CAPILLARY ACTION

Emma Jardine

Dr. 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