The matter around us is incredibly diverse, ranging from simple substances to complex mixtures. Understanding the distinctions between these forms of matter is essential for comprehending their behavior and properties.
Solutions
: One of the most common forms of matter is solutions, which are homogeneous mixtures composed of a solute dissolved in a solvent. Solutions can vary in their composition, with some being saturated (containing the maximum amount of solute at a given temperature) and others being unsaturated (able to dissolve more solute). Solubility, or the ability of a solute to dissolve in a solvent, depends on factors such as temperature.
Suspensions
: On the other hand, suspensions are heterogeneous mixtures where solid particles are dispersed throughout a liquid without dissolving. Unlike solutions, suspension particles are larger and can be observed with the naked eye or under a microscope. Suspensions are typically unstable and settle over time, forming a precipitate.
Colloids
: Colloids are intermediate between solutions and suspensions, with particles that are larger than those in solutions but smaller than those in suspensions. These particles are evenly dispersed throughout the mixture, giving colloids a homogeneous appearance. Colloidal particles exhibit Brownian motion, a zigzag movement first observed by Robert Brown in 1828.
Understanding the properties and characteristics of solutions, suspensions, and colloids provides valuable insights into the behavior of different types of matter in our surroundings.
Tyndall effect: Scattering of light by colloidal particles
The Tyndall effect is a fascinating phenomenon observed when light passes through a colloidal solution. Colloidal particles, being larger than the molecules in true solutions, have the ability to scatter light. When a beam of light is directed through a colloidal solution in a darkened environment, the path of the light becomes illuminated and visible when viewed from the side.
This occurs because the colloidal particles scatter the light in all directions, making the path of the beam visible. It's akin to seeing a beam of light in a dusty room, where the particles in the air scatter the light and make it visible. This scattered light entering our eyes allows us to perceive the path of the beam, showcasing the fascinating interplay between light and matter at the microscopic level.
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Property
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Suspension
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Colloidal solution
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True solution
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-
Particle size
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> 100 nm
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1 to 100 nm
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< 1 nm
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-
Separation by ordinary filtration
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Possible
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Not possible
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Not possible
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-
Settling of particles
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Settle of their own
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Settle only on centrifugation
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Do not settle
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-
Appearance
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Opaque
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Generally
transparent
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Transparent
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-
Tyndall effect
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Shows
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Shows
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Does not show
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-
Diffusion of particles
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Do not diffuse
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Diffuse slowly
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Diffuse rapidly
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-
Brownian movement
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May show
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Show
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May or may not shown
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-
Nature heterogeneous
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Heterogeneous
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Homogeneous
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|
Classification of Colloids
Colloids, fascinating mixtures with unique properties, are classified based on the physical states of both the dispersed phase (solute) and the dispersion medium (solvent). Here are the main types:
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Sol:
In this type, solid particles are dispersed within a liquid medium. An example is a paint.
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Solid sol:
Here, solid particles are dispersed within another solid medium. One example is alloys, like brass.
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Aerosol:
Aerosols consist of solid or liquid particles dispersed within a gas. Examples include smoke and mist.
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Emulsion:
In an emulsion, small droplets of one liquid are dispersed within another immiscible liquid. Mayonnaise and milk are classic examples.
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Foam:
Foam is created when gas bubbles are dispersed within a liquid or solid medium. Examples include whipped cream and foam insulation.
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Solid foam:
In solid foam, gas bubbles are dispersed within a solid medium. Styrofoam and pumice are examples.
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Gel:
Gels have a solid-like consistency but are actually composed of a liquid dispersed within a solid. Examples include gelatin and agar.
Separation of mixture
The separation of mixtures is crucial for isolating and purifying the components within them. Various methods are employed based on the nature of the mixture:
Sublimation:
Used for substances that undergo sublimation, where they transition directly from solid to vapor without passing through the liquid phase. For example, separating ammonium chloride and common salt.
Filtration:
Effective for separating solids from liquids or suspensions. It involves passing the mixture through a filter medium, which traps the solid particles while allowing the liquid to pass through.
Centrifugation:
Utilized to separate suspended particles from a liquid by spinning the mixture at high speeds in a centrifuge. Denser particles settle at the bottom, forming a pellet, while the liquid remains above.
Evaporation:
Involves heating a liquid mixture to evaporate the solvent, leaving behind the solute in solid form. This method is commonly used to recover dissolved solids from a solution.
Crystallization:
By allowing a supersaturated solution to cool or evaporate slowly, crystals of the solute form and can be separated from the solution.
Chromatography:
Separates components based on differences in their affinity for a stationary phase and a mobile phase. This method is often used in chemical analysis and purification processes.
Distillation:
Separates components of a mixture based on differences in their boiling points. The mixture is heated to vaporize the more volatile component, which is then condensed and collected.
Fractional Distillation:
Similar to distillation but used for mixtures with closer boiling points. A fractionating column is employed to achieve better separation.
Separating Funnel:
Used to separate immiscible liquids by allowing them to settle into distinct layers based on their densities, which can then be drained separately.
