4. Separation of Materials

Fig. 4.1 Solution

In order to comprehend solubility, we must familiarise ourselves with the components of a solution. A solute and a solvent combine to form solutions. A solvent is a substance responsible for dissolving other substances, known as solutes.  Refer to the example of saltwater to better understand the distinction between the two. Water acts as the material being utilised to dissolve the salt (solute), water serves as the solvent. Since salt is a substance dissolving into the water, the salt serves as the solute. Typically, solvents are more in quantity in solutions.

Fig. 4.2 Components of a solution

Solutions can exist in any of the three states of matter. This means that not all solutions are liquids.

Examples of solutions:

Solid solutions

Bronze: copper and tin

Gas and Liquid Solutions:

Fizzy drinks

The ability of a solute to dissolve in a solvent and create a solution is known as solubility. This characteristic enables substances, such as sugar to dissolve in a cup of coffee. Although there are a few exceptions, water is referred to as a "universal solvent" since it can dissolve the majority of substances.

Watch this video to recap:3 

Material separation involves sorting and isolating different substances when they are mixed together. It's like the detective work of science and industry, where we use various methods and techniques to pick out specific materials from a mixture of substances. Material separation is super important in recycling, making things, protecting the environment, and doing scientific investigations. It allows us to recover valuable stuff, get rid of unwanted things, and gain a deeper understanding of what's in our mixtures.

There are many other examples in daily life when we need to separate a substance from a mixture.

When making tea, tea leaves are strained from the liquid using a strainer. 

Fig. 4.3 Straining

The butter is separated from milk or curd by churning4. 

Fig. 4.5 Sedimentation

b. Decantation

Decantation is a method used to separate two liquids that don't mix together or to separate a solid and liquid that don’t mix together. The mixture is left undisturbed for some time to allow the solid particles or sediments to settle at the bottom. After this, the clear liquid is gently poured into another container without disturbing the sediments.

For example, decantation can be observed when separating oil from water.

When water and oil are combined, they separate into two distinct layers due to their different densities. Water, being denser, settles at the bottom, while the less dense oil rises to the top and floats above it. Once the oil and water have separated into two layers, carefully tilt the container and pour the oil (the top layer) into another container.9 

Fig. 4.6 Decantation

All water treatment plants, including those for sewage water, use decantation to separate sediments. In sugar industries, while the processing of sugar beets or sugarcane into granular sugar takes place, many liquid-solid mixtures are obtained. An example of this would be syrups and crystals. Decantation is an ideal separation method.

c. Filtration7 

Filtration is a method for separating substances that do not dissolve in a liquid mixture. When you pass a solution through a filter, particles larger than the filter's pores are left behind, while the rest flow through. It's a bit like when you filter out mud from muddy water, leaving the clean water behind.

Fig. 4.7 Filtration

Filtration is a technique used in many industries:

1. Water Treatment 

2. Chemicals
3. Pharmaceuticals 

4. Biotechnology

5. Food Processing.

Watch this video to understand how these processes work:8 

Vid 4.3 Separation of Solutions

Play this quiz to revise our learning: