Page 167 - Chemistry eBook

Base your answers to questions 57 through 59 on the information below and on your knowledge of chemistry.
Starting as a solid at 􏰀25°C, a sample of H2O is heated at a constant rate until the sample is at 125°C. This heating occurs at standard pressure. The graph below represents the relationship between temperature Randehegateadndedttso thQe sample.
Sample
uestions
125
He
ati
ng
C
Base your answers to questions 57 through 59 on the information below and on your knowledge of chemistry.
F
Base your answers to questions 57 through 59 Don the information below and on your knowledge of chemistry.
Starting as a solid1a0t0􏰀. 25°C, a sample of H2O is heated at a constant rate until the 2
urv
e
fo
tOanisdheaartedpatraecsosnustarnet.raTtehuentilgtrhEaephbelowrepresents sample is at 125°C. This heating occurs at standard pressure. The graph below represents
sampleisat125St°aCrtin.gTashaisolhideaatt􏰀in25g°Co,accsaumrpsleaoftHs
the relationshthiepreblaetiotnwsheipebnetwteemn tepmeprearaturreeanad nhedat hadedeadttoatdhedseamdplteo. the sample.
75
r H2
O
50.125
125 100.
25 75
Heating Curve for H2O
Heating Curve for H2O
D
D
F EF
the following three
Regents questions.
100.
C
Use this chart for
0 B
E
50. 25
75 A –25 0 B C
4 12 20. 28 36 44 52 60.
50.–25 A
4 12 20. 28 36 44 52 60.
25
the molecules in the H0 2O sample during interval AB. [1]
Heat Added (kJ) Heat Added (kJ)
57 Describe5w7 hDeastcrihbeawphpatehnapspetnos tbo obotth ththe peotpenotiatleenetrigaylanedntheeragvyeraagenkdinetthicenaervgyeorfage kinetic energy of the molecules in theBH2OCsample during interval AB. [1]
58 Using the graph, determine the total amount of heat added to the sample during interval CD. [1] A
58 Using the graph, d–e2t5ermine the total amount of heat added to the sample during
June 2013 #57
59Explain,intermsofheat4offusio1n2andhea2to0f.vapor2iza8tion,w3hy6thehea4t4addedd5u2ring 60.
interval CD. [1]
interval DE is greater than the heat added during interval BC for this sample of water. [1]
Heat Added (kJ)
59 Explain, in terms of heat of fusion and heat of vaporization, why the heat added during
interval DE is greater than the heat added during interval BC for this sample of water. [1]
57 Describe what happens to both the potential energy and the average kinetic energy of
the molecules in the H2O sample during interval AB. [1]
58 Using the graph, determine the total amount of heat added to the sample during
interval CD. [1]
59 Explain, in terms of heat of fusion and heat of vaporization, why the heat added during
interval DE is greater than the heat added during interval BC for this sample of water. [1] Answer
P.S./Chem.–June ’13 [9] [OVER]
The potential energy stays the same, and there is an increase in the average kinetic energy.
P.S./Chem.–June ’13 [9] [OVER] Explanation:
During a phase change, the potential energy stays the same. In a heating curve chart,thetemP.pS./Ceherm.a–Jutneu’13reincreasesduringa[9]phase.(Ifyouforgotth[OaVtER,] youcansee on the graph that the temperature/average kinetic energy is rising in interval AB.)
UNIT 5: MATTER © 166