Birthday parties and celebrations aren’t the only time kids can have fun with balloons. There are some great science activities with balloons for kids.
Just watching a balloon get bigger and bigger as an adult blows into it is exciting for kids. After blowing up a balloon, before tying it closed, hold the neck of it close to a child’s hand and release it just a little. The child gets to feel the air as it escapes from the balloon. Although we can’t see the air, we can feel it.
A fun activity is to let the balloon go and kids can chase after the quickly deflating and fast moving balloon. This can only be done a few times though before adults run out of breath!
It’s also fun to toss the balloon into the air and try to keep it up. This gives kids a chance to experience how light it feels. (It can also be caught with a bowl.) While we could call this a hands-on activity, when it falls to the floor and kids kick it, is that considered feet-on?
When a balloon pops, it makes a loud noise. This is definitely the science of cause and effect. Deflating is the same idea, but the effect happens over a long time. 
Balloons can be filled with water, which is especially fun in the summer. Let your child compare how light the air one is compared to the water one. The water one feels squishy too and changes shape. If there is one left over, pop it in the freezer. Once the water has frozen, the balloon feels very much different. For kids that are ready, you can explain that one balloon is filled a gas, one filled with liquid, and the other with a solid.
Only balloons with air can be twisted into shapes.
On-line, there are many other suggestions for science activities with balloons. What kinds of fun does your child have with a balloon?