With the water balloon in hand, I helped my son fill a final balloon with air. Then he ran to the freezer and pulled out our project from the night before. "It's cold!" he reported as he brought it back to the table. He laid it next to the other balloons and excitedly began squeezing each one. He talked about what they felt like before I labeled the balloons "solid", "liquid" and "gas".
My little scientist continued his work by inventing different ways to compare the balloons. He dropped them on the ground one-by-one. "WHOA!" he shouted as the solid balloon crashed to the floor. He tapped them on the table to listen to their sound. He compared the weight of the balloons and noticed that the solid and liquid weighed the same. As he worked, I encouraged him to use the words "solid", "liquid" and "gas" so that he began associating the differences with each state of matter. Is it still a complicated concept? Absolutely. But this activity definitely brought one scientist closer to understanding it.