As part of their science topic of chemical changes, Year 5 made bread using yeast. They learnt that the bread rises because of the release of carbon dioxide gas from the yeast. Respiration is a chemical reaction. Baking the bread causes the gas bubbles to expand and so the bread expands. They followed the recipe very carefully and spent a good deal of time kneading the dough before letting it prove twice. They were lucky enough to bake it and enjoy it as part of their lunch.