colloidal
There is daily life, we often come across some products that are a mixture of several substances, but these substances can be mixed uniformly / homogeneous. For example, when mothers make milk for the younger, powder / milk powder mixed evenly with hot water. Products such as it is a colloidal system.
Colloid is a substance mixture heterogeneous (two phase) between two or more substances in which the particles are sized colloidal substance (dispersed phase / broken), spread evenly in another substance (medium dispersing / breaker). Colloidal particle size range between 100-100 nm. The size is meant to be the diameter, length, width, and thickness of a particle. Other examples of colloidal systems is the ink, which consists of powder-powder color (solid) with a liquid (water). In addition to ink, there are many other colloidal systems, such as mayonnaise, hairspray, jelly, etc..
Circumstances colloid or colloid system colloid or a solution or colloidal suspension or a colloid is a mixture of berfasa two dispersed phase and dispersing phase with dispersed particle size ranged from 10-7 to 10-4 cm. The size of the dispersed particles, these particles do not explain the circumstances. The particles can consist of atoms, small molecules or molecules that are very large. Composed of colloidal gold particles with many-sizes, each containing millions of atoms of gold or more. Sulfur colloid consists of particles that contain about a thousand molecules of S8. An example of a very large molecule (also called macro-molecule) is a hemoglobin. The molecular weight of 66 800 sma and this molecule has a diameter of about 6 x 10-7.
2.2 TYPES OF colloidal
Colloidal system composed of the dispersed phase evenly dispersed in the dispersing medium. Dispersed phase and dispersing medium can be either solids, liquids, and gases. Based terdispersinya phase, colloidal systems can be grouped into 3, namely:
1. Sol (solid dispersed phase)
a. Sol solid is a solid sol in dispersing medium
Examples: metal alloy, glass color, black diamond
b. Sol sol liquid is in a liquid dispersing medium
Example: paint, ink, flour in water, clay
c. Sol is the sole gas in the gas dispersing medium
Example: dust in the air, combustion fumes
2. Emulsion (dispersed phase liquid)
a. Solid emulsion is emulsified in the dispersing medium dense
Example: Jelly, cheese, butter, rice
b. Liquid emulsion is emulsified in a liquid dispersing medium
Examples: milk, mayonnaise, hand cream
c. Gas emulsion is emulsified in the dispersing medium gas
Example: hairspray and mosquito coils
3. FOAMS (dispersed phase gas)
a. Solid froth is froth in the dispersing medium dense
Example: Floating Stone, marshmallows, foam rubber, Styrofoam
b. Liquid foam is a froth in a liquid dispersing medium
Example: the whipped egg white, foam soap
- For the grouping of froth, if the dispersed phase and dispersing medium
are both in the form of gas, mixtures classified solution
2.3 PROPERTIES colloidal
· Tyndall Effect
Tyndall effect is the phenomenon of laser beam scattering (light) by colloidal particles. This is because the molecules of colloidal size that is large enough. Tyndall effect was discovered by John Tyndall (1820-1893), a British physicist. Therefore, nature is called the Tyndall effect.
Tyndall effect is the effect that occurs if a solution to light. At the time of the pure solvent (picture left), illuminated with light, then the solution will not scatter light, whereas in colloidal systems (picture right), the light will be scattered. it happens because the particles have colloidal particles are relatively large to scatter light. Conversely, the true solution, the particles are relatively small so that scattering occurs only a few and very difficult to observe.
· Brownian motion
Brownian motion is the movement of colloidal particles that always move straight but erratic (random motion / irregular). If we observe under the microscope ultra colloid, then we will see that the particles will move to form zigzag. Zigzag movement is called Brownian motion. The particles of a substance in constant motion.
The movement may be random as in liquids and gases, or just vibrate in place as in solids. For colloids with medium dispersing liquid or gas, the movement of particles will produce collisions with the colloidal particles themselves. The collision took place from all directions. Therefore, the particle size small enough, then the collision that occurred tended not balanced. So there is a resultant collision that caused a change in direction of motion of the particles resulting in zigzag motion or Brownian motion. The smaller the size of colloidal particles, the faster the Brownian motion occurs. Similarly, the larger the size of colloidal particles, the slower the Brownian motion that occurs. This explains why it difficult to observe Brownian motion in solution and not found in the solids (suspensions). Brownian motion is also influenced by temperature. The higher the temperature of the colloidal system, the greater the kinetic energy possessed pendispersinya medium particles. Consequently, Brownian motion of particles terdispersinya the faster phase. Vice versa, the lower the temperature of the colloidal system, the Brownian motion more slowly.
· Absorption
Absorption is the absorption of incident particles or ions or other compounds on the surface of colloidal particles due to particle surface area. (Note: Absorption should be distinguished from absorption, which means that absorption occurs within a particle). Example: (i) Colloidal Fe (OH) 3 because the surface absorbs positively charged H + ions. (Ii) Colloidal As2S3 absorb negatively charged ions because the surface S2.
· Charge colloids
Known two kinds of colloids, ie positively charged colloidal and negatively charged colloids.
· Coagulation of colloidal
Coagulation is the coagulation of colloidal particles and form a precipitate. With the onset of coagulation, means the substance is no longer form a colloid dispersed. Coagulation may occur physically such as heating, cooling and stirring or addition of chemicals such as electrolytes, the mixing of different colloidal charge.
· Colloid protectors
Protective colloid is a colloid that has a colloidal nature to protect others from the process of coagulation.
· Dialysis
Dialysis is the separation of colloidal ions bully in this way is called the process of dialysis.
· Electrophoresis
Elektroferesis separation of events is that the charged colloidal particles using an electrical current.
2.4 MAKING SYSTEM colloidal
Double decomposition reaction
For example:
- Sol As2S3 made in the style of H2S stream slowly through a cold solution of As2O3 As2S3 sol to form a yellow light;
As2O3 (aq) + 3H2S (g) Ã As2O3 (colloidal) + 3H2O (l)
(Colloidal As2S3 negatively charged ions because the surface absorbs S2-)
- Sol AgCl AgNO3 solution made by mixing dilute and dilute HCl solution;
AgNO3 (ag) + HCl (aq) Ã AgCl (colloidal) + HNO3 (aq)
Nitrate Warming
When heated, most tend to decompose to form nitric oxides, nitrogen dioxide in the form of brown smoke, and oxygen.
For example, Group 2 nitrate as simple as magnesium nitrate decompose by the reaction as follows:
In Group 1, ithium nitrate undergo a process of decomposition of the same - to produce lithium oxide, nitrogen dioxide and oxygen.
However, nitrate from elements other than lithium in Group 1 was not decomposed completely (at least not decompose at temperatures Bunsen) - produces metal nitrite and oxygen, but does not produce nitrogen oxides.
All nitrate from sodium to cesium decomposed according to the above reactions, the only difference is the heat that must be experienced for a reaction can occur. Getting to the bottom group, the decomposition will be more difficult, and required a higher temperature.
Carbonate Warming
When heated, most carbonates tend to decompose to form metal oxides and carbon dioxide.
For example, Group 2 carbonates such as calcium carbonate decomposes simple as follows:
In Group 1, lithium carbonate undergo a process of decomposition of the same - to produce lithium oxide and carbon dioxide.
Carbonates of the elements other than lithium in Group 1 does not decompose at temperatures Bunsen, although at higher temperatures they will decompose. Decomposition temperature was again increased further down the Group.
2.5 USE colloidal
Colloidal systems are widely used in everyday life, especially in everyday life. This is due to the nature of the important characteristics of the colloid, which can be used for mixing the substances can not dissolve each other in a homogeneous and stable for large scale production.
Here is a table of colloidal applications:
Type of industry
Example applications
Food Industry
Cheese, butter, milk, salad dressing
Manufacture of cosmetics and body care
Cream, toothpaste, soap
Industrial paint
Paint
Manufacture of household needs
Soap, detergents
Industrial agriculture
Peptisida and insecticide
Pharmaceutical Industry
Fish oil, pensilin for injection
The following is a description of the application of colloidal:
1. Bleaching Sugar
Sugar cane is still in color can be bleached. By dissolving sugar in water, then the solution flowed through the soil colloid system diatomae or carbon. Colloidal particles will adsorb these dyes. These colloidal particles adsorb dyes from sugar cane so that sugar can be colored white.
2. Blood clotting
Blood contains a number of negatively charged colloidal protein. In the event of injury, the wound can be treated with a pencil or alum stiptik containing ions Al3 + and Fe3 +. Ions are helpful for the protein colloidal particles are electrically neutral so that the blood clotting process can be more easily done.
3. Water purification
Water faucets (taps) that exist today contain colloidal particles of clay, mud, and various other particles which are negatively charged. Therefore, to make it good to drink, to do several steps for the colloidal particles can be separated. This is done by adding alum (Al2SO4) 3.Ion Al3 + contained in the alum will be terhidroslisis form colloidal particles of Al (OH) 3 is positively charged through the reaction:
Al3 + + 3H2O Ã Al (OH) 3 + 3H +
After that, Al (OH) 3 eliminates the negative charges of colloidal particles of clay / mud and coagulation occurs in the mud. Mud is then precipitated with alum who also settles due to gravity. Here is a scheme of water purification process is complete:
