Why is the sky blue is one of those questions most children ask at some point. Show your students the answer by making the sky in a glass. Fill a clear glass with water and stir in a teaspoon of milk. Shine a flashlight through the glass from the top, and the students will see the water turn bluish, just like the sky. As you move the flashlight down the side of the glass, the water turns reddish and then darker red, just like what happens to the sky at sunset. Explain that the milk is acting as particulates in the water, just like dust and smog do in the air. The particulates reflect different spectrum colors, depending on the angle of the light, the same way the sky reflects spectrum colors depending on the angle of the sun.
Students can make their own portable, edible solar systems on paper plates using pieces of candy glued together with cake frosting. By drawing circles on a paper plate that represent each planet's orbit around the sun, students can learn about relative distance and how the sun affects each planet. Place a spoonful of frosting on a piece of wax paper and give each student a wooden craft stick to use to spread the frosting onto candies that represent each planet. The frosting will glue the planets onto their orbits on the paper plate.
Making slime is an introduction to chemistry that most second graders will appreciate. By mixing polyvinyl alcohol in water, students can watch the substances combine into a thick, gooey liquid. When Borax is added, they'll see the liquid turn into an even thicker, slimey gel. Let them experiment with the properties of this new substance by showing them how it spreads when some is set on a plate or how it drips through fingers slowly. Let each student bring some slime home with a note to their parents that it is not to be eaten.
Science and art are often intricately tied. Show your students how color is science by letting them experiment with it. Provide each student with a paper plate filled with 1 inch of milk. Drop three or four colors of food coloring into the milk and let students discover how the color spreads, how the white of the milk affects it and how the dye reacts with the milk. Next, let them mix the colors around using cotton swabs, combining primary colors into secondary colors. Give them another swab dipped in dish soap and have them dip that end into the center of the bowl to see how the soap reacts with the colors, making them swirl all on their own.