Hydrogen and oxygen are two very important elements: water molecules (H2O) consist of two hydrogen atoms and one oxygen atoms. When you perform an experiment to decompose water into these two elements, you can test to see which gas you have. Hydrogen and oxygen react differently and those reactions help to identify the individual gases.
Hydrogen and oxygen are both colorless and odorless gases at room temperature. Hydrogen is a much smaller molecule, having a mass only one-sixteenth the size of an oxygen molecule. Although there is more hydrogen than oxygen in the universe, on Earth oxygen is the more common gas. In total, about 21 percent of the Earth's atmosphere is made up of oxygen gas.
The main way to test for hydrogen and oxygen is through experimentation with a burning splint (a small stick of wood). For this experiment, you need to collect gas samples in a glass jar. While the gas samples should be as pure as possible, a small amount of contamination from outside air is not a problem (most of the air consists of nitrogen gas, which does not affect the experiment). If you insert the burning splint into the glass jar, the result will tell you if you have hydrogen or oxygen.
If you hear a slight popping sound when you insert the burning splint into the jar, you have hydrogen gas. To test for oxygen in your glass jar, blow out the flame on the splint, leaving a glowing ember at the tip. When you insert the splint into the jar, it will burst into flame if the jar contains oxygen.
These experiments work because of the features of hydrogen and oxygen. Hydrogen mixes with the oxygen in air to produce combustion when a heat source is introduced. The heat from the splint ignites the hydrogen to create a small explosion. Burning is the reaction of oxygen with a fuel source, when there is a source of heat to power the reaction.
In these tests for hydrogen and oxygen, the introduction of a heat source is the catalyst for the chemical reactions. Both gases are relatively stable at room temperature; oxygen does react with many materials, but the effects are so gradual that you will not observe them over a short amount of time. The introduction of heat, in the form of the burning splint, allows for the faster and more vigorous chemical reactions that can identify your gases.
- Photo Credit "chemistry" is Copyrighted by Flickr user: Milosz1 (Miłosz) under the Creative Commons Attribution license.
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