Adhira & Samar of Grade IV D, giving a wonderful presentation on how the Heart pumps blood into the body..
The water in the jar represents the blood in the heart. The pumping you do on the balloon mimics how the heart pumps in our bodies. The balloon on the straw works like the valves on the heart. It opens when you push down on the pump and closes as you release. This is what lets the blood flow up through the open straw, but like in the body, it prevents backflow of blood.
