Simple Classification of Substances and Separation of Mixtures: Mixtures

2.0 Simple Classification of Substances and Separation of Mixtures

2.2 Mixtures

Most of the substances around us occur as mixtures, rather than in pure state. That is, they are contaminated with other substances.

What is a mixture?

Think of many pieces of two different things, such as 10- and 20-shilling coins in the same bag. We can easily pick out, say, all the 10-shilling coins because they are loose; that is, not joined to or combined with the 20-shilling coins.

Picking is a physical method or means of separation. Even molecules (tiny invisible particles) of different substances are loose and free from one another; so they can also be easily separated by other physical means. They are mixtures.

Question 2.2(a)

What is the meaning of a mixture?

Answer to Question 2.2(a)

In a mixture, individual substances retain their properties (physical and chemical).

Beans and sand, and sugar and a salt, are other examples of mixtures. Mixtures can be classified in a number of ways.

What are the common classifications of mixtures?

As you view each of the following classes of mixture, think of how they might be separated.

NB: Soluble liquid-gas mixtures also do exist.

Questions 2.2(b)

1. One example of solid-solid mixtures is iron powder and sulphur. Name at least three other solid-solid mixtures.
2. Sand-and-water is an example of insoluble solid-liquid mixtures. Identify at least three other such examples.
3. Sodium sulphate and water form a soluble solid-liquid mixture. Name at least two other such mixtures.
4. Name any two liquids you know, that mix well (uniformly) with each other.
5. Name any two liquids you know, that form two layers (immiscible) when poured together into a container.

Answers to Questions 2.2(b)

Watch the video below, and view pics below to observe water-and-oil, iron-and-sulphur, and muddy water respectively as examples of mixtures.

(courtesy of Youtube ‐ Oil and Water by Graham Shaw),