This is a video guide that accompanies Modern Marvels Gas Tech. I use something like this when I need a break or if I have a sub. There are approximately 60 questions that go in order with the video. An answer guide accompanies this worksheet. Modern Marvels videos can be found on the History Channel or the videos can be purchased online. I found it at this episode on Amazon at the following link: http://www.amazon.com/Modern-Marvels-Gas-Tech/dp/B0019KAQ7W/ref=sr_1_1?s=movies-tv&ie=UTF8&qid=1396640602&sr=1-1&keywords=modern+marvels+gas+tech.
It sells for $19.99 (actually I think it was less on Amazon). These videos are perfect when you have a substitute because the videos last about 45 minutes.