Measuring the Rate of Oxygen in Air

Abstract

Iron Oxidation: Measuring the Rate of Oxygen in Air

Earth’s atmosphere, the huge ocean of air that covers the whole planet, is mostly nitrogen and oxygen, with smaller amounts of other gasses. However, I wanted to know how much oxygen do we really breathe in? How much oxygen is there really at sea level? Atop of a mountain like Mount Everest? For my project, I decided to test this out to see how much oxygen we really breathe in small portions. I decided to use iron rust, or Fe2O, which is the chemical result of iron rusting after being exposed by oxygen. My hypothesis was that if I used more steel wool in a test tube, then the percentage of the tube filled with water will decrease and the percentage of oxygen will increase because iron oxidation is able to remove the oxygen from the air and water.

My equipment included 4 cups, each cup about 10 centimeters tall and holds 300 milliliters; 4 test tubes, each one exactly 14.5 centimeters tall and about 1.3 centimeters wide; 4 ring stands with clamps to hold each test tube in the air; and 1 pad of steel wool. Firstly, I set up each of the 4 ring stands with a cup and a test tube. Next, I ripped off steel wool and rolled 4 balls of steel wool; one with a diameter of 1.5 cm, one with 2 cm, one with 3 cm, and one with 2.5 cm. I used a long, skinny wooden stick to put each sphere of steel wool into the bottom of each test tube. Afterwards, I filled each cup with 200 milliliters, and used the clamps on the ring stands to hold each test tube 50 milliliters above the bottom of the cup. I measured the water level for each cup, and every test tube had 4.5 centimeters of it submerged in water. I let the project sit for 6 days. This would be enough time for the iron oxidation to come into effect.

After 6 days, I took out my project and saw that each of the cups had similar, but decreased water levels. The first tube, the one with a 3 centimeter steel wool ball, was consisted of 20.7% oxygen. The next one, with a 2.5 centimeter steel wool ball, was consisted of 17% oxygen. The third test tube, with a 2 centimeter steel wool ball, was consisted of 13% oxygen. The fourth and last one, with a 1.5 centimeter steel wool ball, was only consisted of 10.3% oxygen.

There wasn’t much of a difference in each test tube in terms of the steel wool ball sizes. However, the percentages of oxygen in each tube showed a dramatic difference. My hypothesis was correct in the fact the more steel wool used, the lesser the water level inside the tube and the more oxygen in the tube. The only downside to this experiment, however, is the fact that it isn’t the exact amount of oxygen in each tube. There is still a percentage of the tube that is occupied by the steel wool ball. I could have improved this by doing more tests or trying other methods to reduce the water level. However, this was a learning experience because from this project I learned that when iron rusts, it traps the oxygen that rusts it, while also lowering the water level by replacing the empty space with oxygen.

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