Question

How does yeast cause bread to rise?

Answer 1

Yeast can use carbohydrates as food. When they do this they produce carbon dioxide as a waste product. The carbon dioxide gas makes the bread dough rise.

Explanation:

Both fermentation and aerobic respiration break down carbohydrates to release energy the yeast cells use to power their activities and produce carbon dioxide as a waste product

Here is a video which shows an experiment using yeast fermenting a solution of sugar water. Yeast cells can carry out either fermentation or aerobic respiration depending on environmental conditions.

Video from: Noel Pauller

Hope this helps!