3.03 phase changes of matter - san diego miramar...
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Aug ‘171 3.03 Solid-Liquid-Gas, Phase change
3.03 Phase Changes of Matter
Dr. Fred Omega GarcesChemistry 100Miramar College
Water crystal
Heating-Cooling Curve
Aug ‘172 3.03 Solid-Liquid-Gas, Phase change
Phases of Matter: Terminology
Energy is required for phasechanges to occur.
Solid-Liquid-GasTriangle
Aug ‘173 3.03 Solid-Liquid-Gas, Phase change
Heating Cooling CurveFrom Ice to Steam and Vice-versa
What is the energy needed to take 1g H2O at 0°C to 100°C ? 80 +100+ 540 =720cal
Stage1
Stage2
Stage3
Stage4
Stage5
Heat Addition
6.01 kJmol
540 calg
4.184 Jg °
1 calg o
40.7 kJmol
80 calg
1.84 Jg °
0.43 calg
2.09 Jg °
0.50 calg
Aug ‘174 3.03 Solid-Liquid-Gas, Phase change
Heating Cooling CurveFrom Ice to Steam and Vice-versa
What is the energy needed to take 1g H2O at 0°C to 100°C ?
80 +100+ 540 =720cal
Stage1
Stage2
Stage3
Stage4
Stage5
Units Stage1S.h.ice
Stage2Heatfusion
Stage3specificheat(s.h.)water
Stage4Heatvaporization
Stage5S.h.gas
cal/g 0.50cal/gK
80cal/g
1.0cal/gK
540cal/g
0.50cal/gK
Jg-1K-1 2.11J/gK
334J/g
4,18J/gK
2257J/g
2.08J/gK
calmol-1 9.01cal/molK
1441cal/molK
18.102cal/molK 9728cal/molK
9.01cal/molK
Jmol-1K-1 38.1J/molK
6.02kJ/molK
75.33J/molK
40.1kJ/mol
37.5J/molK
1 calg o
4.184 Jg °
540 calg
40.1 kJmol
80 calg
60.2 kJmol
Aug ‘175 3.03 Solid-Liquid-Gas, Phase change
At the molecular level:Molecules or matter is held together by “glue” called
intermolecular forces
Intermolecular Forces
Energy added (K.E. increases)
SOLID LIQUID GAS
Aug ‘176 3.03 Solid-Liquid-Gas, Phase change
Intramolecular Forces -Force which keeps molecule together,
i.e., bonds.
Intermolecular Forces -Attractive force between molecules.
Responsible for keeping matter in solid or liquid phase.
Keeping Matter together
Aug ‘177 3.03 Solid-Liquid-Gas, Phase change
Heating / Cooling CurvesFrom Steam to Ice and Vice-versa
.334 kJg
80 calg
2.26 kJg
540 calg
4.184 Jg °
1 calg o
540+100+80=720cal
2.09 Jg °
0.50 calg
1.84 Jg °
0.43 calg
What is the energy needed to take 1g H2O at 0°C to 100°C ?
Aug ‘178 3.03 Solid-Liquid-Gas, Phase change
SAMPLE PROBLEM 2.12Heat of Fusion
STEP 1 Given 26 g of H2O(s) Need joules to melt iceSOLUTION
Ice cubes at 0 °C with a mass of 26 g are added to your soft drink.a. How much heat (joules) must be added to melt all the ice at 0 °C?b. What happens to the temperature of your soft drink? Why?
b. The soft drink will be colder because heat from the soft drink is providing the energy to melt the ice.
STEP 2
STEP 4 Set Up Problem
STUDY CHECKIn a freezer, 150. g water at 0 °C is placed in an ice cube tray. How much heat, in kilojoules, must be removed to form ice cubes at 0 °C?
STEP 3 Equalities/Conversion Factors
Aug ‘179 3.03 Solid-Liquid-Gas, Phase change
SAMPLE PROBLEM 2.13Using Heat of Vaporization
In a sauna, 150 g of water is converted to steam at 100 °C. How many kilocalories of heat are needed?
STEP 1 Given 150 g of H2O(l) to H2O(g) Need kilocalories of heat to change stateSOLUTION
STEP 2
STEP 3 Equalities/Conversion Factors
STEP 4 Set Up Problem
STUDY CHECKWhen steam from a pan of boiling water reaches a cool window, it condenses. How much heat, in kilocalories (kcal), is released when 25 g of steam condenses at 100 °C?
Aug ‘1710 3.03 Solid-Liquid-Gas, Phase change
SAMPLE PROBLEM 2.76Combining Heat Calculations
2.76 A pitcher containing 0.75 L of water at 4°C is removed from the refrigerator. How many kilojoules (and Calories) are needed to warm the water to a room temperature of 22 °C
Stage1
Stage2
Stage3
Stage4
Stage5
Heat Addition
6.01 kJmol
540 calg4.184 J
g °
1 calg o
40.7 kJmol
80 calg
1.84 Jg °
0.43 calg
2.09 Jg °
0.50 calg
Aug ‘1711 3.03 Solid-Liquid-Gas, Phase change
SAMPLE PROBLEM 2.37Combining Heat Calculations
2.37 Calculate in Joules and calories the following:
a) Energy required to heat 25.0 g of water from 12.5°C to 25.7°C
b) Energy required to heat 38.0 g of copper from 122°C to 246°C
c) Energy lose when 15.0 g of ethanol cools from 60.5 °C to -42.0 °C
d) Energy lose when 112 g of iron cools from 60.5°C to -42°C
Aug ‘1712 3.03 Solid-Liquid-Gas, Phase change
SAMPLE PROBLEM 2.14Combining Heat Calculations
Using Table 2.13 and the specific heat of ethanol (2.46 J/g °C), calculate the total heat, in joules, needed to convert 15.0 g of ethanol at 25.0 °C to gas at 78.0 °C.
STEP 1 Given 15.0 g of ethanol at 25.0 °CNeed heat (J) needed to warm the ethanol and change it to gas
SOLUTION
STEP 2 When several changes occur, draw a diagram of heating and changes of state.
Total heat = joules needed to warm ethanol from 25.0 °C to 78.0 °C+ joules to change liquid to gas at 78.0 °C
Aug ‘1713 3.03 Solid-Liquid-Gas, Phase change
Vapor PressureEvaporation occurs when molecules have sufficient energy to escape the interface of a liquid substance.
Vapor Pressure - The pressure exerted by the liquid’s vapor at equilibrium.Normal Boiling Point - The temperature at which the vapor pressure of a liquid equals the atmospheric pressure.
Aug ‘1714 3.03 Solid-Liquid-Gas, Phase change
Phase Diagram (Revisited)Heating -Cooling Curves and their relation to the Phase Diagram
Aug ‘1715 3.03 Solid-Liquid-Gas, Phase change
SummaryThe equilibria between the three phase of a substance is a
function of the pressure and the temperature as shown in a
phase diagram. Equilibria between any two phase are
indicated by a line. The line through the melting point usually
slopes slightly to the right as pressure increases (solid is
more dense than liquid). For water this slope is to the left.
Features of the phase diagram is the normal melting point
(freezing point) and the normal boiling point. The triple point
is the condition in which all three phases of matter exist and
the critical point is the condition in which the liquid and the
gas phase are indistinguishable.