Warm gas is expanded gas and occupies more space, and if it passes through your meter, it will be registered as more gas than if it were cooled and more compact. The gas company gains if gas is warm when it goes through your meter because the same amount of warmer gas has a greater volume. Every part of a metal ring expands when it is heated-not only the thickness, but the outer and inner circumference as well. Hence the ball that normally passes through the hole when the temperatures are equal will more easily pass through the expanded hole when the ring is heated. Blacksmiths mounted metal rims in wooden wagon wheels by first heating the rims.
Brass expands and contracts more than iron for the same changes in temperature.
Since they are both good conductors and are in contact with each other, one cannot be heated or cooled without also heating or cooling the other. Cooling the two will not result in separation either, for even at the lowest temperatures the shrinkage of brass over iron would not produce separation. The gap in the ring will become wider when the ring is heated. When you heat the ring, the lines will be farther apart-the same amount as if a real gap were there. Every part of the ring expands proportionally when heated uniformly-thickness, length, gap and all.