Another cool place I never knew about until I started homeschooling (my kids): Lake Issyk Kul, located in Kyrgyzstan. We read about this gigantic saline lake today in The Silk Road by Kathy Ceceri.
We watched this video and then this one, just to get an idea of what the lake and the area look like. We also learned that Issyk Kul means "warm lake" in Kyrgyz. (It's not actually warm; the lake never freezes because of its salt content.)
Then I decided to give the kids a challenge. I gave them a small bowl with exactly one cup of water in it. I told them that I had put some salt in the water. How much? It was their job to find out!
Then, I just set them free. They talked together for a moment, then got out the food scale. They asked me for the tool that I had used to measure the salt (a tablespoon), and also wanted to know which container of salt I had used.
They carefully weighed the bowl of salted water. 346 grams, according to this scale.
Then they filled a bowl just like it with a carefully-measured cup of water and began measuring salt into it...
Within a minute they figured out how many tablespoons of salt they needed to put in to get to 346 grams!
Then we tried another salt experiment. One of these bowls is salted water (our Issyk Kul "sample") and one is plain water (our freshwater lake "sample.") We checked the temperature of each bowl, just to make sure they were roughly equal, then put both bowls in the freezer.
While we waited for our "lake samples" to freeze, we read this wonderful book by Mark Kurlansky. We had read it once before, when we did our salt nature study, but I think a great book always deserves revisiting!