"Silver and Gold Coins Recovered from Ocean Shipwreck" is a possible news headline, while "Iron Coins Recovered..." would be less likely to appear. The differences in reactivity among metals is very important in selecting building materials and the types of products we use.

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To determine the relative reactivity of several metallic elements.

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Wear protective glasses and an apron at all times. Avoid skin contact with solids and solutions. Dispose of all solutions and solid metal samples in the containers provided by your teacher. Wash your hands before leaving the laboratory.

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Part I: Teacher Demonstration

Your teacher will demonstrate the reaction between copper metal, and silver nitrate solution, AgNO3(aq). Record your observations at these time intervals: Start, Two minutes, Ten minutes, and Next day.

Part II: Comparing the Activity of Two Metals

Certain metals are more chemically active than others. You can rank the reactivities of metals by comparing their behavior in the presence of the ions of other metals.

1. Clean all solid metal samples with steel wool.
2. Pour 10 mL of 0.5 M copper(II) chloride solution, CuCl₂(aq), into each of two petri dishes.
3. Drop a small piece of magnesium metal, Mg(s), into the solution in one dish and a small piece of copper metal, Cu(s), into the second dish.
4. Pour 10 mL of 0.5 M magnesium chloride solution, MgCl₂(aq), into two other petri dishes.
5. Drop a small piece of magnesium metal, Mg(s), into the one petri dish containing MgCl₂ solution and a small piece of copper, Cu(s), into the other dish.
6. Observe, describe, and record what occurs in each petri dish in a data table larger than the one below.

Part III: Designing Your Own Experiment

You will be given solutions containing the ions aluminum, Al³⁺; magnesium, Mg²⁺; iron(III), Fe³⁺; copper(II), Cu²⁺; and zinc, Zn²⁺; and the corresponding metals aluminum Al; magnesium, Mg; iron, Fe; copper, Cu; and zinc, Zn.

1. Create and complete a procedure that will enable you to determine and rank the assigned metals in terms of their ability to replace other ions in solution. Create a data table and record what occurs in each case.
2. Rank the activity of these metals; Al, Cu, Fe, Mg, and Zn. Start the list with the most active metal.
3. Wash hands thoroughly before leaving the laboratory.

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Part I

1. List all the evidence suggesting that a chemical reaction occurred when copper metal was placed in the silver nitrate solution.
2. What is the difference between the number of silver ions remaining in the solution at the end of one day and the number of silver ions present in the solution initially?
3. How are the physical properties of silver ions different from those of the silver atoms produced?
4. What change in the number of electrons occurred as one silver ion, Ag⁺, became a silver atom, Ag?
5. Which metal ion could be responsible for the solution color observed at the end of the copper and silver nitrate demonstration in Part I? What was the source of these ions?

Part II

1. Does Cu metal react with Cu²⁺ solution?
2. Does Mg metal react with Cu²⁺ solution?
3. Does Mg metal react with Mg²⁺ solution?
4. Which metal (Cu or Mg) is more active? Justify your answer.
5. Discuss the replacement reaction that occurred.
6. How did the number of electrons present in each magnesium atom change as this reaction occurred?
7. How did the number of electrons present in each copper(II) ion change as this reaction occurred?
8. What do chemists mean when they say a "replacement reaction" occurred?

Part III

1. Why should the metal samples be polished before testing?
2. What visible changes, if any, occurred in the following combinations?
   1. zinc metal and zinc chloride
   2. zinc metal and iron(III) chloride
   3. iron metal and copper(II) chloride
3. List the metals used in that were able to replace copper(II) ions in the copper solution.
4. List the metals used in that were able to replace iron (II) ions but could not replace magnesium ions.

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1. For the copper wire and silver nitrate reaction in Part I, draw a set of diagrams to show what happens to the individual atoms or ions as the reaction proceeds (pretend it is possible to see individual atoms and ions). Create your own symbols to represent the individual units. Be sure to label all parts of your drawings.
2. Using correct symbols, write balanced equations for the reactions between the following materials. Assume that iron forms iron(III) ions in solution. If no observable reaction occurs write no reaction.
   1. zinc metal and copper(II) chloride
   2. iron metal and copper(II) chloride
   3. magnesium metal and zinc chloride
   4. aluminum metal and iron(III) chloride
   5. iron metal and aluminum chloride
   6. copper metal and zinc chloride
3. Dipping iron nails into molten zinc results in galvanized nails. Why are such nails manufactured?
4. Individuals living near copper mines sometimes earn extra money by leaving iron objects suspended in the waste waters flowing from the mine area. What is their "secret"?

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Teachers Guide

Preparing for the Laboratory Activity

• Major Chemical Concept
• Level
• Expected Student Background
• Time
• Safety
• Materials

Conducting the Laboratory Activity

• Pre-Lab Discussion
• Teacher/Student Interaction
• Anticipated Student Results
• Answers to Data Analysis
• Answers to Imply, Apply
• Possible Extensions

Assessing the Laboratory Learning

• Laboratory Practical
• Written Exercises
• Answers to Student Assessment
• Written Exercises:

Preparing for the Laboratory Activity

Major Chemical Concept

On the basis of experimental data, metals can be ranked in terms of their relative reactivities.

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General and advanced chemistry

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Students should be able to:

• Balance equations
• Describe atomic structures in terms of electrons, protons and neutrons
• Recognize the difference between atoms and ions
• Recognize the visible signs of a chemical reaction
• Organize data into tabular form
• Extract information from data tables
• Develop a systematic approach to data collection

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Day 1: 15 min

Day 2: 50 min

(Demonstration must be completed during Day 1.)

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• Eye protection must be worn at all times.
• Metal salts can be toxic; be sure students wash their hands at the end of the activity.
• 3 M HCl solution can irritate skin, spills must be washed thoroughly with water.
• Solid metals should be collected and recycled.
• Waste solutions are NOT to be poured down the sink. Wash all materials into the waste collection jars or the THINK Tank (see p. 8).

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Part I (Demonstration)

Non-Consumables

• 1 Beaker, 250 mL
• Consumables
• Copper wire, 12 gauge (formed into a tree)
• 0.05 M AgNO₃, 1.7 g/200 mL

Part II (per lab team)

Non-Consumables

• 4 Petri dishes (a 24-well microscale test plate will also work)

Consumables

• 0.5 M CuCl₂, 10 mL (dilute solution from Part III)
• 0.5 M MgCl₂, 10 mL (dilute solution from Part III)
• Magnesium, small pieces
• Copper, small pieces
• Part III (per lab team)

Non-Consumables

• 1 Microscale testing plate, 24 - well (spot plates will also work).

Consumables

• Wire or foil samples of Aluminum, Copper, Zinc, Magnesium, Iron
• Sand paper or steel wool for polishing metal samples
• 5 Thin-stem pipets (or dropper bottles) filled with the following solutions:
• 1 M Aluminum chloride, 121 g AlCl₃.6H₂O per 500 mL solution
• 1 M Copper(II) chloride, 85 g CuCl₂.2H₂O per 500 mL solution
• 1 M Zinc chloride, 68 g ZnCl₂ per 500 mL solution
• 1 M Magnesium chloride, 102 g MgCl₂.6H₂O per 500 mL solution
• 1 M Iron (III) chloride, 135 g FeCl₃.6H₂O per 500 mL solution (Iron(II) chloride will not work.)

All students should have individual sets of materials for observations, but they can work in groups of two or three for brainstorming.

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Conducting the Laboratory Activity

Pre-Lab Discussion

Part I of this laboratory activity opens with a teacher demonstration designed to help students develop the notions that ions and atoms have different physical and chemical properties and that ions can be transformed into atoms and atoms can become ions.

Demonstration: Bend the copper wire into a tree-like shape small enough to be completely covered by the silver nitrate solution. Allow this system to stand undisturbed until the next day. Use a heavy gauge wire so there will still be enough copper to support the shape of the tree. The dramatic change in physical properties of the solids and solutions while the silver crystallizes, helps emphasize that silver ions (Ag+) have become silver atoms (Ag) while copper atoms (Cu) have become copper ions (Cu²⁺).

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Part II: Be sure that students think through the need to compare the metal (atoms) with both of the solutions (metal ions). This reaction may form hydrogen gas, and should be noted, but students should not include hydrogen in their rankings at this time.

Part III: Work with students in small groups to help them devise the experimental procedures and make the data table (see answer section for table design). Students should be sure they have checked all possible combinations.

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Part I

Observations:

Start: Answers will vary

Two minutes: Black surface forming on wire; blue color appearing near the wire.

Ten minutes: Black/silver gray surface on wire; distinct blue color appearing.

Next day: Long moss-like crystals, silver gray to black color crystals, intense blue color to solution.

Part II

Part III

*Note: these two metals are adjacent in the activity series. Many students may not observe this replacement since it is very slow.

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Part I

1. Answers will vary but should include that a solid (metallic silver) is formed and that a color change occurs (appearance of the blue copper(II) nitrate solution).
2. There is less silver (technically, silver ions) after 24 hours. The discussion should be linked to the idea of conservation of matter since the silver that appeared had to come from somewhere.
3. Answers will vary but should include that silver ions are soluble in solution but silver atoms are not soluble; silver ions are colorless but silver atoms have a metallic luster.
4. The number of electrons increased. Silver ions have acquired electrons from the copper atoms and thus become silver atoms while copper atoms become copper ions.
5. The copper wire (atoms) is the source of the copper ions that cause the blue color.

Part II

1. No.
2. Yes, magnesium atoms are converted to magnesium ions while copper ions become copper atoms and plate onto the magnesium.
3. No.
4. Magnesium. Answers should include the generation of a gas and the plating of metallic copper onto the magnesium.
5. The magnesium formed magnesium ions and replaced copper ions in solution as copper ions formed copper atoms.
6. The magnesium lost electrons. Magnesium atoms have given electrons to the copper ions resulting in the formation of copper atoms.
7. The copper gained electrons. Magnesium atoms have given electrons to the copper ions resulting in the formation of copper atoms.
8. Answers will vary but should attempt to identify that the metals changed in some manner with metal ions in solution taking the place of the solid metal while solid metal atoms became ions in solution. Technically, these reactions involve a transfer of electrons from the more active metal to the less active partner. Do not attempt to introduce oxidation-reduction at this time; rather seek the notion that the appearance of one metal occurs at the expense of the other metal.

Part III

1. Answers will vary. The main reason is to remove any coatings and expose pure metal.
2. 1. No apparent reaction.
   2. Answer will vary, but zinc metal does react with the iron(III) solution.
   3. Answers will vary, but the formation of the copper plate on the iron is most apparent.
3. Al, Zn, Mg, Fe
4. Zn, Al
5. Mg, Al, Zn, Fe, Cu (Evaluation of student answers depends upon student data.)

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1. See figure:
2. .
   1. Zinc and copper(II) chloride: Zn(s) + CuCl₂(aq) --> Cu(s) + ZnCl₂(aq)
   2. Iron and copper(II) chloride: 2 Fe(s) + 3 CuCl₂(aq) --> 3 Cu(s) + 2 FeCl₃(aq)
   3. Magnesium and zinc chloride: Mg(s) + ZnCl₂(aq) --> Zn(s) + MgCl₂(aq)
   4. Aluminum and iron(III) chloride: Al(s) + FeCl₃(aq) --> Fe(s) + AlCl₃(aq)
   5. Iron and aluminum chloride: Fe(s) + AlCl₃(aq) --> No reaction
   6. Copper and zinc chloride: Cu(s) + ZnCl₂(aq) --> No reaction
3. This item evaluates students' abilities to link the replacement reaction observed with protection of metals. The coating of zinc prolongs the useful life of the iron nail by corroding before the iron.
4. The iron will replace the copper ions, producing metallic copper and iron ions. Assuming the recovered copper metal is more valuable than the original iron, monetary gain is possible!

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Industrial methods of metal recovery and smelting

Importance of corrosion control

Societal issues of energy demands to produce new metals versus recycling of metals.

Expansion of this lesson could lead to introducing oxidation/reduction; include such activities as "ripping" an aluminum can. (See T5. What is the Copper Formula, Post-Lab Discussion.)

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Assessing the Laboratory Learning

Laboratory Practical

Give students samples of three different metals labeled J, K, and L along with three thin-stem pipets containing chloride salts of the three metals. Use J for copper and copper(II) chloride, L for aluminum and aluminum chloride, and K for magnesium and magnesium chloride.

1. Design a procedure to confirm, using the minimum number of tests, the proposed activity series shown below.

   K --most active

   L

   J -- least active

2. Conduct your proposed procedure.

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1. Given samples of metals J, K, and L along with solutions of their chloride salts.
   1. What is the minimum number of tests necessary to confirm the proposed activity series listed below?

      K -- most active

      L

      J -- least active

   2. Describe the sequence of procedures you would use to confirm this activity series.
2. Here is a copy of a portion of a data table:

1. Using the data provided this table, rank all the halogens listed, from the most active to the least active.
2. Using the data provided, which ion is most likely to lose electrons? Explain your answer.
3. Write a balanced equation for each reaction that occurred.

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Laboratory Practical: Refer to the answer for assessment item

B. Assign credit in accordance with the logic behind the students' answers in addition to their correctness.

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1. 1. Three
   2. Answers will vary. One suggested method is to test K against L chloride, to test K against J chloride, and to test L against J chloride.
2. 1. Cl₂ (most active), Br₂, I₂ (least active)
   2. I^-, since it reacted with both Cl₂ and Br₂. Zn metal is readily oxidized to Zn²⁺ but as an ion is unable to lose any more electrons.
   3. Cl₂(aq) + 2 NaBr(aq) --> Br₂(aq) + 2 NaCl(aq)

      Cl₂(aq) + 2 NaI(aq) --> I₂(aq) + 2 NaCl(aq)

      Br₂(aq) + 2 NaI(aq) --> I₂(aq) + 2 NaBr(aq)

      Cl₂(g) + Zn(s) --> ZnCl₂(s)

      Br₂(aq) + Zn(s) --> ZnBr₂(s)

      I₂(aq) + Zn(s) --> ZnI₂(s)

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