The Physical Science class had fun with the idea of "balloon powered cars" and Newton's 3rd law (for every action there is an equal but opposite reaction).
But I got a lot more action and QUICKLY in Chemistry. I had finished lecturing on
the quantum model of the atom and had dealt out cards to pairs of students
for them to try to duplicate how Mendeleev made the
original Periodic table. They were working hard to
figure it all out when one student looked outside
and noted with great exclamation that it was snowing!
Top photo is what happened next. I lost my class. All I
had left were cards on the table. (It didn't stick and it
didn't last but it IS cold here tonight. Maybe more
will fall tonight..)