Summary

In this demonstration, students will consider the purpose of using both hand sanitizer and soap to wash their hands. They will observe a model of the interaction between hand sanitizer particles and virus particles, as well as between soap particles and virus particles to gain a better understanding of how soaps and sanitizers work.

Grade Level

Elementary and Middle School

NGSS Alignment

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

• K-2-ETS1-3: Analyze data from tests of two objects designed to solve the same problem to compare the strengths and weaknesses of how each performs.
• 5-PS1-1: Develop a model to describe that matter is made of particles too small to be seen.
• MS-ETS1-3: Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.
• Scientific and Engineering Practices:
  • Developing and Using Models
  • Constructing Explanations and Designing Solutions

Objectives

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

• Explain that the particles that make up different types of matter are unique.
• Describe that some types of matter will mix with each other, while others will not.
• Make connections between molecular structure and the behavior of soap and hand sanitizer.
• Provide a basic explanation of how both soap and hand sanitizer work to destroy a virus particle.

Chemistry Topics

This demonstration supports students’ understanding of:

• Molecular Structure
• Molecular Interactions
• Mixtures
• Observations
• Physical Properties

Time

Teacher Preparation: 10 minutes

Lesson: 15–20 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 wear proper safety gear during chemistry demonstrations. Safety goggles and lab apron are required.
• 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

• This project was originally designed as a lab for high school students, The Chemistry of Hand Sanitizer and Soap. This demonstration is a modification, inspired by that resource, for use in the elementary or middle school classroom.

• For a video walk through of this demonstration, teachers can view this video.
• This is designed as a demonstration, however depending on the age and ability of the students, it can be used as a lab activity instead.
• Depending on the grade level of the students, the teacher may want to complete the provided handout as a class. Alternatively, students could work together in small groups to brainstorm and discuss their observations before sharing them with the class.
• If the teacher plans to do this demonstration multiple times, it’s important that the plate be completely cleaned of any soap or hand sanitizer before doing it again.

Background information:

• Black pepper flakes are used to represent the virus particles in this demonstration. Virus particles are coated with nonpolar fats and proteins and are therefore not soluble in water.
• Soap contains particles that are called “surfactants”. These particles are important because they are attracted to the fatty coating of virus particles. The surfactant will surround the virus particle when it comes in contact, and essentially pull the virus particle apart, destroying it. Since soap is used in combination with water, after the interaction, there is an added benefit—everything is washed away in the sink.
• Hand sanitizers typically contain alcohol as the active ingredient. Alcohol has a similar interaction with virus particles as the surfactants in soap do. Alcohol breaks the fatty coating of the virus particle, which leads to destroying it. However, in order to be effective, a hand sanitizer should contain at least 60% alcohol. Additionally, a lot of hand sanitizer needs to be used to be effective, and it needs to come into contact with the virus particles on the skin in order to work. Some people don’t realize that the alcohol in the sanitizer can evaporate very quickly, which means evaporation can occur before germs or virus particles are destroyed.
• Additional background information about the use of hand sanitizers can be found in C&EN Magazine.
• An Answer Key document is available for teacher reference.