Where in the world do you get dry ice? Try searching http://dryicedirectory.com for a location near you.
Step 2: Impossible Candle Relight
Carefully pour some crushed dry-ice, down around the base of the candle. And within just a few seconds, you'll notice the flame goes out, and the gas turns completely invisible.
Now challenge one of your friends to try and re-light the candle inside the glass. They won't be able to do it and they'll have no idea why.
Even after multiple attempts, the flame goes out every time.
Now simply blow into the top of the glass to push the gas out, and show your friends, that it really isn't that difficult after all. The candle with relight easily
Step 3: Self Inflating Party Balloons
Carefully place one or two of the pieces inside of a balloon, and tie it off. You'll notice the balloon begins to inflate all by itself.
Now try doing this with a bunch of other balloons and throw them all into a basket.
Over the course of about 25 minutes, the balloons will keep growing, until you've got a basket overflowing.