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Capillaries in Action

What You Need:

• Celery stalk with leaves on it
• Butter knife
• Food coloring
• Water
• Two glasses

Question: How do veins work?

1) First, use the butter knife to carefully trim the end of the celery stalk.

2) Then, fill a glass with water and add a few drops of food coloring.

3) Now put the celery stalk into the glass of colored water.

4) You'll soon see the water travel up the veins of the celery stalk.

5) Water can defy gravity and travel up the stalk because of adhesion. Adhesion is the force that attracts water to other surfaces. In this case, the water adheres to the inside surface of the veins. Adhesion is what pulls the water up into the celery stalk. When water travels in this way it is known as capillary action.


A Scientific Explanation:

A celery vein is a simple way to think of the human blood system. Celery veins transport, or carry, water and nutrients in the plant. Blood is transported in a similar manner in the human body. But instead of using capillary action, we have a heart that pumps the blood through our veins and arteries.


Try this again but use two glasses of differently colored water. Split about 1/3 of the celery stalk in half. Place each half into the two glasses of colored water. Can you explain what happens?