The particles of the iron make the noise in expanding.

If a piece of glass be held in the hand, will the glass become warm?

The glass will become as warm as the hand.

What part of the glass will be warmed first?

The part touching the hand will be warmed first.

What part of the glass will be warmed last?

The part farthest from the hand will be warmed last.

Which part of the glass will be expanded first?

The part touching the hand, because it is first warmed.

Which part will be expanded last?