Empty cans, such as recycled coffee cans, are versatile, free and easy to find tools for a science classroom. They can be used for a number of experiments - in these videos we make a sound wave oscilloscope, a pinhole viewer (by putting two cans together), displacement cylinders, an air cannon and a space suit simulator. For more ideas, take a look at this article called "Science in a Can".
Bring them in from home, or, to build up a large set, ask your students to bring some in as their homework. If possible, remove the top and bottom of the can in such a way that no sharp edges remain. Also, when preparing a class set of cylinders made from recycled cans, run the entire set through a dishwasher for sanitation.
Do you have any recommended science experiments using inexpensive materials? Did you find these ones useful? Let us know what you think.