A report on Colloid

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Colloidal silica gel with light opalescence
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Examples of a stable and of an unstable colloidal dispersion.
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Measurement principle of multiple light scattering coupled with vertical scanning
Aerogel
Jello cubes
Whipped cream
Mist
Tyndall effect in an opalite: it scatters blue light making it appear blue from the side, but orange light shines through; opal is a gel in which water is dispersed in silica crystals
Milk - emulsion of liquid butterfat globules dispersed in water

Mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance.

- Colloid
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43 related topics with Alpha

Overall
A suspension of flour mixed in a glass of water, showing the Tyndall effect

Suspension (chemistry)

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Heterogeneous mixture of a fluid that contains solid particles sufficiently large for sedimentation.

Heterogeneous mixture of a fluid that contains solid particles sufficiently large for sedimentation.

A suspension of flour mixed in a glass of water, showing the Tyndall effect

This distinguishes a suspension from a colloid, in which the colloid particles are smaller and do not settle.

Coagulation-flocculation process in a water treatment system

Flocculation

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Coagulation-flocculation process in a water treatment system

Flocculation, in the field of chemistry, is a process by which colloidal particles come out of suspension to sediment under the form of floc or flake, either spontaneously or due to the addition of a clarifying agent.

Making a saline water solution by dissolving table salt (NaCl) in water. The salt is the solute and the water the solvent.

Solution (chemistry)

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Special type of homogeneous mixture composed of two or more substances.

Special type of homogeneous mixture composed of two or more substances.

Making a saline water solution by dissolving table salt (NaCl) in water. The salt is the solute and the water the solvent.
Water is a good solvent because the molecules are polar and capable of forming hydrogen bonds (1).

Counter examples are provided by liquid mixtures that are not homogeneous: colloids, suspensions, emulsions are not considered solutions.

A representation of the 3D structure of the protein myoglobin showing turquoise α-helices. This protein was the first to have its structure solved by X-ray crystallography. Toward the right-center among the coils, a prosthetic group called a heme group (shown in gray) with a bound oxygen molecule (red).

Protein

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Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues.

Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues.

A representation of the 3D structure of the protein myoglobin showing turquoise α-helices. This protein was the first to have its structure solved by X-ray crystallography. Toward the right-center among the coils, a prosthetic group called a heme group (shown in gray) with a bound oxygen molecule (red).
John Kendrew with model of myoglobin in progress
Chemical structure of the peptide bond (bottom) and the three-dimensional structure of a peptide bond between an alanine and an adjacent amino acid (top/inset). The bond itself is made of the CHON elements.
Resonance structures of the peptide bond that links individual amino acids to form a protein polymer
A ribosome produces a protein using mRNA as template
The DNA sequence of a gene encodes the amino acid sequence of a protein
The crystal structure of the chaperonin, a huge protein complex. A single protein subunit is highlighted. Chaperonins assist protein folding.
Three possible representations of the three-dimensional structure of the protein triose phosphate isomerase. Left: All-atom representation colored by atom type. Middle: Simplified representation illustrating the backbone conformation, colored by secondary structure. Right: Solvent-accessible surface representation colored by residue type (acidic residues red, basic residues blue, polar residues green, nonpolar residues white).
Molecular surface of several proteins showing their comparative sizes. From left to right are: immunoglobulin G (IgG, an antibody), hemoglobin, insulin (a hormone), adenylate kinase (an enzyme), and glutamine synthetase (an enzyme).
The enzyme hexokinase is shown as a conventional ball-and-stick molecular model. To scale in the top right-hand corner are two of its substrates, ATP and glucose.
Ribbon diagram of a mouse antibody against cholera that binds a carbohydrate antigen
Proteins in different cellular compartments and structures tagged with green fluorescent protein (here, white)
Constituent amino-acids can be analyzed to predict secondary, tertiary and quaternary protein structure, in this case hemoglobin containing heme units

Sanger correctly determined the amino acid sequence of insulin, thus conclusively demonstrating that proteins consisted of linear polymers of amino acids rather than branched chains, colloids, or cyclols.

A diagram representing at the microscopic level the differences between homogeneous mixtures, heterogeneous mixtures, compounds, and elements

Mixture

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Material made up of two or more different chemical substances which are not chemically bonded.

Material made up of two or more different chemical substances which are not chemically bonded.

A diagram representing at the microscopic level the differences between homogeneous mixtures, heterogeneous mixtures, compounds, and elements

A mixture is the physical combination of two or more substances in which the identities are retained and are mixed in the form of solutions, suspensions and colloids.

Example for a dissolved solid (left)

Solubility

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Ability of a substance, the solute, to form a solution with another substance, the solvent.

Ability of a substance, the solute, to form a solution with another substance, the solvent.

Example for a dissolved solid (left)
Formation of crystals in a 4.2 M ammonium sulfate solution. The solution was initially prepared at 20 °C and then stored for 2 days at 4 °C.
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Dissolution of sodium chloride in water
Thermodynamic cycle for calculating solvation via sublimation
Thermodynamic cycle for calculating solvation via fusion

The term "soluble" is sometimes used for materials that can form colloidal suspensions of very fine solid particles in a liquid.

Scheme of particle agglomeration. Particles are dispersed individually in a functionally stable suspension, while they agglomerate in a functionally unstable suspension. As agglomeration proceed from early to later states, the agglomerates grow in size, and may eventually gel.

Particle aggregation

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Scheme of particle agglomeration. Particles are dispersed individually in a functionally stable suspension, while they agglomerate in a functionally unstable suspension. As agglomeration proceed from early to later states, the agglomerates grow in size, and may eventually gel.
Schematic stability plot of a colloidal suspension versus the salt concentration.
Structure of larger aggregates formed can be different. In the fast aggregation regime or DLCA regime, the aggregates are more ramified, while in the slow aggregation regime or RLCA regime, the aggregates are more compact.

Particle agglomeration refers to formation of assemblages in a suspension and represents a mechanism leading to the functional destabilization of colloidal systems.

Diagram showing the ionic concentration and potential difference as a function of distance from the charged surface of a particle suspended in a dispersion medium

Zeta potential

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Electrical potential at the slipping plane.

Electrical potential at the slipping plane.

Diagram showing the ionic concentration and potential difference as a function of distance from the charged surface of a particle suspended in a dispersion medium
[A] pH-dependant ionisation of a weak acid [HA] and its conjugated base [A-] drawn using Henderson-Hasselbalch equation; [B] Ionisation and solubility of a pH-responsive polymer as a function of pH [C] A schematic showing the potential difference as a function of distance from the charged surface of a particle in a medium; [D] Dissolution mechanism of pH-responsive polymers reproduced with permission from. The encircled numbers in [D] represent (1) Diffusion of water and hydroxyl ions into the polymer matrix to form a gel layer, (2) Ionization of polymer chains in the gel layer, (3) Disentanglement of polymer chains out of the gel layer to the polymer-solution interface, (4) Further ionization of polymer chains at the polymer interface, (5) Diffusion of disentangled polymer chains away from the interface toward the bulk solution.

Zeta potential is a scientific term for electrokinetic potential in colloidal dispersions.

Principle of chemical precipitation in aqueous solution

Precipitation (chemistry)

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Aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution.

Aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution.

Principle of chemical precipitation in aqueous solution
Illustration of the Walden reductor. Copper from a wire is displaced by silver from a silver nitrate solution it is dipped into, and metallic silver crystals precipitate onto the copper wire.
Reddish brown stains on a limestone core sample, corresponding to precipitates of oxides/hydroxides of.
Crystals of meso-tetratolylporphyrin from a reflux of propionic acid precipitate on cooling. Photograph of the Büchner funnel on top of a Büchner flask.
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Without sufficient attraction forces (e.g., Van der Waals force) to aggregate the solid particles together and to remove them from solution by gravity (settling), they remain in suspension and form colloids.

Excluded volumes of hard spheres overlap resulting in an increase in the total volume available to depletants. This increases the entropy of the system and lowers the Helmholtz free energy

Depletion force

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Excluded volumes of hard spheres overlap resulting in an increase in the total volume available to depletants. This increases the entropy of the system and lowers the Helmholtz free energy
Two plates in a solution of macromolecules. Macromolecules are excluded from between the plates. This results in pure solvent between the plates and a force equal to the osmotic pressure acting upon the plates.
The Derjaguin Approximation relates the force between two spheres to the force between two plates.

A depletion force is an effective attractive force that arises between large colloidal particles that are suspended in a dilute solution of depletants, which are smaller solutes that are preferentially excluded from the vicinity of the large particles.