The Geoff on Nostr: 2nd year class (~13yrs) doing a salol experiment, how cooling rate changes crystal ...

2nd year class (~13yrs) doing a salol experiment, how cooling rate changes crystal size. Lots of them are a bit "meh" until I mention that really hot rocks cooled really fast give you almost glass-like obsidian...

"Anyone heard of obsidian?"
"Minecraft!"
"How do you get obsidian?"
"You have to make lava meet water!"
"Why?"
"So it cools rapidly!"
"Exactly!"

They'll remember that.

"Then you can make a Netherworld portal!"
"That's university stuff, needs a special risk assessment."