For this experiment, you need two glass beakers or other containers, a kettle to heat water, a rock or other rough object, a string, salt or sugar, water and, optionally, a magnifying glass. You will also need either a coffee filter or tissue.
Prepare the experiment by dissolving as much salt or sugar into the water as you can. Use the kettle to heat the water first to maximize dissolvability and stir vigorously. Continue to add salt or sugar until it’s clear that no more will dissolve. Divide the solution between the two dishes and place the rough object into one. Dangle the string into the other, tied to a pencil or straw set across the top. Cover with the tissue or coffee filter to keep out dirt and bugs.
Place your dishes in a sunny, warm spot so that the water will evaporate as quickly as possible. Check on them every day. With your magnifying glass, watch as crystals begin to form on the rock and string. Once crystals start to form on the sides of the dish, make a new solution in a new dish and move the rock and string, with their newly formed crystals, leaving behind the original dishes to continue to evaporate.
Keep a log book, writing down your observations of the crystals on a daily basis. Notice how quickly they grow, and what shape they take. Also notice the appearance of the crystals on the bottom of the abandoned dishes. Compare them to the salt or sugar crystals that were originally dissolved and see how they’re different.
At the same time that you’re conducting the main experiment, do a simple second one to compare the evaporation rate of plain water to that of a salt or sugar solution. First, make sure that you have measured the amount of solution in each dish. Place another dish of the same amount of water next to the others and see which one evaporates first. For this experiment to be accurate, all dishes should be identical.