Physics strikes fear into the hearts of many adults; however, the its basic aspects are extremely easy to explain. One of the simplest, yet most counterintuitive, facets of physics is gravity. Studies stemming from Einstein's work show that gravity manipulates space-time, meaning it doesn't act in the same way as a magnet. Demonstrate this concept by having four students suspend a sheet horozontally in midair. Roll a marble, tennis ball and basketball across the sheet. Each one will cause a different level of indention in the sheet, which parallels how gravity works: Each indention represents the level of gravity from an object as well as showing its far-reaching effects.
The moon circles Earth much like Earth circles the sun, except each orbit takes only 27 days. By cutting marshmallows and placing them on a chart, labeling the full moon, half moons, quarter moons and new moon, students can learn how to spot the relative moon phases. If your second graders are up for it, have them place each moon in its relative location around a central Earth placed in the middle of the chart, as well as a sun shining from one opposing side. This demonstration will also help your students grasp the concept of why each moon phase looks the way it does.
Chemistry is fairly easy to study, requiring only a few common household items. One of these demonstrations makes use of red cabbage to test acids and bases. Acids and bases can change the color of some vegetables, one of which is red cabbage.
Simply prepare red cabbage extract by mixing together two cups of cut red cabbage and one cup of water in a blender. Blend the mixture well until fine, then strain it to obtain the extract. Pour 1/2 cup of vinegar into a clear glass and 1/2 cup of ammonia in another. Mix in 1 tsp. of the extract in each glass, and watch the color change. The vinegar extract mixture will turn red, as it is an acid, while the ammonia-extract mixture will turn blue because it is basic.
Plant biology will usually fascinate second graders, as it's a subject they commonly encounter around homes. Prepare eight white carnation stems (other flowers can substitute) and two clear vases. Pour 1/2 cup of water into each vase. In one vase, mix several drops of food coloring, placing half the stems within the jar. Place the remaining stems in the other vase. After about half a day (12 hours), return to the vase and have the student compare and contrast the differences between the stems within the two different vases. Because the capillaries transport water, you should be able to see a slight change in color within the stems containing food coloring.