premise: To clean a penny
hypothesis: Mix together 1 teaspoon of salt and 1/4 cup white vinegar in a glass or plastic bowl, and stir until the salt is completely dissolved. Place a half dozen old, tarnished pennies into the solution, wait 10-20 seconds, then remove them and place them into a bowl of water. Take them out of the water, dry them on a paper towel and voila, shiny new pennies!