What it shows
The heart pumps blood in a loop through the lungs and the body, and valves make it flow one way. The model shows double circulation with two pumps, one for each side of the heart, and two tube loops.
The science
The heart has four chambers; the right side sends oxygen-poor blood to the lungs and the left side sends oxygen-rich blood to the body. Valves keep it flowing in one direction. Each squeeze bottle stands for one side of the heart and pushes the coloured water through the tubes like heart muscle pushing blood. The blood returns through veins and the cycle repeats, so each blood drop passes through the heart twice per round trip: right side, lungs, left side, body, and back to the right side.
Materials
Cost: under Rs 500. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- Two small soft squeeze bottles with caps, one for each side of the heart
- Four one-way valves (aquarium air-line check valves from a pet shop, or flaps cut from a balloon)
- Transparent tubes, about 2 metres
- A little food colour for the water
- Red and blue tape for marking the tubes
- A tray and a bucket
- Cardboard backboard
- Hot glue or clay to seal the caps
Safety
For this project: An adult must cut the tubes, make the holes in the caps and use the hot glue. Do the experiment over a tray to catch spills. This is a learning model of circulation and not a way to measure anyone’s health.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
Step by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Fix the backboard flat and draw the heart in the middle with the lungs on one side and the body on the other, marking the right and left halves of the heart.
An adult makes two holes in the cap of each bottle and fits a tube with a one-way valve in each hole, one pointing in as the inlet and one pointing out as the outlet, then seals the gaps with hot glue or clay.
Join the outlet of the right bottle to the lung drawing with tube, and the lung tube back to the inlet of the left bottle.
Join the outlet of the left bottle to the body drawing, and bring the body tube back to the inlet of the right bottle.
Fill the whole loop with coloured water and push out every air bubble; then wrap blue tape on the tubes carrying oxygen-poor blood and red tape on the tubes carrying oxygen-rich blood.
Squeeze both bottles together gently and watch the water flow in the tubes.
Squeeze about 70 times in one minute, like a resting heartbeat, and measure how much water passes a mark on a tube.
Show how the valves stop the water from going back by watching what happens when you release the bottles.
What you should see
The water circulates in one direction through the lung loop and the body loop, and each squeeze moves a measured amount around.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
01How many chambers does the heart have?
Four.
02What do valves do?
They stop backflow of blood.
03Which side carries oxygen-rich blood?
The left side.
04Why is it called double circulation?
Blood passes through the heart twice in one full round.
Take it further
Compare the flow when you squeeze faster, as in exercise.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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