In a science Experiment showing the splitting of water into oxygen and hydrogen two invert a test tubes of water were placed over the site of the reaction. How can you tell which one was catching the oxygen and which one was catching a hydrogen?

The hydrogen is a positive ion it will be located close to the negative terminal of the battery.

The oxygen is a negative ions which will be located next to the negative terminal of the battery.

There are two hydrogen atoms for every oxygen atom, the hydrogen will take up more space and is pushing the water lower in the test tube.

The hydrogen, being a smaller atom, will take up less space than the oxygen, it will push the water down less.