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Is Matter Around Us Pure

Chapter: Is Matter Around Us Pure

Let us see our surroundings. We see that so many things exist. All these things exist as mixtures of two or more components which are pure for example:- sea water, soil and some minerals etc.

What is a Mixture?

Mixtures are formed by more than one type of form matter called as substance. A substance cannot be divided into any other kinds of matter even by applying any physical process. By the process of evaporation, dissolved sodium chloride can be separated from water. Sodium chloride itself is a substance and it cannot be separated by physical process into its chemical constituents. Similarly, sugar is a substance because it contains only one kind of pure matter and its composition is the same throughout.

Soft drink and soil are not single substances. It will always have similar characteristic properties whatever the source of the substance is. Therefore, we can say that a mixture contains more than one substance.

Types of Mixtures

Depending upon the nature of the components that form a mixture, we can have different types of mixtures.

There are two classifications of mixtures. They are homogenous and heterogeneous. A mixture in which the composition is uniform and each and every part of the solution has similar properties is called as homogeneous mixture. Air is termed to be a homogeneous mixture of gases like oxygen, nitrogen and other substances in small amounts. Substances like salt, sugar etc dissolve in water and form homogeneous mixtures. A mixture in which two or more phases were present is called heterogeneous mixture. A solution is a homogeneous mixture which consists of solute and solvent.

What is a Solution?

A solution is defined as a homogeneous mixture of two or more substances. We come across many types of solutions in our daily life. Lemon juice, soda etc. are examples of solutions. Generally we think of a solution as a liquid that contains either a solid, liquid or some gas dissolved in it. But, we can also have solid solutions (termed as alloys) and gaseous solutions (like air). There is homogeneity at the particle level in a solution. For example, lemon juice tastes the same throughout the solution. This shows that particles of sugar or salt are evenly distributed in the solution.

A solution has a solvent and a solute as its components. Solvent is that component of the solution that dissolves the other component in it and solute is that component of the solution which is dissolved in the solvent. Generally solvent is present in larger quantity and solute is present in lesser quantity.

Properties of a solution

    i-  It is a homogenous mixture.

    ii- The path of light is not visible in a solution as the particle size is very small.

    iii- The solute particles cannot be separated from the mixture by the process of filtration.

    iv- A solution is stable.

Suspension

A suspension is a heterogeneous mixture in which the solute particles do not dissolve but they remain suspended throughout the medium.

Properties of a Suspension

    i- It is a heterogeneous mixture.

    ii- The particles of a suspension can be seen by a naked eye.

    iii- As the particles are visible by naked eye, the path of light is visible in a solution.

    iv- A suspension is unstable.

The solute particles settle down when a suspension is left undisturbed.

Colloidal Solution:

A colloidal solution is a heterogeneous mixture. For example: -  Milk. The particles of a colloidal solution are uniformly spread throughout the solution.

Properties of Colloidal Solution

    i - A colloidal solution is a heterogeneous mixture.

    ii - The size of particles is very small hence cannot be seen by naked eye.

    iii - Colloidal solution is quite stable.

    iv - The particles of this solution do not settle down when left undisturbed.

Types of Pure Substances

There are two types of pure substances:

1. Elements

Element is basically defined as a basic form of matter that cannot be broken down into simpler substances by chemical reactions. This is defined by Laurent Lavoisier. Elements can be normally divided into metals, non-metals and metalloids.

Properties of Metals, Non metals and metalloids:

    i- They are lustrous (shiny appearance).

    ii- They are in silvery-grey or golden-yellow color.

    iii- They are good conductors of heat and electricity.

    iv- They are ductile (can be drawn into wires).

    v- They are malleable (can be hammered into thin sheets).

    vi- They are sonorous (make a ringing sound when hit).

    vii- Non-metals are not good conductors of heat or electricity.

    viii- Metalloids show characteristics of both metals and non-metals hence they are also called semimetals.

2 . Compounds

A compound is defined as a substance composed of two or more elements chemically combined with one another in a fixed proportion.

Difference between mixtures and compounds:

Sr. No

Mixtures

Compounds

1

 A mixture is formed by mixing of elements or compounds.

 Compounds form when elements react.

2

 It has a variable composition.

The composition of each new substance is fixed.

3

 Physical methods are used to separate the constituents of a mixture.

The constituents can be separated only by chemical or electrochemical reaction.

4

 The mixture shows the properties of constituent substances.

 It has entirely different properties.