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LESSON PLAN in Intermolecular Forces, Accuracy, Measurements, Significant Figures, Accuracy, Error Analysis, Error Analysis, Chemical Technical Professionals. Last updated July 14, 2024.

Summary

In this lesson, students will learn about a product recall of baby formula. Students will explore regulations around foods for human consumption and the quality control process that is part of food production. They will use their knowledge of the difference in intermolecular forces between solids and liquids to determine the moisture content in samples of powders. Students will then assume the role of quality control technicians and write a report in which they provide a data-informed decision as to whether their batch should be discarded or is fit for consumption.

Grade Level

High School

NGSS Alignment

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

  • HS-PS1-3: Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles.
  • Scientific and Engineering Practices:
    • Analyzing and Interpreting Data
    • Planning and Carrying Out Investigations
    • Engaging in Argument from Evidence
  • Cross-Cutting Concepts:
    • Cause and Effect

Objectives

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

  • Explain how differences in intermolecular forces can be used to separate a mixture.
  • Develop laboratory skills used by members of the skilled technical workforce, including: accurately weighing and recording mass, organizing data in a data table, analyzing data mathematically, and creating an evidence-based claim in a written report.

Chemistry Topics

This lesson supports students’ understanding of:

  • States of matter
  • Separating mixtures
  • Accuracy and precision
  • Career opportunities
  • Good manufacturing processes

Time

Teacher Preparation: 20 mins on day 1 to gather materials and prepare test samples, another 15-20 mins on day 2 to reweigh them and calculate the moisture content (before students do the lab activity)
Lesson: Two 45-min periods plus homework (completing the report)

Materials

  • A drying oven or incubator. (A regular kitchen oven or toaster oven will work too. See teacher notes for more information.)
  • 500-mL glass beaker with a drying agent such as indicating silica gel or indicating DrieRite (to place in oven for added drying)
  • Hot hands, oven mitts, or tongs (for removing hot jars from oven)

Per lab group:

  • 3 small air-tight glass jars with lids, such as these 4 oz. canning jars
  • Wax pencil (or other heat-resistant implement for labeling jars/lids)
  • 6-12 grams of sample powder to test (2-4 grams for each of the three samples)
    • Powder could be flour, powdered milk, protein powders, etc. (See teacher notes for more detail)
  • Spatulas
  • Electronic balance (400 g x 0.1 g or 0.01 g, or most precise balance available)
  • Desiccator (optional – see teacher notes)

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.
  • Students should be careful when taking samples out of the drying oven; use heat-resistant gloves when needed.
  • Food in the lab should be considered a chemical and should not be consumed.

Teacher Notes

  • The National Science Board estimates that there are over 16 million jobs in the Skilled Technical Workforce (STW) that don’t require a 4-year college degree, but require STEM knowledge such as the use of chemicals, application of arithmetic and algebra, and the knowledge of quality control and other techniques for manufacturing goods. This lesson was developed as part of a content writing team to support the ACS Strategic Initiative on Fostering a Skilled Technical Workforce, with the goal of increasing awareness of and appreciation for STW opportunities in the chemistry enterprise at the high school level.
  • This lesson plan introduces students to quality control in processed food manufacturing. Students practice using some of the skills needed by chemical technicians, including accurately weighing and recording mass, organizing data in a data table, analyzing data mathematically, and creating an evidence-based claim in a written report.
  • The introduction activity has students visit various websites to learn more about the process and importance of quality control in processed food production. This introduction activity requires an internet-connected device for accessing websites and watching videos. All three parts could be completed in class or assigned as homework before the lab activity (or a combination of both), depending on time constraints.
    • For Part 1, which looks at the FDA and food recalls, students may not be able to find every piece of information asked for in question 2 for every recall listed. Encourage them to read the recall announcement thoroughly but not to worry if they can’t find the answer to one of the questions.
    • Part 2 has students read about Good Manufacturing Practices (GMP) and answer a few questions about the benefits and underlying principles of GMP.
    • In Part 3, students watch two very short videos describing the work of quality control technicians and chemical technicians and answer a couple of questions about the skills and qualifications for these types of jobs. The bit.ly link provided in the student handout directs them to this page:
  • You could provide students with the CNN article on the formula shortage referenced in Part 1 of the introduction activity for more thorough background on the 2022 US baby formula shortage.
  • The lab activity is very adaptable and can be done successfully with many easily obtained powders (see table below for suggestions). The idea is that students create an evidence-based claim about the manufacturing quality of a powder, based on its moisture content.
  • It is strongly recommended that you do this lab ahead of time. It should not take you long – weigh a few samples, place them in an oven to dry overnight, and reweigh them the next day. This will give you an idea of moisture content in the samples you will be using, as moisture levels depend on how old the sample is, if and how long it’s been exposed to air, etc.
  • The lab activity has students determine the amount of residual moisture in a sample using the gravimetric method. A sample is heated at low temperature for an extended time (overnight) to drive off any moisture. Any weight loss during the process is attributed to moisture evaporating. The moisture content of the tested product (in %) is calculated based on the weight loss.
    • While a drying oven is standard for this type of analysis in a real-world setting, a hot plate on a low setting can be used as an alternative if there is no oven available. Heat the samples on low heat, with the lids off. The drawback is that the powders immediately attract moisture from the air again when the hot plates are turned off. As long as students close the lids as soon as they stop heating, the experiment will still allow them to collect meaningful data and compare it to acceptable values.
  • Ideally, samples are allowed to reach equilibrium at room temperature after drying. This is done by placing them in a desiccator for 1-2 hours. Whilst this is part of the official guidelines for this method, it is not necessary for students to meaningfully engage with this task and create evidence-based conclusions).
  • Drying time is variable – the sample data in the answer key were obtained after 2 hours of drying at 100℃. Overnight drying can be done at a much lower temperature (40℃).
  • There are different ways to have your class do this experiment – you can assign different ‘batches’ of powder to each student group. You can expose some batches to high moisture, so students get to experience a setting where some batches are acceptable, and others are not. You can also have each group test samples of the same batch and pool data as a class. That opens up opportunities to discuss accuracy and precision in quality control experiments.
  • This task can also be completed in a different context: freeze-dried (veterinary) vaccines. If this is more relevant to your students, feel free to change the background accordingly. For more information, see: Residual Moisture Testing (The European Agency for the Evaluation of Veterinary Medicinal Products). You can still use common household powders in the lab, either as a model for the actual vaccine, or call it a ‘fake’ vaccine.
  • Below is a table with suggested powders and their approximate maximum allowed moisture content. This information can be tricky to find; the info below is to the best of my ability and should be used for the high-school context only.
Dried milk powder < 5%
Protein powder < 5%
Flour 10-15%
Dried grated parmesan cheese <20%
  • Because sugar will start to caramelize (at about 180°C) and baking soda (sodium bicarbonate) will decompose into sodium carbonate, water, and carbon dioxide (at around 80°C), these are not ideal powders to use for this lab activity. Powdered milk/dairy products, other powdered drinks, and flour are better options.
  • You can use this activity to explore intermolecular forces at a more detailed level. For example – though a boiling point for sugar is provided, sugar will start to decompose before it reaches its boiling point. Adjust pre-lab questions accordingly.
  • Make sure students label the jar and its lid with the same number so they will remember which jar goes with which lid. Mixing up jars and lids will throw off the data since not all jars + lids can be assumed to have the exact same weight. One of the post-lab questions addresses this.
  • This activity can be used to introduce or review significant figures/accuracy/precision in calculations.
  • Though not preferable, the task can be completed with a kitchen scale. If this is what you’ll be using, increase the sample size to about 10-15 g for increased reliability and precision. A more sensitive scale (0.01 g or more) results in more reliable data.
  • If pressed for time, the post-lab questions can be removed from the student document to allow students to focus on completing the report. Instead, teachers could ask those questions to the students informally while they are completing the relevant steps of the procedures to get them thinking about why these steps are important.
  • In their final report, students are asked to include an expiration date and batch number/manufacturing date. You can use what is on the packaging of your powder or assign these as you wish, particularly if you have created one or more “batches” that have been exposed to high moisture environments. Provide the information to students when they obtain their samples for testing.

For the Student

Introduction to Processed Food Manufacturing

Part 1 – FDA Recalls

In the Spring of 2022, the US experienced a huge shortage in baby formula. Chances are that you remember a relative, neighbor, sibling, or parent being worried about how to feed their infant. Stores like Target, CVS, and Walmart limited the number of cans of formula customers could purchase. In May 2022, 40% of formula was out of stock according to CNN.

One of the reasons behind the shortage was a product recall at one of the largest suppliers of baby formula. A product recall is costly in many ways. Companies put a lot of practices in place to prevent a product recall. Some of these practices are chosen by the company. Others are mandated by the US Food and Drug Administration (FDA). These are called Good Manufacturing Practice (GMP).

Answer the following questions about the FDA and food recalls:

  1. What do the letters ‘FDA’ stand for?
  2. Go to the FDA’s list of recent recalls and safety alerts: https://www.fda.gov/safety/recalls

    On the “Product Type” drop-down menu, select “Food & Beverage.” Click on one of the recently recalled food items (in the “Brand name” column) and identify as much of the following information as possible:
    1. What type of food was recalled?
    2. When and where did the recall happen? Provide a date and the state(s) and/or country(ies) that were impacted.
    3. What was the cause for the product recall? What went wrong at the manufacturing or processing plant?
    4. How many people got sick or died from the issue with the food?

Part 2 – Good Manufacturing Practices

Good Manufacturing Practices (GMP) play a vital role in the production of foods that are safe for human or animal consumption. The FDA has regulated food safety since its beginnings in 1906, but food safety regulations started before that; since the mid-1800s, local and state regulators have worked towards increased safety of foods that were created for human consumption. GMP is an extensive set of descriptions and requirements. Collectively they aim to cover the entire process of producing processed food – from the people who carry out each step to the premises where it takes place.

Visit https://safetyculture.com/topics/gmp/ and use the information on this page to answer the following questions:

  1. How does implementing GMP benefit companies?
  2. How does implementing GMP benefit consumers?
  3. What are the “5 P’s” of GMP?
  4. If you had to pick just one, which of the “5 P’s” do you think is the most important to successfully implementing GMP? Explain why you picked that one.

Part 3 – Quality Control Jobs

GMP requires that every time a new batch of processed food (baby formula, for example) is finished, the manufacturer needs to take a sample and test it to ensure the amounts of nutrients in the product meet the requirements that are specified for each nutrient. The sample also needs to be tested for moisture content, as a high moisture content makes it easier for unwanted microorganisms to grow. If the moisture content of a powdered food is too high, the batch of powder is not fit for human consumption and must be discarded.

The people who test these products are quality control (QC) technicians, sometimes also called chemical technicians. QC technicians work in a variety of industries to ensure the quality of many kinds of products – food (such as baby formula), clothing, car parts, cosmetics, pharmaceuticals, etc. They check the quality of the products that their company produces to determine whether the product lives up to the standards set for it. QC technicians are examples of skilled technical workers – people without advanced degrees, but with well-developed science and engineering skills. Skilled technical workers are in high demand. Jobs are relatively well paid and come with benefits.

Learn more about QC/chemical technician positions and answer the questions below by reading/watching the video on the following website: https://bit.ly/ChemTechInfo

  1. What is the median wage of a chemical technician in the United States?
  2. What education and experience does someone starting in this career usually have?
  3. What percentage of chemical technicians have an education level less than a bachelor’s degree?
  4. What are three activities a chemical technician might do in the course of their job?
  5. What are three subject areas chemical technicians should be knowledgeable about?
  6. What are three skills a chemical technician needs to have?

Fit for Consumption?

Background

In this lab task, you will take on the role of a quality control technician. Your company has received reports that some of their powdered food products may have made some consumers ill. Most powders have some residual moisture – small amounts of water that are mixed in with the powder but are not enough to be identified visually. However, if the residual moisture content is too high, microorganisms could grow and make people sick. Your supervisor wants you to determine if this is the case for your company’s products. High moisture levels would lead to a recall of the affected products to prevent more consumers from becoming ill.

However, recalls are expensive, and it is important that you have evidence that this is what actually happened. Your teacher will provide you with a sample of the powder and will tell you the maximum acceptable moisture content of the powder. After collecting data, you’ll write a report to your supervisor with an evidence-based conclusion about the quality of your powder and whether or not a recall should be initiated.

Prelab Questions

  1. The table below shows the approximate boiling points of some common substances that can be found inside food.

Substance

phase

Approximate Boiling point (℃)

alcohol

liquid

80

water

liquid

100

sugar

solid

400

salt

solid

1400

baking soda

solid

850
  1. What do you notice about the boiling point of liquids compared with the boiling points of solids?
  2. When a powder with some moisture in it is exposed to heat, the moisture slowly evaporates. The powder does not evaporate. Use the information in table 1 to explain how this works. You can use words and/or drawings in your explanation. Refer to intermolecular forces in your explanation.

Problem

Is this batch of powder fit for human consumption?

Materials

  • Goggles
  • 3 glass jars with lids
  • Wax pencil
  • White powder sample
  • Spatula
  • Balance

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.
  • Be careful when taking samples out of the drying oven; use heat-resistant gloves when needed.
  • Food in the lab should be considered a chemical and should not be consumed

Procedure

Day 1

  1. Label your glass jars and their lids with a number. Each jar should have a different number, and each lid should have the same number as its jar.
  2. Record the mass of an empty glass jar with its lid in the data collection table.
  3. Open the lid and weigh 2 grams of the white powder into the glass jar. Break up any lumps in the powder.
  4. Close the lid and weigh again. Record the exact mass in the data collection table.
  5. Gently shake the jar to evenly spread out the powder.
  6. Repeat step 1-4 with 2 new mason jars.
  7. Place your mason jars in the drying oven. Check that the temperature is around 45℃ Take the lids off and place them next to the jar in the oven. Make sure the oven is closed. Leave to dry overnight.
  8. If you have time, you can calculate the mass of each sample and record it in the first column of the data analysis table.

Day 2

  1. Take your jars out of the drying oven.
  2. Close the lids as soon as you possibly can. The dry powders will otherwise attract moisture from the air.
  3. Record the mass of each jar + lid + sample in the appropriate line in the data collection table.
  4. Dispose of your samples according to the teachers’ instructions.
  5. Proceed to complete the data analysis table and create your report.

Data Collection

Jar #
Mass of empty jar + lid (g)
Mass of jar + lid + powder (g) (day 1 - before drying)
Mass of jar + lid + powder (g) (day 2 - after drying)
1
2
3

Data Analysis

For each jar, perform the following 3 calculations:

  1. Mass of sample = (mass of jar + lid + sample, day 1) - (mass of jar + lid)
  2. Mass of water lost = (mass of jar + lid + sample, day 1) - (mass of jar + lid + sample, day 2)
  3. Moisture content in original sample (%) = Trulli
Jar #
Mass of sample (g)
Mass of water lost (g)
Moisture content in original sample (%)
1
2
3
Average moisture content (%)

Post-lab Questions

  1. If you have not already done so, round all answers in the data analysis table above to the correct number of significant digits.
  2. A student accidentally mixes up the lids of their jars. The lid they used on day 2 has a lower mass than the original lid. Explain how this will impact their result. Will the calculated % moisture be too high, too low, or remain unchanged? Use math to support your answer.
  3. Step 5 of the Day 1 procedure instructs you to spread the powder evenly.
    1. Consider the drying process and explain why it is important to spread the powder evenly.
    2. A student’s powder was lumpy when they weighed it. Evaporation of residual moisture happens mostly at the surface of the powder. Would his calculated moisture content be higher than, lower than or equal to the actual moisture content? Support your answer with mathematical reasoning.
  4. In day 2, step 2, you were told to close the lids on the jars as soon as possible. If you left the jars uncovered for a while, how might that affect your results? Would your calculated moisture content be higher than, lower than or equal to the actual moisture content? Support your answer with mathematical reasoning.
  5. This experiment assumes that all mass lost during the experiment is caused by evaporation of moisture. Think of at least 1 other reason that could cause a loss in mass during this experiment and explain how.
  6. Good Manufacturing Practice requires precision in lab work.
    1. Review what precision in science means and summarize your answer here.
    2. Why do you think that a high level of precision is important in Quality Control?

Report

Compare your average moisture content with the information about acceptable limits that your teacher will provide.
Create a brief 1-page report to share with your supervisor. Your report should contain the following elements:

  1. A description of your powder. Include any information you have been provided with or can find on the packaging: best before dates, manufacturing dates, color, smell, appearance etc.
  2. Your test results. Clearly state your average moisture content. Support that with a copy of your data analysis table.
  3. A conclusion based on your evidence. The conclusion needs to address the question stated in the problem/objective section.
  4. Your signature: your name(s) and the date you completed the report.

A layout is provided on the next page.