Is Saltwater A Homogeneous Or A Heterogeneous Mixture

So, is saltwater a homogeneous or a heterogeneous mixture? The answer to this is, saltwater can be both homogeneous and heterogeneous mixture. Saltwater contains dissolved salt, so it’s a homogeneous mixture as we can’t separate salt from it directly. But it is also called a heterogeneous mixture because of the presence of impurities and insoluble components like sands, shells made up of calcium carbonate, and microbes in it. You might be thinking that we can make a salt solution at home as well. What could that mixture be? You must keep in mind that we cannot directly separate the dissolved salt from the solution. So, the salt solution is a homogeneous mixture. If you’re curious to learn more about homogeneous and heterogeneous solutions, stay with us till the end.  

What are Mixtures?

Before we dwell on the definitions of homogeneous and heterogeneous mixtures, do you know what mixtures are in terms of chemistry? Mixtures are all around us, such as the food that we consume. However, in terms of chemistry, food is not a mixture but actually the result of an irreversible chemical reaction. Could you ever obtain the raw vegetable after it is cooked? Never, which is proof of the occurrence of an irreversible chemical reaction. A mixture is a substance that is formed by combining two or more substances. When two or more substances combine to form a single mixture, they do not undergo any kind of chemical reaction. This means that all the properties of each of the substances remain intact. When a mixture is formed with different substances with every chemical property intact, you can also separate them easily. And although the properties of the constituents of a mixture will remain intact, the mixture itself can have unique properties. For instance, the mixture of alcohol and water has a different boiling point and melting point when compared to each of its constituents. Now, based on the composition of mixtures, they can be of two types: homogeneous mixtures and heterogeneous mixtures. And if we are to learn what kind of mixture saltwater is, we’ll first need to understand what each mixture means and how they are different from one another.  

What are Homogeneous Mixtures?

Homogeneous mixtures are mixtures where the amount of all the components are uniformly distributed in the mixture. Even if we extract a portion of the mixture and calculate the proportion of each component, we will find it to be the same as the entire mixture.

Is Saltwater a Homogeneous Mixture?

Now, let’s take the example of a saltwater sample. As we’ve mentioned earlier, saltwater is considered homogeneous because it is uniformly distributed throughout the entire sample. You can get confused between regular water and a saltwater sample. It is because they are both transparent in appearance. However, the amount of salt in each salt solution can vary. You might be wondering that if salt gets dissolved in water, how are we sure that it is a mixture? How are we sure that no chemical reaction takes place? We are sure because salt and water can both be separated from one another easily as separate components. This can be done by simply carrying out the process of evaporation. And since we can separate them completely without making any changes in their properties, we can conclude that no chemical reaction has taken place between them.  

Properties of Homogeneous Mixtures

The following are the properties of homogeneous mixtures:

1. The size of the particles in this type of mixture is less than one nanometer.
2. The particles present in a homogeneous mixture do not exhibit the Tyndall effect.
3. In a homogeneous mixture, we can’t really separate the boundaries of different particles.
4. The processes of centrifugation and decantation cannot separate the particles of the components of a homogeneous mixture.  

What are Heterogeneous Mixtures?

Heterogeneous mixtures are mixtures where the amount of all the constituents in the mixture are not uniformly distributed throughout. When we extract different parts from the entire mixture and calculate the proportions of each component in each of the extractions, we’ll find them to be different from one another.

Is Saltwater a Heterogeneous Mixture?

You might be wondering that if the saltwater sample is homogeneous, then seawater, too, must be homogeneous, but that’s not quite true. Actually, seawater is both a homogeneous and heterogeneous mixture. We have earlier discussed why a saltwater sample is homogeneous. But why is seawater heterogeneous, too? Let’s find out. Other than the presence of various kinds of salts, seawater contains many other impurities and insoluble components. Due to the presence of these components, the composition of seawater is different in different places, and we can easily differentiate between the boundaries of seawater and these impurities.  

Properties of Heterogeneous Mixtures

The following are the properties of heterogeneous mixtures:

1. Usually, most of the mixtures fall under this category other than solutions and alloys.
2. The size of particles in these mixtures ranges from one nanometer to one micrometer, or it can be more than the mentioned range.
3. In heterogeneous mixtures, we can easily separate the boundaries of different components present in the mixture.
4. The particles present in heterogeneous mixtures are scattered by light, i.e., they exhibit the Tyndall effect.

The solubility of different salts in seawater

Salts can be of various types other than the standard table salt of sodium chloride. There are a variety of salts present in seawater. Each type of salt has different kinds of chemical properties and chemical compositions. Did you know that salts of different types appear as distinct rings when seawater evaporates with a slight curve? This is surprising, isn’t it? What could be the reason behind this? When seawater evaporates, the salinity of the solution increases. At different levels of salinities, various salts become insoluble in seawater. Whenever a particle kind of salt becomes insoluble, it precipitates, which is falling out from the solution and forms crystals of the salt. The ring of salts which usually appears first is calcium carbonate. It is because carbonates have the lowest level of solubility in seawater. After calcium carbonate, potassium and magnesium salts become insoluble. These two types of salts are very much soluble in seawater and thus forms the innermost rings of salts. The taste of each of the salts varies due to differences in chemical composition. The following are the solubility and tastes of different salts present in seawater:

1. Calcium carbonate: This salt becomes insoluble at 50 percent evaporation of seawater on the shores. It is present with a concentration of about 70 parts per thousand or ppt. It has a chalky taste.
2. Gypsum: Gypsum is a calcium salt that becomes insoluble at 80 percent evaporation of seawater on the shores. It is present with a concentration of about 100 parts per thousand. It has a chalky taste.
3. Sodium chloride: This is the common salt. It becomes insoluble at 90 percent evaporation of seawater on the shores. It is present with a concentration of about 130 parts per thousand. It has a salty taste.
4. Potassium chloride and magnesium chloride: They are potassium and magnesium-based salts. It becomes insoluble at 95 percent evaporation of seawater on the shores. It is present with a concentration of about 150 parts per thousand. It has a salty taste.

How can we use seawater?

With seawater covering more than 70 percent of the Earth’s surface, there are increasing problems of water shortages. It is because salt water cannot be used for drinking, irrigation, and industrial purposes because of its salinity. Sometimes slightly salty water can be converted into freshwater resources by applying special techniques. In the Dead Sea, located in the Middle East, the seawater is so dense with salts that you don’t sink at all, opposing to what usually happens in other seas and oceans, where you sink.  

Using Saline water

With the help of its advanced technologies, the US has managed to use salt water in different fields. This is done to conserve the small percentage of freshwater resources. In the year 2015, about 16 percent of the water used was saline water. Saline water can only be used for certain purposes, such as thermal power plant cooling. It also has industrial uses; about 5 percent of the water used in industries is taken from the sea. In fact, in mining activities, the percentage of saline water used is much higher, i.e., 53 percent of total use. However, removing salts from saltwater is a very costly process, which is why it is not carried out on a large scale.    

Conclusion

As we reach the end of the article, we have learned that saltwater can be both homogeneous and heterogeneous mixture. It is through the different definitions of homogeneous and heterogeneous mixtures that we realize why and how saltwater is both kinds of mixtures. After learning that the use of saline water is very little in comparison to the uses of freshwater, we must use freshwater resources very carefully to prevent its wastage.