In early December, all Class 4 students joined Ms. Berg’s Zoom room to meet microbiologist Dr. Denise Tombolato-Terzić. A native of Brazil, Dr. Tombulto-Terzić currently works in the Department of Molecular Biology and Chemistry at Christopher Newport University and, on this day, joined Class 4 to share her vast expertise.
“Welcome Class 4 scientists! I’m excited for our first ‘Meet the Scientist’ this year,” Ms. Berg announced.
“Thank you for this opportunity,” Dr. Tombolato-Terzić said smiling, with luscious greenery surrounding her. “I also have a 4th grade girl. She’s upstairs on her own Zoom!”
Dr. Tombolato went on to tell the students that she came to the United States to acquire her masters and PhD. “When you’re a doctor – but not a medical doctor – that means you have a PhD. That’s what I have!”
The captivated students listened intently as she continued. “Be skeptical,” she advised. “Don’t believe me just because I have a PhD. You should always be asking questions. I love when people ask me questions!”
Dr. Tombolato then began by offering a brief introduction to pH (a scale from 0-14 used to specify the acidity or basicity of an aqueous solution). “Do you know what contributes to climate change? The same culprit causes change in pH,” she prompted.
“Methane!” Several students exclaimed. While this is true, Dr. Tombolato noted that 81% is due to Carbon Dioxide (CO2).
So, what does CO2 do exactly? Dr. Tombolato demonstrated its effects by setting up an experiment with nothing but a clean, clear cup of water. By exhaling through a straw into the cup, she added CO2 to the water. The observers noted, however, that they couldn’t immediately tell the difference.
“Right. You can’t see with your eyes just yet,” Dr. Tombolato said. She then repeated the experiment, this time using cabbage juice. As she exhaled, the pigment of cabbage juice began to change from a dark purple to a lighter pink hue.
“CO2 lowers the pH of water,” she explained, using Legos to represent H2O and CO2 molecules. “With more CO2, water becomes more acidic – like vinegar. The more hydrogen ions, the lower the pH,” she noted that we want water to be in the middle of the pH range (typically 6.8-7.8). Dr. Tombolato, a humorous and kind guest speaker, kept the students, who hung on her every word, engaged throughout.
But why did the color change? What does that have to do with pH? She conducted a new experiment using three clear cups, with the first being composed of only cabbage juice to be used as the control.
In the second cup, she added baking soda (a basic element with a pH greater than 7) to the cabbage juice. With a quick swirl, the dark liquid became a turquoise blue.
Next, she added an acidic powder (with a pH less than 7) to the third cup of cabbage juice and it transformed into a vibrant pink liquid. Amazed, a student exclaimed, “Tiny things can make such a big difference!”
The mixture becomes more acidic as more CO2 is added, thus, the pinker it became. “When you’re doing science, you want to be having fun!” encouraged Dr. Tombolato.
After giving their guest many thanks and a round of applause, the Class 4 scientists headed off to lunch, minds churning with inspired ideas.