Summary

In this lab, students will carry out seven reactions and classify their reaction types. They will make observations, predict products, and balance the equations that represent the chemical reactions that are occurring.

Grade Level

High School

NGSS Alignment

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

• MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
  
• 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.
• HS-PS1-7: Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
• Scientific and Engineering Practices:
  
  • Developing and Using Models
  • Analyzing and Interpreting Data

AP Chemistry Curriculum Framework

This lab supports the following unit, topics, and learning objectives:

• Unit 4: Chemical Reactions
  • Topic 4.1: Introduction for Reactions
    • 4.1.A: Identify evidence of chemical and physical changes in matter.
  • Topic 4.2: Net Ionic Equations
    • 4.2.A: Represent changes in matter with a balanced chemical or net ionic equation: a. For physical changes. b. For given information about the identity of the reactants and/or product. c. For ions in a given chemical reaction.
  • Topic 4.4: Physical and Chemical Changes
    • 4.4.A: Explain the relationship between the macroscopic characteristics and bond interactions for: a. Chemical processes. b. Physical processes.
  • Topic 4.7: Types of Chemical Reactions
    • 4.7.A: Identify a reaction as acid-base, oxidation-reduction, or precipitation.

Objectives

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

• Perform synthesis, decomposition, single displacement, and double displacement reactions.
• Make observations of chemical reactions and categorize them.
• Write and balance chemical equations.

Chemistry Topics

This lab supports students’ understanding of:

• Classification of reactions
• Predicting products
  
• Balancing equations
• Chemical change

Time

Teacher Preparation: 45 minutes—1 hour

Lesson: two 50-minute class periods or 1 block class

Materials

For each group:

• goggles
• 7 graduated cylinders (10 mL)
• 8 test tubes
• test tube rack
• steel wool
• scoopula
• magnesium ribbon (2-3 cm)
• crucible tongs
• Bunsen burner
• copper wire (2-3 cm)
• zinc strip (2-3 cm)
• pH strips
• water
• rubber stopper
  
• wooden splint
  
• matches
  
• catalase/potato piece
  
• hydrogen peroxide (5–6%)
  
• calcium chloride (solid)
  
• calcium oxide (solid)
  
• 1.0 M hydrochloric acid
  

0.1 M of the following:

• copper(II) sulfate solution
• potassium carbonate solution
  
• sodium oxalate solution
  
• copper(II) chloride solution

Safety

• Always wear safety goggles when working in with chemicals.
• Pour all of the solutions in the designated chemical waste container.
• When working with acids, if any solution gets on students’ skin, they should immediately alert you and thoroughly flush their skin with water.
• When lighting the match and wooden splint, be cautious with the flame.
• 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.

Teacher Notes

• Prior to completing this lab, students should be familiar with identifying signs that a chemical reaction has occurred, classifying reactions, predicting products, and balancing equations.
• This lab can be used in a variety of settings and, depending on the level of the students, could be used in a general chemistry class up to an AP level class. If using at the AP level, rather than using the categories of synthesis, decomposition, single displacement, and double displacement in analysis question 1, you could have students classify reactions as acid-base, oxidation-reduction, or precipitation to align better with the AP curriculum learning objectives. The answer key includes categorizations for both non-AP- and AP-aligned courses.
• There is an accompanying PowerPoint available for download that can be used as a prelab or postlab activity. Answers are provided in the “notes” section of the PowerPoint.
• Prepare salt solutions so they are 0.1 M. The following directions will create enough solution for approximately 20 lab groups.
• Directions for preparing the necessary solutions (each will be 0.1 M)
  • Copper (II) chloride (Molar mass CuCl₂ = 134.45 g/mol)
    To prepare 200 mL of 0.1 M aqueous solution of copper (II) chloride, dissolve 2.69g of CuCl₂ in 200 mL of water.
  • Copper (II) sulfate (Molar Mass CuSO₄ = 159.61 g/mol)
    *Note: Students will not use as much copper (II) sulfate as the rest of the solutions. To prepare 100 mL of 0.1 M aqueous solution of copper (II) sulfate, dissolve 1.60 g of CuSO₄ in 100 mL of water.
  • Potassium carbonate (Molar Mass K₂CO₃ = 138.21 g/mol)
    *Note: Students will not use as much potassium carbonate as the rest of the solutions. To prepare 100 mL of 0.1 M aqueous solution of potassium carbonate, dissolve 1.38g of K₂CO₃ in 100 mL of water.
  • Sodium Oxalate (Molar mass Na₂C₂O₄ = 133.999 g/mol)
    To prepare 200 mL of 0.1 M aqueous solution of sodium oxalate, dissolve 2.68g of Na₂C₂O₄ in 200 mL of water.
• Many of the reactions in this lab are exothermic, some noticeably so. Since relatively small quantities of materials are used in this lab, they should not get too hot, but you may want to warn students so a) they can notice and make observations about the temperature changes, and b) they are not surprised and know to exercise caution to prevent injuries or spills.
  • Similarly, some of the solutions the teacher prepares for this lab have exothermic heats of solution and may cause the container to heat up when the solutes are mixed with water, so solutes should be added carefully.
• To make the potato catalase for Reaction E, simply cut a potato in small pieces (make sure that it will fit in the test tubes used in the lab). This is also a good opportunity to introduce or reinforce the concept of how catalysts speed up the reaction but do not get consumed. Emphasize that after the bubbling/fizzing stops and the reaction is complete, the potato is the same. Be sure students understand that this reaction would still happen without the catalase from the potato, but it would occur much more slowly. You can ask them whether they think the glowing splint would reignite if they put it near the non-catalyzed reaction, and hopefully they would recognize that the O₂ would form slowly and not be concentrated enough to have the same effect if the reaction hadn’t happened as quickly. (Maybe if there’s time, they could test it out!)
  • Remind students to not force the stopper into the test tube for this reaction (E).
• Ideally, use DI or distilled water for Reaction G. The pH of tap water can vary greatly by location, so it could be anywhere from 4-8. Additionally, water that is open to the atmosphere absorbs CO₂, which combines with a water molecule to form carbonic acid, H₂CO₃, and acidifies the water. You may notice more acidic water samples, even if using DI or distilled water, if it has been left sitting exposed to the atmosphere for some time. In any case, the water alone should always be more acidic (lower pH/less basic) than the test tube containing Ca(OH)₂.
  • In Reaction G, the product of CaO (s) + H₂O (l) is Ca(OH)₂, which is a “slightly soluble” compound (solubility of about 0.16 g/100 g H₂O). The small amount that does dissolve will produce a basic solution, which is why the pH strip should indicate a basic pH (probably around pH=12, with some variation based on the water used to make the solution). However, adding the CaO to water will likely form more Ca(OH)₂ than can be dissolved, so students are likely to see a precipitate as well. Since both a change in pH and the formation of a precipitate occur, if you are using the AP curriculum reaction categories of acid-base, oxidation-reduction, and precipitation, consider accepting acid-base and/or precipitation as correct answers.
• This lab uses principles of green chemistry. The chemicals used are much less toxic than similar labs that use silver nitrate, lead, sulfur compounds, etc.
• If you don’t have enough graduated cylinders for each group to use a new one for each chemical, make sure student properly wash the glassware before measuring a new chemical. Alternatively, you could set up materials for each reaction at a different station and have students move from station to station so they could all use the same graduated cylinder for the solution(s) at each station. This would involve students moving around the room with their test tube racks, so they would need to move carefully.
• If time allows, discuss question 5 in small groups or as a class. Students usually learn the law of conservation of mass early in chemistry class, and it seems straightforward, but it is not always easy to prove in every reaction (particularly those involving gases). It is a good place to think about the study of chemistry in an historical context, as the presence of clear, colorless gases as reactants/products challenged scientists for centuries as they tried to understand how matter changed. (AACT’s Antoine Lavoisier Video provides a good overview of this!)