Elephant Toothpaste
Last week we pivoted in science from a focus through a series of lessons on how engineers solve problems to deeper work on the nature of science and how scientists think and work. Mrs. Swanson took the group through a demonstration that involved catalyzing the breakdown of hydrogen peroxide. The result of the very exciting demonstration was that a huge swath of thick foam poured out of the graduated cylinder, and the timely addition of food coloring made the foam look like large toothpaste, or “Elephant Toothpaste."
As we carefully observed, Mrs. Swanson mixed hydrogen peroxide with some liquid soap. Then she added yeast as a catalyst to make the hydrogen peroxide break down really quickly. Hydrogen peroxide breaks down into oxygen and water. Since there's a lot of oxygen trapped in peroxide, this rapid decomposition results in lots of oxygen that needs to quickly push out of the graduated cylinder. As the peroxide breaks down, the soap that was mixed in combines with the water (from the break-down process), and turns into foam. The oxygen gushing out makes the soap bubbles move and some food coloring strategically added before the catalyst results in a big column of foam that gushes out and looks just like toothpaste. To say we were surprised to see the "toothpaste" pour out of the graduated cylinder was an understatement!
One of the goals of the demonstration was to support the children as they learned, organically, about experiments. As the kids observed and discussed together, Mrs. Swanson helped them assign names to the steps and also begin to use the language of scientific experiments: hypothesis, variable, constant, data. Lastly, she modeled how a scientist tracks everything he or she does in a notebook, recording the procedure, the materials used and his/her observations, as well as noting outstanding questions at the conclusion of the experiment.
She then gave the kids time to interact with the materials and explore on their own, and facilitated each child developing some “what if” questions to drive his or her own individual experiments.
The kids then embarked on designing and doing their own experiments with this idea in mind: What happens if you change one part of the procedure for Elephant Toothpaste?
After preparing in their science notebooks by writing out their question, noting their hypothesis, detailing their materials and methods, and isolating their changing variable and responding variable, everyone went to work carrying out their “what if” experiments and using their science notebooks to record data and observations. The kids did a fantastic job, and really understood for the first time how fluid the process needs to be of going back and forth between observing, testing, tweaking the process, and then testing again. And without the good use of our science notebooks, we also learned that it would be easy to get lost and not be able to learn from this systematic testing and observation process.
Once the kids finished their experiments, they discussed whether the hypothesis driving their experiment was correct, what evidence supported this, and then provided further explanation. Their work with argument protocols – claims and evidence and reasoning – supported this critical thinking. We'll soon put all of these new understandings to work with a new set of experiments next week.