**Unformatted text preview: **Name Date Pd Unit 3 Worksheet 3 — Quantitative Energy Problems Energy constants (H20)
334 J /g Heat of fusion (melting or freezing) Hf
2260 J/g Heat of vaporization (evaporating or condensing) HV 2.1 J lg°C Heat capacity (c) of solid water
4.18 J/g“C Heat capacity (c) of liquid water For each of the problems sketch a warming or cooling curve to help you decide
which equation(s) to use to solve the problem. Keep a reasonable number of sig ﬁgs
in your answers. 1. A cup of coffee (140 g) cools from 75°C down to comfortable room temperature 20°C.
How much energy does it release to the surroundings? {Cray :M 99/73 Cf/‘fsfoéi LO
17,1795 a: WAT -W{
i 8/26 71001 _,
, “spitejoites : 3211) L/
2. Suppose during volleyball practice, you lost 2.0 lbs of water due to sweating. If all
of this water evaporated, how much energy did the water absorb from your body?
Express your answer in kJ. 2.2 lbs = 1.0 kg ﬁ-Z MA HUT- 2.0 9100 MS 7 (N gong-3003 3. Suppose that during the Icy Hot lab that 65 kJ of energy were transferred 130151) g l g
of water at 20"C. What would have been the ﬁnal temperature of the water? it;
0003 Modeling Chemistry 1 U3 w53 v2.0 391551! “6: T} — 201; TLC 4. The heat capacity of solid iron is 0.447 J/g°C. If the same quantity of energy as in
#3 were transferred to a 450 g chunk of iron at 20. “C, what would be the ﬁnal
temperature? 9% or: 3’4"“ 7:5“ W“
I er: (5 5‘ 23 +72
-_ .. W 3 “’C H: 4449'“ ‘f 714,3?9
M
,_ a. ‘0?" ”341,. 3w3.19~8390°cl
(ﬁnppose a bag full of me (450 g) at 0.0 “C sits on the counter and begins to me 1: to quid water. How much energy must be absorbed by the me if 2/3 of it melted? ﬁvim AH; Ci“: :23 IQ§DQB3QT "I lmmj ‘gwocJ—J
Orl {00 Id 1 //
6. A serving of Cheez- Its releases 130 kcal (1 kcal= 4.18 kJ) when digested by your
body. If this same amount of energy were transferred to 2 5 kg of water at 27° C, What would the ﬁnal temperature be? Vl/ / /
7. If this same quantity of energy were transferred to 2.5 kg of water at its boiling pt, what fraction of the water would be vaporized? it MAHV M M. Modeling Chemistry 2 U3 ws3 v2.0 ...

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- Winter '17
- lidia berbeci
- Chemistry, Vaporization