"They do make their homework difficult these days don't they?"
Sorry, Sasperilla, I disagree - it's the same question I was asked in a Junior School science lesson about *cough* 30-odd years ago! And we had to bring samples into school aswell !
I still remember my teacher's reaction when, having seen countless yoghurt pots and jars with blobs and dribbles of soap, vinegar, lemon juice, washing powder etc. - he looks at my sample and asks what it was, and I explaianed to him that I "came across it" inside my dad's car battery........