What experience confirms that there are gaps between molecules?

Take a beaker and fill it first with peas, and on top with millet of the same volume. Let’s note the top level of the beaker’s contents. Let us assume that peas and grains of millet are models of molecules of two different substances. Shaking the beaker, mix the millet and peas. The volume of the mixture is proved to be less than the sum of their initial volumes. Grains of millet occupied the gaps between the peas. The same thing happens when sugar is put into tea. This proves that there are gaps between the molecules.

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