I'm looking for some interesting online science games, videos, or courses that my 1st grade DS6 can use independently while the rest of his class is in math. He goes to math one grade up, and has an hour to kill each day during 1st grade math. We've been sending him with science books and questions to answer, but his reading skills are far behind his cognitive abilities, and I'd like to find something more advanced that he can do online.

He's particularly interested in physical science, but anything would do. I know I've read about lots of good online science sites on this forum, but I'm not finding any of the old posts through the search feature. Thank you!