SURFACE TENSIONINTRODUCTION

SURFACE TENSIONRESULTS FROM THE COHESIVE FORCES BETWEEN LIQUID MOLECULES

THE MOLECULES AT THE SURFACE DO NOT HAVE OTHER LIKE MOLECULES ON ALL SIDES OF THEM AND CONSEQUENTLY THEY COHERE MORE STRONGLY TO THOSE DIRECTLY ASSOCIATED WITH THEM ON THE SURFACE.

THIS FORMS A SURFACE “FILM” THAT ALLOWS IT TO RESIST AN EXTERNAL FORCE

SURFACE TENSION•AT LIQUID-AIR INTERFACES, SURFACE TENSION RESULTS FROM THE GREATER ATTRACTION OF WATER MOLECULES DUE TO COHESION THAN ITS ADHESION (IS THE ATTRACTION BETWEEN TWO DIFFERENT SUBSTANCES) TO AIR.•THE NET EFFECTS IS AN INWARD FORCE AT ITS

SURFACE THAT CAUSES WATER TO BEHAVE AS IF ITS SURFACE WERE COVERED WITH A STRETCHED ELASTIC MEMBRANE.

COHESION•DEFINITION:

IS THE FORCE OF ATTRACTION BETWEEN MOLECULES OF THE SAME SUBSTANCE

SURFACE TENSION•AT LIQUID-AIR INTERFACES, SURFACE TENSION RESULTS FROM THE GREATER ATTRACTION OF WATER MOLECULES DUE TO COHESION THAN ITS ADHESION (IS THE ATTRACTION BETWEEN TWO DIFFERENT SUBSTANCES) TO AIR.•THE NET EFFECTS IS AN INWARD FORCE AT ITS

SURFACE THAT CAUSES WATER TO BEHAVE AS IF ITS SURFACE WERE COVERED WITH A STRETCHED ELASTIC MEMBRANE.

SURFACE TENSION

SURFACE TENSIONBECAUSE OF THE RELATIVELY HIGH ATTRACTION OF WATER MOLECULES FOR EACH OTHER, WATER HAS A HIGH SURFACE TENSIONHAS A DIMENSION OF FORCE PER UNIT LENGTH (DYNES PER CM) OR ENERGY PER UNIT AREA ( ERGS PER SQUARE CENTIMETRES)