Crash, Flash, Splat!

This week I did two outreach activities. One was making PVA slime and alginate worms with around 50 ten and eleven year olds from a local primary school, and the other was a demo lecture as part of the Salters’ Festival of Chemistry. Keele hosts two festivals, organised by Dr Jane Essex, part of the PGCE team, Education.

The demo lecture is quite standard really, based around gases in air but each year I attempt to modify a demonstration to make it a bit different or better. Last year I modified my Elephant’s Toothpaste demonstration to make it glow in the dark []. ┬áThis year, following the advice of our excellent regional coordinator, Dr Heidi Dobbs, I modified the hydrogen balloons.

In the interests of full disclosure, I really don’t like loud bangs and prefer not to set them off. I usually ensure I have a handy volunteer so I can cower at the other side of the room. I’m not going to debate the virtues of flash-bang lectures in the context of outreach either. Of course, modifying this experiment meant that I had to practice the day before.

A similar modification is detailed in Education in Chemistry, essentially using metal salts to colour the hydrogen flame []. On Heidi’s advice, we put a tiny quantity of grease on the outside of the inflated balloon shortly before the lecture started, then sprinkled on copper acetate. It must be tiny quantities of grease and metal salt otherwise the balloon sinks. While this turns things into high comedy, not many school managers appreciate their lecture theatre benches being scorched from a low flying copper yielding hydrogen balloon!

The practice runs worked and on the day we did copper acetate and strontium oxide. With more preparation, I’d get a series of the chlorides probably. The grease method worked well so I can’t comment on the injection version.

It went down well anyway so I’d recommend it to anyone who generally does a flash bang lecture.

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