With NGSS there is renewed focus on providing learners time to wrestle with ideas and construct explanations, both individually and collaboratively through the science and engineering practices. So it is important to reflect on the difference between description and explanation. I've been thinking about how many times I asked my students (on a test, a worksheet, in a lab, or class discussion) to explain something and whether I was really looking for them to explain - or if sometimes I really meant describe. So I suppose the first question to ask is whether distinguishing between these is actually important. I think it is.
Think about the moon's phases. What answers do we expect if we ask students to, "explain the phases of the moon?" Explain means that students provide a causal account for the phases, which would include things like, the moon orbits the Earth approximately every 28 days, and as it position changes within the Earth-moon-sun system, the one side of the moon that is lit due to reflection of sunlight from its surface is seen either wholly or only in part by an Earth-based observer. When we see the whole side of the sunlit portion of the moon we see a full moon. But when we can see only a proportion of the sunlit side, say only a sliver of it, then the moon is said to be in a different phase - the crescent phase. (Video explanation)
If we only ask students to describe the phases, then they can describe what an Earth-based observer sees, but they don't need to have any greater understanding of the Earth-moon-sun system if they are only describing. With NGSS we need students to go beyond description and develop explanations of phenomena. But this requires giving them time to develop understanding and the tools (practice with the practices) that help one make sense of the natural world. Thinking of "Depth of Knowledge," NGSS requires DOK 3 and 4, so our teaching must push students to these greater DOK levels, with appropriate scaffolding to help them achieve at those levels. One great scaffolding strategy is asking students guiding questions that require explanation rather than description. When working with student groups, you can ask questions that remain unanswered - you can pose questions to a group and then leave the students to work collaboratively with each other to develop explanations (video).
Does the difference between describing and explaining really make a difference in learning?
Read more at these links:
@NGSS_tweeps is a community Twitter account: each week a different educator tweets about NGSS, providing a window into their classroom