give any two characteristics of colloid and suspension
Answers
Explanation:
Suspensions
Take a glass of water and throw in a handful of sand or dirt. Stir it and stir it and stir it. Have you made a solution? Sand and dirt do not dissolve in water, and, though it may look homogeneous for a few moments, the sand or dirt gradually sinks to the bottom of the glass (Figure below).
A suspension is a heterogeneous mixture in which some of the particles settle out of the mixture upon standing. The particles in a suspension are far larger than those of a solution, so gravity is able to pull them down out of the dispersion medium (water). The diameter for the dispersed particles in a suspension, such as the sand in the suspension described above, is typically at least 1000 times greater than those in a solution. Unlike a solution, the dispersed particles can be separated from the dispersion medium by filtering. Suspensions are still considered heterogeneous because the different substances in the mixture will not remain uniformly dispersed if they are not actively being mixed.
Colloids
A colloid is a heterogeneous mixture in which the dispersed particles are intermediate in size between those of a solution and a suspension. The particles are spread evenly throughout the dispersion medium, which can be a solid, liquid, or gas. Because the dispersed particles of a colloid are not as large as those of a suspension, they do not settle out upon standing. The table below (Table below) summarizes the properties and distinctions between solutions, colloids, and suspensions.
Properties of Solutions, Colloids, and Suspensions
Solutions Colloids Suspensions
Homogeneous Heterogeneous Heterogeneous
Particle size: 0.01-1 nm; atoms, ions, or molecules Particle size: 1-1000 nm, dispersed; large molecules or aggregates Particle size: over 1000 nm, suspended; large particles or aggregates
Do not separate on standing Do not separate on standing Particles settle out
Cannot be separated by filtration Cannot be separated by filtration Can be separated by filtration
Do not scatter light Scatter light (Tyndall effect) May either scatter light or be opaque
Colloids are unlike solutions because their dispersed particles are much larger than those of a solution. The dispersed particles of a colloid cannot be separated by filtration, but they scatter light, a phenomenon called the Tyndall effect.
Tyndall Effect
Colloids are often confused with true homogeneous solutions because the individual dispersed particles of a colloid cannot be seen. When light is passed through a true solution, the dissolved particles are too small to deflect the light. However, the dispersed particles of a colloid, being larger, do deflect light (Figure below). The Tyndall effect is the scattering of visible light by colloidal particles. You have undoubtedly “seen” a light beam as it passes through fog, smoke, or a scattering of dust particles suspended in air. All three are examples of colloids. Suspensions may scatter light, but if the number of suspended particles is sufficiently large, the suspension may simply be opaque, and the light scattering will not occur.
(A) Light passes first through a colorless solution and is not scattered. When it passes through a diluted milk solution, the light is scattered by colloidal particles, an observation called the Tyndall effect. (B) The Tyndall effect allows sunlight to be seen as it passes through a fine mist.
Examples of Colloids
Listed below (Table below) are examples of colloidal systems, most of which are very familiar. Some of these are shown below (Figure below). The dispersed phase describes the particles, while the dispersion medium is the material in which the particles are distributed.
Classes of Colloids
Class of Colloid Dispersed Phase Dispersion Medium Examples
Sol and gel solid liquid paint, jellies, blood, gelatin, mud
Solid aerosol solid gas smoke, dust in air
Solid emulsion liquid solid cheese, butter
Liquid emulsion liquid liquid milk, mayonnaise
Liquid aerosol liquid gas fog, mist, clouds, aerosol spray
Foam gas solid marshmallow
Foam gas liquid whipped cream, shaving cream
Some common colloids: (A) gelatin dessert (gel); (B) smoke (solid aerosol); (C) butter (solid emulsion); (D) mayonnaise (liquid emulsion); (E) fog (liquid aerosol); (F) marshmallows (foam); (G) whipped cream (foam).
Another property of a colloidal system is observed when the colloids are studied under a light microscope. The colloids scintillate, reflecting brief flashes of light because the colloidal particles move in a rapid and random fashion. This phenomenon, called Brownian motion, is caused by collisions between the small colloidal particles and the molecules of the dispersion medium.
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