All about Mixtures + 2 exercises

What is a material system?

If we want to learn everything about a mixture, we have to talk about material systems. A material system is referred to as a single body, a part of that body, a group of bodies, or part of that group of bodies that Chemistry considers for study. For example, water with diluted sugar, a piece of ice, or sand with iron shavings are material systems.

Material systems can be classified into:

HOMOGENEOUS SYSTEMS / HETEROGENEOUS SYSTEMS

There’s another type of system classified as an inhomogeneous system, in which if nearby portions are examined, they possess similar properties, but they will not if points very far apart from each other are analyzed. This is the case with the Earth’s atmosphere. In many books, the atmosphere is considered a heterogeneous system given the amount of smog and non-dissolved particles it presents.

Let’s look at each of them. But first… Would you rather read it or see it? We recommend the following video on our channel, where we explain all of this and more.

HOMOGENEOUS SYSTEMS

A homogeneous system has equal qualitative properties in all its portions, regardless of which one is analyzed. This means that if a specific part of diluted saltwater is examined and the same operation is repeated with another part, their qualities are the same. The system, when homogeneous, does not present any discontinuity in it. Those systems that have equal chemical and physical properties throughout their mass belong to this classification.

What does this mean in simpler words?

Very simple: if we analyze a material system and see that all its points have the same characteristics, then it’s a homogeneous system.

Here’s an example:

The content of this glass is homogeneous.

Let’s only look at the contents of the glass. Do you see that the liquid is the same at all points and that we cannot differentiate any other characteristics? Everything seems to have the same color, there are no air bubbles standing out, everything is perfectly uniform. That is undoubtedly a homogeneous system.

Keep observing a bit more the drink in the glass. We just mentioned that everything has the same color. That “zone” that has identical properties is called a phase and is a very important concept in chemistry, because every homogeneous system has ONLY one phase.

But be careful, that phase can often be made up of more than one component. In this way, the drink inside the glass in the photograph may be made up of alcohol, water, and a lot of other ingredients. But all of it together forms only one phase. That is why it is a homogeneous system. (Please read this paragraph again, as it is essential to understand the difference between homogeneous and heterogeneous systems.)

HETEROGENEOUS SYSTEMS

Systems in which different parts of it have different chemical and physical properties, presenting surfaces of discontinuity, belong to this classification. A heterogeneous system, unlike the previous one, has different intensive properties in all its portions (whatever is analyzed), and surfaces of separation can also be observed. For example: water with oil, mist (air with water droplets), or river water with gold nuggets.

Let’s look at this image again:

Heterogeneous System: This lemonade with lemon pieces inside.

This system is quite different from the previous image of the glass. Notice that it has very distinct parts: the solid parts (the pieces of lemon and the straw), the liquid part (the water in the glass), and the gaseous parts (the air filling the rest of the glass and the bubbles). Oh, and should we count the air as well? Yes, don’t forget that our system (the portion of the universe we mentally isolate to study) is the inside of the glass. As you can see, it is not very uniform because it has the three phases we mentioned. And since there is more than one phase, it is a heterogeneous system.

We could also delve into the concept of components. Often, a system can have many components and still be homogeneous. For example, tap water has many dissolved minerals; each mineral is a component that, along with the H2O substance, forms the tap water you drink. However, only one phase is visible, so it is homogeneous.

Other times, a system may have many phases but only one component. For instance, a glass containing water vapor, liquid water, and ice. This system would be heterogeneous from any angle (you can observe three different phases), but all the phases are formed by only one component: water.

Conclusion

Mixtures are combinations of two or more substances that retain their individual properties and are physically combined. There are two main types of mixtures: homogeneous and heterogeneous. Homogeneous mixtures are uniform in composition and properties throughout, meaning that they have only one phase.

Examples of homogeneous mixtures include saltwater and alloys. On the other hand, heterogeneous mixtures are not uniform in composition and properties throughout, meaning that they have two or more phases.

Examples of heterogeneous mixtures include sand and water, salad dressing, and blood.

Understanding the difference between these two types of mixtures is important because it can help us identify and classify materials, as well as predict their behavior and properties. By studying mixtures, we can also gain insights into the underlying principles of chemistry and physics.

Activities

1. True or false? If false, tell why.

• A mixture is a combination of two or more substances that are chemically combined.
• Homogeneous mixtures have a uniform composition throughout the mixture.
• Heterogeneous mixtures have only one phase.
• The components of a mixture can be separated by physical means.
• The properties of a mixture are the same as the properties of its individual components.

   2. Classify the following mixtures as homogeneous or heterogeneous:

• Pizza
• Blood
• Milk
• Ethanol.
• Sugar water
• Trail mix (containing nuts, raisins, and M&Ms)

More information on the Internet:

There are many online resources where you can find simulations and videos about mixtures, homogeneous mixtures, and heterogeneous mixtures. Here are a few links to get you started:

1. ChemCollective: This website offers a variety of interactive simulations and activities related to chemistry, including mixtures. You can access their mixtures simulations here: https://chemcollective.org/sims.
2. PhET Interactive Simulations: PhET offers a large collection of interactive simulations covering a range of science and math topics. You can find their simulations on mixtures here: https://phet.colorado.edu/en/simulations/category/chemistry/mixtures.
3. Khan Academy: Khan Academy offers free educational videos and exercises on a wide range of topics, including chemistry. You can find their videos on mixtures and solutions here: https://www.khanacademy.org/science/chemistry/matter-and-properties-of-matter/mixtures-and-solutions.
4. Do you want to read this article in Spanish? Click here: https://www.ensambledeideas.com/sistemas-homogeneos-y-heterogeneos/