Colloid And Surface Chemistry: Surface Tension Of Liquids

UDEC 2214 Colloid and Surface Chemistry

Experiment 1: Surface tension of liquids

Nama : YONG LI YING
Student ID : 1307642
Group Members : Bernard Hiew and Yong Zhi Rhen
Practical Group : P4
Date of Experiment : 13/8/2015
Lecturer : Dr. Yip Foo Win

Objective:
To understand the basic concept of surface tension in liquids and how it affects the properties of liquids.
Introduction:
Surface tension is a force acting at right angles to any line of unit length on the liquid surface. It accuracy will be increased due to increasing the area of the surface isothermally and reversibly by unit amount. Surface is the term used when the boundary between two phases contain gas as one phase while interface is the term used when the boundary is between

Clean water was poured into a petri dish.
2. Powdered sulfur was dusted on the surface of clean water. The observation was recorded.
3. The surface of water was touched with a toothpick. Observation was recorded.
4. The tip of the toothpick was dipped in detergent. Surface of the water was touched and the toothpick was hold in place for a while. Observation was recorded.
Procedure B:
1. Low-fat milk was poured into a petri dish.
2. A couple of drops of four differently colored food coloring were added. The drops were kept closed together in the centre of the petri dish. Observation was recorded.
3. The surface of the milk was touched with toothpick. Observation was recorded.
5. The tip of the toothpick was dipped in detergent. Surface of the milk was touched and the toothpick was hold in place for a while. Observation was recorded.
4. The process was repeated by replacing low-fat milk with full cream milk and later with

In part a, the sulphur powder was sprinkled on the water surface and the sulphur powder was floated on the surface. Once the surface was touched by the toothpick, the sulphur powder starts to float further from the centre where the place touched by the particular toothpick. In part b and c, the colourings are floated on the surface when added on the surface of milk. When the toothpick was used to touch on the surface of milk, the food colourings were disrupted insignificantly. In part d, food colourings were added on the surface of water. The colourings were sunk to the bottom of water. This shows that when detergent is introduced to the liquid, it acts as the surfactant which reduces the surface tension of the liquid. With the aid of the food colouring, thus, ‘milk rainbow’ is