Follow Up Experiments

 

After observing our petri dishes for days, we continue to be baffled. Why do we consistently grow more germs in the samples of the washed hands than the unwashed hands? The children created a list with over twenty reasons they THINK we could be getting strange results. They've developed lots of follow- up questions from,  "Did we treat the perti dishes correctly?" to "Does it matter how long you rinse your hands?"

 

Some questions have been answered over time and through other experiments. The children are designing new experiments to answer some of the remaining questions.

 

Today we set into motion the one of the experiments designed to determine how to best grow cultures in a petri dish. They wonder if our lack of knowledge might be affecting our samples.This group is specifically asking, "Do germs grow best in light or dark?" in partnership with another group designing an experiment to test if germs grow best in warm or cold temperatures. 

 

I've struggled a bit with this science investigation because there are SOOOO many variables to control. It is very hard in my adult heart to feel like our results are accurate. But on the other hand, the greatest weakness of this medium has also been its greatest strength because I've never seen a group of children this young become so adept in thinking about all of the subtleties that are affecting our results.

Today as our atelierista, Anna, and I were watching the experiment and listening to the children's conversations, we were both struck by how sophisticated their thinking had become. They were thinking and planning so many subtle details to help control their experiments ... and not just because that's the way their teacher told them to do it. Sure I posed a few questions to help probe for deeper thinking, but all in all they were making their own decisions about how to run their experiments "fairly."


They decided ahead of time who would open the door, turn on the water, push the soap dispenser.
There was a person timing to make the washing more accurate.

We all became "checkers" to be sure the experiment was happening as planned.
Were we labeling the dishes correctly? Swabbing for a fair amount of time on each hand?
 

Swabbing on the dishes for the same amount of time?

 

"We wanted to test the same person for all of the petri dishes so that the germs are the same."
"But we didn't want to swab the same hand because the first time we swab we might remove a lot of the germs. That wouldn't really be fair."
"We're going to have the person rub their hands together before we start to even out the germs on their hands. Then we can swab the right hand for one dish and the left for the other."
"We wanted a clean and dirt hand for both the light and the dark, just to see how each one reacts. It will tell us more information."

A clean and dirty hand sample are in place under the light.

A clean and dirty sample are in place in the darkness of the filing cabinet.
Time will tell!