Balloon Rockets - I've done this in several science camps I've conducted. Kids have fun with it. But, when the balloon deflates it may fall off the straw because it's surface area changes - another good thing to show and explain to kids.
32 Fun Activities for 1-Year Olds (You’ll Never Run Out of Things to Do
32 Fun Activities for Olds (You'll Never Run Out of Things to Do) It is helpful to have a variety of activities while working with the limited attention span of a 1 year old due to the exploratory stage they are in.