At this site from The Franklin Institute you can practice classifying objects according to physical structure and characteristics.

Students go outside take a closer look at leaves on a tree. The students collect leaves of different shapes or colors, and then sort into categories, and compare and contrast them to leaves that are non-native to Minnesota.

Compare the size and shape of crystals grown in different temperature conditions in this science fair project. The Science Buddies project ideas are set up consistently beginning with an abstract, objective, and introduction, followed by...