Difference Between Colloid and Emulsion

The key difference between colloid and emulsion is that colloid can form when any state of matter (solid, liquid or gas) combine with a liquid whereas emulsion has two liquid components which are immiscible with each other.

A colloid is a mixture of a compound (that is in solid, liquid or gas state) and a liquid. An emulsion is a form of colloid. A colloid generally contains two components; a continuous phase and a discontinuous phase. The discontinuous phase distributes throughout the continuous phase.

CONTENTS

1. Overview and Key Difference
2. What is Colloid
3. What is Emulsion
4. Side by Side Comparison – Colloid vs Emulsion in Tabular Form
5. Summary

What is Colloid?

A colloid is a homogeneous non-crystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance. The dispersed particles do not settle down spontaneously because colloids are very stable.

There are several different categories of colloids that are grouped based on different parameters. The four major categories are as follows:

• Sol – a colloidal suspension which has solid particles distributed in a liquid
• Emulsion – a colloidal suspension containing a combination of two liquids
• Foam – this forms when gas particles get trapped in a liquid or a solid
• Aerosol – forms when solid or liquid particles distribute throughout the air

In addition, there are three forms of colloids; multimolecular colloids, macromolecular colloids, and micelles. This classification categorizes colloids according to the particle size and behavior of those particles in a colloid. A multimolecular colloid forms if the molecules of a compound aggregate when we dissolve the compound in a suitable solvent. In a macromolecular colloid, the individual particles are large enough to call this a colloid. In micelles, it contains an aggregate of molecules in a colloidal solution, such as those formed by detergents (in a circular manner).

What is Emulsion?

An emulsion is a fine dispersion of minute droplets of one liquid in another in which it is not soluble or miscible. Therefore, it is a mixture of two liquids which are immiscible with each other. They are a type of colloids. Although these two terms are in use interchangeably, the term emulsion specifically explains the mixture of two liquids that form a colloid.

An emulsion has two phases; a continuous phase and a discontinuous phase. The discontinuous phase distributes throughout the continuous phase. If the continuous phase is water, then the colloid is a hydrocolloid. The boundary between the two liquid in an emulsion is the “interface”.

An emulsion has a cloudy appearance. That is because it has phase interfaces that can scatter a light beam which passes through the emulsion. When all the light rays are scattered equally, an emulsion appears as a white liquid.

What is the Difference Between Colloid and Emulsion?

Summary – Colloid vs Emulsion

An emulsion is a form of a colloid. Other forms of colloids include sol, foam and aerosols. The difference between colloid and emulsion is that a colloid can form when any state of matter (solid, liquid or gas) combine with a liquid whereas an emulsion has two liquid components which are immiscible with each other.

Reference:

1. Libretexts. “Colloids.” Chemistry LibreTexts, Libretexts, 9 Jan. 2017. Available here 
2. “Emulsion.” Wikipedia, Wikimedia Foundation, 30 Apr. 2018. Available here 

Image Courtesy:

1.’Emulsions’ By Fvasconcellos 14:24, 17 April 2007 (UTC) – Own work, (Public Domain) via Commons Wikimedia