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ACTIVITY in Percent Composition, Concentration, Quantitative Chemistry, Mole Concept, Dimensional Analysis, Measurements, Chemical Technical Professionals. Last updated January 14, 2026.

Summary

In this activity, students will use decision making and critical thinking skills, and apply their understanding of dimensional analysis, mole calculations, solutions, and organic chemistry to solve a fictional, scenario-based problem.

Grade Level

High School

NGSS Alignment

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

  • Scientific and Engineering Practices:
    • Using Mathematics and Computational Thinking
    • Analyzing and Interpreting Data
    • Engaging in Argument from Evidence

Objectives

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

  • Demonstrate a strong understanding of unit conversions using dimensional analysis.
  • Choose the correct volumetric flask for a specific need.
  • Accurately calculate moles and molarity from provided data.

Chemistry Topics

This activity supports students’ understanding of:

  • Dimensional analysis
  • Unit conversions
  • Measurements
  • Mole calculations
  • Percent composition
  • Laboratory equipment
  • Solutions
  • Concentration
  • Organic chemistry
  • Functional groups

Time

Teacher Preparation: 10 minutes

Lesson: 45-60 minutes

Materials

  • Student handout
  • Scientific calculator
  • Option items (for visualization purposes only)
    • Quadruple beam balance
    • Mortar and pestle
    • Volumetric flasks (sizes: 25 mL, 50 mL, and 100 mL)

Safety

    Teacher Notes

    • If students are not familiar with quadruple beam balances, volumetric flasks, or mortar and pestles, have them displayed on a table or bench. Explain the uses of each:
      • The mortar and pestle have been used for crushing reagents to a fine powder since ancient times and is common in kitchens around the world for crushing and mixing spices.
      • A quadruple beam balance was common in laboratories, metallurgical assay, and apothecaries before electronic analytical balances. They can be precise to 0.0001 g.
      • Volumetric flasks are accurate in volume to 0.05% of the nominal (marked) value. They are used to make solutions of accurate concentrations.
    • Knowledge in the use of a balance to determine mass, making solutions, and making dilutions is helpful for this activity. A quick demonstration can accomplish this.
    • I have observed that some students can struggle at specific points during this activity:
      • Conversions from pounds to kilograms: dosages are usually given in mg of medicine per kilogram of body weight, or mg/kg mass. It is a precise way to calculate the amount of medicine.
      • Choosing between volumetric flask sizes: I explain that smaller sizes are more concentrated, and the amount of the solution the child needs to take is less. Larger sizes are less concentrated, but the child will need to take more of the solution. If they have been around younger siblings who don’t like taking medicine, this can influence their decision.
      • Use of fruit juice as a solvent: acetaminophen is a very bitter substance and if dissolved in water could be unpalatable. Fruit juice can mask the taste and is usually familiar to a small child.
    • This activity is a good assessment of students’ understanding of the mole concept and converting between units using dimensional analysis.
    • It is suggested that students work in pairs or small groups.
    • Students interested in a career in the health or medical industry can find this activity eye-opening as it relates to medicines and dosages, and how they are calculated.
    • An answer key document is available for teacher reference.

    Resources

    For the Student

    The Tylenol Project

    *Important Note to students: The advice and calculations in this scenario are not to be used for a real-life situation. Always consult a medical professional.

    Scenario

    You are having a family reunion with several generations of your family, staying at a spacious mountain lodge. The closest neighbor or town is at least an hour drive away.

    As everyone is settling in for the night, one of your youngest cousins starts to complain that he does not feel well. After a quick check, his mother says he has a fever and wants to give him some Tylenol (active ingredient: acetaminophen). But there are a couple of problems.

    1. It is starting to snow heavily, and the roads are icy and too treacherous to drive.
    2. The only drug store in the nearby town is already closed for the night. The on-call pediatrician’s office has not returned the mother’s phone calls.
    3. No one brought any children’s Tylenol, but someone has regular Tylenol® tablets meant for adults.

    Problem

    Can you determine the appropriate dose of medicine to give to your cousin?

    Helpful Conversions

    1000 mg = 1 g

    453.5 g = 1 pound

    4.9 mL = 1 teaspoon

    1000 g = 1 kg

    16 ounces = 1 pound

    1000 mL = 1 L

    Directions

    Answer the following questions and show all work, rounding answers appropriately.

    Part 1:

    1. A therapeutic dose of medicine is the amount to be given as one dose to a patient. Your cousin is only 2 years old, and weighs 21.5 pounds, so the therapeutic dose recommended for a child that age and size is 10 mg/kg body mass.

    How much acetaminophen should he receive?

    1. The only Tylenol® available is the regular strength tablet meant for adults. The concentration of acetaminophen is 325 mg per tablet.
      1. Is one tablet the correct amount of medicine dosage for a 21-pound child?
      1. Is the tablet too much or too little medicine?

    Part 2:

    With your background in chemistry, you decide that you can help. If you crush a tablet and dissolve it in some fruit juice, you can determine how much your cousin should take to reduce his fever. Fortunately, the lodge you are staying in used to belong to a goldminer, and in one of the rooms there are some scientific instruments that were used to determine the amount and purity of the gold.

    On a desk you find:

    • A quadruple beam balance able to weigh out to 0.0001 g
    • A mortar and pestle used to crush samples into a fine powder
    • Several volumetric flasks: 25 mL, 50 mL, and 100 mL
    1. Using the mortar and pestle, you carefully crush 1 tablet of regular strength Tylenol into a fine powder and weigh it on the balance. Even though the tablet says it contains 325 mg acetaminophen, the entire tablet weighs 635.62 mg because of the binders to keep the tablet together.
      1. Determine the % composition of acetaminophen in the tablet.
    1. After crushing the tablet, you transfer the amount you weighed out to one of the volumetric flasks. Which size flask do you use? Justify your choice with an explanation.
    1. You add fruit juice to the calibrated mark of the flask, stopper it, and shake it until all the powder dissolves.
      1. What is the total volume of the powdered tablet and fruit juice? How do you know?
      1. Determine the concentration of just the acetaminophen, in mg/mL. (Assume the flask has a precision of 0.01 for rounding purposes.)
    1. You now know the concentration of the acetaminophen in the fruit juice and the amount of acetaminophen your cousin needs.
      1. Determine the amount of the solution, in mL, to properly dose him.
      1. There is a set of measuring spoons in the kitchen, and the mother gets them out. How many teaspoons of solution should she measure out?
    1. After a little while, your cousin’s fever seems to be going down and he is resting comfortably. Since the medicine is working, his mother wants to be able to give him more if he needs it.
      1. How many more doses are left in the flask?
    1. The chemical formula for acetaminophen is C8H9NO2. The structure is shown below.
      1. Determine the molecular weight of the compound.

      1. Determine the % composition of oxygen in the compound.
      1. Determine the % composition of carbon in the compound.
      1. Circle the functional groups of the compound. Name them.
    1. Even though you SHOULD NEVER do something like this in real life, it is the basic process pharmacists and doctors use to determine how to formulate medicines in the pharmacy.
        1. Why is this knowledge important for them?
        1. What are some consequences if the calculations are done incorrectly?
        1. How would this impact both the patient and the medical professional?
        1. What is the value of knowing how to convert units, even if it is not related to chemistry?
        1. Why are significant figures and rounding properly important to precision and correct answers?