Observation vs. Inference
Student observe two cups, one slightly smaller and skinnier than the other, with one put inside the other. The cups are turned upside-down and the smaller one is caught as it falls out of the larger cup. The larger cup is filled up about half way with water and the smaller cup is smooshed into the larger until they fit together. The cups are turned upside-down and then let go of the bottom. The smaller cup should stay in the larger.