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This document contains everything you need to do the Monday's CW
assignment at home. You need pages 73 (a (^) table of all values of specific heats needed), p^ 81 (you already got (^) this as a handout before) and 82
from the Zumdahl textbook with questions. (^) You also have the directions
that were given in class with helpful hints on solving many of the problems,
as well as the grading RUBRIC.
Page 1 (this page)
Page (^2) - Zum p. 73 (specific (^) heats) Page (^3) -Zum p. (^81)
Page (^4) -Zum p. Page (^5) - Directions Page (^6) - RUBRIC
This was an 8 point assignment with up to 4 pts ex cr possible.
-t-
i l i
iBecause water is such (^) a fanriliar and
converrieni,'..' substance to use vuherr solvinq
,specitic lteat problclt)s,^ stLtdet)ts^ someiimes :believe (^) that these calculations are fol water i'-,'^^ only. Iable 3.2 qivcs the specific heat
lcapacities for a verriety of substances. lt!
,probably a^ good^ ic'lea^ to^ Ltse^ Il.tese^ for lexamples in adclition to using water. ;
rt (^) is r:sel'trl (^) to mal(e sLlrc' studonls know that :here is ;r dif'ferent specific lreat capacity fc,r lach of the tlrree physical^ states.
3.6 Energy and Energy Changes
TABLE 3.
The Specific Heat Capacities of Some Common Substances
0:
the followi
\
-\L_/
? joules
'i,
Substance Specific Heat Capacity (J/g'C)
water (0*^ (liquid)
water (s)^ (ice)
water (9) (steam)
aluminum (s)
iron (s)
mercury (/)
carbon (s)
silver (s)
gold (s) *The (^) symbols (s), (^) (0, and (9) (^) indicate the solid, liquid, and gaseous states, respectivelv.
There is another important factor: the identity of the substance,
Different substances respond differently to being heated. We have seen
that 4.184 J of energy raises the temperature of 1 g of water 1 oC,^ In con-
trast, this same amount of energy applied to 1 g of gold raises its tempera-
ture by approximately 32 "C! The point is that some substances require rel-
atively large amounts of energy to change their temperatrlres, whereas others
reqlrire relatively little. Chemists describe this difference by saying that sub-
stances have different heat capacities. The antount of energy required to
change tlrc tentltercfitre of one grcmt of a sr,tbstance by one Celsius clegree is
cdlled its specific heat capacity or, more commonly, its specific heat. The
specific heat capacities for several substances are listed in Table 3.2, You can
see from the tabie that the specific heat capacity for water is very high com*
pared to those of the other sllbstances listed. This is why lakes and seas are
much slower to respond to cooling or heating than are the surrounding land
MASSCS.
EXAMPLE (^) 3.6 Calculations lnvolving Specific Heat Capacity
a. What quantity of energy (in joules)^ is required to heat a piece of iron
weighing 1.3 g^ from 25 oC^ to 46'C?
b. What is the answer in calories?
ilnlu'i:ioli
a. It is helpful to draw
.t^ T*--: l.J^--.----_-l s uon I
I t'^ I^ T=)\o(--""^ |I
ng diagram to represent the
F€.*f"""r] I r=a6ic^ I
problem.
82 3 Matter and Energy
- g of methane is burned, and the heat released is trans-
fened to 500, g^ of water at 25 oC,^ what final tempera-
ture will be reached by the water?
72. A^ 5.00-g^ sample of aluminum pellets^ and a 10.00-9 sam-
ple of iron pellets are placed together in a dry test tube,
and the test tube is heated in a boiling water bath to 100.
oC. (^) The mixture of hot iron and aluminum is then poured
into 97.3 g^ of water at 22.5 oC.^ To what final tempera-
ture is the water heated by the metals?
73, A 50,0-9 sample of water at 100, oC^ is poured into a
50.0-9 sample of water at25 "C, What will be the final
temperature of the water?
74. 425.0-9 sample of pure iron at 85 'C is dropped into
75 g^ of water at 20. oC.^ What is the final temperature of
the water-iron mixture?
75. Discuss the similarities and differences between a liquid
and a gas,
76, In gaseous substances, the individual molecules are re1-
atively (close/far^ apart) and are moving freely, rapidly, and randomly.
77. The factthat the substance copper(Il) sulfate pentahydrate
is bright blue is an example of a _ propefiy.
- The fact that the substance copper(Il) sulfate pentahy-
drate combines with ammonia in solution to form a new
compound is an example of a _ property.
(For Exercises 79-80) Solutions containing copper(Il) ions are bright blue in color. When sodium hydroxide is added to such a solution, a solid material forms that is colored a much paler
shade of blue than the original solution of copper(Il) ions.
79. The fact that a solution containing copper(Il) ions is
bright blue is a
property,
80. The fact that a reaction takes place when sodium hy-
droxide is added to a solution of copper(Il) ions is a
property.
- The processes^ of melting and evaporation involve
changes in the _ of a substance.
is the process of making a chemical reaction
take place by passage of an electric cuffent through a
substance (^) or solution.
83, Classify the following as physical or chemical proper-
ties/changes,
a. Milk curdles if a few drops of lemon juice^ are added.
b. Butter turns rancid if left exposed at room tempera-
ture.
c, Salad dressing separates into layers after standing.
d. Milk of magnesia neutralizes stomach acid,
e. The steel in a car has rust spots.
f. A person is asphyxiated by breathing carbon, monox-
ide,
g. Sulfuric acid spilled on a laboratory notebook page
causes the paper^ to char and disintegrate,
Sweat cools the body as it evaporates from the skin.
Aspirin reduces fever.
Oil feels slippery.
Alcohol burns, forming carbon dioxide and water.
84, Classify the following mixtures as homogeneou,r or as
heterogeneous. .
a. the freshman ciass at your^ school
b. salsa
c. mashed potatoes
d, cream of tomato soup
e. cream of mushroom soup
85. Classify, the following mixtures as homogeneou,r or as
heterogeneous, a. potting soil
b. white wine
h. i,
j.
1. .
"..-,.\c, your sock drawer
;-,:^.86r'If it takes 4.5 J
'from of^ energy^ to warm 5,0^ g of^ aluminuin
25 oC^ to a certain higher temperature, then it wil;
. t//^ )iake^ J^ to^ warm^ 10.^ g^ of^ aluminum^ over thr
'''.- (^) same temoerature interval.
87. If it takes 103 J of energy to warfn a certain mass of iror
from 25^ oC^ ro 50. oC, then it will take _ J tc
warm the same mass of iron from 25 'C to 75 oC.
88. Convert the followins numbers of calories/kilocalode.
into joules^ (J).
a. 44.21ca|
b. 162,4 cal
d, window glass
c. 3.721X 103 cal
d. 746.2kcal
c. 5.433 x 103 J d, 455.9 kJ
89. Convert the following numbers of jouleslkilojoules^ intc
kilocalories,
a. 52.18 kJ
b, 4.298I
90. Perform the followine conversions,
a. 5.442 x 104 J to illojoules
b. 5.442 X^104 J to calories
c..352.6 kcal to kilojoules
d. t7.24 kJ to kilocalories
9 1. Calculate the energy required to heat 25.0 g^ of gold^ fron
20.0 'C to 75,0 oC,^ Express your answer in joules,^ kile
joules, (^) calories, and kilocalories.
92. Calculate the energy required (in^ joules)^ to heat 75 gai
water from 25 'C to 39 oC,
DIREGTIONS (^) - Classwork due end (^) of period^ 4/21114: Use 3pp (3 problems on each side of each of 2 papers for (^) this assignment). On you
own piece of paper or scratch from the front of the room, put your name date and period
in the top right corner:
Your problems are in the Zum (^) textbook: p. 81 -82 (^) Below I have specified the
problems to work, and given you hints to help in solving the problems.
You will (^) be showing given, (^) find, and circling the correct answer. All calculations must be shown on your paper. (^) Chart for specific heats needed in problems is (^) on p.
67. a, b, c
68. hint: water is in the liquid state
69. hint: it is not enough to show answer, you must tell why
86. hint: a and b are in the question in the book. l've given you help to figure a & b,
then l'm asking you something I made up in c
a. GIVEN: 4.5 J,5.0 g Al FIND: (^)? AT , b. GIVEN: 10 g^ Al, AT is your answer from (^) a FIND: (^)? J c. myquestiontoyou is: weretheJ in a&bproportional (^) totheg in a&b (show
the 2 fractions side by side in your answer)?
87. hint: a and b are in the question in the book. I've given you help to figure a & b,
then I'm asking you something I made up in c
a. GIVEN: 103 J, AT (^) = 50 - (^25) "C FIND:? g (Fe) b, (^) GIVEN: g (^) Fe (is ans from a), AT (^) = 75 - 25'C FIND: (^)? J c, myquestiontoyou (^) is: weretheJ in a & b proportional (^) totheg in a & b (show
the 2 fractions side by side in your answer)?
88. a, b, c, d
ALL PROBLEMS ARE DUE AT THE END OF THE PERIOD
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