At first, I was a bit leery to teach a group of preschoolers through third graders chemistry. It was assigned to me, and quite frankly, it seemed too tough a subject, with too much for them to comprehend. However, a generous mom lent me several fabulous resources.
One is Teaching Chemistry with Toys. When I skimmed the age appropriate lessons I found one called "Smell-Good Diffusion Ornaments." Turning to the page, I found the very same ornaments we have making for years: cinnamon and applesauce ornaments. We have always used the ornaments to demonstrate evaporation as they dry. However, the book had many alterations on the recipe and accompanying science activities that focused on scent. As it was the same basic materials and method, I excitedly added the activity to our first December co-op meeting. The children learned about evaporation and were introduced to the chemistry of smell.
Wednesday, during our second December science co-op meeting, the children made a solution. They were introduced to concepts like dissolving and saturation while making snowflakes. All went reasonably well, except my youngest son's jar ended up looking like a blizzard occurred. I'm not sure if I added too much or if he added extra. Regardless, his blizzard like jar resulted in a very quickly formed snowflake that had the appearance of something from a nor'easter wet snow storm. He is not pleased with it and did not want a photograph taken of it. My daughter's snowflake is pictured below. Her jar was cloudy when the solution made, but not blizzard-like. The snowflake formed within a few hours, and I suspect her experiment went just like the instructions had intended.
This snowflake activity can be found at Enchanted Learning.