Intro to chemistryTherm 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 ______ _____. heating curve

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Intro to chemistryThermo

Intro to chemistryTherm 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.

Q=mCΔTsingle

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

highero

Intro to chemistryThermo Example with H2O

AB: 100. g • 2.10 J/gºC • 20.0ºC = 4,200 J

Intro to chemistryThermo Example with H2O

CD: 100. g • 4.18 J/gºC • 100.ºC = 41,800 J

Intro to chemistryThermo Example with H2O

EF: 100. • g 1.70 J/gºC • 25.0ºC = 4,250 J

Intro to chemistryTherm 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.

constant

between

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

fusion

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

vaporization

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Intro to chemistryTherm

Q=n•∆Hfus or Q=n•∆Hvap (where n is number of moles)

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Intro to chemistryThermo Example with H2O

BC: Q = (100 g • 1mole/18g) • (6.01 kJ/mole) = 33.4 kJ

Intro to chemistryThermo Example with H2O

DE: Q = (100 g • 1mole/18g) • (40.7 kJ/mole) = 226 kJ

Intro to chemistryTherma. 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.

constant

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

uniqueo

Intro to chemistryTherm 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 _____.

length

longer

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Intro to chemistryThermo

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

specific heat

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Intro to chemistryTherm 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.

steeper

gentler

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Intro to chemistryTherm C. Similar information can be portrayed in a ______ curve. cooling

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Intro to chemistryTherm 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.

average kinetic energy

diagonal

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single

Intro to chemistryThermB. 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.

horizontalNO

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Intro to chemistryTherm1. Remember the 3 Ps:

Plateau, Phase change, and Potential Energy Change.

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