Questioning minds

A normal walk to school this morning, chatting about the day ahead, when Alec pipes up "What is fire?"

Where the question came from, goodness knows, but it got us all thinking. My initial response was, when something gets hot it releases energy, and that's what fire is, the release of energy. "But why does one thing burn and one thing melt?",
"Is the sun fire?"
"Why do dome solids burn, like wood, but other things like gases burn?"

All from walking to school! Typical that these questions pop up when we have no way of finding out! I have suggested to them all that they ask their teachers, see if they have any better answers.

This one to go down with the classics I've had in the past such as "why is air invisible?" (Luke aged three!) and "if God is in everything, if I chop down a tree, am I killing God?" (Luke aged 4)

They constantly amaze me with their enquiring minds. I think I must have just taken things for granted as a child, and never questioned why. I certainly can't remember being so inquisitive!