Get creative with juice and pennies to find out what happens when they are combined with one another. Pennies naturally tarnish, not rust, over time and the acid in juice can help to clean the tarnish off. Have children put on their thinking caps to help discover what type of juices are most acidic and what ones clean pennies the best.
The Set Up
Work on a clean, flat surface. Set up five tall clear cups to observe the different juices and the effect on the pennies. Place paper towels, napkins or cloths down under the cups to catch any excess juice when taking pennies out. Give each child or group five pennies to use. The pennies should be tarnished or discolored. Each child or group should have a sheet to record their observations on.
The five different cups will be labeled with the juice that is inside, only one type of juice per cup. Use grape juice, apple juice, pickle juice, grapefruit juice and lemon juice. Pennies become cleaner in more acidic juice such as grapefruit juice, pickle juice and lemon juice. Less acidic juice, such as grape and apple, may have little or no effect on the pennies.Use a pH strip to test the levels of acid in the juices before the children drop the pennies. Record the answer and then let them drop one penny in each cup.
Once the children have dropped their pennies and recorded their answers, let them experiment with salt and vinegar. Adding salt to different juices may speed the reaction. Pour vinegar into a cup and let the children watch another tarnished penny react. Once observations are recorded, add salt to the vinegar and record the answer.
Every child or group will have a different answer for their observations about the pennies. There is no right or wrong answer because no two pennies are tarnished the exact same. What may work for one penny may not work for another. Have the children compare their pH findings to find what works best for pennies.