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Aspirin Tablets: Are they all the Same? (12 Favorites)

LAB in Solubility, pH, Molecular Structure, Buffers. Last updated August 19, 2019.


Summary

In this lab, students will design an experiment to test the time and completeness of dissolution of various types of aspirin in different pH environments.

Grade Level

High School

AP Chemistry Curriculum Framework

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

  • Unit 2: Molecular and Ionic Compound Structure and Properties
    • Topic 2.5: Lewis Diagrams
      • SAP-4-A. Represent a molecule with a Lewis diagram.
  • Unit 3: Intermolecular Forces and Properties
    • Topic 3:10: Solubility
      • SPQ-3.C: Explain the relationship between the solubility of ionic and molecular compounds in aqueous and nonaqueous solvents, and the intermolecular interactions between particles.
  • Unit 7: Equilibrium
    • Topic 7.13 pH and Solubility
      • SPQ-5.C: Identify the qualitative effect of changes in pH on the solubility of a salt.
  • Unit 8: Acids and Bases
    • Topic 8.6: Molecular Structure of Acids and Bases
      • SAP-9.F: Explain the relationship between the strength of an acid or base and the structure of the molecule or ion.
    • Topic 8.8: Properties of Buffers
      • SAP-10.B: Explain the relationship between the ability of a buffer to stabilize pH and the reactions that occur when an acid or a base is added to a buffered solution.

Objectives

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

  • Design a reliable experiment to test time of complete dissolution.
  • Collect relevant qualitative and qualitative data to assist in determining dissolution capabilities of each type of aspirin tablet.
  • Determine the relationship between the experiment materials and how aspirin interacts with the human body.

Chemistry Topics

This lab supports students’ understanding of

  • Acids & Bases
  • pH
  • Buffers
  • Solutions
  • Solubility
  • Evidence of Chemical Change
  • Molecular Structure

Time

Teacher Preparation: 5-10 minutes

Lesson: 60 minutes

Materials

  • 3 tablets each of: regular, buffered, and enteric aspirin
  • Water
  • White vinegar
  • Baking soda
  • Measuring Cup
  • Teaspoon measure
  • 3 clear colorless glasses (plastic will work as long as clear and colorless)

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.
  • Do not consume lab solutions, even if they’re otherwise edible products.

Teacher Notes

  • This resource could be used as a post-AP Chemistry exam activity.
  • I use this lab experiment as a take home lab assignment. Find out more about my take home labs in the March issue of Chemistry Solutions or in the AACT Webinar archive.
  • This particular lab is used with my AP students as optional extra test credit to help students who are not good test takers from the ‘paper and pen’ perspective, but are still willing to challenge themselves academically. I try to design these labs so that they offer experimental design and a little bit of research on new material.
  • The materials are commonly found at home, so have students to check for availability. If this is difficult, allowing students to complete the lab in the classroom before or after school is a good option.

For the Student

Background

The primary ingredient in aspirin is acetylsalicylic acid, which is usually combined with a nontoxic binder (which may be insoluble). Many people have found that aspirin can cause stomach irritation, so drug companies and manufacturers have developed a variety of coatings or additives that make the aspirin easier on your stomach. “Buffered” aspirin includes an ingredient to lessen the effect of the acid in the aspirin, while safety coated aspirin, also called enteric, prevents dissolving in certain conditions. Your task is to test three (3) types of aspirin in different conditions to see how they respond, and then do a little bit of research about why they respond the way that they do.

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.
  • Do not consume lab solutions, even if they’re otherwise edible products.

Materials

  • 3 tablets each of: regular, buffered, and enteric aspirin
  • Water
  • White vinegar
  • Baking soda
  • Measuring Cup
  • Teaspoon measure
  • 3 clear colorless glasses (plastic will work as long as clear and colorless)

Exploration

  1. You need to perform an experiment using the materials supplied, to explore how the different types of aspirin tablets behave in different types of liquids. The three liquids are: water, white vinegar, and a solution of baking soda (1 tsp per ½ cup water).
  2. The data you collect should be both qualitative and quantitative, with a component that can be graphed. Qualitative data can include both anecdotal evidence and pictures.
  3. To ensure some consistency, let’s assume that most people take aspirin with at least ½ cup of water. This means that the amount of liquid used for each tablet in your experiment design should be at least ½ cup and should be held to a constant amount. Also, remember that aspirin takes about 20-30 minutes to take effect, part of which time is spent dissolving; therefore your observations should take at least 5-10 minutes per set, to ensure sufficient time for observing any differences in behavior.

Data

Use the following data table as a guide.


Water

Vinegar

Baking Soda Solution

Regular Aspirin




Buffered Aspirin




Enteric Aspirin




Research questions

  1. Write both the chemical and structural formula for aspirin (acetylsalicylic acid).
  2. These questions are about the vinegar observations:
    • Aside from water, what is the other major ingredient in vinegar (please give a name and formula) and what does it have in common, chemically, with your stomach?
    • Was there evidence of a chemical reaction for any of the aspirin tablets in the vinegar? What obvious type of product appeared?
    • What is a buffer?
  3. These questions are about the baking soda solution observations:
    • What is the chemical makeup of baking soda?
    • Is a solution of baking soda acidic, basic, or neutral?
    • Is the pH of a baking soda solution more aligned with the pH of your stomach or your small intestine?

Conclusion

  • Write a paragraph conclusion that restates your purpose, what you observed, and your conclusion about how your observations are connected to the purpose of the experiment.
  • Have a parent sign your work.