Great hands-on science lesson. Conducting experiments is a great way to hold student interest. The idea of posting the results to a blog is a great way for the students to practice technical or scientific writing. It should also be a motivation to do their best since their audience will theoretically be the whole world.
I did wonder if the lab, perhaps, also focused on how salt solutions keep the roads from icing over. It wasn't directly mentioned in the lesson plan, but it was alluded to in the section about motivation under the sub-heading "meaningfullness."