Replacement Chem Teacher requires help: fumigenes?

Question

I am a replacement maths/physics/chem teacher, kids from 10 to 16. To get their interest, I make small experiements with "effects".
I am looking for a mixture/experiement that would produce some coloured smoke that would be opaque and abundant enough to be well visible, dissipate rapidely and ESSENTIALLY, harmless!
(making chlorine is easy and nice, but won't do!)
Maybe the formula to make the (white) fumigenes used on stages in concerts?

Bruce, done the balloons already (and H2 & O in a pyrex and a bang for a drop of water)! But thanks.

Answer 1

Try placing a mound of magnesium powder on an asbestos mat, stick a piece of magnesium ribbon in it as a fuse and light it.(Don't forget the screens etc). The kids love this, magnesium oxide 'smoke' fills the room, very spectacular and popular experiment.

Answer 2

Sounds fun...i really can't help you on the fumigenes.

I really can't remember what i did exactly, it was about 6 years ago (while in highscool), but we had a science day for the elementary school kids.

Basically made a rainbow of colors. Mixed solids with some liquids and some liquids with liquids...all in different containers....then lit them on fire. Made a small but visible flame (with the lights off)......so 7 dishes..mixed stuff...lit on fire...made the a rainbow of color.

One thing that students always love, might not really be the "effects" you want is to blow up a baloon filled with hydrogen.

Have a regular balloon with air..one with just hydrogen...and then one with a hydrogen/ oxygen mix.

I'm talking about massive baloon that you use 2 yard sticks taped together with a candle at the end in order to light.