CAPILLARY ACTION

Emma JardineDr. Fritz period 7

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

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

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

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

Example Lab

Materials A glass of water An empty glass Paper towels

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

The Beginning The paper towel starts to get wet

Half An Hour Later The second cup is starting to fill with

water

An Hour Later The second cup is filling up with more

water

A Few Hours Later The second cup has almost the same

amount of water as the first cup

The End Result There is an even amount of water in

each glass

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