Steve asked me if I wanted to do the Carbon Dioxide experiment and I excitedly said YES! After three days of reading the manuals, observing the experiments and shadowing the facilitators, I finally felt I was ready to lead one of the experiments on my own.
"Playing" with the kids before the experiment
We conduct experiments at the Spark!Lab every hour on the hour from 11am to 3pm. I was going to do the first experiment of the day. Since it was still early into the day, there were not too many kids around, which was good because a smaller group is easier to manage. I announced that we will be conducting an experiment in five minutes and kids who want to participate should grab a seat on the lab’s bench.
I handed each kid a pair of safety glasses while explaining the importance of listening and paying attention during the experiment. Although we do not use any hazardous chemical, the safety goggles add a touch of seriousness and excitement to the experiment. I asked if anyone knows what carbon dioxide (CO2) is and some of the kids volunteered information such as it’s what we breathe out. I gave them additional background information about CO2, including the fact that it’s odorless and colorless. I asked them to inhale deeply then exhale and explained that, as one of the kids pointed out, we breathe out CO2. Then I asked: what living organism uses CO2 to make their food? Some kids replied plants and trees. So I told them the importance of trees and the relationship between humans and plants: we breathe out CO2, the plants use CO2 in photosynthesis and as a by-product release oxygen, which we need.
Their faces lit up as soon as I took out I took out a chest filled with frozen CO2 (dry ice).
Dry ice is extremely cold, with temperatures below minus 100 degrees Fahrenheit, and as such should not be touched by our bare hands as it could cause cold burns. I asked the kids what would happen if I left the dry ice on the table and left to eat my lunch? Some of them said that it would melt and leave a puddle of water. So I explained the difference between regular ice and dry ice: ice melts then evaporates while dry ice sublimates- it turns directly into gas from solid.
They all exclaimed “wow” when I added the dry ice into a water-filled flask and it started bubbling.
I then lit a candle then asked what would happen if I put a beaker over it. We all watched the fire die as soon as the oxygen inside the beaker was consumed and converted to CO2. I took this opportunity to tell them about how one guy thought of using CO2 to put out fire thereby inventing a CO2 fire extinguisher. To prove that CO2 truly puts out fire, I asked them to each draw a cupful of vapor from the chest. They got all excited as the fire from each of their candles was put out when they poured CO2 onto it!
On to more cool stuff: Is CO2 an acid or a base?
I asked for a show of hands to find out how many think that it is, how many think that it’s not and how many just want to find out. We gave each child an Erlenmeyer flask and told them to pour 50 ml of Bromothymol Blue (BTB) into it. BTB is used as chemical indicator for weak acids and bases. It changes color when acid is added into it. Then we gave each of them drinking straws to blow bubbles into the BTB. You can just imagine how they reacted when the solution turned yellow!
Then I asked them to pour lime water into their flask and there were more excitement when it turned back to blue! One kid asked: “can we turn this back to yellow again?” Instead of telling them the answer, I asked them to blow bubbles into the solution again. And yes, there were more “whoas” when it turned yellow again.
I ended by reminding them that we should wash our hands after doing an experiment. I added liquid soap into a flask of water then dropped a few dry ice pellets into it. Kids became extremely animated when they saw what happened next! Suddenly, there were over thirty hands reaching out to touch the soap foam!
I participated in the carbon dioxide experiment during my first visit to the National Museum of American History (while I was on an Asian Cultural Council fellowship to observe education programs of museums in the US). That experience became one of the biggest factors that affected my decision to apply for an internship at the NMAH. Who knew that eight years later I will be on the other side of the bench conducting the experiment myself!
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