1. Identification of a Sample Based on Chemical Properties
Problem
Identify Components
Homogenous
Similar Densities
Distinguish The Components Chemically
Element
Density (g/mL) Ni
8.90 Cu
8.96
Note the difference between a heterogeneous mixture (penny) and heterogeneous (nickel).
It is also useful to think about the pros and cons of each analysis. A chemical surface test on a penny tells us relatively little since the jacket is only 5% of the total mass but is near to pure copper while density, which did a very good job revealing the major component of a penny, is of little value in confirming the presence of copper or nickel in a five cent coin owing to their similar densities.

2. Identification of a Sample Based on Chemical Properties
Pennies
Heterogeneous
5 Cent Coins
Homogeneous
Nickel and Copper
Different Chemical Properties
React Differently
Stress that the surface is the same as the interior for the homogeneous five cent coin, in contrast to the penny!
Also, stress the importance of the controls!!!

3. hydrogen peroxide and vinegar
5 Cent Coin Solution
hydrogen peroxide and vinegar
Copper and Nickel
React With H2O2 and HC2H3O
Release Metal Ions
Heat
Ni2+
Cu2+
Cu2+
Ni2+
DO NOT POUR EXCESS BACK IN BOTTLE!!!

4. Control Solutions Control Solutions CuSO4 NiSO4 CuSO4  Cu2+ + SO42-
Aqueous Solutions
Individual Metal Ions
Observe Individual Reactions
CuSO4
NiSO4
H2O
CuSO4  Cu2+ + SO42-
H2O
NiSO4  Ni2+ + SO42-

5. Metal Solutions Test Solutions 4 x 3 Well Plate 2-3 Drops
5 cent coin
Nickel
Copper
Ammonia
Dimethyl-
Glyoxime
Test Solutions
Potassium
Iodide
Discuss the logic of a well plate and the importance of arranging the tests as shown in the procedure in order to facilitate reading the results.
Note also that the test is qualitative and that while it may show the presence of copper and nickel in a five cent coin, it says nothing about the relative amounts.
2-3 Drops
Record Observations

6. Best Indicator Control Solution Color Observation Color
Most Dramatic Change?

7. DO NOT POUR EXCESS REAGENTS or SAMPLES BACK IN BOTTLE!!!
Surface Test
ammonia
hydrogen peroxide
Paper Towel
Repeat if Leakage
Blot with Paper Towel (#13)
DO NOT POUR EXCESS REAGENTS or SAMPLES BACK IN BOTTLE!!!

8. ? Surface Test Alloy Surface? Penny NH4OH and H2O2 5 Cent Coin
Metal Ions Released?
NH4OH and H2O2
Releases Metal Ions
5 Cent Coin
Metal Ions Released?
Alloy
Surface? ?