Question: How can you hold air? (One answer will be balloons, but we’ll also talk about all the containers that hold air inside them.)
Balloon Pump and Let Go: A really simple and cheap activity that can keep kids entertained for hours: give them a balloon pump and a pile of balloons. (Note: Kids age 4 and up can do this alone. The 2 and 3-year-olds needed help getting the balloon on and off the pump, but could pump by themselves.) They pump it up, then pull the balloon off, and let it go – it flies around the room as the air flows out. Hilarious! You can also talk about thrust if you want to and how the wind flowing out pushes the balloon forward. (This post does a great job of describing how to talk about the science of this with your child.)
Balloon Rocket Races: Make a track – thread a string through a straw. Tie the string from one side of the room to the other. Blow up a balloon, but don’t tie the end, just hold it carefully closed. Tape the balloon to the string, let go of the balloon, watch it fly (See pictures here). Another way to do this is to make a rocket out of an empty water bottle – mount the rocket on the straw. Then blow up the balloon and tape it to the bottom of the rocket.
Can air pressure hold up a cup: Watch the video. Basically, you put an uninflated balloon inside a plastic cup. Blow it up till it fills the cup – lift it up, it lifts the cup.
Balloon Face with Ears: Child can draw a face on an uninflated balloon. Then you blow up the balloon slightly. Have them hold two plastic cups – one on each side of the balloon – they need to apply pressure. Then you blow up the balloon – the air pressure should hold cups there. Apparently this is easier if you wet the cups first.
Helium Balloon vs. Balloon I blow up. Compare a helium balloon with a balloon your child has blown up. How are they the same? How are they different? Why?
How many balloons does it take to lift… Get some helium balloons. Find a basket or bag to tie on – try filling the bag with a variety of items (dominoes? coins? plastic dinosaurs?) How many objects can one balloon lift? If you add a second balloon, how many can you lift? You can also choose a heavy object and guess how many balloons you’ll need to lift it (Source). Just for fun, you could show a clip from the movie Up, with the house being carried away by balloons.
DIY Hot Air Balloon. We built a hot air balloon shape from tissue paper and blew a hair dryer into it to create the hot air to make it rise. It was moderately successful, but the balloon kept leaking air. You might have better luck with paper lanterns, using a hair dryer instead of candle/fuel burner. Or you can use a plastic trash bag or dry cleaner’s bag.
Hovercraft: Build a hovercraft with a balloon and CD. (I haven’t tried this one yet.)
Books to Read: Curious George and the Hot Air Balloon or Balloons over Broadway: The True Story of the Puppeteer of Macy’s Parade by Sweet.