Joe is blowing up a red balloon. The balloon is getting very big. Joe does not tie the balloon. He lets go of the balloon. It shoots off and all the air comes out. What happens to the size of the balloon?

Materials don’t always stay the same. If you stretch a rubber band, it will bounce back again. But if you chop up a carrot, you can’t put the carrot back together again. When you are baking a cake, the ingredients all look different. But when you mix them together and cook them, they change and become a new material. The cooked cake doesn’t look like any of the ingredients.