Measuring vocabulary is one of the easier ways to test learning. That's unfortunate, because learning vocabulary is one of the least important parts of learning science. However, it's often what is used to decide whether today's classroom experience or museum visit was worthwhile. Of course we want children to learn the proper vocabulary eventually. They will need the words and the mathematics to communicate efficiently as their learning develops.
Classrooms are usually better places than museums for learning vocabulary.
But learning vocabulary either before or in the absence of internalization of the concepts and the generation of interest is likely to be a short-lived success, as the Harvard graduates demonstrated. One of my favorite exhibits at the new Science Playground exhibit at the New York Hall of Science is the Standing Spinner. You hold onto a post in the center, which rotates with you. If you stand on the platform and shove off with one foot, you begin spinning around. The fun part is leaning in or leaning out.