Children need no external curriculum, children need no external directions, children need no external initiators, children need no external motivation.
2y4m picks various items to experiment on filtering(sieving), and, that's not all, she puts all the stuff that she had picked, back in their places from where she picked.
She had picked up three kinds of strainers, some glasses, filled a glass with water herself, she sets the right amount of flow from tap so that water does not overflow the glass, settles down to explore.
After all her play, she put back all the items in their places!
To put it in terms of labels - free play is an opportunity where children are the initiators, directors of their learning, responsible for the learning starting from collection of raw materials to putting them back in their places, accepting to fail in their experiment, trusting that they succeed even after a failure and many more.
Giving labels to a child's activity or learning only limits their ability to the language of that label.
Let's just let the kids be!