Surface tension.

surface tension and all about it
how to find it in nature, examples, and measurements

1. GROUP MEMBERS Maryam Akhtar BS CHEM 19002067004 Malaika Jabeen BS CHEM 19002067005 Umme habiba BS CHEM 19002067014 COURSE: PHYSICAL CHEMISTRY SUBMITTED TO SIR KHIZAR

2. Surface tension

3. Introduction Causes Effects Physical Units Examples Factors Affecting Phenomenon Observed Due To Surface Tension METHODS OF MEASUREMENT: Capillary rise method Max bubble pressure ,method Oscillating jet method Drop analysis method DU NOUY method CONTENTS APPLICATION OF SURFACE TENSION

4. HOW TO EXPLAIN SURFACE TENSION

5. CAUSES: The  surface tension of a liquid results from an imbalance of intermolecular attractive forces, the cohesive forces between molecules: A molecule in the bulk liquid experiences cohesive forces with other molecules in all directions. A molecule at the  surface  of a liquid experiences only net inward cohesive forces. ADHESION FORCES. CONTACT ANGLE WETTING

6. COHESION FORCE:

7. ADHESION FORCE:

8. CONTACT ANGLE:

9. WETTING:

10. Effects of surface tension 1.Water:

11. 2.SURFACTANTS

12. PHYSICAL UNITS OF SURFACE TENSION :

13. SURFACE TENSION

14. Capillary rise method Max bubble pressure ,method Oscillating jet method Drop analysis method DU NOUY method

15. CAPILLARY ACTION

16. COMPLICATIOB OF CONTACT ANGLES

17. CAPILLARY RISE

18. Du Nuoy RING METHOD

19. CORRECTION FACTOR

20. EFFECTS

21. EFFECTS

22. APLICATIONS

23. Applications of surface tension:

24. Applications in Chemical Industry: Determination of efficiency of detergent Formulation: Surface tension determines the efficiency of detergent formulation. How?

25. Cont. Defect free coatings of paints: Defect free coatings of paints can be done by optimization of surface tension. How?

26. Cont. Application in emulsions: Emulsions are a type of colloid in which surface tension plays a role. Water and oil Tiny fragments of oil suspended in pure water will spontaneously assemble themselves into much larger masses. But the presence of a surfactant provides a decrease in surface tension, which permits stability of minute droplets of oil in the bulk of water (or vice versa)

27. Cont.

28. Applications as diagnostic tool: Surface tension changes in biological phenomena can determine various diseases in the human body. Respiratory distress syndrome : RDS is more frequent in male infants and infants of diabetic mothers. These infants have little or no phospholipid in their surfactant content which causes a high surface tension value. Luckily, this disease can be treated by applying naturally modified or synthetic surfactants to replace surfactant content of the lung and lower the surface tension properties of the lung and help for an easier breathing cycle.

29. Obstructive sleep apnea : Cont. Obstructive sleep apnea is caused by the negative pressure in upper airway and the imbalance of forces to maintain an open airway. Surface tension forces between mucosal surfaces play an important role in the pathogenesis of the disease. Topical application of synthetic surfactant to the upper airway at night may reduce the severity of the disease, decrease surface tension and facilitate opening of the upper airways.

30. Applications in daily life: Small insects such as the water strider can walk on the surface of the water because their weight is very less so they can’t penetrate the water.

31. Cont. Disinfectants are mainly the solution of low surface tension so that when we use them in the field they can float on the water and spread out on the cells to destroy them. Soaps and detergents also work based on surface tension. They lower the surface tension of the water so that the soaps and detergents easily soak into the pores and holes. A small needle can be floated on the surface of the water.

32. Cont. The water bubbles are round because the surface tension of water provides the tension to form the bubble with the water and the surface tension minimizes the bubble into spherical shapes.