Atoms Keep Score

everything on the right got there from the left. there is nowhere else.

pull atoms off their bonds and across the arrow — the count has to come out even

Nothing here balances because a rule says so. Exactly the atoms that exist on the left fit exactly the sockets that exist on the right, and your finger is the only way one crosses the arrow. An atom dropped in mid-air springs back to the bond it came from, because it has nowhere else to be. That is conservation of mass: atoms rearrange into new molecules, and the count of each element that leaves is the count that arrives.

Concepts: chemistry, conservation.

An interactive you play with one thumb, on Wundr.