What experiments confirm that substances are composed of the smallest particles?

1.Experience with copper (or brass) ball and ring. In an unheated state, the ball freely passes through the ring. If it is heated, then it will expand and will no longer pass through the ring.

2.Pour water into the flask to the very top and close tightly with a stopper. Pass a glass tube through the cork. The water will partially fill the straw. Mark the liquid level in the tube. Then heat the flask. When heated, water will flow out of the vessel.

These experiments indicate that substances consist of the smallest particles, between which there are gaps.