define colloids?Dicuss natural , technical and analytical applicaltion of colloids ?
Answers
In chemistry, a colloid is a mixture in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance. Sometimes the dispersed substance alone is called the colloid;[1] the term colloidal suspension refers unambiguously to the overall mixture (although a narrower sense of the word suspension is distinguished from colloids by larger particle size). Unlike a solution, whose solute and solvent constitute only one phase, a colloid has a dispersed phase (the suspended particles) and a continuous phase (the medium of suspension). To qualify as a colloid, the mixture must be one that does not settle or would take a very long time to settle appreciably.
The dispersed-phase particles have a diameter between approximately 1 and 1000 nanometers.[2] Such particles are normally easily visible in an optical microscope, although at the smaller size range (r < 250 nm), an ultramicroscope or an electron microscope may be required. Homogeneous mixtures with a dispersed phase in this size range may be called colloidal aerosols, colloidal emulsions, colloidal foams, colloidal dispersions, or hydrosols. The dispersed-phase particles or droplets are affected largely by the surface chemistry present in the colloid.
Some colloids are translucent because of the Tyndall effect, which is the scattering of light by particles in the colloid. Other colloids may be opaque or have a slight color.
Colloidal suspensions are the subject of interface and colloid science. This field of study was introduced in 1845 by Italian chemist Francesco Selmi[3] and further investigated since 1861 by Scottish scientist Thomas Graham.
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✏COLLOIDS = A colloid is a mixture in which one substance of microscopically dispersed insoluble particles are suspended throughout another substance....
✏NATURAL APPLICATIONS :
✔Blue colour of the sky : Colloidal particles scatter blue light. Dustparticles along with water suspended in air scatter blue light which reaches our eyes and the sky looks blue to us..
✔Food articles : Milk, butter, halwa, ice creams, fruit juices, etc., are all colloids in one form or the other.
✔Blood : Blood is a colloidal solution of an albuminoid substance. The styptic action of alum and ferric chloride solution is due to coagulation of blood forming a clot which stops further bleeding.
✔Soils : Fertile soils are colloidal in nature in which humus acts as aprotective colloid. On account of colloidal nature, soils adsorb moisture and nourishing materials......
✏TECHNICAL APPLICATIONS :
✔Photographic plates and films :The photographic plates or films are prepared by coating an emulsion of the light sensitive silver bromide in gelatin over glass plates or celluloid films.
✔Rubber industry : Latex is a colloidal solution of rubber particles which are negatively charged. Rubber is obtained by coagulation of latex.
✔Industrial products : Paints, inks, synthetic plastics, rubber, graphite lubricants, cement, etc., are all colloidal solutions....
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