COLLOIDS Definition and Properties of Colloids Classification of Colloids Importance of ColloidsTo Daily Life
Classify Them! brine solution ice cream soda muddy water starch solution marshmallow marbles in water butter gelatin air brass paint ruby sand and water pebbles and water soda
Solution Colloid Suspensionair butter marbles inbrass gelatin waterbrine solution ice cream soda muddy watersoda marshmallow pebbles andstarch solution paint water ruby sand and water
Comparison of the Properties of Solutions, Colloids, And Suspensions Property Solution Colloid SuspensionParticle Size Less than 1 nm 1 to 100 nm More than 100 nmAppearance Clear Cloudy CloudyHomogeneity Homogeneous Homogeneous or Heterogeneous HeterogeneousTransparency Transparent but Often translucent Often opaque but often colored and opaque but can be translucent can be transparentSeparation Does not separate Does not separate Separates or settlesFilterability Passes through Passes through Particles do not filter paper filter paper pass through filter paper
Unique Properties of Colloids Tyndall Effect A beam of light passing through a transparent pure colorless solid, liquid or gas cannot be seen except at the point where it enters and leaves the object. scattering of light
Brownian Movement If a colloid is viewed under a special microscope, the dispersed particles will be seen moving in a rapid, random, zigzag motion through the dispersion medium. This motion in a colloid is one of the reasons why particles remain suspended indefinitely.
Electric Charge A dispersed colloidal particle can adsorb electrically charged particles on its surface. opposite attracts; same repel prevents coagulation and OMG! precipitation of dispersed colloidalYou’re my particles exactopposite! I think I am attracted to you!
activated carbon Adsoptive Property Adsoption is the process of collecting a thin layer of molecules or ions of a substance with which it is in contact. Surfaces of solids and liquids can adsorb molecules from fluid phases (liquids and gases) onto their surface. • Chemisorption – fairly strong, resembling chemical bonds, and difficult to break ex: activated charcoal • Physisorption – weak, involves only Van der Waals forces and the adsorbed material can usually removed again. ex: silica gel silica gel
Animation References Animation of Tyndall Effect: http://www.yteach.com/page.php/r I want to esources/view_all?id=mixture_collsee those… oid_solubility_molarity_solution_c oncentration_dilution_ion_titration _mass_percent_t_page_3&from= search Animation of Brownian Movement: www.edumedia- sciences.com/en/a247-brownian- motion
Classification of Colloids components : dispersed particles (solute) and dispersing medium (solvent) can be classified according to: Phase Affinity Between Phases Fabulous!
Dispersed Dispersion Name ExamplesParticles MediumSolid Gas Soild aerosol Smoke, dust in airSolid Liquid Sol Paint, starch mixture, hot chocolate, gelatinSolid Solid Solid sol Colored glass, gem glass like ruby and garnet
Classification According ToPhase AEROSOLS suspension of liquid or solid particles in gas
solid foam FOAMS colloidalliquid foam dispersions of gas bubbles in liquids (liquid foams) or solid (solid foams)
EMULSIONS colloidal dispersion of liquid either a liquid or a solid. The 2 components of an emulsion are usually immiscible and require an addition of emulsifying agent or peptizing agent to form stable emulsion. If the dispersed particles in an emulsion are relatively large, they still tend to separate from the dispersion medium. This could be prevented by the a process called homogenization.
SOLS a solid dispersed in either a solid or a liquid
GELS a colloidal system in which the dispersed phase consists of fibrous, interwoven particles called fibrils which exert a marked effect on the physical properties of the dispersing medium
Classification According toAffinity Between Phases Lyophilic solvent – loving; have a strong attraction for the molecules of the dispersing medium. Lyophobic solvent –fearing; dispersed phase are actually immiscible with the solvent under normal conditions.