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"Let us strive to make each moment beautiful."
Saint Francis DeSales
painting by Katie Bergenholtz

Synthesis of H2O

Now that we have decomposed water to its separate elements, let's synthesize the elements to make water. Take a candle (one a little bigger than this works better) and put it on the cap of a jar.
Once it is lit, put the jar on the lid and screw it shut.

Once the candle has used up all the free oxygen, and goes out, water will form on the inside of the jar. The oxygen and hydrogen have synthesized into water.

You can open the jar and if you are quick you can feel the water before it
evaporates away.


  1. Huh, I didn't know it did that. What a cool experiment.

  2. I love your current series on Chemistry. Although my kids are too young at this stage, it is a good opportunity for me to take my time to revise schoolwork!

  3. This is an example of combustion (or burning). Combustion of any organic substance (like the candle wax and wick) will produce carbon,carbon monoxide, carbon dioxide and water. This is where the water comes from. It isn't synthesis of water from hydrogen (gas) and oxygen in the air in the jar - there simply isn't enough hydrogen in normal air for it to do this.

  4. Yes, you are right, it is an example of combustion, but it is also an example of synthesis. I am sorry if it sounded like the hydrogen and oxygen were from the free air in the jar. The gases were produced by the combustion process, but they were still synthesized into water, and that is all the experiment was trying to show. A definition of synthesis can be found in many places that give chemistry terms; one that specificly mentions water synthesis is here:
    Hope I cleared up any misunderstandings. :)


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