What is a Mixture? – Definition, Types, Properties, Examples
In our day to day life, we find a number of products labelled as pure. You would have noticed it on the packs of milk, butter, ghee etc. What does the term pure mean for us? For a common man, anything that is free from adulteration or any foreign substances can be termed as pure but from a scientific point of view, it is not true. In Science, anything that is made up of only a single element is known as pure. Thus for science, even though the pack of milk is labelled as pure, it is not so. It is not pure for science but it is considered to be a mixture. Let us look at the mixture and various types of mixtures in more depth.
What is a Mixture?
Mixtures are substances that are made up of two or more different types of substances. Physical means can be used to separate them. A solution of salt and water, a combination of sugar and water, various gases, air, and so on are examples. The different components of any combination do not unite through any chemical changes. As a result, the components retain their distinct characteristics.
In addition, unlike in a compound, the components in a mixture do not combine chemically to produce new material. Instead, they just mix and maintain their original characteristics. Because the components are not in set quantities, the lemonade shown above is a combination. It might be made with more or less lemon juice, or with more or less sugar, and still be called lemonade.
Some of the important properties of Mixtures are:
- All the components or substances in a mixture retain their original physical properties.
- The mixture can be separated into its components physically by using some techniques
- The components in a mixture may or may not be in a fixed proportion and can vary in quantity.
Common Examples of mixtures are:
- Sugar and water,
- Salt and water,
- Air ( mixture of gases),
- Salt and sugar,
- Sand and water,
- Oil and water, etc.
Types of Mixtures
Mixtures can be broadly classified into 2 main categories. These are
- Homogeneous Mixtures
- Heterogeneous Mixtures
Homo means sane. The mixtures in which the components have a uniform distribution throughout the mixture are known as homogeneous mixtures. For example, salt and water is homogeneous mixture as the taste of the water will be the same if you take a sip from any portion of water. This shows that salt is uniformly distributed in the mixture.
e.g. Salt and water, Sugar and water, Alcohol and water, etc.
Properties of Homogeneous Mixtures:
- These have a uniform distribution of components throughout the mixture.
- The centrifugal force cannot be used to separate the components.
- Homogeneous mixtures do not exhibit the Tyndall effect i.e. the scattering of light by the particles in the medium when a light beam is an incident on the mixture. The path of light becomes visible due to the scattering of the light beam.
- The particle size is <1nm.
- All the solutions are homogeneous mixtures.
Hetero means different. The mixtures in which the components do not have a uniform distribution throughout the mixture which means in which the components are unevenly distributed are said to be heterogeneous mixtures. For example, sand and water is an example of the heterogeneous mixture as sand does not distribute uniformly in water. e.g. Sand and water, Sugar and salt, Ice in water, etc.
Properties of Heterogeneous Mixtures:
- The components of heterogeneous mixture do not uniform distribute throughout the mixture
- You can draw a boundary between the components by just looking at the mixture.
- The particle size ranges between 1nm to 1 μm.
- They can exhibit the Tyndall effect.
The solutions may be further divided into three types based upon the particle size. These are as follows:
- Solutions: These are a type of homogeneous mixtures. The particle size in solutions is less than 1nm. The solutions cannot be separated into their components using centrifugation or decantation. Example: Air, Sugar and water, Salt and water, etc.
- Colloids: Colloids have a particle size from 1 nanometer to 1 micrometre. These are heterogeneous in nature and the different components can be seen only under a microscope but not with the naked eye. Example: Fog, Smoke, etc.
- Suspension: Suspensions have a particle size larger than 1 micrometre. The components in a Suspension are in continuous zig-zag motion known as Brownian Motion. The stabilizing agents in a Suspension are responsible for isolating the particles from one another. In absence of stabilizing agents, the Suspension separates into its components itself. Example: Milk, cream, butter, etc.
Question 1: What do you mean by homogeneous mixtures?
Homogeneous mixtures are those mixtures in which the substances are uniformly distributed throughout the mixture. Example: Sugar and water, salt and water, etc.
Question 2: What are heterogeneous mixtures?
Heterogeneous mixtures are those mixtures in which there is no uniform distribution of substances. All the substances are unevenly distributed in the mixture. Concentration of a substance may be high or low at certain points in the mixture. Example: Sand and water, Salt and sand, etc.
Question 3: State any two differences between homogeneous and heterogeneous mixtures.
The following are the differences between homogeneous and heterogeneous mixtures:
Homogeneous Heterogeneous Substances are uniformly distributed throughout the mixture. Substances are unevenly distributed throughout the mixture. They do not exhibit Tyndall effect. They exhibit Tyndall effect only in case of colloids.
Question 4: Explain the Tyndall effect.
Tyndall Effect refers to the scattering of light by the particles of a medium when a beam of light is incident on it. As a result of scattering the path of light becomes visible.
Question 5: What is the particle size for solutions, colloids and suspensions?
The particle size for solutions, colloids and suspensions is as follows:
- Solutions: <1 nm
- Colloids: 1 nm to 1 μm
- Suspensions: >1 μm
Question 6: What is Brownian Motion?
Brownian Motion is the random movement of the particles suspended in a suspension. It is the continuous and random zig-zag movement of the particles in the medium.
Question 7: What is the correct definition for a pure substance?
Pure substance is the one which is composed of particles of only one element or compound. Example: Sugar, Salt, etc.