Donating Blood Using … Capillary Action!

Contributor: Kaitlyn Zimmerman. Lesson ID: 12694

Capillary action comes in handy when you wash your car, take a bath, and water plants. Did you know it can also be used to save lives? Donating blood uses capillary action to draw life-saving fluid!


Chemistry, Physical Science

learning style
personality style
Golden Retriever
Grade Level
Primary (K-2)
Lesson Type
Quick Query

Lesson Plan - Get It!

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Did you know that capillary action is occurring when you are using a sponge? Let that soak in for a minute, then continue on with this lesson!

Here is an absorbing fact about your blood!

As you may have learned by now, blood is a very important part of your body.

  • Did you know that your body is able to make more blood cells when more are needed?

However, there are some cases when people need to receive more blood in order to live. This is a big reason why many people all over the world donate blood to trusted organizations!

Before continuing, if you missed or would like to review the previous lessons in our Capillary Action series, go to the Related Lessons in the right-hand sidebar.

  • Did you know that when people donate blood, it is another example of capillary action?

Before someone donates blood, the nurse will want to check nutrient levels, such as iron and calcium in the blood. Capillary action takes place as the nurse places a small tube, known as a capillary tube, into the blood stream inside the body. Because the tube is so thin, the bond between the blood molecules is stronger than the force of gravity, therefore rising up the small tube!

  • But why talk about this when Dr. Z can give us an explanation AND experiment to show how this works?

Dr. Z, here we come!

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In the words of Dr. Z, “Isn’t that crazy?” As shown in the experiment, the colored water was able to “climb up” the capillary tube! This is because it was small enough that the bond between the water molecules is greater than the force of gravity inside the small tube. However, the water inside the larger piece of tubing was unable to travel as far because the bond between the water molecules was overcome by the stronger gravitational force than that inside the capillary tube.

Move on to the Got It? section to revisit the sponge!

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