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Investigating Oxidation-Reduction Reactions (1 Favorite)

LAB in Reduction, Activity Series, Redox Reaction, Classification of Reactions, Oxidation. Last updated March 8, 2021.


Summary

In this lab, students will observe, classify and predict the products of single replacement, combination and decomposition reactions and provide a rationale for how reactions are classified using evidence from the lab and classroom.

Grade Level

High School

NGSS Alignment

This lab will help prepare your students to meet the performance expectations in the following standards:

  • HS-PS1-2: Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
  • Scientific and Engineering Practices:
    • Planning and Carrying Out Investigations
    • Developing and Using Models
    • Analyzing and Interpreting Data
    • Constructing Explanations and Designing Solutions
  • Crosscutting Concepts
    • Patterns

Objectives

By the end of this lab, students should be able to

  • Observe and predict the products of single replacement, combination and decomposition reactions.
  • Classify the reactions experienced one of the three types: single replacement, combination and decomposition reactions
  • Provide a rationale for how reactions are classified using evidence from the lab and classroom

Chemistry Topics

This lab supports students’ understanding of

  • Chemical Reactions
  • Classification of Reactions
  • Oxidation-Reduction Reactions

Time

Teacher Preparation: 60 minutes
Lesson: 60 minutes

Materials (For each lab group)

Part A: 

  • Four small pieces (0.6 cm wide x 4-5 cm long) of solid metal (copper, magnesium, zinc, and iron) that are pre-cut and reusable
  • 4 small test tubes
  • Test tube rack
  • A dropper bottle of 0.1 M AgNO3
  • Forceps
  • Steel wool or Sand paper

Part B: 

  • One piece of copper metal (1.5 cm wide x 2-3 cm long)
  • Crucible tongs
  • Bunsen burner
  • Striker
  • Ceramic mat

Part C: 

  • Approximately 2 grams of copper (II) sulfate pentahydrate
  • Evaporating dish
  • Scoop
  • Bunsen burner
  • Striker
  • Ring stand
  • Ring clamp
  • Wire gauze
  • Distilled water
  • Ceramic mat

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Students should wash their hands thoroughly before leaving the lab.
  • When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
  • Always use caution around open flames. Keep flames away from flammable substances.
  • Always be aware of an open flame. Do not reach over it, tie back hair, and secure loose clothing.
  • An operational fire extinguisher should be in the classroom.
  • Silver nitrate solution will stain skin and clothing.

Teacher Notes

  • Students should have prior knowledge of different types of chemical reactions before completing this lab.
  • Students should start with Part A and then allow the products in the test tubes to sit while they complete Part B and Part C. While Part B and Part C are cooling, students should go back and investigate the products of Part A. If the students work sequentially and wait for everything to react and cool before going on to the next part it takes much longer to complete.
  • Do not let students sand or use the steel wool on the lab bench, it will ruin the surface. They should sand on their paper or multiple paper towels.
  • Depending on length of time the iron and zinc are in the solution, they may not visibly react in the time allotted, even though the Activity Series indicates that they should. This lends to a discussion on the time it takes to react and the difference between theoretical results and lab results.
    • Before the class, you may want to prepare a set of test tubes containing this reaction, that shows the final results to use as a sample for your students.
  • As a pre-lab assignment the students can write the predicted reactions before completing the lab activity instead of doing so after the lab activity. You might also consider having your students complete the Metals in Aqueous Solutions simulation, located in the AACT multimedia library.
  • Differentiation: Consider that students do not have to complete all reactions. Or some of the reactions could be completed as demonstrations for different ability levels (especially the copper in the Bunsen burner and the copper (II) sulfate pentahydrate) because they are both visual reactions.
  • Expected observations:
    • Part A: Silver is below copper, magnesium, zinc and iron in the activity series and should displace each of them. Students should observe a silver “fur” growing on each. They may also see the solution in the test tube containing copper turn blue as the reaction progresses.
    • Part B: When copper metal is heated in a Bunsen burner, it reacts with oxygen to form copper (II) oxide, which is black and not soluble. Students may also see the burner flame turn green due to the copper electrons being excited by the heat. As the electrons return to the ground state, energy is emitted as photons. For copper the energy is in the visible light range and is seen as a green color.
    • Part C: Copper (II) sulfate pentahydrate is a bright blue crystal solid. When heated, it turns white due to the loss of water. If you put a watch glass cover on the evaporating dish, students will see the water condensing. You might also consider having them measure the mass of the evaporating dish before and after heating to observe that the mass is less due to the loss of water.

For the Student

Background

Classification of different types of reactions can happen in many ways. What is the pattern in chemical behavior shown in oxidation-reduction reactions? How do we know when reactions occur and when they do not occur? How can one classify reactions into specific types and determine which of the reactants in the reactions is oxidized and which is reduced?

Prelab Questions

  1. Explain the pattern in chemical behavior behind oxidation-reduction reactions.
  2. Describe the difference between single replacement, combination/synthesis and decomposition reactions.
  3. What does it mean when a reactant is oxidized in a chemical reaction?
  4. What does it mean when a reactant is reduced in a chemical reaction?

Objective

To determine if reactions occur, write the chemical equations for the reactions, and explain the different types of reactions that occurred.

Materials (per group)

Part 1: 

  • Four small pieces (0.6 cm wide x 4-5 cm long) of solid metal
  • 4 small test tubes
  • test tube rack
  • 0.1 M AgNO3 in dropper bottle
  • Forceps
  • Steel wool or sand paper

Part 2: 

  • One piece of copper metal (1.5 cm wide x 2-3 cm long)
  • Crucible tongs
  • Bunsen burner
  • Striker
  • Ceramic mat

Part 3: 

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Wash your hands thoroughly before leaving the lab.
  • Follow the teacher’s instructions for cleanup of materials and disposal of chemicals.
  • Always use caution around open flames. Keep flames away from flammable substances.
  • Always be aware of an open flame. Open flames can cause burns. Do not reach over it, tie back hair, and secure loose clothing.
  • Silver nitrate will stain skin and clothing.

Procedure

Part A: Type A Reactions

  1. Obtain one small piece of each of the following solid metals: copper, magnesium, zinc, and iron.
  2. Write qualitative observations of the metals in a data table.
  3. Sand each gently with a piece of steel wool/sand paper. Do not do this on the lab bench, but on a piece of paper or on a stack of paper towels.
  4. Obtain four small test tubes and rack. Thoroughly rinse the test tubes with distilled water. Drying is not necessary.
  5. Place 10 drops of silver nitrate (AgNO3) into each of the test tubes.
  6. Write observations of the silver nitrate in a data table.
  7. Place one metal strip into each test tube with the silver nitrate. DO NOT fold or roll the metal strips.
  8. Allow the strips to sit and start Parts B and part C before making observations of the Part A reactions.
  9. Make observations of the products (both solids and aqueous solution) after allowing them to sit. Be sure to indicate not only what took place, but to what degree. (Quick, slow, a little, a lot, small, large)
  10. When all observations have been complete, wash the solutions down the drain with lots of water. Wash and dry the metal strips and return to your teacher.
Mg Cu Zn Fe AgNO3/solution
Before
After

Part B: Type B Reaction

  1. Obtain and sand a large piece of copper metal. Do not do this on the lab bench, but on a piece of paper or on a stack of paper towels.
  2. Make observations of the copper metal after sanding.
  3. Light the Bunsen burner with the striker. Adjust flame to get 2 distinct blue cones.
  4. Holding one end of the copper metal with the crucible tongs, heat the other end in the outer blue cone of the Bunsen burner flame for at least 2 minutes. Note observations made while the metal was heating in the flame.
  5. Place metal on ceramic mat to cool. Watch carefully as it cools and describe the product of the reaction.

Copper before Copper during Copper after

Part C: Type C Reactions

  1. Mass approximately 2 grams of copper (II) sulfate pentahydrate into an evaporating dish.
  2. Set up the ring stand with a ring support and wire gauze.
  3. Place evaporating dish on wire gauze.
  4. Light Bunsen burner with striker and place under evaporating dish.
  5. Heat contents of evaporating dish strongly for 2-3 minutes. Make observations of any changes that take place during heating.
  6. Turn off Bunsen burner.
  7. Take evaporating dish off wire gauze and place on ceramic mat to cool for at least 5 minutes.
  8. When cool, add several drops of distilled water to the evaporating dish with the product. Record any observations in data table.

Copper II Sulfate pentahydrate before heating Copper II Sulfate pentahydrate during heating Copper II Sulfate pentahydrate after heating Copper II Sulfate pentahydrate after addition of water

Analysis

  1. Classify the three types of reactions as single replacement, combination and decomposition. (Can use the classifications more than once if necessary). Provide data from the lab results to support your classification. Use the movement of electrons to explain if the reactions are oxidation-reduction reactions.
  2. Write the balanced equation for each reaction and if it is an oxidation-reduction reaction, identify which reactant was oxidized and the reactant that was reduced.
  3. Did all the reactions react the way that they should have reacted using the activity series to check? Provide an explanation if there was a difference.

Conclusion

  1. Explain the driving force so one knows when reactions occur in oxidation-reduction reactions.
  2. Did these experiments help to classify reactions and determine whether reactions are oxidation-reduction reactions?