My chemistry teacher
whom we'll call Mr C to preserve at least some of his anonymity, had a penchant for 'dangerous' science, and in particular, explosions.

He used to demonstrate the combustion of hydrogen thus:

He would fill up two balloons, one with pure hydrogen, and one with a stoichiometric mixture of hydrogen and oxygen, tie strings to them and affix them to his bench. He would then instruct us pupils to open all the windows and doors, and sit on the benches round the outside of the classroom (this was on the third floor, by the way, with proper fully opening windows - none of your restricted opening health and safety pish in those days).

Then he'd get a taper, sellotaped to the end of a metre stick, light it and hold it at arm's length under the first balloon.

WHUMP!

A big flash of yellow flame, and a fair old bang would emanate from the balloon. He would explain to the slightly shellshocked class that the hydrogen was burning as it met the oxygen in the air, and so burned very quickly. So what would it be like, he asked, if the oxygen was mixed in already, in just the right ratio for perfect combustion?

Enter the second balloon.

The taper was duly relit and held below the swelling rubber bladder of explosive gas.

A few seconds passed until the rubber melted and the flame touched the escaping gas mixture.

BOOOOMM!!!

An explosion which caused our hearing to go a bit funny rocked the room. We were lucky not to have fallen out the windows with the shockwave. Even the floors vibrated. Doors down the corridors opened, with concerned teachers of less violent and hazardous subjects looking worriedly towards the lab.

We learned a lot that day though, and it helped illustrate his point.

Mind you, we learned a bit more come sixth year, when he admitted to us that he had never used hydrogen for the experiments, he'd just attached the balloon to the gas tap in the lab and filled it with natural gas. He just didn't want us all to go home and fill balloons from the gas cooker! Thinking back on it, they didn't seem particularly buoyant, but we didn't notice this at the time.

Happy days.
( K2k6 has a proper job these days, Fri 30 Jan 2009, 15:50, 2 replies)

Brilliant!

( Enzyme is powered by sunlight, Fri 30 Jan 2009, 15:56, closed)

My chemistry teacher
was an odd and harmless looking little man. He looked like (and therefore earned the nickname) "Penfold" from the Dangermouse cartoons.

He did similar with a treacle tin.

As it ricocheted off the ceiling and bounced around the room and we picked ourselves up off the floor wondering when our hearing would return, we began to hold him in new regard.
( warmfuzzies Isn't here, Sat 31 Jan 2009, 11:45, closed)