What happens when you leave a penny in soap?

When you leave a penny in soap, particularly in a solution with soap and water, the soap can help remove oxidation and tarnish from the penny's surface. The soap molecules interact with the copper, breaking down grime and allowing the penny to become cleaner. Additionally, the soap's surfactant properties can help disperse any oils or dirt on the penny. However, prolonged exposure may not be beneficial, as soap can leave a residue.