Surface Chemistry — Chemistry STD 12 — Question

1. Emulsions arc colloidal solution in which a liquid dispersed in another liquid.2. Two types of emulsions

• Oil in Water (O/W) e.g., mayonnaise
• Water in Oil (W/O) e.g., Butter

3. The process of preparation of emulsion by the dispersal of one liquid in another liquid is called emulsification.4. Identification of types of emulsions. The two types of emulsions can be identified by the following tests

• Dye test – A small amount of dye soluble in oil is added to emulsion. The emulsion is shaken well. The aqueous emulsion will not take the colour whereas oily emulsion will take up the colour of the dye.
• Viscosity test – Viscosity of the emulsion is determined by experiments. Oily emulsions will have higher value than aqueous emulsions.
• Conductivity test – Conductivity of aqueous solutions are always higher than oily emulsions.
• Spreading test – Oily emulsions spread readily than aqueous emulsion when spread on an oily surface.