Discrepant Event : Belon Kembang Sendiri

What you need:

balloon
empty bottle
baking powder
vinegar
small funnel

Pour the baking powder into the empty bottle. It's easier using the funnel




Take the balloon and fill half of it with vinegar. Again, use the funnel.



Now put the balloon over the bottle top. Let the vinegar filled part of the balloon hang down at the bottle side, so that no vinegar gets into the bottle yet.

Now that the balloon sits tightly on the bottle top, lift the balloon and let the vinegar flow inside the bottle. Swirl the vinegar around a bit to make sure it mixes well with the baking powder.

Now the balloon will be pumped up.

So what happens here? Here comes the educational part...

The baking soda (also known as sodium bicarbonate) reacts with the vinegar (with the contained acetic acid to be exact) producing carbon dioxide (among others). The carbon dioxide (CO2) usually makes cakes to rise, but here it builds up pressure inside the bottle and pumps up the balloon.