The Chemistry of Hand Sanitizer and Soap Mark as Favorite (133 Favorites)
LAB in Intermolecular Forces, Polarity, Molecular Structure, Molecular Structure , Functional Groups, Unlocked Resources, ChemMatters Teaching Resources. Last updated April 19, 2023.
Summary
In this lab, students will model the interaction between hand sanitizer particles and virus particles, as well as between soap particles and virus particles. They will apply their understanding of molecular structure and intermolecular forces to analyze their observations and behavior of the particles, in order to gain a better understanding of how soaps and sanitizers work.
Grade Level
High School
NGSS Alignment
This lab will help prepare your students to meet the performance expectations in the following standards:
- HS-ETS1-1: Analyze a major global challenge to specify qualitative and quantitative criteria and constraints for solutions that account for societal needs and wants.
- HS-ETS1-3: Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics as well as possible social, cultural, and environmental impacts.
- Scientific and Engineering Practices:
- Developing and Using Models
- Constructing Explanations and Designing Solutions
Objectives
By the end of this lab, students should be able to:
- Identify parts of a molecule as polar and non-polar.
- Predict the types of intermolecular attractions between molecules based on their structures.
- Make connections between molecular structure and the observed behavior of substances.
- Explain how both soap and hand sanitizer work to destroy a virus particle.
- Differentiate between the behavior of hand sanitizer and soap on the particle level.
Chemistry Topics
This lab supports students’ understanding of:
- Molecules & Bonding
- Intermolecular Forces
- Polarity
- Molecular Structure
Time
Teacher Preparation: 10 minutes
Lesson: 30 – 40 minutes
Materials
- 2 Small Paper Plates
- Tap Water
- Black Pepper
- 1 drop of Liquid Soap
- 1 drop of Hand Sanitizer
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.
Teacher Notes
- Teachers should begin this activity by showing the following ACS Reactions videos to students:
- For a video walk through of this activity, teachers can view this video.
- You may want to assign reading from the accompanying ChemMatters article titled What is Hand Sanitizer, and Does it Keep Your Hands Germ-Free?
- An answer key has been included for teacher reference.
- This activity has been made available in the AACT Classroom Resource Library with the consent of the original publishing source, McGraw Hill.
- Special thanks to Chemistry in Context, 10th edition. A partnership between ACS and McGraw Hill. Click here to request a review copy and/or order.
For The Student
Background
The behavior of soaps and hand sanitizers is an application of the principle “like dissolves like.” Polar molecules such as alcohols contain certain functional groups (-OH in the case of alcohol) that are attracted to water, forming strong intermolecular interactions. In contrast, nonpolar molecules such as oils and biomolecules (ex: fats, proteins) are composed of hydrocarbon groups (-CxHy-), which are not attracted to water. The active ingredients of soaps and hand sanitizers feature the best of both worlds, with both polar and nonpolar regions in their molecular structures. As a result, part of the molecule is attracted to organic molecules such as proteins and fats, whereas the other part is attracted to water:
Objective
What happens when soaps and sanitizers interact with a virus? Since viruses are coated with a variety of fats and proteins, the nonpolar regions of the soaps and sanitizers are attracted to this coating, effectively pulling apart the virus structure. In this activity, you will model this behavior.
Materials
- 2 Small Paper Plates
- Tap Water
- Black Pepper
- 1 drop of Liquid Soap
- 1 drop of Hand Sanitizer
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.
Procedure
- Add tap water to two empty paper plates.
- Sprinkle black pepper flakes onto the water surfaces.
*Note: The black pepper represents the virus particles, which are coated with nonpolar fats and proteins and are therefore not soluble in water. - Add a drop of soap to the first plate. Describe your observations in the data table below, using the “like dissolves like” principle.
- Add a drop of hand sanitizer to the second plate. Describe your observations in the data table below, using the “like dissolves like” principle.
Observations
Analysis
- Describe how your observations of the soap differed from your observations of the hand sanitizer.
- It is widely reported that washing your hands with soap is more effective against bacteria and viruses than using hand sanitizer alone. Is this premise plausible based on what you observed in the activity?
- Use the internet to find out more about the structures of soaps and detergents. Explain why hand sanitizers would not be as effective as detergents to clean your clothes in washing machines.