Given that math can be a difficult concept for many students, your sequencing of the lesson seems very appropriate. The video is a great way for students to see and hear the lesson. If they need to see or hear it again they can do it as many times as they need to without holding other students back. Google Docs is a great way for students to collaborate with one another and share information. Teaching others is the best way to know you learned material, by using Google Docs, students will have the confidence to know they learned how to calculate moles. As a teacher, you can see who participated as well.
In order to make this a more social assignment, students could blog about what they learned and reply to another student’s response.