Explanation Acids and bases are the stuff of chemistry. Measuring acidity in foods is not only fun, it can lead to surprising results. You may think you can taste which foods contain acid, like any of the citrus juices. For some foods that's true. But, it's difficult for your tongue to rank them as to which is more acidic.
Procedure Pour the apple juice into the jar.
It's important NOT to cover the jar. Remember, the bacteria you need comes from the air. Leave the jar on the kitchen counter in a safe place where it won't get knocked over. Be sure you let everyone in your family know you are working on an experiment. Test the apple juice for vinegar every day until you get a positive result.