Canvas Classes - Free JEE & NEET Chemistry Preparation

Chemistry is the branch of science that studies the composition, structure, properties, and reactions of matter — from the aspirin in your medicine cabinet to the Teflon coating on your pan. Everything you see, touch, or breathe is chemistry. This chapter builds the quantitative foundation you need: how matter is classified, how atoms combine, and how chemists count invisibly small particles using the mole.

Nature of Matter

Anything that has mass and occupies space is matter.Matter exists in three physical states — solid, liquid, and gas — determined by how tightlythe constituent particles are packed and how freely they move:

State	Particle arrangement	Volume	Shape
Solid	Very close, ordered, almost no movement	Definite	Definite
Liquid	Close, but free to move past each other	Definite	Takes shape of container
Gas	Far apart, move rapidly and randomly	Not definite	Not definite

These three states are interconvertible by changing temperature or pressure:

$\text{Solid} \xrightarrow{\text{heat}} \text{Liquid} \xrightarrow{\text{heat}} \text{Gas}$

Particle arrangement in solid, liquid and gaseous states — 📸 Fig 1.1 — Particle arrangement in solid (tightly packed, ordered), liquid (close but mobile), and gas (widely spaced, fast-moving). All three are interconvertible by changing temperature or pressure.

Classification of Matter

At the chemical level, all matter is either a pure substance or a mixture.The full classification tree:

Pure substance — fixed composition; cannot be separated by physical methods
- Element — made of only one type of atom (e.g. $\ce{Cu}$ , $\ce{Au}$ , $\ce{O2}$ )
- Compound — two or more elements in a fixed ratio (e.g. $\ce{H2O}$ , $\ce{C6H12O6}$ )
Mixture — variable composition; components retain individual properties
- Homogeneous mixture — uniform composition throughout (e.g. sugar solution, air, alloys)
- Heterogeneous mixture — non-uniform; different components visible (e.g. sand + salt, gravel)

Classification of matter tree diagram — 📸 Fig 1.2 — Classification of matter. All matter splits into pure substances and mixtures; each branches further into elements/compounds and homogeneous/heterogeneous mixtures respectively.

Pure Substance vs Mixture

Pure Substance

Fixed, definite composition
Cannot be separated by physical methods
All particles are chemically identical
Has sharp melting and boiling points
Examples: $\ce{NaCl}$, $\ce{H2O}$, $\ce{Au}$, $\ce{O2}$

Mixture

Variable composition
Components separated by physical methods (filtration, distillation, hand-picking)
Components retain their individual properties
No sharp melting/boiling point
Examples: air, sea water, alloys, soil

Pure Substance

Fixed, definite composition
Cannot be separated by physical methods
All particles are chemically identical
Has sharp melting and boiling points
Examples: $\ce{NaCl}$, $\ce{H2O}$, $\ce{Au}$, $\ce{O2}$

Mixture

Variable composition
Components separated by physical methods (filtration, distillation, hand-picking)
Components retain their individual properties
No sharp melting/boiling point
Examples: air, sea water, alloys, soil

✦JEE / NEET Exam InsightJEE / NEET

◆Homogeneous vs Heterogeneous: Both are mixtures. Homogeneous = uniform at the molecular level (you can't see the components). Heterogeneous = non-uniform (you can see/identify components).

◆Element vs Compound: Both are pure substances. Element = one type of atom only. Compound = two or more elements in a fixed ratio.

◆Is air a compound or mixture? — Mixture (heterogeneous in terms of minor components; treated as homogeneous). Its composition varies.

\ce{O2}

and

\ce{N2}

can be separated physically by fractional distillation.

◆Intensive vs Extensive properties — tested frequently:

◆Intensive (independent of amount): density, temperature, refractive index, boiling point, colour

◆Extensive (depends on amount): mass, volume, heat capacity, enthalpy

Quick Check

Q1.Which of the following is a homogeneous mixture?

Nature of Matter

State	Particle arrangement	Volume	Shape
Solid	Very close, ordered, almost no movement	Definite	Definite
Liquid	Close, but free to move past each other	Definite	Takes shape of container
Gas	Far apart, move rapidly and randomly	Not definite	Not definite

These three states are interconvertible by changing temperature or pressure:

$\text{Solid} \xrightarrow{\text{heat}} \text{Liquid} \xrightarrow{\text{heat}} \text{Gas}$

Classification of Matter

At the chemical level, all matter is either a pure substance or a mixture.The full classification tree:

Pure substance — fixed composition; cannot be separated by physical methods
- Element — made of only one type of atom (e.g. $\ce{Cu}$ , $\ce{Au}$ , $\ce{O2}$ )
- Compound — two or more elements in a fixed ratio (e.g. $\ce{H2O}$ , $\ce{C6H12O6}$ )
Mixture — variable composition; components retain individual properties
- Homogeneous mixture — uniform composition throughout (e.g. sugar solution, air, alloys)
- Heterogeneous mixture — non-uniform; different components visible (e.g. sand + salt, gravel)

Pure Substance vs Mixture

Pure Substance

Fixed, definite composition
Cannot be separated by physical methods
All particles are chemically identical
Has sharp melting and boiling points
Examples: $\ce{NaCl}$, $\ce{H2O}$, $\ce{Au}$, $\ce{O2}$

Mixture

Variable composition
Components separated by physical methods (filtration, distillation, hand-picking)
Components retain their individual properties
No sharp melting/boiling point
Examples: air, sea water, alloys, soil

Pure Substance

Fixed, definite composition
Cannot be separated by physical methods
All particles are chemically identical
Has sharp melting and boiling points
Examples: $\ce{NaCl}$, $\ce{H2O}$, $\ce{Au}$, $\ce{O2}$

Mixture

Variable composition
Components separated by physical methods (filtration, distillation, hand-picking)
Components retain their individual properties
No sharp melting/boiling point
Examples: air, sea water, alloys, soil

Quick Check

Q1.Which of the following is a homogeneous mixture?