The Science of Disappearing in Water

Young children will enjoy this simple science experiment about water solubility. My daughter especially enjoyed the pouring and the mixing.

You don't need to use the fancy terms but this lesson is all about discovering what items will dissolve in aqueous solutions. This experiment works best with clear containers, but any small containers will work. A pitcher of water and a spoon for mixing are the basics. Then choose several household items to test. I chose table salt, pepper, granulated sugar, brown sugar, rock salt, corn meal, milk, oil, cinnamon and a life saver. Place each item in a small container.

Then set the child or children at the table and talk about one of the items on the table. Is it a liquid or a solid? Big or small? Try to get your child or children to describe the item. Then ask them if they think the item will dissolve in the water. Pour the water into the container with the item. Allow them to mix the contents with the spoon then discuss the results.

If the item "disappeared" you may want to allow your child to taste the water so he or she knows that the item is still present in the water even if he or she can't see it. If it didn't mix in (and it may take some time for it to settle if your child was vigorous with the mixing) did it settle on top or on bottom? If you are using rock salt and life savers discuss how larger objects take longer to mix in then small objects like table salt and sugar.

If you do decide to use life savers I recommend breaking them into smaller pieces as a solid piece took to long to dissolve. Or if your child is a little older (or more patient) you might compare the dissolving rate of a broken life saver versus a whole life saver.

As the experiment progresses your child will probably be less interested in talking about the experiment and more interested in just doing it. However, this will give you the chance to explain the science to your child as he or she revels in the joys or pouring and mixing.

If you need to brush up on your scientific terms here is a quick refresher. If you dissolve salt in water the salt is the solute and the water is the solvent. Solubility is the maximum amount of a solute that dissolves in a solute at equilibrium. Equilibrium is the point at which the solute and solvent are in balance and no more solute can be dissolved in the solvent (i.e. you dissolved all the salt in the water that it will hold and any more would settle to the bottom).

If you child is old enough you can discuss why some things dissolve. I will use salt as an example. Salt dissolves because its ionic bonds, when broken, give off less energy than the energy formed by creating new bonds with water. In other words the salt molecules can be easily broken into ions which are attracted to the very polar water molecule creating a more energy favorable state. So things that dissolve have bonds that are more easily broken.

I hope you and your child enjoy exploring water solubility together.