Day 159: Splitting Water Molecules with a 9-V Battery


Got the idea from this video. The water has baking soda added to increase conductivity (seems to work better than salt). However, I wasn’t getting quite as much gas produced (lots of hydrogen, not much oxygen). And the kids were having a hard time balancing the cup on the battery while holding the test tubes. So after class, I just dropped the 9 V battery into the cup. Great results! I was able to completely fill small test tubes with hydrogen and oxygen. I was able to get a small “pop” by holding a flaming splint under the hydrogen test tube. I was not able to get a glowing ember to brighten by putting it inside the oxygen test tube. (The chem teachers told me they have similar troubles even when using the Hoffmann apparatus.)

It was also hard to get a 2:1 ratio of H2:O2 — chem teachers said that O2 readily dissolves in water, so I’m not collecting all the O2 that is produced.

However, I like how simple this is…very easy for kids to recreate at home and show their siblings and parents!

UPDATE: Via @ryanabuckWhy O2 isn’t produced when using salt water.


About Frank Noschese

HS Physics Teacher constantly questioning my teaching.

3 responses to “Day 159: Splitting Water Molecules with a 9-V Battery”

  1. Chris K says :

    Frank – this is fantastic! Love the simplicity of this. One extra fun thing you could do is to squeeze out the gases into a concentrated mix of detergent and water and then light it with a match/taper. I did it using a syringe and the Hoffman apparatus and it went off in a big way!

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