The beginning of March 2020 seems like a memory of some time ago, yet it was the start of the life we are all presently living. The threat of the COVID 19 pandemic was increasing, and precautious measures were being taken almost everywhere. It was during this time, I received an email from my school director saying, “Can we please do this with the kids? I think this is a great way to show why washing hands is so important.” Attached to the email was an article describing an experiment that a teacher in Idaho had conducted with her students entitled the Power of Hand-Washing. Washing hands has always been a basic and important skill that you learn as a child and continue to use through life, but in March 2020 the world became obsessed with hand washing. After reading through the article I thought it seemed like a well-structured experiment, and a good segue into reintroducing the Scientific Method for future labs.
The original Idaho bread/hand-washing experiment took place across a four-week period and clearly illustrated the importance of the aforementioned task. Each slice of bread was touched by hands with varying levels of cleanliness, labeled, and put into Ziploc bags. By the end of the fourth week, the results on each bread sample demonstrated the levels of bacteria through the mold growth observed. Following the Idaho teacher’s guidelines, I set up the experiment with each of my three science classes, making it like a challenge to grow the most bacteria. The students were excited and hoping to get the “best” results. Big Questions ranged from: Which science class has the dirtiest hands? to Does washing hands really matter? Students then made hypotheses based on personal experience and educated inferences.
Each class set up the experiment as follows using a store brand white bread:
Five Ziploc sandwich bags per class
Bag 1 - Classes’ choice of what to wipe on the bread, e.g. students’ laptops, pencils, and the school water bubbler
Bag 2 - CONTROL bread untouched by hands and carefully placed in a Ziploc bag
Bag 3 - Touched by dirty unwashed hands
Bag 4 - Touched by hands washed with warm soapy water
Bag 5 - Touched by hands cleaned with hand sanitizer
Each student constructed a table in their science journals to collect data and record their observations over the next four weeks. As expected, by the end of the first week, students recorded ‘No Change’ under observations in their table. Although there was no change in the white bread, there was a “big change” for our school that week. We were transitioning to a remote learning mode with a potential end date of April 8,, 2020. This meant taking all personal belongings as well as anything that a teacher may need for teaching remotely for approximately four weeks. As I carried several bins full of folders and materials to my van, I passed the fifteen slices of white bread contemplating their value. Not having a clear path of where my first week of remote teaching would lead me, I decided that bringing home the bread could be an essential piece in starting that journey.
For the next two weeks, students were excited to observe the bread samples remotely through the “eyes” of my computer’s camera. However, after five weeks they were still recording “NO Change” into their data table. Each bread sample was fresh and devoid of visible bacteria and mold. This raised a few questions; were our school laptops, pencils and water bubbler perfectly clean? Did the students have clean hands to begin with? What is in the bread? Even if these items were clean to begin with, there was still the issue of no mold growth on the bread after five weeks, and that was enough time to raise an eyebrow. Our initial experiment was now changing into a new learning experience. I decided to put my eighth grade chemistry class to the task of investigating bread preservatives. A new Big Question was developed: What is in this bread that is allowing it to maintain its freshness? The culprit…calcium propionate.
Together we learned about calcium propionate and that it is used in many types of bread to extend the shelf life by fighting off the growth and reproduction of microbes such as molds and bacteria. We explored safe amounts of calcium propionate vs. the side effects of consuming too much. This raised an interest in finding more about the chemistry inside food preservatives. I created a WebQuest that introduced students to the chemistry of food preservation via several food preservative videos and websites. Each experience detailed why and how preservatives are used to extend the shelf life of foods. This introduction led into the study of preservatives in other items, such as cosmetics, wood, animal taxidermy, paints, and spices. Each student chose one of the listed products to research and created a slide deck illustrating the need of preserving it, how it is preserved, and what chemicals are used in the process. Eagerly, my eighth grade chemists prepared and presented their slides to the class in Google Hangouts. This was a first remote presentation for us, as students took turns sharing their screen and their discoveries.
Another week had passed and our bread samples still yielded no mold. Seeing that students were maintaining an interest in the preservative topic, I decided to take it a step further. What is the importance of food packaging relative to preserving its contents? Through our remote learning chemistry lab, aka my kitchen, I presented a variety of product packaging samples to students. We took a look at paper bags of flour, plastic bottles containing liquids such as water or soda, metal soup cans and chip bags. I let them think about, discuss, and propose reasons as to why the design of the packaging was such for the food that it contained. Students talked about how the containers were based on the materials used, the structure of the container, and it’s physical and chemical properties. We held discussions about what chemical reactions the design of the product’s packaging would prevent. Referring back to our bread lab, with each slice carefully sealed in a Ziploc bag, one class of students suggested that we make a change to the packaging of their class’ slices. By doing so we could possibly observe chemical reactions.
Learning about the importance of food packaging led students into designing their own food-packaging product. I supplied each student with the name of a specific food, and they were asked to create a quick vignette of a product that:
- Keeps the food clean.
- Protects the food product from unwanted physical and chemical changes.
- Clearly labels the product and provides sales appeal.
In the class time available, the eighth grade team produced fun, creative sketches as solutions to this design problem, detailing many of the packaging needs.
As I stand in my at-home chemistry lab examining each bread specimen, hoping to find even a small sample of bacterial cells, I reflect on the 11-week bread experiment: Ten of the fifteen slices of white bread still remain fresh and unmarked by microbes, bacteria, and mold. The five slices, which were exposed to air, show beginning signs of oxidation as they slowly become crusty and stale. Finally, the ‘take-away’ of this bread investigation demonstrates the true purpose of experimentation: What did we learn from the outcome? and How can we expand our inquiry further? In this case, the hypothesis of the bread experiment may not have proved correct, nor yielded any change, but the learning which it spawned, was well worth bringing home the bread.