It was a spectacular day: somewhere between science, numbers and magic.
We ran dry ice experiments — smoke that sinks instead of rising, water that bubbles without being hot — and talked about why that happens, that is, about the direct passage from solid to gas. We then practised numbers in an entertaining way, and at the end turned ourselves into detectives from the magical world.
Together we solved the mystery of the seven bottles, a logic riddle inspired by Harry Potter. The problem runs like this: danger lies ahead and safety behind; two of the seven bottles will help you, one carrying you forward and one sending you back; two hold nothing but nettle wine, and three hide poison.
There are four clues. The poison always sits to the left of a bottle of nettle wine. The bottles at either end are different, but neither takes you forward. All the bottles are different sizes, but neither the smallest nor the largest holds poison. And the second bottle from the left and the second from the right hold the same liquid, however different they may look.
The riddle is a proper logic exercise: it cannot be guessed, only solved by eliminating the impossible options one by one. The children worked as a team, wrote things down, crossed them out, started again — exactly the kind of thinking we want them to practise.
Which bottle lets you go forward, and which sends you back?