1. Emma Jardine Dr. Fritz period 7

2. What happens when a paper towel absorbs water?  Water molecules have a negative and positive end  They are attracted to opposite charges on other molecules  Water molecules can be attracted to each other and paper  The water is attracted to the paper towel and spreads out

3. Adhesive Forces  Adhesive forces are the attractive forces between unlike molecules  They are caused by forces acting between two substances  Adhesion causes the liquid to cling to the surface on which it rests

4. Cohesive Forces  Cohesive forces are the intermolecular forces which cause a tendency in liquids to resist separation  These attractive forces exist between molecules of the same substance  This force tends to unite molecules of a liquid because the molecules' dislike for its surrounding

5. Effects  When liquid is placed on a smooth surface, the relative strengths of the cohesive and adhesive forces acting on that liquid and determine the shape it will take  If the adhesive forces between a liquid and a surface are stronger, they will cause it to wet the surface  If the cohesive forces between the liquid are stronger, they will resist the adhesion and cause retain its shape

6. Example Lab

7. Materials  A glass of water  An empty glass  Paper towels

8. Directions  1. Fold the paper towel into a thin strip  2.Place one end of the paper towel into the glass filled with water and the other into the empty glass  3. Record what happens

9. The Beginning  The paper towel starts to get wet

10. Half An Hour Later  The second cup is starting to fill with water

11. An Hour Later  The second cup is filling up with more water

12. A Few Hours Later  The second cup has almost the same amount of water as the first cup

13. The End Result  There is an even amount of water in each glass

14. Why did this happen?  The water used capillary action to move along the tiny gaps in the fiber of the paper towels  This happens because of the adhesive force between the water and paper towel being stronger than the cohesive forces inside the water itself