Matter is composed of two or more components known as substances. In science, a substance is a form of matter that cannot be separated into other forms by physical means. A "pure substance" refers to only one component, with no other mixed substances. When different substances are combined, the result is called a mixture.
Students can now download free PDF notes for CBSE Class 9 Science Chapter 2, Is Matter Around Us Pure, created to simplify concepts and enhance learning. These notes provide a clear understanding of mixtures, compounds, types of solutions, and various methods of separation used in daily life and industries.
Matter around us can be classified into pure substances and mixtures based on its chemical nature
Pure Substances
A pure substance consists of only one type of particle and is divided into:
Mixtures
Mixtures contain two or more pure substances physically combined, retaining their individual properties:
A solution is a homogeneous mixture of a solvent (major component) and a solute (minor component). Examples include lemonade and soda water.
Properties of a Solution:
It is the amount of solute in a given solution. Based on solute quantity, solutions can be dilute, concentrated, or saturated (when no more solute can dissolve at a given temperature). Concentration is commonly expressed in three ways:
Mass by Mass Percentage: Mass of solute per mass of solution.
Mass by Volume Percentage: This measures the solute's mass relative to the solution's volume.
Volume by Volume Percentage: Volume of solute per volume of solution.
A suspension is a heterogeneous mixture in which solid particles are dispersed in a liquid but remain undissolved.
Properties of a Suspension:
A colloid is a heterogeneous mixture in which particles are uniformly distributed but not visible to the naked eye.
Properties of Colloidal Solutions:
Components of a Colloid:
The following table clearly compares the properties of true solutions, suspensions, and colloidal solutions:
Elements: Form of matter that cannot be broken down into simpler substances by chemical reactions. First defined by Antoine Lavoisier, elements are classified as:
Compounds: Formed when two or more elements chemically combine in fixed proportions. The properties of compounds differ from their constituent elements, and their composition is uniform throughout.
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