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Water Droplets on Different Surfaces-Cohesion, Adhesion and Surface Tension

This is a great center activity.  I give my students droppers, a cup of water and a small piece of each of these materials: wax paper, parchment, foil, paper towel and paper. 

Drop water on the different materials and observe how the water looks and behaves.

What do you notice?
How do the water droplets behave?
How is the reaction different with the different materials?

One of these materials will allow you to separate a single drop into several drops and then reunite them by dragging the dropper.  Can you figure out which material will do this?  Why does it work on this material?

If you put a tiny drop on one of these materials and slowly turn the piece upside down the drop may remain on the material.  Can you figure out which one does this?  Why? 

Which material is the most absorbent?  Which material does not absorb water at all? Why do water drops on some materials look round?
How close together can you put two drops of water without them touching? Can a drop of water bounce off another drop of water? What shapes are the drops of water as they fall through the air? 

Does water do the same thing on all surfaces?  What evidence do you have to support your claim?

Students record their observations about each material.

Teacher Background Information:  In all systems within which water interacts with another surface, both adhesion and cohesion are factors.  When cohesion is more of a factor, the water forms spherical droplets; when adhesion is more of a factor, we get sheets of water. 

How Does Water Move Through Paper?

Paper is made of plant fibers. In the process of making paper, the fibers overlap forming a massive network of tunnels in all directions throughout the paper. The chemical molecules making up the fibers are attractive to water molecules. 
Adhesion is the name of the force of attraction between two unlike molecules. Paper absorbs water because the paper molecules and water molecules attract, thus stick together. 

Other Properties at Work:

Cohesion is the force of attraction between like molecules. When you see a round drop of water it is because the water molecules (like molecules) are sticking together. 
Surface Tension is the ability of water to form a rounded surface.  This is a cohesive property.
Can you name the property represented in each photograph?

Here is a fold template that you can save to your desktop and print and use.  Have students add a bit of each material to the cover and write observation underneath. 
This activity is part of a complete integrated unit on Properties of Water available here Integrated Unit on Properties of Water

Lessons from this unit are also available individually.
If you like using interactive notebooks you may also like my templates for foldable graphic organizers available in my TPT Store.  Pull Out and Slide Foldables  Pop-Up and Pop-Out Foldables Super Pack of Foldables Circles and Wheels
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NGSS PS 5.1 Make observations and measurements to identify materials based on their properties.

This lesson is aligned with the NGSS Crosscutting Concepts of Systems and Matter and Energy. 

This post and lesson are also aligned with the NGSS Science Practices of Planning and Carrying out Investigation, Constructing Explanations, Engaging in Argument from Evidence and Obtaining, Evaluating and Communicating Information.

FREE Chemical Reaction Resource

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