The heart has two features that keep blood flowing in the right
direction. These are chambers and valves. Chambers fill with blood, then
squeeze to pump the blood out.

Each side of the heart has an entry chamber  ( atrium ) and an exit chamber ( ventricle ).
These pump one after the other to keep the blood flowing around.

Valves stop blood flowing backwards. When the ventricle contracts the atriums exit valve closes so blood cannot fall back into it. When the ventricle relaxes its exit valve closes to stop blood flowing backwards.

Easy Heart Pump Model - made using a jar, two straws and a balloon #scienceforkids #heartmodel

You can make a model of one chamber and valve easily to show how they work.

How to make a Heart Model

 A clean, transparent jar

1 balloon


Food colouring

2 plastic straws

Food colouring




Fill the jar just over half full and add a few drops of food

Cut the neck off the balloon and stretch the rest over the opening
of the jar. Save the balloon neck.

Use the scissors to carefully poke two holes in the balloon. These
should be smaller than the straw as you need them to fit tightly.

Push each straw through a hole in the balloon.

Place the neck from the balloon over the end of one straw and

Seal the end of one straw with the balloon neck and attach in
place with tape. The is your valve.

Press down on the balloon and watch what happens. Water should be
forces out of the straw that isn’t sealed.

The balloon end valve stops water going back down the straw.

Take the balloon valve off the straw. You should find that water
now goes back down the straw.

When you push down on the balloon this is like your heart contracting and squeezing the heart chambers. This pushes blood out of the heart and into arteries.

Easy Heart Model - make a model of one chamber of the heart using a jar, balloon, straws and water.

More Human Body Science Experiments

If you enjoyed this activity we’ve got lots more human body science experiments to try.

Listen to your heart with this super simple homemade stethoscope.

This digestion model is great messy fun and a fantastic way to demonstrate the journey of food through the human body.

Learn about the different parts of the brain and their functions with our easy play dough brain model.

Science Books for Kids

Don’t forget we also have a couple of science books for kids available from bookstores in the US and Amazon in the UK.

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Originally posted at Science Sparks