I recently attended a conference in covering the Next Generation Science Standards that guide science curriculum in the United Stated. After 10 years of teaching science it seems to me that we are finally centering in on what it means to educate students to be scientific thinkers. Science is more than just facts that need to be learn. After a good science education students should be able to not only recount facts, but should know how to ask questions, observe the world around them, create models, make claims based on evidence/models and be able to explain and modify their models when needed.
At its very essence, science as a practice is centered around the understanding of natural PHENOMENON and that is where good science teachers start with any unit/lesson. Only after making observations and discussing with colleagues can we start to tap prior knowledge to try to make sense of the world around us. This video is an example of a natural phenomenon that can be observed by students. Notice the lack of words and complicated explanations. The students should be the ones doing the sense-making, let's not cut the scientific process off at the knees before we even start.