Contains the keyword Science--Study and teaching (Primary)
Hard-to-teach science concepts : a framework to support learners, grades 3-5. Arlington, Va.: National Science Teachers Association; 2011.
"The four hard-to-teach concepts examined are the flow of matter and energy in ecosystems (life science); matter and its transformations and understanding changes in motion (physical science); and Earth's shape and gravity (Earth and space science)."

