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Asked by alamin to David, James, Mike, Suze, Will on 13 Jun 2011.
Question: What's the best practical you've done?
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Mike Dodd answered on 13 Jun 2011:
The screaming jelly baby experiment at school: http://en.wikipedia.org/wiki/Screaming_jelly_babies
It shows how much energy is stored in the sugar in the jelly baby
Don’t try this at home!
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James Marrow answered on 13 Jun 2011:
I remember a really cool experiment when I was a university student – it was about density. As far as I can remember it, we had two liquids which we carefully put into a glass chamber. One was blue and it had a density that was constant. This was put at the bottom. The liquid at the top was clear and transparent. It had been heated, and was less dense than the blue liquid. As it cooled, it became more dense than the blue liquid and started to sink to the bottom.
We’d made a kind of “lava-lamp” – great fun and very pretty. I think I was also meant to be learning about interfaces and their stability, but that was lost on me at the time!
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Suze Kundu answered on 13 Jun 2011:
Mike, the screaming jelly baby is awesome!
I have to say that every day brings a new favourite experiment for me in the lab. This was especially true when I was an undergraduate, and all my friends were adventurous boys, intent on seeing what would burn the fastest / brightest / etc. My favourite experiments still generally revolve around things that go bang, things that I can freeze (imagine putting a feather in liquid nitrogen, then lifing it out an dropping it on the ground. It shatters! Crazy!), and things that change colour!
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William Eborall answered on 13 Jun 2011:
I think the best practical I’ve ever seen was in a first year lecture.
The lecturer filled a fish tank with water, then floated a layer of alcohol on the top of the water to the top. He then set fire to the alcohol. While it was burning he wiped a cotton bud inside a students ear then touched the cotton bud onto the burning surface. The wax from the students ear spread over the surface of the alcohol putting out the fire. Pretty amazing to see! Although it did prove you should clean your ears out more often.
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David Ingram answered on 13 Jun 2011:
The exploding treacle tin http://www.youtube.com/watch?v=WsEQgoPEbYg
It demonstrates the transition between a flame (which travels slowly) and a detonation wave (which is supersonic). It also shows the difference between the being above and below the upper limit of flammability for a gas [when there is too much fuel and not enough air].
The squeky-pop hydrogen in a test tube does the same but is boooooring 🙂
Comments
James commented on :
Other odd experiments using liquid nitrogen that I remember seeing (and have sometimes used). The ones that change properties are really good scientifically.
1: drive a steam engine with it (it provides pressure as it evaporates)
2: band a nail into wood with a frozen banana
3: pour into a bucket of soap solution (creates a foam monster that I remember spread uncontrollably out of the lab into the corridor – do not try this at home or even at work 🙂 )
Suze commented on :
*will be trying this at work…!*
James commented on :
You might want to add some glycerin to the soap solution 🙂
Suze commented on :
*BIG BANG!*
James commented on :
Glycerin!, not nitro-glycerin! 🙂
Suze commented on :
Lol, sorry – it’s the pyro in me!
alamin commented on :
Awesome! I love the screaming jelly baby!