The following lesson was developed because the students wanted to know why the ocean is salty. For students to observe how salt concentration increases in water. Also, how the salt remains after the water evaporates. The student will be able to explain why the sea is salty. Rock salt, water, containers, strainers.
Students pour water over the rock salt which is contained in a strainer.
The water plus dissolved salt will be collected in a plastic cup. Students will taste the water sample. Students will allow the water to evaporate, observing that the salt remains. The above procedure is repeated over a 3 or 4 day period. The students will observe that the salt increases each time new water is added.