Suited for grades 4 through 8, this lab sheet walks your student through constructing a closed-loop cardiovascular model using two 500 mL plastic bottles, clear plastic tubing, Y-connectors, red food coloring, and a large syringe or hand pump. The seven numbered steps guide them from filling the heart bottle one-third full with colored water to sealing every connection with modeling clay or tape, then pumping the system and watching the red water circuit through the lungs, split into the body branches, and return to the heart. A materials list, an objective statement, a reference diagram labeling the heart, lungs, and body connections, and a Did You Know fact about daily blood volume are all printed on the same sheet.

The model of the human cardiovascular system pairs naturally with a circulatory system unit study or a broader human body sequence, sitting well after lessons on the heart’s chambers and before lab work on pulse and blood pressure. A What Happened section asks your student to describe in two to three sentences what they observed when they pumped the system, and five Think and Reflect questions push them to compare the model to the real system, identifying what each component represents and where the model falls short. Completing the sheet demonstrates understanding of blood flow direction, the role of the lungs as a circuit stop, and the difference between pulmonary and systemic circulation.