The goal of this inquiry activity is to evaluate a variety of skin-care products on simulated skin cells using Orbeez, a brand of superabsorbent polymers. These small beads can quickly absorb water but will dry out in the air, thus perfectly representing our own skin cells. This property makes Orbeez an acceptable model for human skin, and test material for evaluating various skin-care products. Students will observe the quantitative changes that happened to the mass of the samples to determine the percent change. They will also observe the qualitative changes that happened throughout the lab investigation and record their observations in a lab notebook. After completing the experiment, students will create a presentation of the quantitative and qualitative results.

Maria Montessori once said that the human “hand is the instrument of intelligence” (Montessori, 1946). But what if your hands are dry, cracked, and tender? Dry skin is called xerosis. It is usually a result of environmental factors such as extreme cold or hot weather, taking too long of a shower or bath, or using abrasive detergents on your hands. The skin is our largest single organ and does an amazing job at insulating us, protecting us from infections, maintaining the water content of the body, regulating body temperature, and allowing certain molecules in and out – while keeping our insides inside where they should be (Marieb, 2004). Assessing the skin is one of the easiest ways to evaluate a person’s circulation, perfusion, blood oxygen level, and body temperature. Human skin has two main layers: the outermost layer, or epidermis, which is waterproof and gives our skin its tone; and the dermis, which is made up of tough connective tissue and contains the hair follicles and sweat glands. Water makes up a large portion of our bodies, and the skin is no different. The outermost epidermis layer of human skin cells is naturally absorbent, which prevents the skin from being constantly dry, cracked, and sore (Pollak, 2017). The Orbeez beads will lose water – and thus mass – if not adequately protected in a way that is similar to human skin. This provides students the opportunity to analyze the protective, hydrating factors of skin-product samples.

To combat dry skin, many skin-care products on the market claim to be “replenishing,” “hydrating,” “antioxidant infused,” and “age reversing” – but what do these adjectives really mean? Is skin lotion a liquid time machine? Are skin cells silently screaming for a nice vanilla-scented, water-infused serum? Or are the companies simply trying to tell consumers, like yourself, to buy this product using terminology that preys upon socially reinforced insecurities? The world may never know. But hopefully, upon completing this lab, students will have an evolved knowledge of how some common skin-care products affect the skin. For alignment with the Next Generation Science Standards (NGSS) and definitions of key terms, see Table 1.

Table 1.

Activity curricular context.

 StandardHS-LS1. From Molecules to Organisms: Structures and Processes Performance ExpectationHS-LS1-2. Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.The chart below makes one set of connections between the instruction outlined in this article and the NGSS. Dimension Name & NGSS Code/Citation Specific Connections to Classroom Activity Science and Engineering Practices Modeling in 9–12 builds on K–8 experiences and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed world(s). In this learning activity, students develop models, with guidance, to analyze and evaluate the effectiveness of common skin-care products. Disciplinary Core Ideas Systems of specialized cells within organisms help them perform the essential functions of life. In this learning activity, students use knowledge of cellular functionality to develop an effective model with which to carry out testing of environmental stimuli on skin cells. Crosscutting Concepts Models (e.g., physical, mathematical, computer) can be used to simulate systems and interactions – including energy, matter, and information flows – within and between systems at different scales. In this learning activity, students develop models to test objective properties of various consumer products. Definitions of Key Terms Dermis Middle skin layer, made up of tough connective tissue, containing the hair follicles and sweat glands (Pollak, 2017). Epidermis Outermost skin layer, which is waterproof and gives our skin its tone (Pollak, 2017). Orbeez Small beads of superabsorbent polymers, which can quickly absorb water but will dry out and shrivel if left out of water (Spinmaster, 2020: https://mayatoys.net/pages/orbeez). Xerosis Generically called dry skin. It is sometimes called xerosis cutis or xeroderma. The xero is from the Greek for “dry” (Pollak, 2017).
 StandardHS-LS1. From Molecules to Organisms: Structures and Processes Performance ExpectationHS-LS1-2. Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.The chart below makes one set of connections between the instruction outlined in this article and the NGSS. Dimension Name & NGSS Code/Citation Specific Connections to Classroom Activity Science and Engineering Practices Modeling in 9–12 builds on K–8 experiences and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed world(s). In this learning activity, students develop models, with guidance, to analyze and evaluate the effectiveness of common skin-care products. Disciplinary Core Ideas Systems of specialized cells within organisms help them perform the essential functions of life. In this learning activity, students use knowledge of cellular functionality to develop an effective model with which to carry out testing of environmental stimuli on skin cells. Crosscutting Concepts Models (e.g., physical, mathematical, computer) can be used to simulate systems and interactions – including energy, matter, and information flows – within and between systems at different scales. In this learning activity, students develop models to test objective properties of various consumer products. Definitions of Key Terms Dermis Middle skin layer, made up of tough connective tissue, containing the hair follicles and sweat glands (Pollak, 2017). Epidermis Outermost skin layer, which is waterproof and gives our skin its tone (Pollak, 2017). Orbeez Small beads of superabsorbent polymers, which can quickly absorb water but will dry out and shrivel if left out of water (Spinmaster, 2020: https://mayatoys.net/pages/orbeez). Xerosis Generically called dry skin. It is sometimes called xerosis cutis or xeroderma. The xero is from the Greek for “dry” (Pollak, 2017).

### Goal

The goal of this inquiry activity is to evaluate a variety of skin-care products on simulated skin cells using Orbeez, a brand of superabsorbent polymers (SAPs). These small beads can quickly absorb water but will dry out in the air, thus perfectly representing our own skin cells. This property makes Orbeez an acceptable model for human skin, and test material for evaluating various skin-care products.

### Why Use Orbeez?

Orbeez was chosen for this inquiry activity for two reasons. First, this product is the most widely available type of SAPs. Second, it has a consistency that is reliable from lab to lab and year to year. Other, generic types of SAPs can be used in this activity; however, their cheaper quality will limit their consistency and reliability.

### Brief Activity Description & Learning Objectives

The students began this learning activity by determining the control and skin-product samples of their choice, followed by setting up each sample and control with the same amount of Orbeez (skin cells). Next, the students observed the quantitative changes that happened to the mass of the samples to determine the percent change. They also observed the qualitative changes that happened throughout the lab investigation and recorded the observations in a lab notebook. The Orbeez beads represent our skin and, as such, to be a good skin-care product, the more protection of the skin from desiccation the better. Thus, students’ data should show less change in mass of the Orbeez treated with the better skin-care products (i.e., more protection from desiccation) compared to the control Orbeez in air (i.e., less protection).

After completing the experiment, students created a presentation of the quantitative and qualitative results. The presentation included a formal description of the results as well as possible reasons why the results were obtained, based on evidence. Evidence was derived from the chemical composition of the skin-care products (using the formula or ingredient labels and company websites) and the composition of the Orbeez model of human skin. The activity targeted five main learning objectives. Upon completion of this lesson, students should be able to

1. design an effective experimental design to test scientific questions;

2. openly discuss properties of skin layers using correct anatomical terminology;

3. interpret and evaluate scientific results based on evidence;

4. draw conclusions pertaining to scientific results, using scientific principles; and

5. use models to study biological samples, understanding the potential of modeling as well as its limitations.

• Orbeez

• Water

• Containers (3–5 per group)

• Variety of skin-care products

• Scale

• Spoons/popsicle sticks (optional for product application)

• Lab handout

Prior to conducting the Evaluating Skin-Care Products lab, students should have a basic understanding of skin layers and the structures of individual skin layers and specialized cells, as well as the ability to use correct anatomical terminology. Prior exploration of skin anatomy might include such activities as direct instruction, modeling, diagramming, investigative microscopy, or some combination of the aforementioned. Promoting a basic understanding of skin anatomy before the lab is crucial to students’ engagement with lab activities, understanding of observed phenomena, and later interpretation of results (Orion, 1989).

First, separate the class into groups of two to four students and instruct groups to sit together to facilitate discussion. Teacher Tips: Begin the class by posing questions to the students’ groups pertaining to their background knowledge of skin-care products’ composition and method of function; questions could be posed verbally, written on a board, or provided with other lab materials in a handout. Such questions may include

• What makes a “good” skin-care product?

• Does it matter to you what ingredients are in the skin-care products you use?

• How does a brand name and/or the way a product is marketed influence your perception of the product?

Cooperative group instruction should be encouraged, and teachers of larger classes may find it useful to designate a time when each group will briefly report their initial thoughts.

Second, explain that the purpose of this lab is multifaceted. The students themselves will design the parameters of their investigation and, hopefully, develop a deeper understanding of common products they regularly use. After this discussion, the teacher can pass out the lab handout to the class (see the Supplemental Material available with the online version of this article).

Third, instruct the class to consider and discuss questions 1–5 in the pre-lab handout within their groups and devise potential methodology to study the effects of various products. Teacher Tips: Each group will report their thoughts to the class, so taking brief notes may be helpful, but students should not fill out the lab handout entirely until the class has come to a consensus about the lab protocol to be followed. Remind students to consider items available in the classroom, as no additional materials will be purchased (i.e., what containers are available in sufficient quantities for the class – if only 200 mL beakers are available, those beakers will have to do as the test containers). As groups report out their proposed methods, keep a record on a board. Encourage the class to consider pros and cons of each preferred method. Once most of the class seems on board with standard protocol, instruct the class to record the protocol in the designated space on the handout so that they have directions to reference in upcoming classes.

Fourth, instruct groups to discuss how many samples each group will set up and how long the experiment should continue. Teacher Tips: Before approaching question 6 of the pre-lab, it may be necessary to review, as a class, the difference between control and experimental variables as well as differences in quantitative and qualitative data. Note resource availability, number of class sections, and typical daily schedule while guiding these conversations. Instruct the class to look through the rest of the lab packet to infer how data will be collected (question 9 of prelab).

Fifth, encourage groups to reflect on the protocol they have developed with their classmates. Ask what potential problems they see with the design as it pertains to the original objective of the investigation. Explain that these factors are experimental errors that must be accounted for when interpreting results. Teacher Tips: Reiterate to the class the importance of honest data collection; errors occur within experiments, and sometimes results do not align with initial hypotheses – and that is perfectly okay. However, these errors and results still need to be honestly communicated to be considered reputable in the scientific community.

Sixth, end the class by allowing students to choose what products they want to test. Teacher Tips: Sample-sized products are sufficient for lab purposes and may be purchased from a variety of chain retailers for around $0.50 to$3.00. If budgetary restraints are an issue or if students would like to test pricier products, students may bring in their product of choice for class use.

While collecting products for testing, review student allergies and known skin conditions. Common allergens associated with skin-care products include essential oils, fruit extracts, gluten, nuts, and some preservatives. All students should wear sterile disposable gloves throughout the lab. Students with sensitive skin, eczema, or allergies should refrain from handling products, including applying products to skin samples, and all students should be required to wash hands before leaving the lab. Additionally, impress upon students the purpose of testing skin-care products and reiterate that products should not be applied to their own bodies in lab. Be sure all students know how to work a scale before beginning the lab, and consider individual students’ needs throughout the lab. For example, a student with autism spectrum disorder or similar sensory disorder may find the physical sensation of various products and smells overwhelming and should be grouped appropriately and checked in with often. Students could also investigate the safety of skin-care products using the website of the Environmental Working Group (EWG.org), which shows ingredients in products, allergenics, and the safety of ingredients.

Orbeez should be placed in warm water at least 12–24 hours in advance of lab to allow maximum water uptake. If time management is a concern with particular classes, set short-term deadlines within the lab setup. For example, dictate to students that they will have five minutes to set up their control or 20 minutes to set up all samples and clean up their area. Accountability can also be delegated by designating roles within each group, such as “time keeper/task master,” “material collector,” “constructor,” and “data collector.”

While setting up skin samples, students should revisit the protocol they developed during the last class within their groups. All samples should appear fairly uniform, product samples should be measured before application, and all skin samples should be placed in approximately equal environmental conditions (i.e., equal distance from air vents and windows). Initial mass and qualitative data should be accurately recorded; mass data can include the mass of the container, as it will not affect percent change values. In addition, students should make a list of control factors in the experimental design that will be constant for all groups, like time and temperature.

At the beginning of each subsequent class during the data selection period, students should be reminded to record accurate data. To limit traffic, one group member can be designated as data recorder each day and may then share results with their group.

At the end of the lab, Orbeez can be thrown in the garbage. Orbeez should not be washed down sink drains, to minimize microplastic pollution.

Before gathering material and beginning the experimental setup, make sure your entire group understands what is going on.

1. Send one person to gather your skin containers and one person to gather skin cells while your other group members begin making masking-tape labels.

2. All control and experimental containers must be labeled with group initials and product being tested/control. Place the label on the bottom of the container so that it does not impede your view of the skin layers.

3. Place the desired amount of skin cells in each container.

4. Set one container to the side and label this as your control group. The control should have no product applied.

5. Carefully apply each skin-care product to each experimental container by mixing the skin cells and sample product together. Also, be sure to label each container so that you can make accurate observations later on.

6. In the table, record the initial mass of each skin model and sample product. This is one method of collecting quantitative data. Be sure to record which product has been applied to each container.

Included in the back of the Evaluating Skin-Care Products lab handout (see Supplemental Material) is a rubric for a final presentation of experimental results. If this avenue of data analysis is chosen, students will require one to three class periods to construct the presentation. Students should be encouraged to analyze both quantitative and qualitative results, and to draw conclusions with special attention given to total percentage change data. Emphasis should be placed on inferring conclusions from root-cause data – that is, each group should carefully examine the chemical composition of their tested products as well as consider all sources of error within their experimental design. Evaluations of products should be based in collected evidence and demonstrate deeper thought pertaining to the interactions and subsequent effects of products on skin. Groups should also consider the measured impact of the product in relation to the product’s marketed action claims.

The provided rubric could also be adapted to fit traditional lab report models, claim-evidence-reasoning (CER) reports, or small-group collaborative seminars where groups communicate results to one another.

Tables 2 and 3 are samples for experimentation. We recommend using ~1 teaspoon of Orbeez beads to experimental samples and collecting measurements across five or six days.

Table 2.

Sample quantitative data table.

Initial Mass, Day 1
(g)
Mass, Day 3
(g)
Final Mass, Day 5
(g)
Total % Change
Beads + Equate Cocoa Butter Lotion
Beads + Dove Men + Care Dry Spray
Initial Mass, Day 1
(g)
Mass, Day 3
(g)
Final Mass, Day 5
(g)
Total % Change
Beads + Equate Cocoa Butter Lotion
Beads + Dove Men + Care Dry Spray
Table 3.

Sample qualitative data table.

Initial Mass, Day 1
(g)
Mass, Day 3
(g)
Final Mass, Day 5
(g)
Control: Beads in air only Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Beads + Vaseline Petroleum Jelly Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Beads + Equate Cocoa Butter Lotion Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Optional Sketch
Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Beads + Dove Men + Care Dry Spray Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Initial Mass, Day 1
(g)
Mass, Day 3
(g)
Final Mass, Day 5
(g)
Control: Beads in air only Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Beads + Vaseline Petroleum Jelly Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Beads + Equate Cocoa Butter Lotion Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Optional Sketch
Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Beads + Dove Men + Care Dry Spray Description of Observations
Optional Sketch
Description of Observations
Optional Sketch
Description of Observations
Optional Sketch

The Evaluating Skin-Care Products lab fits well within the intermediate portion of an integumentary system unit, following introduction of skin anatomy and acting as a segue into discussion of complex skin physiology. The lab hits on independent thinking and design engineering advocated by the NGSS and supports facets of NGSS High School Life Science standards pertaining to operation of organ systems. Furthermore, teachers and students are afforded great freedom within the Evaluating Skin-Care Products lab to alter experimental design to fit the diverse parameters of public, private, or home education.

For optimal results, collect sample data over a period of five to six days. Remember, SAPs, although relatively cell-like, are not living organisms and thus do not metabolize or allow diffusion in a uniform fashion to human skin tissue. The five- to six-day period allows analysis of the products’ ability to retain moisture and, to some degree, prevent damage from environmental stress. Less than five days typically does not yield measurable differences in data-giving, only a murky view of each product’s properties. Impress upon students as they analyze results that Orbeez is intended to be used as an effective model, based on diffusion properties; before conducting the experiment, teachers may find it useful to review the concept of scientific modeling.

For extension and discussion activities, teachers could lead a discussion on identifying independent and dependent variables. In addition, teachers could incorporate math skills into this lab, such as graphing and determining averages. Further, teachers could include another group of plant cells, such as pieces of carrots or any fruits or vegetables that could be compared to animal cells.

Lastly, this lab was created with an intent to foster student enjoyment and connection to science. The core value and integrity of the lab can still be maintained while students explore other properties of superabsorbent polymers. If time allows, let students play with the Orbeez and/or conduct independent follow-up experiments. Observe what students come up with given some freedom – as an educator, this may further facilitate healthy, productive relationships with students, as well as enhance knowledge of students’ individual needs, wants, and goals.

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