Asubstance that affect the reaction without being changed

The oxidizing agent our bodies use to obtain energy from food is oxygen (from the air). if you breathe 15 times a minute (at rest), taking in and exhaling 0.5 l of air with each breath, what volume of air do you breathe each day? air is 21% oxygen by volume. what volume of oxygen do you breathe each day?

How long does it take a skateboarder going 6.0 m/s to come to a complete stop if she slows down at a rate of 2.0 m/s^2

3differences between bacteria and other 2 cells