What Happens When You Add Oil to a Baking Soda Experiment

11 January

I think everyone has made a baking soda volcano at some point; I mean who can resist that bubbly explosion! Every time I get the chance, I mix up another baking soda volcano. Well, maybe not quite that often, but a year, maybe even a semester, doesn't go by without one.

We have also added dawn dish soap and glitter to form our foamy Fairy Potion. The kids repeated the fairy potion over and over as well, so I started wondering what else could I add? What could I show them?

My answer: oil.


Why oil you are probably wondering, well have you seen the homemade lava lamps? They are a fun experiment that proves oil doesn't mix with water. In fact oil is less dense then water, so it sits right on top of the water.

Turns out, oil is less dense then vinegar as well. So how would that layer of oil affect the baking soda and vinegar reaction? We were going to find out.

Supplies Needed for a Controlled Baking Soda and Vinegar Experiment

  • 3 glasses or jars
  • 3 pans with sides 
  • vinegar
  • baking soda
  • vegetable oil
  • dish soap
  • food coloring (optional)


To Control a Baking Soda and Vinegar Reaction


To set up your experiment start with 1 glass in the middle of each pan. In the first glass and vinegar and food coloring if you like. In the second glass add vinegar with dish soap and another color, and in the final glass add vinegar, a third color, and a thin layer of vegetable oil.



The first 2 glasses in this experiment act as controls because they behave in an expected way. We could have used a negative control as well where we filled a fourth glass with only oil and added baking soda which produces no reaction.

Now for the fun! First we added baking soda to our plain vinegar and got an erupting glass of fizz! Acted just as expected, but because baking soda and vinegar is awesome I still got ohhhs and ahhhs from my girls.


Then we added baking soda to our vinegar and dish soap glass and got an erupting glass of foam. At this point the girls really just wanted to play in the fluffy foam, but I convinced them to move on promising we could play after.


Finally we added baking soda to our glass with the vinegar and oil.  The baking soda immediately started making bubbles, but it had a hard time getting past the oil.  So instead it created a fizz at the top of the glass very similar to what happens when you pour warm soda on ice.  


Once it calmed down a little you could see the bubbles moving through the oil similar to the Lava Lamps we made last year.

 The oil allowed us to control the reaction and not make a huge mess!


After some time just watching the bubbles go up and down, but never escaping, I grabbed some more dish soap. We knew from the magic milk experiment the soap would grab onto the oil.  So in it went! We gave it a little stir, and out came foam!  The dish soap grabbed the oil allowing the bubbling vinegar underneath to escape the glass.


I think this experiment definitely demonstrated how adding different things can change the end result. It also reinforced the fact that oil is less dense then other liquids, that soap really does grab oil (or fat) to help wash it away, and that baking soda and vinegar is simply awesome kitchen chemistry!

As promised the girls played with all the bubbles from all the glasses, and they even repeated it because baking soda and vinegar just never gets old!


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