Hand inside vacuum chamber experiment - GIF

[bruce.desertrat]

My 7th grade science teacher taught us the rule about "Add Acid To Water" quite graphically. He had a large Pyrex beaker (5 or 6 liter) with about a liter of Sulfuric Acid into which he poured about 250ml of water. The contents immediately started boiling vigorously. He took the beaker to the back of the class and stuck it in the big heavy sink, then came back up front and started talking about more of the subject. At the end of the class he said "I want to show you something"

He went back and picked up the beaker.

Still steaming .

That firmly fixed that rule in my head!