Biology SL Conclusion and Evaluation on Oxygen Concentration Experiment

Conclusion and Evaluation

        The experiment carried out in class was designed to test:

• How Oxygen concentration changes in lungs when a person’s breath is held.
• How hyperventilating lungs affects Oxygen concentration in lungs.

Oxygen concentration in the air is 20.9%. The oxygen measuring device measured an 18% concentration in the air, which is perfectly acceptable. A plastic bag was wrapped around the end of the oxygen measuring apparatus and the air in it was removed. The plastic bag had a hole at its bottom. The person being tested held their breath for an extended period of time (about 60 seconds) and then exhaled into the plastic bag. The oxygen measuring device recorded a drop of 3% in Oxygen concentration. This means the concentration of oxygen in a person’s lungs changed from 18% to 15% when their breath was held for about a minute. Therefore we can say that not much oxygen is used up by the lungs when your breath is held. In fact only about 16.6% of the all the Oxygen inspired is used when your breath is held. A problem that occurred frequently with other groups was that the hole at the bottom of the plastic bag was very big. This resulted in an unwanted exchange between oxygen richer and oxygen poorer airs and this made oxygen concentrations fluctuate. A simple reminder that could prevent mistakes like these from happening would be to add a reminder in the experiment guidelines such as “(REMINDER: be sure not to make the hole too large in the bag. It must be small and tight enough to fit your mouth in.)”