Now that we have gone to so much trouble to dissolve crystals in water, we will see how we can un-dissolve them. ("Undissolve" is not a real word.) Actually, what we will do is remove the water (either all of it or some of it) from the solution, so that we have crystals of the substance we dissolved in the water.

We will do it in both of two ways:

(1) We will heat water until it dissolves all the salt we put into it, then put a small amount into a shallow dish, and put it in a sunny window. This may take a day or so. (2) We will heat the rest of that salt-water until the water has evaporated. When the water is nearly gone, we will turn off the heat, and allow the pan to cool, and set it aside until the water in the saucer has evaporated.

When both containers are dry, let's take a close look at the crystals left behind. Since the crystals in the saucer took longer to form, do they look any different from those we dissolved on the hot-plate?

Let's do the same things with sugar-water, and see if we get similar results.