Science Buddies: "Ask an Expert"

My son put seven different kinds of fruits in plastic bottles and covered with a balloon. We wanted to see which balloon would inflate the most as the fruit decomposes. Some of the balloons were sucked inside the bottles and inflated. What would cause this to occur?

Off the top of my head, if the reaction is aerobic (uses oxygen), I can envision a chemical reaction where oxygen is utilized in the breakdown of certain chemical compounds, and fixed to a new resulting chemical compound. Thus a gas is converted into a solid or liquid and their is a net loss of gaseous volume in the balloon.

There is an interesting discussion of aerobic and anaerobic compost teas on this web site:

http://faq.gardenweb.com/faq/lists/orga ... 09975.html

There is also a great discussion of composting on this site:

http://faq.gardenweb.com/faq/lists/orga ... 09975.html

They go into discussions of aerobic and anaerobic bacteria and their use in composting, which is after all decomposition of organic material like the fruits that you used.

It's also possible that nitrogen fixing bacteria are involved and the nitrogen component of air is the part that is decreasing. I would think that this would be a less likely explanation, however.