Any teaching is always best done when accompanied by a demonstration. I remember many such demonstrations from Chemistry classes at school: the exploding bowl of water when the teacher put in just a little bit too much potassium, or the test tube flying across the room at high velocity when the manganese wool (or magnesium, I forget after all these years) got a little bit too excited.

Yesterday I decided to help Esther on her way to adulthood with a little demonstration about the dangers of plastic cups with inbuilt straws.  For those of you unfamiliar with these contraptions, it is just a regular plastic cup, with a straw built into the side (and a little hole at the bottom through which to suck up the liquid).  Anyway, as any sensible person knows, you don’t tip the cup when drinking through the straw.  I momentarily forgot about this while drinking some chocolate milk.  The result was chocolate milk all down my shirt.

It was the perfect demonstration of why you should never tip the cup when using a straw.  I hope Esther learned the lesson.