Making Colloids – Hello Sinaumed’s, in this article we will discuss colloids. Starting from the definition, types, properties, to how to make colloids. While reading this article, you may not have imagined what a colloid is, what shape it is. It’s okay, Sinaumed’s, because the word “colloid” is rarely used in everyday life.
However, that doesn’t mean you’ve never found it at all, huh. Because colloids are all around us. When I was little, Sinaumed’s must have eaten agar agar which was sold in front of the school, on the side of the road, or anywhere else ! Agar agar is a food in the form of a gel made from seaweed. Well according to chemistry, gels are included in colloids.
Colloid itself is one of three types of mixtures that exist in chemistry, the other two are solutions and suspensions. Apart from agar, milk, ice cream, mayonnaise, shampoo, and also ink are examples of other colloids that you can find easily.
So that you get enlightened, let’s just get into the discussion about colloids.
Actually, what is colloid?
Colloids are a type of heterogeneous mixture that originates from the dispersion of one substance into the other substances it is mixed with. Therefore, if Sinaumed’s learns about this mixture, he will definitely find the terms “dispersed phase” and “dispersing medium”.
Okay, here’s a new term that you don’t know what it means. But don’t give up just yet, the discussion is still long. The dispersed phase is a substance that is evenly distributed among other substances. Then, the dispersing medium itself is the cause of the uniform distribution of the dispersed phase.
To make it easier to understand, let’s use coconut milk as an example. You know coconut milk? Yup , the white liquid that mothers often use for cooking. Just FYI, coconut milk actually has oil droplets in the water. The oil droplets are the dispersed substance (dispersed phase), while the water is the dispersing medium (the dispersing medium).
As mentioned earlier, in chemistry there are 3 types of mixtures. The first is colloid, the second is solution, and the third is suspension. So what’s the difference between these three types of mixtures?
Simply put, colloids are a mixture of suspension and solution. Means colloid is not a suspension and not a solution at the same time. Because it is in the middle, colloids are included in metastable mixtures, meaning they can separate within a certain time.
For more details, you can see the comparison table between solutions, suspensions, and colloids below:
| Solution | Colloid | Suspension |
| Cannot be filtered | Can be filtered but only with a semipermeable membrane | can be filtered |
| 1 phase | 2 phase | 2 phase |
| stable | stable | Unstable, between substances will definitely separate. |
| homogeneous | heterogeneous | heterogeneous |
| The particle diameter is <10-7cm | The size of the particle diameter is 10-7-10-5cm | The particle diameter is > 10-5cm |
To understand more about suspensions, solutions and colloids, Sinaumed’s can read Basic Chemistry, Principles & Modern Applications, Edition 9 Volume 1, written by Petrucci.
Types of Colloids
Colloids can be divided into 8 types based on the difference between the dispersed phase and the dispersion medium. See an explanation of each type below.
1. Solid Sole
Solid sol has a dispersed phase and a solid dispersion medium. This type of colloid is formed due to the influence of temperature and pressure which produces solid and hard solids. One example of a solid sole is colored glass.
2. Sol
This type of colloidal sol has a solid dispersed phase in a liquid dispersing medium whose properties do not change easily. So, what distinguishes between sol and solid sol is the dispersing medium. An example of a sole is wall paint.
3. Solid Aerosol
Aerosols have a solid dispersed phase in a gas dispersion medium. For example, vehicle exhaust. Of course, Sinaumed’s has had a moment when a motorcycle or car emitted quite thick smoke, right? Well, the cause of the opacity is the solid (dispersed phase) that is in the smoke (dispersing medium).
4. Aerosols
Aerosol is a type of colloid which has a liquid dispersed phase in a gas dispersion medium. So, what distinguishes aerosols from solid aerosols is the dispersed phase. And aerosols themselves don’t last long.
For example, like a perfume whose fragrance can disappear within a certain time. When you spray perfume into the air, the liquid perfume (dispersed phase) will be dispersed in the air in the form of a gas (dispersion medium).
5. Solid Emulsion
The fifth type of colloid is a solid emulsion. This colloid has a liquid dispersed phase and a solid dispersion medium. Like agar which is a mixture of water (dispersed phase) and agar agar powder (dispersing medium).
When you heat agar powder in water, the fibers of the agar move freely and then contract when cooled. In other words, water is dispersed in the agar particles.
6. Emulsion
Colloids in which the dispersed phase and dispersion medium are liquids are called emulsions. These types generally do not mix with each other like milk. The reason is because there is a difference between the polarity levels.
In milk, water and milk particles have different levels of polarity, so they don’t mix perfectly. Therefore, milk is included in the colloid category, not a solution.
7. Solid Froth
Solid froth is a type of colloid with a gaseous dispersed phase and a solid dispersion medium. For example, like a sponge that looks solid but when squeezed it turns out it’s only filled with air.
8. Froth
The eighth type of colloid is froth in which the dispersed phase is a gas and the dispersing medium is a liquid. For example, like soap scum. If you pay attention, in the soap foam there is air (dispersed phase) which is trapped in the soap solution (dispersing medium), right?
Properties of Colloids
Because colloids are the result of a mixture of two substances, they have their own properties that are different from those that form them, namely:
1. The Tyndall effect
The first property of colloids is the Tyndall Effect which states that colloidal particles can scatter light. If you’re wondering what that means, try taking two glasses. Fill the first glass with water, then fill the second glass with milk.
After that, take your cellphone then turn on the flash and direct the light from the cellphone to the first glass and the second. See the difference, the light directed at the first glass shouldn’t be visible. While in the second glass can be seen traces.
How did it happen? The answer is because the light is directed at the water which is a solution, then it is continued by the water so it cannot be seen. However, the light that is directed at the milk (colloid) is scattered so the traces are visible.
2. Brownian motion
Around 1827’s, Robert Brown, who works as a botanist, managed to observe the movement of colloidal particles. According to his observations, colloidal particles move randomly in a zigzag path microscopically when they are in the dispersing medium. This movement is caused by collisions between colloidal particles and the dispersing medium.
3. Adsorption
In short, adsorption is the term for the attachment of ions to the colloidal surface because colloidal particles have the ability to attract small particles. And this ability arises due to the relatively high surface tension of colloids.
Interestingly, when colloidal particles adsorb ions with a positive charge, the colloid also has a positive charge. Conversely, if what is adsorbed is a negatively charged ion, then the colloid becomes negatively charged. In addition to ions, colloidal particles can also absorb static electricity.
You can find adsorption properties in everyday life because it is used in several ways. Such as in the manufacture of silica and aluminum gel, pollution masks, manufacture of medicines, charcoal gas masks, water purification using alum, or fogged windows.
For those of you who are curious about how chemistry can help in the process of making medicine, the book Medicinal Chemistry: Fundamentals of Drug Design by PROF. MUCHTARIDI, PH.D., APT, Prof. Muchtaridi, Ph.D., Apt is the right learning resource.
4. Colloid Coagulation
Colloid coagulation is the process of clumping colloidal particles. If charged colloids are connected with charges of the same type, they will repel and not agglomerate.
However, if the colloidal charges are neutralized, they will not repel each other and will coalesce or agglomerate so that coagulation occurs.
In other words, colloid coagulation can only occur if the colloid is uncharged or neutralized. The methods commonly used to neutralize it are:
- Mix positive colloids and negative colloids so that the charges neutralize each other.
- Adding an electrolyte solution to a negatively or positively charged colloid
- For example, like eggs that turn into lumps when heated.
- Decay, cooling, or stirring.
Another example of colloid coagulation in everyday life is spoiled milk turning into a lump.
5. Dialysis
The fifth property, namely Dialysis, is a process of purifying colloids from the ions that interfere with them. You do this by using a semipermeable membrane. So when water is poured into the colloid, the colloid will push the ions out.
Why only ions come out? This is because the ion size is smaller than the semipermeable membrane while the colloid size is larger. Thus, when a colloid charged with interfering ions passes through a semipermeable membrane, the interfering ions are separated. This property is used in the process of dialysis or hemodialysis.
6. Electrophoresis
Electrophoresis is the movement of colloidal particles in an electric field. The benefits of this trait are usually used in the process of separating gene fragments in biotechnology. For example, the process of filtering factory dust in the chimney. In addition, electrophoresis is commonly applied in DNA identification or in the process of detecting genetic disorders.
7. Lyophilic and Lyophobic colloids
Lyophilic and lyophobic properties are usually found in colloids of the sol type. So you could say that there are two types of soles, namely lyophilic soles and lyophobic soles.
Lyophilic sol is a sol in which the dispersed substance particles are able to attract the dispersed medium because there are hydrogen bonds in it. The nature of lyophilic sol is usually more viscous, has a large particle size, and has a small Brownian motion.
Meanwhile, lyophobic soles are soles in which the dispersed substance particles are not able to attract the dispersing medium so that there is no interaction process in them. The nature of lyophobic soles is usually more dilute than lyodil soles.
8. Protective colloid
Because the lyophilic sole has attractive properties, it is commonly used as a protector of the lyophobic sole so that coagulation does not occur even though it contains an electrolyte solution. For example like gelatin in ice cream which keeps the ice cream together and maintains its elasticity.
In addition, several other human activities that take advantage of the protective properties of colloids are:
- Adding silicone grease to the paint
- Add casein to milk
- Add lestin to margarine
Colloid Manufacturing
As previously explained, colloids are not solutions and not suspensions, aka they are in the middle. Because it is in the middle, colloids can be created from solutions and suspensions.
The process of making colloids themselves is usually divided into two, namely condensation and dispersion.
1. Condensation
Condensation is the process of making colloidal solutions which in the process are further divided into two, namely physically and chemically. In physics, the process is done by changing the solvent. While chemically involves several chemical reactions such as:
- Redox, reduction and oxidation reactions
- Hydrolysis reaction
- A substitution reaction or a double decomposition reaction
2. Dispersion
Dispersion is the opposite of condensation, meaning it is a process of making colloid from suspension. This process converts large colloidal particles into smaller particles.
In the process of making colloids using dispersion techniques, it is divided into three processes. The first is mechanical, the second is peptization, and the third is arc-diagonal.
a. mechanically
Making colloids mechanically is usually done by grinding or mashing so that the colloidal particles become smaller. After that, hot liquid medium was added. For example, sulfur sole is made by grinding sulfur powder with an inert substance (similar to sugar) and then mixing it with water.
b. In peptization
This method is usually done by adding ions of the same type to a precipitate. For example agar is peptized by water, rubber is peptized by gasoline, then nitrocellulose is peptized by acetone, and others.
c. In an arc berdia (berdig)
The principle of this method is to flow a high voltage current on two electrodes. These electrodes are metal and must be immersed in water. Initially the metal atoms will be thrown into the water. After that, these atoms will experience condensation and become colloidal particles. In other words, this method is a combination of the condensation method and the dispersion method.
Benefits of Colloids in Everyday Life
After knowing what colloids are, types, properties, and how to make colloids, Sinaumed’s is certainly curious about the benefits of colloids in everyday life. Because even though the term is rarely used, its benefits are very close to human life. Examples like:
- In the cosmetic industry, colloids are used to make shampoos, deodorants, foundations, facial cleansers, and body moisturizers.
- In the textile industry, colloidal sol is used to dye clothes
- In the pharmaceutical industry, colloids are used in the process of making drugs
- In the coir industry, colloids are very useful for producing soap or detergent.
- In the food industry, colloids are used to make soy sauce, milk, mayonnaise, butter and sauces.
- In the world of health, colloids can be used to identify DNA, or the process of dialysis.
At school, colloids are usually taught to grade 11 students. For those of you who are just going to grade 11, it’s best to make the book SMA/MA Class XI Chemistry Learning Guide: Theory & 1551 Questions written by Budiman Anwar as an additional source of learning to complement the material you receive at school. class later.
The material in the chapters in this book is made very complete so that it can be used as a reference source for students in independently developing their knowledge and understanding of chemical concepts and their application in everyday life.
Thus the discussion about colloids, starting from understanding to how to make colloids. Hopefully all of the article discussion above can be useful for Sinaumed’s.