We started their off by singing some math songs, first a few that I know - Alice the camel and counting backwards, the first ten numbers in Spanish in singsong, knick knack paddywack and five in the bed. Then we asked the girls to think of a song they know that uses math or counting. One of our Sparks came up with the one two buckle my shoe rhyme, so we sang that too.
Then we went into the kitchen and tried blowing some things up. We talked about what a chemical reaction is (a change of state) and then I dropped some method into diet coke. We tried it several different ways, with the girls predicting every step along the way. We tried a mentho in diet coke, then in a can of diet coke instead of a bottle. Then I cut a mentho in half and dropped it in. Then we dropped it into a bottle of Pepsi. The girls loved it - they also loved the mess.
A note for other leaders trying this - we used a 591ml bottle of diet coke and Pepsi, and one of the minicans of diet coke. This kept the mess contained to a single sink, and not on the ceiling.
The other experiment we did was dripping vinegar onto baking soda. I first mixed the vinegar with blue dye so the girls could really see the reaction happening. They each got a chance to put some on, then I dumped the rest in the bowl. They really enjoyed it!
Then we passed out salt dough for the girls to shape into animals. They each got a chunk, and then I popped it into the oven for 15 minutes as we ran into our next activity.
Which was... Inventing! We had them draw out their invention, and then we sat in a circle as they went one by one explaining what they had invented, and why they thought it was cool.
Then we went home with our freshly baked salt dough animals. I prefer sending them home the same day we do things. It's easier that way :)