Nature of Matter: Overview, Questions, Preparation

The definition of Matter as per the NCERT is, “Anything which has mass and occupies space is called matter”. 

Explanation: As per the above definition, any object or substance that has mass and takes up space is called matter. For example, books, pens, pencils, water, air, all living beings, etc.

Matter is classified into two types: Physical and Chemical. The detailed classification matter is mentioned below.

Physical Classification

Matter can exist in three primary states:

Solids: Definite shape and volume, incompressible, particles tightly packed.

Liquids: Definite volume but no definite shape, slightly compressible, particles less tightly packed than in solids.

Gases: Neither definite shape nor volume, highly compressible, particles far apart.

Chemical Classification

Pure Substances: Consist of only one type of particle; homogeneous. Examples: Elements (Oxygen, Hydrogen), Compounds (Water, CO₂).

Mixtures: Two or more different particles; can be homogeneous (air) or heterogeneous (oil and water).

 

Physical Properties

Can be measured without changing the composition. Examples: Density, Colour, Melting point, Boiling point.

Chemical Properties

Can only be observed when a substance undergoes a chemical change. Examples: Reactivity, Flammability.

Matter can change states by changing temperature and pressure.

Melting: Solid to Liquid

Freezing: Liquid to Solid

Vaporization: Liquid to Gas

Condensation: Gas to Liquid

Sublimation: Solid to Gas directly (e.g., Camphor)

Deposition: Gas to Solid directly

Democritus (400 BC) proposed that matter is made up of small, indivisible particles called atoms. Dalton's Atomic Theory (1808) expanded on this, suggesting atoms are indivisible, identical for an element, and combine in simple ratios.

Atom: The smallest unit of an element.
Molecule: Two or more atoms bonded together.

Law of Conservation of Mass: Mass can neither be created nor destroyed.

Law of Definite Proportions: Compounds always contain elements in fixed ratios.

Law of Multiple Proportions: When two elements form multiple compounds, their mass ratios are simple whole numbers.

Gay-Lussac's Law: Gases react in simple volume ratios.

Avogadro's Law: Equal volumes of gases contain equal number of molecules.