Details of the digestive tract suggest a repulsive sort of fun for youngsters. Lessons on saliva, bile and human wastes drive home the message that whatever goes into a child's mouth comes right back out the other end. Digestive system experiments for kids encourage students to imagine the journey that their foods and beverages embark on through the stomach, bowels and other organs.
Differentiating between the stomach and the intestines is easy when a child feels normal abdominal rumblings. Ask students to place their hands on their stomachs, and they most likely will touch just above their navels. The correct location of the stomach is actually 2 inches below the left side of their chests, just below the ribcage. Instruct youngsters to place their hands back on their belly buttons, and explain that this is where the intestines reside. Ask students to guess what causes all those funny rumbling noises. Describe how the stomach breaks up food for easier absorption in the intestines. Explain that mere anticipation of food stimulates stomach acid and muscles in the digestive system.
KidsHealth recommends asking children to rub their tongues with paper towels before sampling dry snacks, such as pretzels or crackers. Without saliva on their tongues, they will be unable to taste these foods. Have each child swallow some water and repeat the test. Not only will kids taste their snacks this time, but swallowing will be much easier with moist mouths. This experiment highlights the importance of saliva and tongues during digestion.
Another way to illustrate human digestion is to watch the breakdown of hard candies. Take four separate baby food jars and four pieces of hard candy. Smash two candies with a hammer to replicate the chewing process. Add a whole candy to a jar with water, as well as a broken candy to another jar of water. Drop an entire candy into a jar of vinegar, and do the same with candy fragments in a separate jar of vinegar. Like food particles, broken bits of candies dissolve faster. Students should set timers as they watch the progress during class. Note that the vinegar is acidic, which breaks down the candy. Relate the experiment back to how acid, enzymes and muscles of the stomach grind up and break down food as part of the digestive system.
In another experiment, students consume foods that are harder for humans to digest. Kids typically find this science project to be gross and cool at the same time. Students add either corn or lettuce to their meals. They watch to see how long those items work themselves through the digestive tract before being expelled from their bodies in their feces. Unlike some animals, humans lack a specific enzyme to break down corn and lettuce.