We’ve learned that microorganisms can be helpful or harmful to human life. Today we learned about a single-celled microorganism that has been around for hundreds of millions of years and is very useful in baking. Yeast.

We did this experiment – Yeast is added to a warm sugary solution in a bottle and it starts to feed on the sugar and produce carbon dioxide. A balloon placed over the neck of the bottle inflates as the carbon dioxide is released. Here’s our bottle and balloon after about 20 minutes.


Earlier in the day, each table team had made bread dough – some with yeast and some without – and we’d left it to prove in the school boiler room. After a couple of hours, we could see that the dough with the yeast had risen and the other hadn’t. We learned that this was because the yeast, feeding on sugars in the flour, produces carbon dioxide (just as in the balloon experiment), which is then trapped in millions of bubbles in the dough, causing it to expand and leaving air pockets in the eventual baked bread. We baked our bread and ate it at the end of the day and it wasn’t bad!



Author: class6TM

We are a Year 6 class at Rosendale School in West Dulwich, London.

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