To begin, you need to recall two important definitions: The particles that form suspensions are sometimes classified into various size ranges.Ĭolloidal particles need not fall within the indicated size range in all three dimensions thus fibrous colloids such as many biopolymers may be very extended sizes along one direction.
Colloidal dispersions appear to be homogeneous, and the colloidal particles they contain are small enough (generally between 1-1000 nm) to exhibit Brownian motion, cannot be separated by filtration, and do not readily settle out.Within this size range, thermal motions maintain homogeneity by overcoming the effects of gravitational attraction.
Solutions are homogeneous mixtures whose component particles are individual molecules whose smallest dimension is generally less than 1 nm.Colloid science is central to biology, food science and numerous consumer products. As such, they possess some of the properties of both, which makes colloidal matter highly adaptable to specific uses and functions. In a sense, they bridge the microscopic and the macroscopic. and we ourselves are built largely of colloidal materials.Ĭolloids occupy an intermediate place between suspensions and solutions, both in terms of their observable properties and particle size. As you will see, we encounter colloids in the food we eat, the consumer products we buy. This is the world of colloids which we will survey in this lesson. There is, however, a vast but largely hidden world in between: particles so tiny that they cannot be resolved by an optical microscope, or molecules so large that they begin to constitute a phase of their own when they are suspended in a liquid. At the opposite end of the size scale, we have individual molecules which dissolve in liquids to form homogeneous solutions. You can usually see the individual particles directly, although the smallest ones might require some magnification. Sand, salt, and chalk dust are made up of chunks of solid particles, each containing huge numbers of molecules. Describe the role of colloids in wastewater treatment.Describe some of the colloid-related principles involved in food chemistry, such as the stabilization of milk and mayonaisse, the preparation of butter, and the various ways of cooking eggs.Explain why freezing or addition of an electrolyte can result in the coagulation of an emulsion.Give some examples of how colloidal dispersions can be made.Define: surfactant, detergent, emulsifier, micelle.Explain the mechanisms responsible for the stability of lyophilic and lyophobic colloidal dispersions.
Describe the electric double layer that surrounds many colloidal particles.Describe the origins of Brownian motion and how it can observed.For the various dispersion types (emulsion, gel, sol, foam, etc.), name the type (gas, liquid, or solid) of both the dispersed phase and the dispersions phase.Summarize the principal distinguishing properties of solutions, colloidal dispersions, and suspensions.Eggs: colloids for breakfast, lunch, and dessert.4 Making and breaking colloidal dispersions.Optical properties of colloidal dispersions.
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