Take a look at some of the graphics found in children's science books or science textbooks. There are usually many diagrams and pictures that describe natural processes. Have your students make little booklets or posters recreating the graphics with their own descriptions of the processes. Subjects I have used for this are volcanic mountain creation, plant growth, and the water cycle. A game I play with students involves presenting them with a picture of an elaborately furnished room, and telling them I hid some money in there.
Students have to guess where the money is by using prepositions of location.