Elephants' toothpaste - or should it be elephants' sneeze!

Peter Sigsworth

COMMITTEE
Before anyone says it - it was an online demo for a group self isolating - teacher said 'make it as good as you can' I replied should be done outside with maximum safety precautions - full PPE and screens just in case the flask breaks. she said - 'no chance of it breaking I've done it loads of times!!'
Afterwards - she was a bit flustered and said 'should have done it outside good job I had the safety screens!!!'
'You can lead a horse to water but you can't make them drink'
I finally said 'how are you going to get the mess off the roof?' and left it with her.
 
How much did they use? We are quite boing here and only do it very small would love for them to do it bigger! ( maybe not that big)
 

Peter Sigsworth

COMMITTEE
How much did they use? We are quite boing here and only do it very small would love for them to do it bigger! ( maybe not that big
You need to use a vessel which has a narrow neck the constriction increases the force of the foam coming out - I use a 2L volumetric flask. The Potassium Iodide must be as saturated as possible ie keep adding the solid to water until no more will dissolve. The Hydrogen peroxide must be 100vol (30%). Put up safety screens round the flask (just in case it breaks) and make sure this is done outside with the audience at a suitable distance and wearing safety specs.

You must wear lab coat gloves and safety goggles (and/or face shield).

Mix 200ml H2O2 with some fairy liquid and food colouring, pour into the flask. Quickly tip 50-100ml of the saturated KI solution (depending on how violent you want the reaction to be) into the flask and move away as quickly and safely as possible whilst continually watching the apparatus.
 
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Peter Sigsworth

COMMITTEE
Fairly sure this is one of the ones CLEAPSS says not to mess with their recipe
Not quite - 'Schools are advised NOT to deviate'. Contact them for advice and new RA if they do. There were no children present when we did this - online lesson
 
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In the past we have uses very small quantities (about 20mls H202 and 5mls of KI) in a measuring cylinder it does quite well for making the point but its not exactly spectacular. Makes it very easy to clean up as everything stays within a tray. Our teachers rarely use demos which I want to encourage them too. So making it more WOW would be great I will have to experiment with scale when I have more time.
 
A conical flask works well, I use a 500ml one in a washing up bowl, the foam rises up but then falls down a forms a spiral on the outside of the conical flask. a bit like a snake coiling round the flask. Keeps the mess to a minimum.
 
we had a chemistry teacher who liked to put a smoldering spill next to the foam to show the O2 produced. Went up with a huge woosh once. Scared the sh*t out of us but the kids loved it :laughing:
 
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