This week we worked on ways to separate mixtures and solutions. One of the labs we did was a beach in a bucket. The kids first made their beaches by combining in a bucket 1 cup of sand, 2 tablespoons of salt, 1 cup of gravel, 4 larger rocks, and 1 cup of water. After we mixed all the ingredients together, we discussed what part of our beach was the mixture (sand, rocks, gravel) and what part was the solution (salt and water.) We began separating the rocks with a spoon, then we used a sieve to separate the gravel. This left our sand, water, and salt. Many of the kids initially thought sand would be part of the solution because the sand would dissolve in the water. We proved this was not the case by letting the sand, salt, and water sit overnight. When we returned the next morning, the sand had settled to the bottom of our beaker.
|Separating rocks from our beach|
|What is left after taking out gravel|
We used a colander lined with a paper towel to separate our sand from our water and salt.
Finally, we were left with our solution, which we knew was going to be much more difficult to separate. After some discussion, the kids decided we needed to use a hot plate to evaporate the water. Some kids thought the salt would be left behind, but some were sure it would also evaporate because it had dissolved in the water. We used our hot plate to boil the water for a while, and when we returned, we found a cup full of dry salt!
|The salt left in the beaker|
|Separating water and salt|