1. Do Now Answer these in your notes:
Draw a coffee cup calorimeter in your notes.
How do we use a coffee cup calorimeter?
When looking at q (heat) how can we tell is a value is endothermic or exothermic?

2. Exothermic
A reaction that is exothermic gives off heat and the change in enthalpy is negative (ΔH° < 0). The temperature of the surroundings increases during an exothermic process.
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3. Endothermic
A reaction that is endothermic absorbs heat and the change in enthalpy is positive (ΔH° > 0). The temperature of the surroundings decreases in an endothermic process.
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4. A Coffee–Cup Calorimeter Made of Two Styrofoam Cups
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5. Calorimetry Calorimetry is the measurement of heat flow.
It allows us to calculate the amount of energy required to heat up a substance or to make a substance change states.

6. Direction of Heat Flow Surroundings ENDOthermic EXOthermic qsys > 0
System
ENDOthermic
qsys > 0
EXOthermic
qsys < 0
System
H2O(s) + heat  H2O(l)
melting
H2O(l)  H2O(s) + heat
freezing
Kotz, Purcell, Chemistry & Chemical Reactivity 1991, page 207

7. Experimental Determination of Specific Heat of a Metal
Typical apparatus used in this activity include a boiler (such as large glass beaker), a heat source (Bunsen burner or hot plate), a stand or tripod for
the boiler, a calorimeter, thermometers, samples (typically samples of copper, aluminum, zinc, tin, or lead), tongs (or forceps or string) to handle samples, and a balance.

8. A Coffee Cup Calorimeter
Thermometer
Styrofoam
cover
cups
Stirrer
A Coffee Cup Calorimeter
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 302

9. Calorimetry Energy released (heat) = m × c × ΔT
s (sometimes c) = specific heat capacity (J/°C·g)
m = mass (g)
ΔT = change in temperature (°C)
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10. Calorimetry Coffee Cup Calorimetry
Experimental way of measuring heat generation/consumption by essentially catching all the heat energy in a water bath or water bath + metal apparatus.
Coffee Cup Calorimetry
Styrofoam cup insulates the contents so any heat generated or consumed in the water can be measured by the temperature change
-qmetal = mCH2O∆T

11. Calorimetry Surroundings SYSTEM Tfinal = 26.7oC “loses” heat H2O Ag
m = 75 g
T = 25oC
m = 30 g
T = 100oC

12. - [(sFe) (mFe) (DTFe)] = (Swater) (mwater) (DTwater)
240 g of water (initially at 20oC) are mixed with an unknown mass of iron (initially at 500oC). When thermal equilibrium is reached, the system has a temperature of 42oC. Find the mass of the iron. Fe
T = 500oC
mass = ? grams
s = 0.45 J/goC
T = 20oC
mass = 240 g
-qFe= qwater
- [(sFe) (mFe) (DTFe)] = (Swater) (mwater) (DTwater)
mFe = g Fe
Calorimetry Problems 2
question #5

13. - [(sAu) (mAu) (DTAu)] = (Swater) (mwater) (DTwater)
A 97 g sample of gold at 785oC is dropped into 323 g of water, which has an initial temperature of 15oC. If gold has a specific heat of 0.129J/goC, what is the final temperature of the mixture? Assume that the gold experiences no change in state of matter. Au
T = 785oC
mass = 97 g
T = 15oC
mass = 323 g
-qAu= qwater
- [(sAu) (mAu) (DTAu)] = (Swater) (mwater) (DTwater)
- [(0.129 J/goC) (97 g) (Tf - 785oC)] = (4.184 J/goC) (323 g) (Tf - 15oC)]
Tf = oC
Calorimetry Problems 2
question #8

14. A 322 g sample of lead (specific heat = 0
A 322 g sample of lead (specific heat = J/goC) is placed into 264 g of water at 25oC. If the system's final temperature is 46oC, what was the initial temperature of the lead?
T = ? oC Pb
mass = 322 g
Ti = 25oC
mass = 264 g Pb
Tf = 46oC
-qPb= qwater
- [(sPb) (mPb) (DTPb)] = (Swater) (mwater) (DTwater)
- [(0.138 J/goC) (322 g) (46oC - Ti)] = (4.184 J/goC) (264 g) (46oC- 25oC)]
Ti = 568oC
Calorimetry Problems 2
question #12