Session three preparations

When I (Marine) knew that I was going to have to take care of the third session “Why do we fart?” and it was going to follow on from the session where the kids made edible poo, I seriously asked myself how it would be possible to make my session as enjoyable and interesting for the kids as the previous week’s. My idea formed relatively quickly: some yeast (representing the gut microbiota), some sugar or flour (representing the different foods we eat), and some warm water in a flask, all topped off with a balloon. I knew fermentation of the sugar by the yeast in the flask would produce gases (farts!) and make the balloon inflate. And in my mind I could definitely see the kids enjoying the role of mini chemist and having fun with the inflating balloons, wondering whether they would explode at some point!

Combining food (sugar or flour), gut microbes (baker’s yeast) and water in a flask (the intestines) would mimic the way gut microbes produce gases responsible for flatulence.

I prepared my session by looking at some experiments posted on the Internet, and adapting what I found. Initially, the experiment I designed involved seven flasks per group of four students and was quite complex. However, following the first session, run by Holly and Grace, I realised I was being ambitious in what could be achieved in one hour, so I simplified the experiment. I wanted the kids to remember the main take-home messages of the session – that gut bugs make us fart, and they need food and warmth to do this. I had two practice runs prior the session, to adjust the quantities of ingredients needed for the experiment and to ensure the required results would be achievable within one hour.

Each group of four students would set up four flasks to determine what makes us fart. The first flask would contain warm (37 °C) water, sugar and gut microbes. The second would contain warm water and sugar but no gut microbes. The third would contain warm water, flour and gut microbes. The fourth would contain cold tap water, sugar and gut microbes. The kids would then put a balloon on top of each flask to capture gas produced. They would then be asked to predict what would happen in each tube during a 15-20 minute incubation.

Before the hands-on part of the session, I planned to give the kids a brief explanation about what flatulence is and why we fart, so they could understand what we were trying to do with our experiments. After the kids had set up their experiments, I wanted to take the opportunity to introduce them to the concepts of a hypothesis, variability and replicates. By discussing with the kids what would they thought would happen, I thought it would give them a better understanding of how gut microbes make us fart. The students would be split into three groups, each of them doing the same set of four experiments. This would allow them to compare their results, and understand variability and why repeating an experiment and taking mean results is more accurate than doing an experiment only once. They would also learn how to analyse and report their results.

At the end of the incubation, the kids in each group would measure the height of each of their balloons and record the results. They would then compare their results with those from the other two groups, and discuss the differences in results between each flask and each group.

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