Yes! It was balloon number 3. Pop rocks have pressurized carbon dioxide gas in them. When they dissolve in your mouth (from your saliva) or from the liquid of a soda the gas is released (which is the fun popping noise you hear). The soda also contains pressurized carbon dioxide gas. When the Pop Rocks are dropped into the soda some of the carbon dioxide escapes, inflating the balloon. Balloon number 3 became the largest because it had the most gas released. You can find more information about this experiment by clicking here.
Tomorrow we will write up our lab reports and then take a closer look at all three states of matter interacting at one time on Wednesday. Stay tuned!