Why Do We Add Salt to the Conductive Dough?
Squishy Circuits uses conductive dough to move electricity (electrons) from our batteries through the components. The conductive dough allows these electrons to flow because it contains salt and water! You may have heard that water and electricity shouldn’t mix, but did you know that pure water is actually a good insulator – meaning that electricity cannot flow through it easily? Pure water (distilled or deionized) is made of hydrogen and oxygen and these elements are bound together and are electrically neutral So, if you try to pass electricity through pure water, it cannot pass through.
However, very rarely do we have access to truly pure water. Most water has dissolved impurities such as minerals and salts and they can conduct electricity when they’re in water. So, it’s best to avoid combining electricity and water (unless you’re using Squishy Circuits of course!). We add table salt to our conductive dough to increase the amount of electricity that can flow and keep our circuits powered.
That’s the quick answer, but to fully understand let’s dive even deeper (and get a lesson in chemistry!)
Water molecules are made of hydrogen and oxygen atoms. Hydrogen has a +1 charge and oxygen has a -2 charge. To remain electrically neutral there are two hydrogen atoms for each oxygen atom. Hence, the abbreviations, H20 that you may have seen. Despite being electrically neutral, water molecules are uniquely shaped (like a Mickey Mouse head) such that they have a positive and negative side. This means they are ‘polar’.
Salts are made of a positive and negatively charged ion. In Squishy Circuits we use table salt which is made of Sodium (Na+) and Chlorine (Cl-). They combine to make NaCl which is also electrically neutral since Na has a +1 and Cl has a -1 charge (last time you sprinkled salt on your food it didn’t shock you!). But, once you add a salt into water, the polar water molecules arrange themselves so that they pull the salt molecule apart into Na+ and Cl- ions.
When using Squishy Circuits, the two terminals of the battery holder create a positive and negative side of the conductive dough. The Na+ ions are attracted to the negative side, and the Cl- ions are attracted to the positive side. This causes the ions to begin to flow in opposite directions.
It may seem that the movement of ions should cancel each other out, but remember that they have opposite charges. So, the positive ion moving in one direction and the negative ion moving the opposite direction (but with an opposite charge) causes their movements to actually cause a net positive electrical current flow.
This positive flow is the same as flowing electricity and completes our circuits!