COLLOIDS- SOME OF ITS PROPERTIES.

Some of the important properties of colloids are

1- Brownian motion2- Thermo-Reversibility3- Filterability(dialysis)4- Electrical property5- Tyndal effect

Activity—1Brownian motionThe 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.