To try to answer the question, I will focus on one simple object provisioned for a recent setup at the water table. The object is a watering can with a long narrow spout. What are some of the ideas children have when working with a watering can and how do they express them? My conjecture is that children express their ideas through asking their own questions.
Let's start with an simple action. In the picture below a child is using the watering can to fill a bottle. Her idea, then, is to fill the bottle. Even a simple idea like this harbors several questions if she wants to realize it. When is it full? What happens if I keep pouring? How do I coordinate my fine and large muscles to get the water into the bottle?
With children, one question leads to another. In trying to answer the question at hand, the children continually ask new questions. Sometimes those questions are verbal but so often they are non-verbal and must be seen in their actions. Here are a few more questions just from the children playing with the watering can.
These two children are each using the watering can to pour water into a hole in the side of the container for the rocking chair waterfall. What happens to the water when it is poured into the hole? What does it look like? What does it feel like?
The children actually fill the water in the planter tray to the level of the spout. At this point, water starts to drain through the spout back into the watering can itself and then into the water table. Leave it to the children, however, to keep asking questions.
In the video below, the two children see that the water is draining through the spout. One of the boys starts to re-position the watering can so the tip of the spout is again under water. Why does he do that? One of the questions he seems to be asking is where does the water go? He bends down to see the water coming out of the sides of the watering can underneath the tray. A new question immediately forms about what is happening to the water in the tray. He stands back up and looks right into the water in the tray again. I ask: "What is happening." Very quietly he answers: "It's falling down." Both boys then look at the water and the spout as the level of the water in the tray reaches the level of the tip of the spout wondering what will happen next. At this point, something quite amusing happens: as the end of the water drains into the spout there is a sucking sound. Watch!
Watering can plug from Thomas Bedard on Vimeo.
One child laughs at the sound and the other child seems to be imitating the sound he hears from the spout. The unexpected outcome continues to fuel there curiosity so they continue to create new questions and new ideas.
By featuring what children do with one simple object around the water table, the questions and thus, the ideas, are too numerous to name. Now add in all the other objects, the setup and people the children are working with and there is an infinite trove of children expressing their ideas---and that is just at the sensory table, a throw-away corner in far too many classrooms.
Here is an inverse conjecture based on the first one earlier in the post. Since children are continually asking questions, they are continually expressing their ideas in their actions to answer those questions. This is a generative process that showcases their ideas in real time. These ideas are fleeting and bifurcate in strange and wonderful ways that cannot be predicted. If you value children expressing their ideas in many and varied ways, make room for their questions both verbal and non-verbal in every part of the classroom.