!#8# Cohesion and adhesion - Two activities for primary school teachers

!±8± Cohesion and adhesion - Two activities for primary school teachers

Here are two simple activities to show students the basic concepts of cohesion and adhesion.

COHESION

"Niagara Falls"

MATERIALS

A Penny
Pipette
Detergent

PROCEDURE

Ask: "How many drops of water you think you can put on this fall without a cent over the edge?" Place the pot dime on a flat surface. With the pipette drops of liquid drops on a penny at a time, counting the drops until they have the oil spillEdge.

Take the same coin, and rub a solvent.

Provide the number of drops of water that you can rely on the dime now, pay without it over the edge.

With a pipette, the droplets of liquid on the penny drops and counting.

STATEMENT

Water molecules have a strong sense of cohesion, or attraction to other water molecules. This binding of the molecules is like the skin as a liquid surface, called surface tension. Soap reduces surface tension so thatto remain a few drops on the penny out with soap.

MEMBERSHIP

"PASS THE PEPPER"

MATERIALS

Cereal Bowl
Pepper
Liquid detergent for dishwashers

PROCEDURE

Fill bowl with water and brush a little pepper on top.

Ask: "What do you think will happen with pepper, if we add detergent?"

Drop a few drops of detergent in the center of the plate.

STATEMENT

Membership is the molecular force of attraction that holds together the various organs of contact. TheThe water is covering the pepper evenly from all directions. The detergent reduces the adhesive force between the liquid and pepper. The liquid around the edges of the bowl, untouched by the detergent industry, still has its pulling power.