Using Properties of Zinc to Identify an Unknown MetalJennifer Donovan - Warren MottRyan Gohlke - Sterling Heights

Purpose

• To prove whether the unknown metal rods were Zinc by measuring the specific heat and linear thermal expansion, and comparing it to Zinc’s known values.

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Terms

• Specific Heat – the heat required to raise the temperature of a unit mass of a given substance of a given amount by one degree

• Linear Thermal Expansion – the change in linear dimension, length

• Intensive propertiesDonovan - Gohlke 3

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Terms (continued)• First Law of Thermodynamics – Energy is

neither created nor destroyed, only changed

• Isolated System – system that releases neither energy nor matter

example: Calorimeter

• Kinetic Molecular Theory – Observed when an object is heated up

Background• Initially discovered through ores

• 1374 - eighth metal known to man in that point in time

• 1743 - first European Zinc smelter used a vertical retort procedure

• Zinc production in the United States started in 1850

• Today, U.S. and Canada are leading producers of Zinc

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Retort Procedure• Heating Zinc Sulfide, ZnS, concentrate to 950°C • Produces Zinc Oxide, ZnO• Purer state with process called electrowinning

converting into Zinc Sulfate, ZnSO4

• Separated through electrolysis containing Zinc ions, Zn

ZnS(s) + 3 O2(g) → 2 ZnO(s) + 2 SO2(g)

ZnO(s) + H2SO4(l) → ZnSO4(s) + H2O(l)

2 ZnSO4(s) + 2 H2O(l) → 2 Zn(s) + 2 H2SO4(l) + O2(g)

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Properties of Zinc

• Symbol: Zn• Atomic number: 30• Atomic weight: 65.38• Standard state: solid at 298 K• Electron Structure

1s2

2s22p6

3s23p6

4s2 3d10

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Utilizing Zinc

• Air-batteries • Brass• Countertops• Deodorants• Healing wounds and sore eyes• Paints• Produced in the U.S. one cent penny• Chocolate and cocoa powder

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Why Specific Heat?

• Important quality in the food industry because it determines the amount of energy that must be supplied or withdrawn from a material in order to increase or decrease its temperature by a given amount

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Why Linear Thermal Expansion?

• Gaining knowledge of fluctuating temperatures do not cause the roads and structures to crumble from being expanded easily

Hypothesis

• Zinc will equal unknown metal if the average is less than 5% error • Specific heat of 0.39 (J/g*°C)• Linear thermal expansion coefficient of 3.02 × 10-5 °C-1

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Specific Heat

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Electronic Thermometer

Known/ Unknown

Metal Rods

CalorimetersTemperature Probe

Logger Pro

Specific Heat Procedure

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Specific Heat for Zinc

Trials Rod

Initial Temperatur

e (°C)Equilibriu

m Temperatu

re (°C)

Change in Temperatur

e (°C)

Mass(g)

Specific Heat

(J/g*°C)Water Metal Water Metal Metal

Water

Average N/A

20.4 98.9 23.4 3.0 -75.528.1 65.0

0.385

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Specific Heat Unknown

TrialsRod

Initial Temperature (°C)

Equilibrium

Temperature (°C)

Change in Temperatur

e (°C)Mass(g)

Specific Heat

(J/g*°C)Water

Metal Water MetalMeta

l Wate

r

Average

N/A23.0 99.2 30.2 7.2 -69.0

72.98 65.0 0.389

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Specific Heat

ZincExperimental Value

Percent Error

Average 0.385 -1.37

UnknownExperimental Value

Percent Error

Average 0.389 -0.21

Specific Heat Conclusion• Two-Sample t-test• H0: µz = µu

• Ha: µz ≠ µu

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• Fail to reject H0

• P-value 0.4001 is greater than the alpha level of 0.10

• Evidence the two metals could be the same

• 40.01% chance of having Zinc

Linear Thermal Expansion

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LTE Jig with Dial Measuring 0.01 mm

Known/Unknown Metal Rods

Caliper

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Linear Thermal Expansion Procedure

Linear Thermal Expansion for Zinc

TrialsRod

Final Lengt

h (mm)

Initial Lengt

h (mm)

Net. Chang

e in Lengt

h (mm)

Final Temp. (°C)

Initial

Temp. (°C)

Change in Temp. (°C)

Alpha Coefficient (°C-

1)

Average N/A

129.55

129.39 0.16 24.9 98.9 -74.0

1.691E-05

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Linear Thermal Expansion Unknown

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TrialsRod

Final Lengt

h (mm)

Initial Lengt

h (mm)

Net. Chang

e in Lengt

h (mm)

Final Temp.

(°C)

Initial

Temp.

(°C)

Change in Temp. (°C)

Alpha Coefficient (°C-

1)

Average

N/A132.2

8132.1

4 0.14 23.6 98.8 -75.21.409E-

05

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Linear Thermal Expansion

ZincExperimental Value10-5 °C-1

Percent Error

Average 1.69 -44.01

UnknownExperimental Value10-5 °C-1

Percent Error

Average 1.41 -53.36

Linear Thermal Expansion Conclusion

• Reject H0

• p-value of 0.0000 is less than the alpha level of 0.10

• Evidence the two metals are not the same

• 0% chance the two metals are the same

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• Two-sample t-test• H0: µz = µu

• Ha: µz ≠ µu

Conclusion

• Reject hypothesis•Specific Heat: • Zinc: -1.37% •Unknown: -0.21%• Linear Thermal Expansion:• Zinc: -44.01% •Unknown: -53.36%

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Flaws• Temperature of water in calorimeters was not

constant

• Heat was lost when the metal was transferred from the boiling water to the calorimeter

• When the metal was transferred from the boiling water to the linear thermal expansion jig, the metal rod would shrink in a fractional length before being placed in the jig.

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Limitations

• Time

• Assumption that the heat of the metal was the same as the heat of the water

Further Research

• Density• Melting point• Conductivity

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Acknowledgements• Special thanks to Mr. Koburg

• Thank you to the upper classmen

• Thanks to Mrs. Hilliard, Mrs. Dewey, and Mr. Supal

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International Zinc Association, "History of Zinc." Zinc History. N.p., n.d. Web. 24 Mar. 2013. <http://www.zinc.org/basics/history_of_zinc>.

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<http://www.kwanga.net/chemnotes/specific-heat-lab.pdf>.St. Louis Community College. "Coefficient of Thermal Linear Expansion." 23 Sept. 1997. Florissant Valley. 7 Apr. 2013 <http://users.stlcc.edu/cburkhardt/sum/lab/thermal.pdf>.Tipler, Paul A. "Thermal Expansion Equations and Formulas Calculator."

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Any Questions?