Preschool Science Experiment

We read The Secret Science Project That Almost Ate the School, which is about a third grade student's science experiment gone wild.  It's a great rhyming book about how she orders a science fair project from the internet.  After it arrives, it begins to eat everyone, even the cat.  It follows her to school where it eats the teacher.  Finally remembering the instructions that came with it, the girl feeds it sugar to make it swell and then disintegrate, although there's a big mess left behind.  Luckily, everyone is recovered, including the cat.  I wouldn't normally think of this as a book for preschoolers, but my 3 year old has asked for it over and over again.

After we read it, I started thinking about that elephant toothpaste experiment that has been floating around lately.  But I didn't have the supplies and I also didn't want to spend the entire time yelling at the kids not to touch it because of the hydrogen peroxide.  The only thing I could think of that I had on hand for a fun experiment was vinegar and baking soda.  I googled it, convinced that somebody had improved on this in some way and sure enough, Amanda at Not Just Cute jazzed it up with some food coloring.

I started by dropping food coloring into baby food jars.

I dumped some baking soda on top.  I didn't measure.

Then I gave the kids medicine droppers and those plastic medicine syringes and cups of vinegar and they went to town.

All the fizzing and foaming was a HUGE hit with Drew.  Not so much with Lainey, mostly because I disrespectfully ignored her exclusive relationship with red and gave her other colors in addition to the red.

When he finished the ones I had given him, Drew started mixing the colors and dumping them together.

Then I gave him more baking soda and more vinegar and let him mix his own.

He kept saying, "I never did this before!" (which means it was a good thing).

Anybody have any other fun and easy science experiments for preschoolers?