Did you know when you mix the reactants sulfur, tungsten, and silver, you get the products SWAg? The simulation begins with making sandwiches, to show pupils reactants and products of something familiar. They then can make water, ammonia, and combust methane by determining the number of molecules before and after each reaction. They finish by testing their understanding when given either the reactants or the products side and have to determine the number of molecules needed to balance the equation.