _______ _______, any change in temperature is a change in kinetic energy. All of the _________ line segments on a heating or cooling curve show a temperature change and therefore a change in kinetic energy. During these regions, a ______ state of matter exists and the sample is either getting hotter or cooler.

B. During the _________ line segments, there is ___ change in temperature, so kinetic energy remains constant. However, all the energy that is absorbed or released is related to changes in potential energy.

1. Remember the 3 Ps: Plateau, Phase change, and Potential Energy Change.