Leaves changing colors present the most obvious sign that fall is indeed on its way, so teach preschoolers the secret of the change from green to red, gold, brown and orange. Collect a batch of leaves from different trees on a nature walk and explain to preschoolers that trees and leaves, just like people, need food. Trees need sunlight to make chlorophyll, the tree food that keeps leaves green, and they store this food for times when the sun is not as readily available, like the fall and winter. Lay your leaves on a cookie sheet and let students observe them for one week, coloring a page with a leaf outline on it each day to demonstrate the leaf's colors. Watch as the colors fade and the leaves dry out due to lack of chlorophyll and water.
Use a nature walk to add to your preschoolers' science journals as you match fallen leaves with the local trees. As students pick up leaves, help them glue them into a notebook or onto sheets of paper. Match the leaves to the nearby trees or take them back to the classroom to compare to a nature book. Help students write the names of their leaves into their science journals.
Autumn isn't just about falling leaves, so keep your preschoolers on their toes and take some of the mystery out of Halloween spookiness by teaching them some of the parts of the human skeleton. Use a full-size model or work from pictures, pointing out names of bones and explaining the purpose of the skeleton. Invite students to share stories of broken bones, and discuss foods and habits that make for strong, healthy skeletons.
Take the quintessential autumn vegetable and let preschoolers watch as it turns from the familiar firm orange globe to a squishy, gushy new discovery. Carve the pumpkin into a Jack O'Lantern for faster decomposition and then place the pumpkin where students can see but not reach. Let preschoolers draw pictures of the pumpkin's changes every few days or once a week until it reaches a state of decomposition. If you let preschoolers touch the pumpkins to examine its texture, they must wear gloves. Explain how and why the pumpkin begins to break down, and add the decomposed pumpkin to a local compost pile when you are finished, to demonstrate how our food grows from and returns to the earth.