What happens to the hole in the centre of a metal washer when the washer is heated?
The washer expands but does it expand into the hole and the hole get smaller, does the hole get bigger or remain the same size?
Thanks
Chris

As a guess I would say that the hole gets larger.

When an object is heated the molecules become excited and further apart, if the hole got smaller, surely that would imply the molecules getting closer together?

Yes, the hole gets bigger. Remember that heat expansion is from atoms moving away from each other... so outwards is the only it can go.

(This effect is how they used to get iron tires on wagon wheels and iron hoops on barrels)

SURE the hole gets larger.
Expansion is always on the outer side and not the inner.