Effervescence :: Inquiry in Action

Inspiration struck me the other day while we were enjoying our lunch – Buddy and I had selected sushi while Sweetie, not one inclined to eat fish of any sort, selected mini toasts with an assortment of cheeses and sliced meats.  Once in a while, I allow the kiddos to share a soda with their lunch and this day was one of those occasions.  I asked them to observe the little bubbles that were rising up and asked if they knew what they were.  Sweetie replied, “I think they are carbon dioxide gas escaping into the air.”  
“You are right!” I explained.  “Each bubble we see in the soda is a collection of carbon dioxide gas.  Carbonated beverages like soda are made by dissolving large amounts of CO2 in flavored water.  This excess amount of COis able to stay in the liquid because it is pushed with high pressure into the bottle (or can) and then immediately sealed.  The  bubbles that are rising in the soda re escaping CO2.”    
I then asked them what they thought would happen if I were to drop a teaspoon of salt (NaCl) into the soda.  Buddy hypothesized, “The salt will sink down to the bottom of the glass and  push some of the bubbles up.”  Indeed, that was our result.  I then asked them to sketch their observations / set-up … here is Sweetie’s journal page:

I talked to them about what was taking place during this reaction. NaCl and CO2  are both examples of matter and matter takes up space.  When the salt is added to the soda, it pushes the bubbles of carbon dioxide out of its way. These bubbles rise to the top bringing small amounts of the flavored water (soda) with them.  This movement of the gas forms the foam on the top of the liquid.  Replacing a gas with another substance is called effervescence.  In other words, effervescence is created by dissolving a gas in a liquid and then adding a soluble solid (salt).  

As I explained this to the munchkins, they came up with their own experiment question, “What about sugar then? and flour?  Will they make the soda foam up too?”  “Let’s find out!” I replied.  Indeed, sugar worked!  We didn’t have enough soda (I didn’t want to open another can) to test other solids .. but I promised them we could continue this experiment again.

What intrigues me about this activity is that it is one that is frequently found in science experiment books for children, like Janice VanCleave’s Chemistry for Every Kid.   While these books are excellent introductions to science … they are not considered true INQUIRY by science standards.   The National Science Education Standards (NSES p.23) defines scientific inquiry as “the diverse ways in which scientists study the natural world and props explanations based on the evidence derived from their work.  Scientific inquiry also refers to the activities through which students develop knowledge and understanding of scientific ideas, as well as an understanding of how scientists study the natural world.”


The activities in these books are great hands-on activities that help to demonstrate key scientific processes or concepts yet they are not true inquiry.  This is one of my biggest pet-peeves or frustrations with curricula and books targeted for parents.  Parents must use caution, therefore, when considering these for use in science fairs.  However, most of the activities can easily be adapted or modified … by applying inquiry processes … to achieve the goals and standards set by NSTA and/or the state benchmarks.  


I’ve always said that if the student can phrase their experimental question, to fit the pattern:  How does ________ affect ________ ?  then they are all on their way to developing a successful inquiry project that will do well in a traditional science fair.

About Eva Varga

Eva is passionate about education. She has extensive experience in both formal and informal settings. She presently homeschools her two young children, teaches professional development courses through the Heritage Institute, and writes a middle level secular science curriculum called Science Logic. In addition to her work in education, she is an athlete, competing in Masters swimming events and marathons. In her spare time she enjoys reading, traveling, learning new languages, and above all spending time with her family. ♥