COLLOIDS- SOME OF ITS PROPERTIES. Some of the important properties of colloids are 1- Brownian motion 2- Thermo-Reversibility 3- Filterability(dialysis) 4- Electrical property 5- Tyndal effect

Activity—1 Brownian motion The random movement of small particles due to collision. Aim:To prove that colloid exhibit Brownian movement. Materials: microscope and slides. Water, starch solution. Procedure: Take a drop of starch solution/milk or ink. Make awet mount by adding a drop on a clean slide.

Brownian motion

Activity—2 2. Thermo reversibility.  Colloids may exist in two states SOL or GEL.  Sol shows fluidity.  Gels are almost solid.  Example—gelatin.  Gelatin when heated gets converted to fluid state --Sol state  When cooled it solidifies to form a Jelly—Gel state.  Gelatin has the unique ability to be thermo-reversible  Therefore Sol/Gel transition is reversible and can be repeated.

ACTIVITY---2  OBJECTIVE- In this lab we will understand the thermoreversibile property of colloids.  AIM—To prove that colloids exist in two states (Phases) and there are reversible.  MATERIALS-  Gelatin, Water,  Containers / beakers, test tubes, water bath.  PROCEDURE---  Add gelatin to water  Heat it  Then allow it to cool  Reheat  Observe.

ACTIVITY-3  Objective – To understand the filterability property of colloids.  AIM – To demonstrate the phenomenon of dialysis.  Materials –  Beaker,  Sullivian paper/cellophane membrane,  test tubes, thread,  colloidal starch, sodium chloride solution,  silver nitrate solution, iodine potassium iodide I-KI reagent  Distil water.  PROCEDURE—  Tie a Sullivian paper/cellophane membrane with thread on one side.  Fill the bag with Starch and Sodium chloride solutions.  Seal the bag and hang it in a beaker containing Distil water.  Leave it for some time.  Take equal amounts of water from the beaker 5-10 ml  Add this to two different test tubes labeled A and B  To----- A---- add silver nitrate solution.  To---- B ---- add I- KI Reagent.  Observe the changes in the test tubes.