Pure Substances

Pure substances may be defined as material which contains only one kind of atoms s or molecules. The measure of whether a substance is pure is known as purity.

Elements and compounds are pure substances.

1. A pure substance has uniform composition and properties in all its parts, as it consists of particles of only one kind. For example, sugar and salt are pure substances.
2. It has certain characteristics such as specific temperatures at which it melts and boils. For example, pure water boils at 100°C.
3. The constituents which make up a pure substance cannot be separated by physical means.

Impure Substances

Mixtures are impure substances.

1. A substance is said to be impure if it has particles of other substances mixed in it.
2. The constituents of impure substances may be present in any ratio.
3. The constituents of an impure substance retain their individual properties. For example, the properties of iron and sand do not change when they are mixed together.
4. The constituents of an impure substance can be separated by physical means.

 Types of Substances

Substances are basically classified into two types. They are:

• Pure Substance:  Examples of pure substances include iron, aluminum, silver, and gold.
• Mixtures: Examples of mixture include the salt solution which is a ‘mixture’ of two components, salt, and water.

Compounds

Compound is a pure substance made up of two or more elements combined chemically in a definite ratio.

Characteristics:

1. The properties of compound differ from those of its constituents.
2. Compound has fixed melting point and boiling point.
3. Compound is a homogeneous substance.
4. Constituent elements can be separated by chemical process.

Mixtures

It is made up of two or more elements or compounds mixed in any ratio/proportion.

Properties:

• It may be homogeneous of heterogeneous.
• The properties of constituent substances are retained.
• No new compound is formed.
• Elements can be separated by simple physical processes.
• It does not have fixed melting and boiling point.

Solution

• It is a homogeneous mixture of two or more substances.

 To get in-depth knowledge about class 9 chemistry chapter 2 notes the students can refer to is matter around us pure class 9 notes pdf.

NCERT Solutions for Class 9 Science Chapter 2 – Is Matter Around Us Pure