A new tool being discussed in many places I read is Screencastify. This great, easy to use extension allows for easy screen recorded videos or screen casts that can be done on a Chromebook. I have been considering creating a tutorial to this, but was beat to it and lucky for you, this one is better than I could have done! (Additionally the author, Chris Betcher, has a great accent that is much more enjoyable than my voice.)
Look for Screencastify in the Google Chrome Web Store here!