Recycling paper can help decrease the number of trees that are cut down to produce new paper. You can demonstrate this to a classroom by recycling scraps of different paper into another "new" sheet. Cut pieces of paper into small bits. You can use printing paper, toilet paper, paper towels or notebook paper. When you have collected around two cups of paper, place the paper bits into a pot. Pour one cup of water into the pot and heat the mixture until it boils. Pour the mixture into a blender and blend it on high for three minutes. Dump all the contents of the blender into a large bowl and fill it with water. Insert a piece of grating into the bowl so that it touches the bottom. Shimmy the grating to allow the paper pulp to float up to the surface. Gently pull the grating up; it should contain a layer of paper pulp. Allow the pulp to remain on the grating until it dries completely, then peel off your "new" paper.
Humans naturally have peripheral vision in order to keep themselves safe from harm. This can be demonstrated to a science class by helping students determine where their peripheral vision border is. Paint different 12-inch pieces of cardboard bright colors. Taking turns, have each student stand in a marked place staring forward. Have another student walk very slowly around the side of the first student holding up the colored cardboard. As soon as the first student sees the color, have him yell "stop." This will be the peripheral vision border.
As sound waves pass through a small opening, the pitch becomes higher than if they were to pass through a larger opening. This phenomenon can be demonstrated by helping students create kazoos out of straws. Simply cut of the tip of a drinking straw into a point, then hum through the uncut end. You will be able to hear the kazoo sound right away.