Session three – why do we fart?

A lot of excitement from the kids and stress for me (Marine) the day of the farting session! The session on how our digestive system works the previous week had been a huge success, so the pressure was on to make this session fun and to keep the kids motivated and engaged.

Before the kids arrived, we prepared three “lab benches” with all of the materials for the experiments ready and waiting.

Everything ready for the kids to conduct their farting experiments.

To save time, all the dry ingredients had been weighed out in advance. The kids only had to pour the ingredients into the flasks along with the water. I deliberately placed the lab benches at the back of the classroom, so the experiments could be left to incubate without distracting the kids while I went through some of the theory behind the experiments and what they were going to show us.

When the kids arrived, I gave a short (5 to 10 minute) introduction to the session, during which the kids showed a lot of interest in the subject. Then we started the hands-on part. It was wonderful to see the kids helping each other and working as teams to set up the best experiments they could!

The kids carefully followed their protocol and shared the tasks among group members.

Each group managed to set up their experiments within 15 minutes, and all the kids were quite curious about what would happen next. Like true little scientists, the kids cleaned up their benches before returning to their desks! 🙂 They then sat to watch a video on how gas is produced in the large intestine, and I talked to them about what a hypothesis is and why replicates are important in experiments. They were quite pleased to find out what makes their farts stinky – sulfur. One of the boys said he knew why his Dad’s farts smelled so bad: he must produce a lot of sulfur because he eats lots of eggs!

While the kids learned the theory behind farts, their experiments were left to incubate.


A video explained why some farts smell while most don’t. I then talked to the kids about the hypothesis for our experiments, and asked them which balloon they thought would have most gas in it based on what we’d learned about how gut microbes produce gas from the food they eat.

After going through the theory and leaving the experiments to incubate for 15 minutes, everyone went back to their experiments, excited to see their results! The kids carefully measured the height of each balloon and recorded their results on a graph.

The results of the experiments showed that gut microbes produce most gas when they have a carbohydrate source (sugar) and warmth, conditions similar to those found in our large intestine.


Much to the team members’ delight, the yellow team (group 2) had the balloon with the most gas at the end of the experiment.

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