Taking care of plants. The first thing my niece (3) and nephew (5) do when they get in the house is check what plants need to be watered by sticking their hands in the potting soil. The plants and taking care of them has achieved peak interest for a few months. Two caveats, 1) they do not live with the plants 2) It is a ploy to get the water spraying can out. They also equate it with working somewhat as a few rules have to be abided by - wear shoes because the citrus plants have thorns that fall on the floor. The floor has to be swept... etc. The concept of state phase changes of water was introduced to the newphew this weekend as there is snow outside where we live. We got to the idea that if he knows the right numbers he can add together how much heat is needed to melt the snow. This is all at the 5 year old level but the conversation got there.