Measuring the oxygen content of air project

[zz123r2012]

I have set up my project and am on my first day of taking results.
1. Does this project have to be done outside? I put the test tubes out overnight and two jars of water froze.

2. Are the test tubes supposed to be just slightly above the surface of the water or fully submerged into the jar of water? I put the test tube at the level of water a little bit down from the mouth of the test tube, but how can I make measurements on the side of the tube when it was already air farther into the test tube? Shouldnt I be measuering how much the water evaporated?

[Administrator note: Project URL: https://www.sciencebuddies.org/science- ... f-air-rust ]

[aredlife1]

Hi, it does not look like the experiment has to be done outside. Very low temperatures may in fact slow the oxidation (rusting) process and also freeze the water like it did in your first attempt. The experiment can be done indoors under stable temperatures.

The “mouth” of the test tube should be submerged in the water. This is to ensure that the trapped air inside the tube has no contact or air exchange with the atmosphere. As that air (oxygen from that air) gets used for the rusting, the water level in the test tube will rise. The measurements taken will be of the initial water meniscus and final water meniscus.
Hope these videos help:
https://www.youtube.com/watch?v=xQNl2EdteDE
https://youtu.be/anJiPEjWeO4?si=n8DmFAl2XJMCnNxQ