Working towards a science exhibition...

The 6th graders are putting together a science exhibition for the school. A couple of the students had chosen the Cartesian divers as their project and wanted to present it.

Their presentation lasted 20 s. One child pressed a bottle with the vial inserted while the other gave his spheel. "The syringe goes down when you press the bottle, because of the air and water pressure pushes water into the syringe increasing its density and making it sink."

This is quite stark to how we learnt about them and then I realized that this is how children speak at science fairs. 

[In its context, a fair has a large number of exhibits and short attention spans, everyone is looking for something new and cool and hoping to learn a quick keyword to explain it all (osmosis, multiple reflections, citric acid, dynamo, zinc+copper). 

Sixth graders came back from a recent fair knowing keywords and assuming that it meant that they knew concepts e.g. we know density because oil floats on water (which incidentally started the Cartesian divers affair...). 
Tenth graders who have been there and seen that found nothing interesting (new).]

I could only ask - "Was that fun?", to both the kids presenting and those listening.

We started talking about, if it was fun when they were exploring how the diver works. Yes. Ok, what made it fun? We came up with - We had to keep guessing what would happen next and things became clear in time.

We brainstormed on how we can do it differently and include some questions that can be asked of the audience

1) Show the divers

2) Put the bottle in bottoms up and see what happens

3) Ask:  What happened? Why?

4) Press without closing cap

5) Close cap and press and watch it sink.

6) Ask: What happens when you press it on top?

7) Ask: Is it water or air preassure?

8) Fill water fully and repeat experiment

9) Explanation (if required).

There were some questions for clarity

1) Can this happen with any other object?

2) Will it work in any bottle?

3) Will it work with 2 syringes?

4) Will it work if the bottle is only half full?

5) If you cut out the heavy side of the syringe will it work?

6) What is the name of this thing?

There were some additional suggestions:

1) Make model with all three bottle settings open, partially filled, full.

2) Both people should speak

3) Talk about how much pressure is required for half and fully filled bottles. They are not the same.

I asked if anyone else thought that their projects simply does not fit into this sort of example and got a few, this led to some wonderful discussions on not limiting ourselves to one example, but looking at phenomenon as a whole and exploring more possibilities.

I felt there was still something missing in the presentation of the Cartesian divers both for me and the kids. The diver I bought and they used were still not our own i.e. we didn't build from scratch...perhaps, if we had, we would be looking at putting up a different kind of science exhibition - one in which we can talk about ideas and perhaps a space where visitors can build their own contraptions and design their own experiments to observe...and learn by themselves.