explain colloids and suspensions
Answers
A colloid is a substance in which microscopic particles are dispersed in a medium, but are not dissolved in it. If left undisturbed, the dispersed particles will not settle or form sediment. Pumice could be an example of a colloid: particles of air dispersed in solid stone.
An emulsion is a particular type of colloid, referring to microscopic particles of liquid dispersed in another liquid. Milk could be an example of an emulsion: lipophilic butterfat particles dispersed in a water-based medium.
A suspension is similar to a colloid except that the dispersed particles tend to be larger and will eventually settle or form sediment. Sand in water could be an example of a suspension: if shaken then the sand will disperse in the water, but if left alone it will settle at the bottom.
Answer:
(1) Electrical precipitation of smoke : Smoke is an exerosol or a colloidal solution of solid particles of carbon, dust, arsenic or sulphur compounds, etc. When the smoke is passed through a chimney, provided inside with charged plates, the charge on colloidal particles is neutralise and hence get precipitated on the floor of then chamber. This process is called cottrell process.
(2) Purification of water : Colloidal particles in an impure water are removed by coagulating them by addition of alum. This gives potable water.
(3) Medicines : Colloidal medicines are more effective due to large surface area to volume ratio of colloidal particles and they can be easily assimilated by body. Some of the medicines are argyrol which is a silver sol used as an eye lotion, an emulsion of milk of magnesia is used in stomach disorders.
(4) Rubber industry : Rubber is obtained by coagulation of latex.
(5) Cleansing action : The cleansing action of soaps and detergents is due to their colloidal properties.
(6) Industrial goods : A large number of industrial products like photographic plates, films, paints, rubber, graphite products, etc. are colloid.