Electrolysis Of Water Science Experiment

My daughter is spending time with her grandparents this summer and enjoying every bit of these precious moments. Also, when Grand-dad is a chemical engineer, how can her day go without some science fun?

It's always interesting to learn science through hands-on experiments. Therefore, our Grand-dad and Grand-daughter team is on a science experiments spree. First one in the series is 'Electrolysis of water' which was instantly decided on the dinner table when talking about water (read it the chemical composition of the water).

If you don't know already, water electrolysis is the decomposition of water into oxygen and hydrogen gas due to the passage of an electric current.


electrolysis of salt water experiment

Although my 4-year-old is a little young for this experiment, she totally enjoyed the process and was fascinated by the water bubbles generated by electric current separating the two gases. I think any kind of bubble is fun for kids, won't you agree?

Now, she understands that water is made of hydrogen and oxygen molecule. In the experiment, we are separating the components of the water which she sees as the gas bubbles.

If your kids love STEAM or STEM projects like mine, then do check back on the blog for more science fun in coming weeks. You can also get regular updates on our new post by subscribing to our email list (link at the end of the post) or following us on Instagram or Facebook.

electrolysis of water experiment introduction

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Cardstock Paper
Battery 9V
Lead Pencils (2)
Pencil Sharpener


Step 1: Take a glass and half fill it with water.

Step 2: Add a little salt to the water and stir it well.

Step 3: Sharpen both ends of the pencils. Try to keep the length of both pencils the same.

Step 4: Cut a rectangular piece of cardstock paper such that it covers the glass properly.

Step 5: Carefully push both the pencils through the cardstock paper roughly 0.5" apart.

Step 6: Place the cardstock paper with pencils on top of the glass. Adjust the pencils such that their ends are at the same level in the water.

Step 7: Hold the battery on top of the pencils such the battery nodes are touching the pencil lead. Wait a few seconds for the fun to begin!


In this experiment, electric current moves from the battery through pencils to water and salt. Water is decomposed into oxygen and hydrogen gas as it is made of these basic elements and form bubbles around the pencil tip. Based on the electric polarity hydrogen molecules emerge around the pencil end connected to the battery's positive node(+) and oxygen on the pencil connected to the battery's negative node (-).
2H2O ---- Electric current --> 2H2 + O2

Also, since water has two molecules of hydrogen for every one molecule of oxygen, you can say that pencil tip which has more bubbles is attracting hydrogen and the other one is getting oxygen.

Also, we added salt (sodium chloride or NaCL) in the water because it acts as an electrolyte helping with the flow of electric current. Salt in the water get decomposed too.
2NaCl --> 2Na + Cl2
Chlorine form bubbles smell pungent.

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  1. That's a good fun educational activities for children

    1. Thank you! My daughter loves doing science experiments.

  2. Wow.. please share more of such easy experiments