This is a project I do every year with my students after we learn how to design and conduct an experiment. I offer them several topics to choose from--all involving simple household items. They conduct the experiments at home and turn in a completed lab report upon completion.
With my older students, they complete everything outside of class. With younger students, I assign it in chunks so that I can assess them along the way.
This file is included in my Science as Inquiry Unit bundle, available in my store.