The first four ideas of primary science, each one something a child can check against the world outside the window. No lab, no equipment, no unit system to learn first.
Why these four
Every one of them is a sorting task. Sorting is how a young child builds a category, and a category is what later science hangs on: a child who can say why a log is not alive is ready for what a living thing needs.
All four also build vocabulary in English. A child who plays them will meet "liquid", "stem" and "sense" again in a classroom, and will already know what they mean.