Types of Colloids and Their Properties

Summary

The script by Professor Dave explores colloids, a type of mixture that lies between homogeneous solutions and heterogeneous suspensions. Colloids are characterized by their particle size, which scatters light, causing a cloudy appearance and the Tyndall effect. The video discusses various types of colloids, their preparation methods, including breaking down larger particles or combining smaller molecules, and the role of emulsifying agents in stabilizing emulsions. It also touches on the use of electrostatic precipitation to remove charged colloidal particles from mixtures, highlighting the wide applications of colloids in everyday life and industry.

Takeaways

• 🧪 Mixtures can be classified into homogeneous and heterogeneous types, with colloids being a type that sits between these extremes.
• 🌊 A suspension is a heterogeneous mixture with large, visible particles that do not mix completely, like mud in water.
• 🥛 Colloids are mixtures where the particle size is larger than in solutions but smaller than in suspensions, such as milk.
• 🌈 The Tyndall effect, the scattering of light by colloidal particles, causes colloids to appear cloudy or opaque.
• 🌫 Colloidal particles can consist of many molecules or just one large molecule, like a protein.
• 🔬 The terms 'dispersed phase' and 'dispersion medium' are used to describe the components of a colloid.
• 🍮 Colloids can be found in various forms, such as smoke (solid in gas), milk (liquid in liquid), and jellies (liquid in solid).
• 🔬 Colloids can be prepared by breaking down larger particles or by combining smaller molecules, like in the formation of clouds.
• 🌧️ Emulsions are a type of colloid formed by blending two immiscible liquids, such as oil in water.
• 🥚 Emulsifying agents, like casein in milk and egg yolk in mayonnaise, prevent the coalescence of dispersed droplets in emulsions.
• ⚡ Colloidal particles can carry an electrical charge, which can be used to separate them from mixtures using electrostatic methods.

Q & A

What are the three main types of mixtures mentioned in the script?

The three main types of mixtures mentioned are homogeneous mixtures, heterogeneous mixtures, and colloids.

How does a suspension differ from a homogeneous solution and a colloid?

A suspension is a heterogeneous mixture with large particles visible to the naked eye, unlike a homogeneous solution where components disperse evenly and are not visible. A colloid has particles that are larger than those in a solution but smaller than those in a suspension, and they scatter light, causing the mixture to appear cloudy or opaque.

What is the Tyndall effect and how does it relate to colloids?

The Tyndall effect is the scattering of light by particles in a colloid, which makes the colloidal mixtures appear cloudy or opaque. This effect is used to distinguish colloids from true solutions.

Can colloidal particles be composed of a single large molecule?

Yes, some colloidal particles can be composed of a single large molecule, such as a protein.

What are the terms used to describe the components of a colloid?

In a colloid, the component present in small amounts is called the dispersed phase, and the substance it is dispersed in is called the dispersion medium.

Can you provide examples of colloids involving different states of matter?

Smoke is an example of a solid dispersed in a gas. Clouds, fogs, and mist involve liquid dispersed in a gas. Milk and mayonnaise involve liquid dispersed in another liquid. Jellies and gels have liquid dispersed in a solid, and foams and whipped cream involve gas dispersed in a liquid.

How can colloidal particles be produced?

Colloidal particles can be produced by breaking down larger particles, as seen in the production of paint pigments, or by combining smaller molecules, such as in the formation of clouds where water molecules condense to form tiny droplets.

What is an emulsion and how does it differ from other types of colloids?

An emulsion is a type of colloid that occurs when two immiscible liquids are forcibly blended, with one liquid breaking into colloidal droplets and dispersing throughout the other. This differs from other colloids where the dispersed phase is not necessarily another liquid.

Why are oil spills in the ocean difficult to clean up?

Oil spills are difficult to clean up because the action from waves can cause emulsions to form, where oil droplets disperse in water. These emulsions can coalesce and separate, making it challenging to remove the oil from the water.

What is the role of an emulsifying agent in an emulsion?

An emulsifying agent is a substance that inhibits the coalescence of the dispersed liquid in an emulsion, helping to maintain the stability of the mixture. Examples include casein in milk and egg yolk components in mayonnaise.

How can charged colloidal particles be removed from a mixture?

Charged colloidal particles can be removed by using an electrostatic precipitator, where the charged particles are attracted to electrodes, neutralized, and then deposited as dust, a method used in both industrial processes and home air filters.

Outlines

00:00

🧪 Introduction to Colloids and Mixtures

Professor Dave introduces colloids as a type of mixture that falls between homogeneous solutions and heterogeneous suspensions. He explains that colloids are heterogeneous mixtures with particles large enough to scatter light, exhibiting the Tyndall effect, but smaller than those in suspensions. The video script uses saltwater, milk, and mud to illustrate the differences in particle size and mixture characteristics. The concept of dispersed phase and dispersion medium is introduced, with examples of various colloids in different states of matter.

05:03

🍼 Preparation and Properties of Colloids

This paragraph delves into the preparation methods of colloids, which involve creating particles of colloidal size and dispersing them in a medium. It discusses two main preparation techniques: breaking down larger particles, as seen in paint pigments, and combining smaller molecules, as in cloud formation. The script also touches on substances like gelatin and starch that form colloidal systems when mixed with water. Emulsions, a type of colloid formed by blending immiscible liquids, are explained, with milk and mayonnaise given as examples. The use of emulsifying agents to prevent coalescence is also covered. Additionally, the paragraph discusses the electrical properties of colloidal particles, their role in electrostatic precipitation for removing particles from smoke, and the applications of this method in industrial and home air filters.

Keywords

💡Colloids

Colloids are a type of mixture that falls between a homogeneous solution and a heterogeneous suspension. They are characterized by having particles that are larger than those in a solution but smaller than those in a suspension. These particles are typically between 1 nanometer and 1 micrometer in size. In the video, colloids are central to the theme as they are discussed in detail, including their formation, properties, and examples such as fog and smoke, which scatter light due to the Tyndall effect.

💡Homogeneous Mixtures

A homogeneous mixture is defined as a uniform mixture where the components are evenly distributed throughout the mixture. In the context of the video, solutions formed by ionic or covalent solids dispersing in water are given as examples of homogeneous mixtures. The script contrasts these with colloids and suspensions to illustrate the differences in particle size and distribution.

💡Heterogeneous Mixtures

Heterogeneous mixtures are non-uniform mixtures where the components are not evenly distributed and can be seen as separate entities. The script uses oil and water as an example of a heterogeneous mixture that does not mix at all. This term is used to contrast with homogeneous mixtures and to introduce the concept of suspensions and colloids.

💡Suspension

A suspension is a heterogeneous mixture where large particles are dispersed throughout the mixture but are visible to the naked eye and will eventually settle out. The script describes mud in water as an example of a suspension, which is a mixture that is intermediate between a solution and a heterogeneous mixture but does not disperse evenly.

💡Tyndall Effect

The Tyndall effect is a phenomenon where light is scattered by particles in a colloid or in a very fine suspension. In the video, this effect is used to explain why colloidal mixtures appear cloudy or opaque and how the particles in the air can be seen within beams of bright light, such as spotlights at big events.

💡Dispersed Phase

In the context of colloids, the dispersed phase refers to the particles that are distributed throughout the dispersion medium. The script explains that these particles can be of any phase and are present in small amounts compared to the dispersion medium. The concept is used to describe the composition of colloids, such as smoke where solid particles are the dispersed phase in a gas.

💡Dispersion Medium

The dispersion medium is the substance in which the dispersed phase is distributed in a colloid. The script clarifies that the dispersion medium can be a solid, liquid, or gas, and it is the majority component in a colloidal mixture. Examples given include water in milk, where it serves as the dispersion medium for the fat droplets.

💡Emulsion

An emulsion is a type of colloid that occurs when two immiscible liquids are blended, resulting in one liquid being dispersed in the other in the form of colloidal droplets. The script mentions oil spills in the ocean as an example of naturally occurring emulsions and discusses milk and mayonnaise as common emulsions stabilized by emulsifying agents.

💡Emulsifying Agent

An emulsifying agent is a substance that prevents the droplets in an emulsion from coalescing and separating. The script explains the role of casein in milk and egg yolk components in mayonnaise as emulsifying agents that stabilize the emulsions.

💡Electrostatic Precipitator

An electrostatic precipitator is a device that removes particles from a gas stream by using an electric charge to cause the particles to migrate to electrodes and coagulate as a precipitate. The script describes this process as a method for removing carbon and dust particles from smoke, illustrating the practical application of colloidal particle charge in industrial and home air filtration systems.

💡Coagulation

Coagulation in the context of colloids refers to the process where dispersed particles come together to form larger aggregates. The script mentions that when colloidal particles lose their charge, such as in an electrostatic precipitator, they coagulate and can be removed from a mixture as a precipitate.

Highlights

Colloids are a type of mixture that falls between homogeneous solutions and heterogeneous suspensions.

Colloids are composed of particles larger than those in solutions but smaller than those in suspensions, making them visible to the naked eye.

The Tyndall effect, where colloidal particles scatter light, gives colloidal mixtures their cloudy or opaque appearance.

Colloidal particles can range from hundreds to thousands of molecules or be a single large molecule like a protein.

In colloids, the term 'dispersed phase' refers to the particles present in small amounts, while the 'dispersion medium' is the substance they are dispersed in.

Colloids can have a variety of dispersed and dispersion mediums, including solid in gas, liquid in gas, liquid in liquid, and gas in solid.

Preparation of colloids involves producing particles of colloidal dimensions and distributing them in a dispersion medium.

Colloidal particles can be produced by breaking down larger particles, as seen in paint pigments, or by combining smaller molecules, as in cloud formation.

Certain substances like gelatin and starch spontaneously form colloidal systems when mixed with water.

Emulsions are a type of colloid formed by forcibly blending two immiscible liquids, with one dispersing into colloidal droplets throughout the other.

Emulsifying agents, like casein in milk and egg yolk components in mayonnaise, prevent the coalescence of dispersed droplets in emulsions.

Charged colloidal particles can be removed from mixtures using electrostatic precipitation, where they migrate to electrodes, lose their charge, and coagulate as a precipitate.

Electrostatic precipitation is used in industrial processes and home air filters to remove particles like carbon and dust from smoke.

The difference in particle size is the key factor determining the characteristics of mixtures, distinguishing solutions, colloids, and suspensions.

Colloids have a wide range of practical applications, from the formation of clouds and fogs to the stability of food products like milk and mayonnaise.

Understanding the properties of colloids, such as particle size and charge, is crucial for their preparation and application in various fields.

The formation of colloids can be influenced by various methods, including mechanical breakdown, molecular combination, and spontaneous dispersion in certain substances.

Transcripts

Professor Dave here, I wanna tell you about colloids.

We’ve learned quite a bit about different kinds of mixtures.

For example, we’ve learned about homogeneous mixtures involving ionic or covalent solids

that disperse evenly in water or some other solvent to form a solution.

We have also seen certain heterogeneous mixtures where the components do not mix whatsoever,

like oil and water.

More often than not, a discussion of mixtures will end there.

But the reality is that there are other types of mixtures that do not fall strictly into

one of these extremes, but rather sit in between, so let’s find out what these could be.

One such type of mixture is called a suspension.

This is a heterogeneous mixture composed of large particles that are visible to the naked eye.

An example of this can be generated by mixing mud and water.

They will not remain completely separate, like oil and water do, nor will things disperse

perfectly evenly.

Instead, there will simply be a cloudy mix of water and suspended mud particles.

We can also create a mixture that is in between a suspension and a homogeneous solution.

This will usually form because the particle size is larger than ions or small molecules,

but smaller than the particles in a suspension.

Such a solution is called a colloid, or a colloidal dispersion.

To illustrate the difference between a solution, a colloid, and a suspension, let’s look

at saltwater, milk, and mud.

The difference in particle size is what determines the different characteristics of these mixtures.

The particles in a colloid are large enough to scatter light, which is a phenomenon called

the Tyndall effect.

This is why colloidal mixtures will appear cloudy or opaque, the way that particles in

the air are visible inside the beams of bright lights, which is what illuminates big event

spotlights.

Colloids like fog and smoke are what make these beams so bright, due to their scattering

ability.

Some colloidal particles consist of hundreds or thousands of molecules, but some are just

one large molecule, like a protein.

And when we discuss colloids, instead of solute and solvent, we will call the particulate

component present in small amounts the dispersed phase, and the substance the particulate is

dispersed in will be the dispersion medium.

The dispersed phase and the dispersion medium can each be of any phase.

Smoke is solid dispersed in gas.

Clouds, fogs, and mist involve liquid dispersed in gas.

Milk, mayonnaise, and butter involve liquid dispersed in liquid.

Jellies and gels are liquids dispersed in solids.

Foams and whipped cream involve gas dispersed in liquid.

So we can see that there are quite a wide variety of colloids.

Now that we know what colloids are, let’s discuss how they can be prepared.

In order to prepare a colloid, we must first produce particles of colloidal dimensions,

which means they must be above a size that would generate a solution but below a size

that would generate a suspension, and then we must distribute these particles throughout

a dispersion medium.

There are two ways we can prepare these particles.

The first is by breaking down larger particles.

This is how many paint pigments are produced.

The other way is by combining smaller molecules.

This is how clouds form.

Water molecules high up in the atmosphere where it gets very cold, are able to condense

enough to form tiny droplets that then aggregate.

If the water droplets become too large to remain in the cloud, we get precipitation,

which is what causes rain, sleet, and snow.

There are also some solid substances that spontaneously form colloidal systems when

mixed with water, like gelatin, or starch.

These substances contain particles that are already of colloidal size, the water simply

disperses them.

Another type of colloid is called an emulsion.

This occurs when two immiscible liquids are forcibly blended.

One liquid will break into colloidal droplets and disperse throughout the other liquid.

This is why oil spills in the ocean are hard to clean up, the action from waves causes

emulsions to form.

But sometimes, emulsions will coalesce and separate from the other liquid.

To combat this tendency, an emulsifying agent can be used.

This is a substance that inhibits the coalescence of the dispersed liquid.

Milk and mayonnaise are examples of emulsions.

Milk is an emulsion of butterfat in water, with a protein called casein acting as the

emulsifying agent, and mayonnaise is an emulsion of oil in vinegar with egg yolk components

acting as the emulsifying agents.

Sometimes dispersed colloidal particles will bear an electrical charge.

In any particular system, all the colloidal particles will have the same charge, which

helps keep the particles dispersed, since like charges repel one another.

We take advantage of the formal charges on colloidal particles to remove them from a

variety of mixtures.

We can place charged electrodes in a colloidal dispersion and the charged colloidal particles

will migrate to one of the electrodes.

Once this occurs, the colloidal particles lose their charge and consequently will coagulate

as a precipitate.

This is how we remove the carbon and dust particles in smoke.

If smoke passes through something called an electrostatic precipitator, the charged particles

in the colloid will be attracted to electrodes where they will be neutralized and then deposited

as dust.

This method is used in large-scale industrial processes, as well as simple air filters designed

for home use.

So now we know the difference between solutions, colloids, and suspensions, as well as quite

a few things about different types of colloids and their properties.