Purchase four different teeth-whitening products and divide your students into four groups. Distribute the whitening products among the four groups and ask one volunteer from each group to use the product according to the instructions found on the label. Another member of the group should agree to take photos of the volunteer's teeth before he begins using the product and on every school day for the next four weeks. Other group members should keep research on the various chemicals that their group's whitening product contains. At the end of the four week period, have the groups compile a written report in which they argue either for or against the usefulness of their whitening product using both in-class evidence and formal research.
Ask your students to gather four soil samples from different areas. For instance, a student could take soil from her backyard, the vacant lot across from the high school, the rocky ground near the abandoned mine and the park by the lake shore. They should place these soil samples in jars. Have them pour water into the jars, seal them off and place them near the window in your classroom. Make sure the jars get a large amount of sunlight. After about 10 days, have your students observe the microorganisms living in the soil and ask them to speculate about which of the soil samples provides the best living conditions for plant life.
Gather the following items: poster board, round particles of three different sizes (for example, sand, rice and jelly beans), paper cups, cardboard, protractors and metric rulers. Have your students place poster board on a flat surface. Ask them to dump cups of one of the particles on the poster board in an attempt to create a volcanic-looking cone shape. Students should then place their piece of cardboard vertically against the cone -- being careful not to knock it over -- and measure the angle formed in the space between the edge of the cardboard and the cone. After they record this angle, ask them to make two more volcanoes using the other particles and record these angles as well. This experiment demonstrates how the type and size of rock that compose a volcano determine its angle.
Find a set of weights and gather together a large number of bags of all sizes and materials: plastic bags from your local supermarket, paper bags from the corner grocery, cardboard reinforced bags from mall clothing stores and whatever other bags you can track down. Have students place weights inside a single bag until the bag seems ready to break, then allow them to double and triple bag the weights. Along the way, ask them to record the amount of weight one bag can hold, then two, three and so on. When everyone is finished, ask your students to gather together for a final demonstration. In this demonstration, hang as many bags as possible from a nail hole or a coat hanger and fill them up with weights. Continue to do so and record the amounts until the bag collapses, possibly delighting your students. Have your students make graphs of their bag strength data and ask them if they notice a linear relationship between number of bags and strength.