Definition of Colloid
A colloid is a mixture in which one substance is dispersed throughout another substance in small particles, but is not dissolved. Examples of colloids include fog, milk, and blood. In a colloid, the dispersed substance is called the “dispersed phase,” and the substance in which it is dispersed is called the “continuous phase.” The dispersed phase particles are typically larger than those found in a true solution, but smaller than those found in a suspension.
Definition of Suspension
A suspension is a type of mixture in which the dispersed particles are large enough to settle out of the mixture if left undisturbed. The particles in a suspension are visible to the naked eye, and they do not dissolve in the liquid they are suspended in. Examples of suspensions include mud, paint, and blood cells suspended in plasma. Suspensions are not stable over time and the particle will eventually settle out from the fluid
In contrast to colloid, the particles in suspension are visible to the naked eye and the mixture is not homogeneous, the particle will eventually settle out from the fluid.
Colloid vs Suspension – Differences
Colloids and suspensions are both types of mixtures, but they have some important differences.
- Particle size: The dispersed particles in a colloid are much smaller than those in a suspension. In a colloid, the particles are typically smaller than 1 micrometer, while in a suspension, the particles can be seen with the naked eye and are typically larger than 1 micrometer.
- Stability: Colloids are generally stable and the particles remain suspended for long periods of time without settling out. Suspensions, on the other hand, are not stable, and the particles will eventually settle out of the mixture if left undisturbed.
- Homogeneity: Colloids are homogeneous mixtures, meaning the particles are evenly distributed throughout the mixture. Suspensions are heterogeneous mixtures, meaning the particles are not evenly distributed and will separate over time.
- Tyndall effect: Colloids can scatter light and this phenomenon is known as the Tyndall effect, this effect can be observed in a beam of light passing through a colloid solution, the light scatters and makes the solution appear cloudy. Suspensions do not have this effect.
- Physical properties: Colloids have properties intermediate between those of a true solution and those of a suspension, for example, viscosity, refractive index, and electrical conductivity are intermediate between those of a true solution and a suspension.
Comparison Chart
Here is a comparison chart that highlights the key differences between colloids and suspensions:
| Property | Colloids | Suspensions |
|---|---|---|
| Particle size | Small (typically smaller than 1 micrometer) | Large (typically larger than 1 micrometer) |
| Stability | Stable | Not stable |
| Homogeneity | Homogeneous | Heterogeneous |
| Tyndall effect | Present | Absent |
| Physical properties | Intermediate between true solutions and suspensions | Closer to suspensions |
It’s worth to mention that colloids and suspensions can be distinguished from each other by their physical properties, by microscopy and by centrifugation.
Similarities Between Colloid vs Suspension
While there are some key differences between colloids and suspensions, there are also some similarities between the two types of mixtures:
- Both colloids and suspensions are types of mixtures, where one substance is dispersed throughout another substance.
- Both colloids and suspensions can have a liquid, solid or gaseous dispersed phase, and a liquid, solid or gaseous continuous phase.
- Both colloids and suspensions can exist in a wide range of concentrations.
- Both colloids and suspensions can be separated by centrifugation, although colloids are more difficult to separate than suspensions due to the smaller size of the dispersed particles.
- Both colloids and suspensions are not chemically bonded, the dispersed particles are held in the mixture by physical forces.
- Both colloids and suspensions can be produced by mechanical means, for example, by stirring or shaking.
both colloids and suspensions are mixtures that have dispersed particles, but colloids have smaller particles, tend to be more stable, and have intermediate physical properties between true solutions and suspensions. While suspensions have larger particles, tend to be less stable and have properties closer to suspensions.
Frequently Asked Questions
Here are some frequently asked questions about colloids and suspensions:
Q: What are some examples of colloids?
A: Some examples of colloids include fog, milk, blood, paint, and shaving cream.
Q: What are some examples of suspensions?
A: Some examples of suspensions include mud, paint, and blood cells suspended in plasma.
Q: How can colloids and suspensions be distinguished from each other?
A: Colloids and suspensions can be distinguished from each other by their particle size, stability, homogeneity, the Tyndall effect and their physical properties, by microscopy and by centrifugation.
Q: Can colloids be separated by centrifugation?
A: Colloids can be separated by centrifugation, but it is more difficult to separate colloids than suspensions because the dispersed particles are smaller.
Q: Are colloids and suspensions chemically bonded?
A: No, colloids and suspensions are not chemically bonded. The dispersed particles are held in the mixture by physical forces.
Q: Can colloids and suspensions be produced by mechanical means?
A: Yes, colloids and suspensions can be produced by mechanical means, such as by stirring or shaking.
Reference Books
Here are some reference books about colloids and suspensions:
- “Colloids and Interfaces with Surfactants and Polymers” by Stuart A. Rice
- “Principles of Colloid and Surface Chemistry” by Paul C. Hiemenz and Raj Rajagopalan
- “Introduction to Colloid and Surface Chemistry” by D.Roy Cullimore
- “Suspensions: Fundamentals of the Physics of Suspensions” by Reinhard Hentschke
- “Suspensions and Emulsions” by Andrzej K. Bledzki
- “Colloids and Interfaces in Life Sciences” by David J. A. Cronin
- “Colloids and Surfaces A: Physicochemical and Engineering Aspects” by J. Lyklema
These books provide comprehensive coverage of the fundamental principles, properties, and applications of colloids and suspensions, and can be used as a reference for students, researchers, and professionals in chemistry, physics, materials science, engineering, and the life sciences.
