Same Stuff, So What's the Difference?
Science Connection: Get out the science book! For breathing animals like us, oxygen, of course, is the air's number one chemical in quality, so sometimes students have trouble with the concept that air is not just oxygen. Some may find it surprising that the air we breathe also contains (traces of) neon, krypton (not kryptonite!), helium and xenon.
If your class does the math activity on the 'Interactive Page,' point out that the results are just a rough estimate. To get more scientific results, students would need to consider such things as the body's rejection of excess protein and storage of excess carbohydrates, the role of exercise and other biochemical considerations.
Related topics: chemical content of food; the chemical content of people; the chemical content of things in our environment; the function of taste in determining our diet.
Food for thought: How are foods the same and different at the same time? Why is it true, in a way, that "you are what you eat?"