1: you can make project on dancing balls of phenyl balls.
1 few phenyl balls used for insect repellent
2 vinegar (transparent)
3 baking powder
4 transparent beaker.
fill the beaker with vinegar
and break phelyl balls into smaller peices. Then add little baking powder in vinegar and add phenyl peices and watch phenyl rising up and settling down again and again. This is due to CO2 production by reaction between vinegar and baking powder.
CH3COOH + NaHCO3----> CO2 + H2O.
vinegar + baking powder----> CO2 + sodium acetate + H2O
CO2 formed attach at surface of phenyl and lift it up to surface. There CO2 escape and phenyl sink down. Again it trap CO2 at its surface and rises up.
precaution : donot add baking powder extra as it will reduce visibility due to milkyness.
2 : filling balloon with CO2
1 bottles with nerrow neck like contour bottles
3 vinegar and baking powder
first streach balloon by filling them with air completely. Allow air to escape. Ensure that balloon are dry from inside. Now add baking powder in balloon not more than one or two tea spoons. Now fill bottles about 200 ml of vinegar according to flexibility of balloon and volume of bottle. Do not fill bottle more than half. Now fix balloon on its neck enclosing its mouth complete. Take care so that baking powder doensot enter in bottle. it should be inside the balloon and hang balloon on neck so that it contain powder in it. Now when you have to demonstrate in class just hold balloon up straightso that powder fall down and reaction will start. CO2 formed will inflate balloon.
Donot add excess of baking powder as it cak make balloon wet and slippery and it will cause balloon to eject and whole meterial will spread all arround.