Rather, it collides with these micro-particles and scatters causing the effect of a visible light beam. This effect was observed and described by John Tyndall as the Tyndall Effect.
The Tyndall effect is an easy way of determining whether a mixture is colloidal or not. When light is shined through a true solution, the light passes cleanly through the solution, however when light is passed through a colloidal solution, the substance in the dispersed phases scatters the light in all directions, making it readily seen. We can prepare an emulsion by shaking together or blending two immiscible liquids.
This breaks one liquid into droplets of colloidal size, which then disperse throughout the other liquid. Oil spills in the ocean may be difficult to clean up, partly because wave action can cause the oil and water to form an emulsion. In many emulsions, however, the dispersed phase tends to coalesce, form large drops, and separate. Therefore, emulsions are usually stabilized by an emulsifying agent , a substance that inhibits the coalescence of the dispersed liquid. For example, a little soap will stabilize an emulsion of kerosene in water.
Milk is an emulsion of butterfat in water, with the protein casein as the emulsifying agent. Mayonnaise is an emulsion of oil in vinegar, with egg yolk components as the emulsifying agents. Condensation methods form colloidal particles by aggregation of molecules or ions. If the particles grow beyond the colloidal size range, drops or precipitates form, and no colloidal system results. Clouds form when water molecules aggregate and form colloid-sized particles.
If these water particles coalesce to form adequately large water drops of liquid water or crystals of solid water, they settle from the sky as rain, sleet, or snow. Many condensation methods involve chemical reactions. We can prepare a red colloidal suspension of iron III hydroxide by mixing a concentrated solution of iron III chloride with hot water:.
A colloidal gold sol results from the reduction of a very dilute solution of gold III chloride by a reducing agent such as formaldehyde, tin II chloride, or iron II sulfate:. Some gold sols prepared in are still intact the particles have not coalesced and settled , illustrating the long-term stability of many colloids.
Pioneers made soap by boiling fats with a strongly basic solution made by leaching potassium carbonate, K 2 CO 3 , from wood ashes with hot water. Animal fats contain polyesters of fatty acids long-chain carboxylic acids. When animal fats are treated with a base like potassium carbonate or sodium hydroxide, glycerol and salts of fatty acids such as palmitic, oleic, and stearic acid are formed.
The salts of fatty acids are called soaps. Figure 3. Soaps contain a nonpolar hydrocarbon end blue and an ionic end red. The ionic end is a carboxylate group. The length of the hydrocarbon end can vary from soap to soap. Soaps form insoluble calcium and magnesium compounds in hard water; detergents form water-soluble products—a definite advantage for detergents.
Figure 4. Detergents contain a nonpolar hydrocarbon end blue and an ionic end red. The ionic end can be either a sulfate or a sulfonate. The length of the hydrocarbon end can vary from detergent to detergent. The cleaning action of soaps and detergents can be explained in terms of the structures of the molecules involved. As referred, colloids are common in everydaylife. Whipped cream, mayonnaise, butter, gelatin, jelly, muddy water, colored glass,, and paper are the examples.
They consists of colloidal particles and the dispersion medium in which the colloidal particles are dispersed. Any colloid consisting of a solid dispersed in a gas is called smoke, and a liquid dispersed in a gas is referred to as a fog. Colloids exhibit Brownian movement. Brownian motion is the random motion of particles that we can easily see under a microscope. This movement is caused by the collision of molecules with colloidal particles in the dispersion medium.
Additionally, colloids display the Tyndall effect as referred above. When a strong light is shone through a colloidal dispersion, the light beam becomes visible, like a column of light. A common example of this effect can be seen when a spotlight is turned on during a foggy night. What is the lewis structure for hcn? How is vsepr used to classify molecules? What are the units used for the ideal gas law? How does Charle's law relate to breathing? What is the ideal gas law constant?
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