TED Talks
Ted: Ted Ed: Dark Matter: How Does It Explain a Star's Speed?
Video describes how stars move in a spiral galaxy and how their speeds can be explained by accounting for dark matter. [3:17] Includes a brief quiz and a list of additional resources to explore.
Scholastic
Scholastic: Study Jams! Science: Our Solar System: The Universe
A video and a short multiple-choice quiz on the Universe and what it is made up of.