Over the last couple weeks, our 6th graders have discovered the process of distillation. It started with a curiosity question about the dangers of drinking salty ocean water, which lead to a desire to make ocean water safe to drink. First, we had to find out exactly how salty ocean water is. A quick Google search later, we had made a big beaker of “ocean water”. Now to get the salt out!!
Their first thought was to filter the water. We tried pouring the water through coffee filters, but that didn’t work. We even tried double- and triple-layering the filters, but with no success. The water still tasted very salty. Their conclusion was that a “stronger” filter was needed. I brought in a Brita pitcher, and we ran the ocean water through that filter, and… still salty! Back to the drawing board!
One creative method we tried involved capillary action – the “wicking” of water from one container to another through a paper towel. The idea was that the salt would get stuck in the paper towel. Unfortunately, the students discovered that this method didn’t work either.
The one hint I gave was to put a small amount of water in a shallow dish, and let it sit over a weekend. When we came back to school, the students were surprised that although the water had evaporated, white salt crystals had formed on the bottom of the dish. This led one of our students to come up with a new idea – what if we could make the water evaporate, and somehow “catch” the steam? Using a hot plate, a pot with an upside-down lid, and an empty beaker, we were ready to test this idea.
The salty water in the pot began to boil, and the steam condensed on the lid, which directed the drips into the empty beaker. Once the water was cool enough, we tasted it… SUCCESS! Through their own sense of curiosity, and with a lot of perseverance, they had discovered how to distill water!