In this lesson, students observe chloroplasts, cell walls, and cell membranes of the common aquarium plant, Elodea. Students will then determine the effects of different salt solutions on the Elodea plant cell structures. By adding salt water to the Elodea cell environment, students will observe the process of plasmolysis. The activities in this lesson help students develop an operational understanding of plasmolysis and reinforce their understanding of osmosis and diffusion. This lesson should follow some discussion about the various subcellular structures in animal and plant cells. It does not introduce the cell membrane, cell wall, and chloroplasts to students; rather, it demonstrates the presence of these cell components and the process of plasmolysis. (author/ts)

Students build a mousetrap car as a means to explore the conversion of potential energy to kinetic energy. The design goal is to build a mousetrap car, powered only by the release of a mousetrap spring, that covers a flat distance of 5-meters in the shortest amount of time. This activity could be incorporated into a larger lesson on energy and/or forces and motion. The Teetering to Victory video referenced in the overview can be found at Scientific American's Frontiers Games Machines Play. (author/ts)

In this lesson students engage in activities that demonstrate chemical reactions and the conservation of mass. The reactions require commonly available and safe materials. Students record their findings and offer explanations in journal entries. Interesting extensions and a rubric are included.

This lesson would be an engaging way to introduce chemical reactions to students in grades 3-5 and the conservation of mass to students in grades 6-8. It should be noted that the lesson uses the term weight. Weight is not conserved and the term mass should be used in place of weight. (ts)

In this performance task, students use cardboard models of the North American and Pacific plates and sand to investigate what happens when there is an earthquake or movement along the boundaries of the plates. This performance assessment is part of the PALS (Performance Assessment Links in Science) collection. (author/ts)

How do physics laws affect amusement park ride design? This resource, developed by Annenberg/CPB, provides students with an opportunity to explore the forces behind the fun. Activities include designing a roller coaster, testing for inertia, exploring the cause of motion sickness, predicting the outcome of bumper car collisions, and comparing ride safety. Connections to related literature and relevant web links are provided.

This article takes a "tried and true" activity, seed germination, and makes it better. The article describes a learning cycle activity sequence that enables fourth-grade children to improve their inquiry ability and develop their understanding of factors influencing seed germination. Manipulating variables and observing the effects are natural extensions of children's innate curiosity. Open-ended investigations where children choose a problem, design and conduct an experiment, and analyze and communicate the results catalyze children's curiosity. The active involvement of children in these experiments provides experiential bases for discussions of the nature of science. This article describes open-ended experiments with seeds from the common garden radish (Raphanus sativus). In numerous research studies, learning cycle approaches have been shown to be effective in achieving a variety of educational goals. The phases of the 5-E learning cycle, Engagement, Exploration, Explanation, Extension, and Evaluation, guide this activity series. (kct)