Here is an introduction worksheet to Atomic Mass video from Teacher's Pet (video link is embedded at the top of the worksheet). There are seven questions in total. There are six questions that go along with the video and one assessment question to get the students to calculate the average atomic mass on their own.
This worksheet can be used in class, at home, or for review. Great for middle schools students who are being introduced to this topic. Good review for high school students who need to have a quick review.