Tag Archives: fire

Demonstration, Get Set Demonstrate

Chip pan fire

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No other film in this series provoked more discussion and argument than this. Mostly from me. It’s a classic demo and was highly-requested in the nomination stage of Get Set Demonstrate, yet I argued against filming it.

For many years I made essentially all the science programmes that went out during the UK’s teatime ‘children’s television’ window, and there were only a few demonstrations I flat-out refused to show. This was one of them. You can show a safe method, you can treat the science with due respect… but with video you have precious little knowledge of your audience. You can’t tell when their attention has drifted away and they’ve maybe missed a crucial detail, you can’t be 100% certain of the message they take home, and most importantly you can’t guess what they might be tempted to try for themselves.

In person, the heat from the fireball is impressive: on video, it’s the size of your TV, or a YouTube window, or your phone. And it’s cold.

Film-makers can’t be responsible for the behaviour of their audience (discuss, 20 marks), but in this case the risk is very, very high. If 100,000 children saw the demo in our show, and 1 in 1,000 tried it themselves, and 1 in 100 set the curtains alight… that’s not something I ever wanted on my conscience. It’s not that the demo is too dangerous, it’s that it’s too easy. It’s trivial to perform it yourself in a kitchen, and the results can (and will) be catastrophic. So I never filmed the demo. Until now.

Others on the team eventually convinced me, using effectively the same argument applied backwards. The demo is straightforward to reproduce, and reproducing it is dangerous. Knowing that – understanding how and why oil fires are dangerous – might just save someone’s life, and for that reason alone, the team argued, this demo should be known and used in schools, and hence we should make this film.

I’m glad we did.

Three quick notes:

  1. In a UK school, follow the CLEAPSS guidance (Scotland: SSERC). As a teacher or technician you should consult CLEAPSS as a matter of routine before attempting hazardous activities, and where they issue standard guidance (as here): follow it. ScienceDemo.org doesn’t have access to the CLEAPSS archive so we can’t link directly to the resource, sorry, but you’ll find it easily enough.
  2. The formal government advice on how to react to a chip pan fire in the home is: get out, stay out, and call 999. It’s no longer considered appropriate to attempt the ‘damp tea-towel’ remedy yourself: the casualty rate is too high. We should have mentioned this in the film.
  3. In person, our fires were a little underwhelming, with the water often putting the flame out quickly. We’ve cut around that for the film, but speaking to other demonstrators subsequently it seems we were probably more assiduous than strictly necessary about turning the gas off the instant the flame caught. Give it a few more seconds and you’ll get a more satisfying fireball, we’re told. Do see Bob Worley’s comment below about one-upmanship, however!

Get Set Demonstrate logoThis film was produced for the Get Set Demonstrate project. Click through for teaching notes, and take the pledge to perform a demonstration to your students on Demo Day, 20th March 2014.

Demonstration, Discuss

Flame colours

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A scary article in the NY Times last Friday about a chemistry demo they refer to as “the rainbow”:

“With about 30 students watching from their desks, a snakelike flame tore through the air, missing the students closest to the teacher’s desk, but enveloping Alonzo Yanes, 16, searing and melting the skin on his face and body, according to witnesses. He was in critical condition on Friday[…]”

Just weeks ago, the article relates, the demo was the focus of a safety bulletin from the US Chemical Safety Board, and this film:

Here in the UK, I think we’d more commonly refer to the demo as “Flame colours”, and at the head of this post is a photo I took of it a few years ago. As best I can tell, the cause of the accidents in the US has been demonstrators topping up the flame straight from the methanol bottle, leading to the ignition of a large volume of fuel vapour.

Now, I’d hope most people reading this blog will be wincing right now. It was drilled into us (in school) that you never open a bottle of fuel near a naked flame, and that the correct procedure here is to ensure the watch glasses are cold before adding a small amount of fuel (typically with a pipette), then sealing the fuel bottle and removing it to a safe distance, before lighting the mixture in the watch glasses.

That would be standard lab practice, and it’s near-inconceivable that a teacher would pour meths from a bottle directly onto a flame. However, one thing we learned from SciCast is that we’re into the second generation of science teachers who’ve never really ‘done’ practical science. Recent science graduates don’t necessarily know how to handle flammable materials; they may never have been taught.

That generational knowledge gap was one impetus behind the demonstration films Alom and I have been making for the National STEM Centre and others, and also for this website. So pass this on, please, and let’s not make assumptions.

Oh, and if you’re a teacher in the UK, the version of this demo you should do is probably the one with ethanol spray bottles. That’s the version the Royal Society of Chemistry and Nuffield promote, but – as ever – check with CLEAPSS for their standing advice.

[EDIT 9/1/2014 – The RSC’s Education in Chemistry blog has picked up the story. Their post includes a quote from Steve Jones, Director of CLEAPSS.]

[EDIT 2 15/1/2014 – I somehow missed the NY Times’ follow-up story about the school involved in the incident above being inspected by the Fire Department, and being given notices to improve on a range of issues. Also, for the UK audience I should note that the Scottish equivalent of CLEAPSS is SSERC.]