Perhaps it wasn't Potassium..
But it was something stupidly similar.

A) It was a soft metal which was cut with a ruler
B) It was reacting with my classmate's sweat on his finger tips
C) It combusted with the air (as it was wrapped in paper)
D) It was approx that dimension what I said
E) It was stored away under and students could NEVER handle it

Perhaps it was something less reactive than Potassium, but it happened. It sat in my English Lit lesson for 40 minutes, and obviously some time before that, but for how long I do not know.

I am not lying or exaggerating, but I may have the metal mixed up? The more I think about it, you are probably right. As I mentioned, I'd seen Potassium been put in a water bath which was about the size of a grain of rice and made quite the bang.. A lump my size would have done considerably more damage.

Any ideas what it could have been? There was no bang or noise, just a violent flame spewing out..

This was 10 years ago now.
(Jon_LTD Treat the world like a head!, Sun 11 Sep 2011, 18:12, 1 reply)

Probably
Sodium, it's a little less reactive than Potassium.
( social hand grenade I was a lurker before you were a lurker, Sun 11 Sep 2011, 18:18, closed)

Possibly
You could cut sodium with a metal ruler, probably not a plastic one. And you could conceivably keep a bit out of the oil for half an hour or so if it oxidised neatly. Sodium oxide is quite inert. I still don't buy the bit about painlessly reacting with anyone's fingertips, though.

We used to have a huge tub of sodium that had sat on the shelf for yonks. It was massively unpredictable in the water bath. My theory is that cracks had propagated over time. When it reacted with water then the cracks filled with hydrogen and literally blew each chunk of sodium apart.

It was fucking useless for demonstrating reactivity because it went off with a bigger bang than the potassium.
( ousgg is not seeking approval, Sun 11 Sep 2011, 18:28, closed)

It probably was..
Sodium then. Terrifying none-the-less.

As for the fingertips story, he seemed perfectly cheerful as half a dozen sparks popped on his finger tips. Could have claimed it didn't hurt as he wasn't the sharpest tool in the shed.

Overall, it was a fucking stupid thing to do!
(Jon_LTD Treat the world like a head!, Sun 11 Sep 2011, 21:08, closed)

I remember Mr. B the science teacher
finding a jarful that was "out of date"... Off we all toddled to the school pool to "safely dispose" of said jarful of Na. Apparently it reacts very well with chlorinated water, leaves a salt (EDIT: it wouldn't just be NaCl would it?) which is unpalatable to the school pool vacum & if properly stored in vegie oil pretty much never "goes off"?
(Misery McUglywife an attention seeking sociopathic fuckstain., Sun 11 Sep 2011, 21:28, closed)