I opened with What Do Wheels Do All Day? by April Jones Prince, illustrated by Giles Laroche. (Houghton Mifflin, 2006) This was a great introduction for preschoolers. The children had fun talking about the many different objects with wheels in the various pictures. Sometimes only a very small part is pictured, and the kids debated whether one was a dump truck or a school bus (all that is pictured is a large, bumpy wheel with a bit of yellowy orange color around it.)
Then I talked about wheels being a tool; people had to invent them (they don’t just occur in nature). This was our main idea. Wheels were invented over 5,000 years ago. Wheels make it easier to move things. You can move heavy things that you could not otherwise move and can travel faster with wheels, whether bikes or skates or wagons or buses or trains.
Preschoolers always need to move around, so we did Jim Gill’s “Sliding, Rolling and Jumping.”
Gears Go, Wheels Roll by Mark Weakland (Capstone Press, 2011). Another great introduction at the preschool level. There is a large two page spread of a girl pulling two other children in a wagon. I asked what if the wagon did not have wheels? Would she still be able to pull them? The immediate response was no! too heavy! so they understood the point of a wheel as a tool. A gear is a type of wheel that has teeth. Turning one gear can turn another, or even many others. It was important to understand a gear as several stations involved gears.
Wheels & Axles by Valerie Bodden (Simple Machines series, Creative Education, 2011) would be a good alternative/additional book.
Kids explored gears at several different stations, playing with how the teeth interlock, which way one gear moves when another touches it, etc. They also raced cars on ramps and constructed their own vehicles out of legos to try out the ramps. I set up three ramps at different heights to begin with and asked them to try them out to see which was the fastest. We talked about making predictions before they began. It wasn’t long before some began moving the supports for the ramps in order to make them even higher. This is just the sort of experimentation I like to see during the activity time.
Cultivate Wonder 
[…] our second summer science program we explored Wheels & Gears. In addition to the stations mentioned in the post from last year, we added two stations featuring […]