Science Smarts: Fizzing eyeballs

By Patty Rooks on October 25, 2025.

In continuing with my promise to my loyal readers, it is time to continue preparing for those Halloween celebrations you may have. I think that science and Halloween just go together, and it is so exciting to share the fun ooey, gooey and oozing activities I keep just for this time of the year. This week we will learn about acid/base reactions with some at home materials that will be easy to gather or will they?! Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– NaHCO3 (sodium bicarbonate, or baking soda)

– CH3COOH 3% or 5% (acetic acid, or vinegar)

– H20 (dihydrogen monoxide, or water)

– Food colouring (optional)

– Six plastic eyeballs

– Measuring cup

– Measuring spoons

– Mixing bowl

– Mixing spoon

– Baking tray

– Two or three plastic/clear cups or containers

Procedure

1. In the bowl, mix 500 mL (two cups) of sodium bicarbonate with 125 mL (half cup) of dihydrogen monoxide. Stir well to make a paste.

2. Mold this paste around the plastic eyeballs.

3. Allow the eyeballs to firm up for several hours or overnight.

4. Fill the plastic cups about half full of acetic acid (if you wish add a few drops of food colouring to make it especially eerie.

5. Carefully drop in an eyeball.

6. Observe.

What is going on?

To start off, the experiment may have looked complicated and perhaps you thought that you could not do it because you could not find the “chemicals.” As you learned, sometimes, “chemicals” can be as simple as everyday household objects. I hope you did not give up when you started reading the materials list.

What you did here was a simple chemical reaction. When you added a base (the baking soda eyeballs) to an acid (the vinegar in the glass), fizzing began. This fizzing with all the bubbles and gas escaping as the result of the chemical reaction – an odorless and colourless gas CO2 or carbon dioxide was the result.

If you want to dive more into the chemical reaction, this is what it would look like if you wrote it out (BUT I think explaining it is a lesson for another day!):

NaHCO3(s) + CH3COOH(l) -> CO2(g) + H2O(l) + Na+(aq) + CH3COO-(aq)

Breaking news:

Save the date for the southeastern Alberta Regional Science Fair. It will take place on Saturday, March 21, 2026. Mark your calendars and start thinking of what you will do. I cannot wait to see all of the students from all over southeastern Alberta there. As well, do not forget that Praxis is here to support classrooms and schools with their in house science fairs!

Patty Rooks, senior scientific consultant Praxis Science Outreach Society. Praxis has moved! We are very fortunate to be located in the Community Futures Entre Corp Building at #202 556 Fourth St. SE, Medicine Hat, Alberta, T1A 0K8. For all your science needs, please email praxis@praxismh.ca.

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