The introduction video is very informative and provides great visuals for students to learn the three states of matter. The activity is relevant and interesting for students especially if it's tied into making some ice pops. Ziploc bags work well for this activity if balloons aren't available, but don't completely fill up the bag that is placed in the freezer because as the water freezes it'll expand a bit, so I would suggest filling it up only about half way. Another fun exercise for younger students would be to act out the three states of matter and pretend that the students themselves are water molecules so that the kids can stand up and move around a bit.